Model Sailing Craft, Third Edition by W.J. Daniels and H.B. Tucker – 1952

W. J. DANIELS and H. WITH B. A TUCKER PREFACE C. N. BY THE LATE FORGE Hon. Secretary (1922-1935) and Chairman (1936-1937) of the Model Yachting Association THIRD EDITION (REVISED) – “ESTHER” (QW. J. DANIELS & T. LANCE, SOUTH LONDON 4M.Y.C.). Designed, built and skippered by W. J. Daniels. Winner : M.Y.A, National Championship for International A-class, 1950. [ Mrontispiece. Catalogue No. 471/4. Printed in Great Britain by The Whitefriars Press Ltd., Tonbridge. Bound by G. & J. Kitcat Ltd., London: Flexiback Binding. PREFACE TO FIRST EDITION 1448563 By the late C. N. FORGE Hon. Secretary (1922/1935) and Chairman (1936/7) of the Model Yachting Assoctation. | but throughout the civilised world. Wherever there is a suitable sheet of water, model yacht clubs have been formed, and public authorities recognising the value of model yacht sailing calls for keenness of observation, rapidity of decision, and, above all, good sportsmanship. When one considers these points, the increasing popularity of model yachting is easily understandable. The surprising thing is not the recent boom in the sport, but that the advantages of the pastime have not been and its importance as a healthy pastime, are mote widely appreciated. «ie the last few years public inter- est in model yachting has increased marvellously, not only in Great Britain, gradually building more lakes for the purpose. * The old conception of model sailing as a 2 2 2 childish pastime is practically dead, and the Possibly one thing that has delayed the public to-day understands the difference be- progress of model yachting is the absence of tween a model yacht and a toy boat. In fact, it may be said that model yachting has arrived a teally first-class text-book. have been published on the subject, some better and taken its place as one of the great inter- than others, but there has been a crying need national sports. for just such a2 volume as the present hand- The reason of this is not far to seek when one considers the sport as it really is. In the first place, a model yacht has to be designed and built before it can be sailed. Whilst it is not everybody who is capable of designing and Several books book. As Hon. Secretary of the Model Yachting | Association, J have had every opportunity to see the work that has been done for the sport by the authors of “‘ Model Sailing Craft.” Mr. W. J. Daniels is certainly one of the building his own boat, those who can do this gain a keener pleasure than those who merely most celebrated model yachtsmen in the world. buy their boats. Apart from anything else, six of the eight The design of a model yacht is in all respects analogous to that of a real yacht. International Races that have been held since It is a the war have been won by models of his design scientific business requiring study and calcula- and building, and on five of the occasions he tion, and therefore this branch of the pastime has actually skippered the winning boat.* has a high educational value. Mr. Daniels’ achievements are the result of The building of models again calls for a high lifelong study. In his early days he met with It 1s scant success, but eventually patience and hard futile to design a boat carefully and not to work brought its own reward, and to-day his build her true to design. name is known in every part of the world where degree of accuracy and craftsmanship. Patience and accuracy are, therefore, essential. there are model yachts. In the designing and building one finds an His collaborator, Mr. H. B. Tucker, has ideal indoor hobby, and one that gives its sailed real yachts all his life. Immediately after exponent the chance to express the natural he was demobilised from the R.N.V.R., he creative instinct that lies in every man. started model yachting with a view to experi- The actual sailing, on the other hand, provides a healthy outdoor pastime as a complement to the indoor hobby of designing and building models. Sailing is a sport that * Since this Preface was wtitten in 1932, Mr. W. J. Daniels has won two more international events in Britain and one at Hamburg. Mr. Forge was, of course, referring to the First World War. . PREFACE TO FIRST EDITION menting. He soon made a name in the executive organisation which controls the sport in this country. He served from 1925-1930 as the greatest use and interest to every model yachtsman. Chairman of the Model Yachting Association, * The international association is now known as the International Model Yacht Racing Union. Since Mr. Tucker held office, a number of other gentlemen have held this office. t The Model Yachtsman commenced publication in April, 1928, but in 1933 its scope was extended to cover all aspects of marine modelling and the title altered to Marine Medels. Under Mt. H. B. Tucker as Editor, it enjoyed a world-wide circulation until it was suspended in September, 1939, on the outbreak of the Second World War. During the wat the magazine changed hands and afterwards recommenced publication with a different Editor. It subsequently tan for about a couple of years and has now gone out of existence. and had a large share in drafting the present sailing and rating rules. He founded the International Model Yacht Racing Association, of which he has been the Hon. Secretary since its inception.* amount He has also done an immense of journalistic work in connection with the sport, and acted as Editor of The Model Yachtsman since its foundation.T The combination of these two authorities has produced a book that cannot fail to be of AUTHORS’ PREFACE TO THIRD EDITION HE Second Edition of this Handbook this book was lost when the warehouse, in was published early in 1939 and was which it was stored, was burnt to the ground. selling very well, but when the Second The publication of this Third Edition has World War broke out on September 3rd, 1939, perforce been delayed until now, but the book model yachting in this country virtually came has been very thoroughly revised and many to an end as an organised sport. Likewise, the sections practically construction of model yachts became impos- entirely up to date. re-written to bring New designs to it the sible owing to scarcity of timber and other various racing classes have been included. materials. is hoped that all these alterations will increase It the value of this book to all those interested in The United States, however, remained out Model Sailing Craft. of the War for some years, and during that period Model Sailing Craft continued to sell Then came the great W. J. DANIELS. German Air Raids on London, and in one of H. B. Tucxer. well in that country. these the remainder of the Second Edition of Vi CHAPTER I el Yacht Racing. Why Bateng Rules are Niecessary. The 10-Rater Rule. LY.RU. Class . — . : . . . CHAPTER II istory of Model Yachting as an Organised Sport, and its Influence on Rating Rules. tional Racing. The A-Class. The M-Class (Marblehead). The 36-inch Restricted >) CHAPTER III ipwrights, Ancient and Modern. An Explanation of the Lines used to Delineate a Yacht. Designing to a Rating Rule : . ; . . . 28 CHAPTER IV General Considerations in Designing. Drawing Requisites. Midship Sections. Calculation of Section Areas (Simpson’s and Trapezoidal Rules). sections. Co-efficients y Fineness. The First Steps in Drawing a Set of Lines . Raked Mid- . . . 33 CHAPTER V Completion of the Canoe Body. Curves of Areas. Displacement and Centre ofBuoyancy. The Colin Archer Theory. Speed Factors. Tumble-home. Calculation of Deck Camber 51 CHAPTER VI The Keel Appendage. Lateral Planes and the C.L.R. Forms of Keel Appendage. Drawing the Keel and Rudder. Comparison of Fore-and-Aft Position of Centre of Pagany when Vessel is Upright and Heeled. Calculations of Lead Keels . . , Go CHAPTER VII Fore-and-Aft Trim. Calculation of Centre of Gravity. Vertical Curve of Areas. Calculation of Height of Centre of Buoyancy. Finding Transverse Position of Centre of Buoyancy when Vessel is Heeled. The Metacentre. System of Balance . Stability Calculations. ; . . ; The “ Metacentric Shelf” . . . . . 74 CHAPTER VIII Designing the Sail-Plan. General Considerations. Aftersail and Height to Breadth. Selection of Rig. Proportions of Headsail to Calculation of C.E. and Position of Rig over Hull . Vil 82 Reduction of Effective Sail Area by Heeling. Stabil Building to Different Scales. Ratios for Use in Comparise CHAPTER X Preliminary Remarks on Building. Screws and Fastenings Gluesjr Mode! Plains and Methods a Using Them. T . CHAPTER XI Punts, Barges and Sharpies. Building a 10-Rater Sharpie CHAPTER XII How to Lay Off a Bread-and-Butter Hull. Method of Building. Removable Keels CHAPTER XIII The Construction of Planked Yachts. Setting Up. Planking Up. Warious Systems Explained. Multi-skinned Hulls. Making the Moulds and : : . 126 CHAPTER XIV Lead Keels. Making Plaster Moulds for Casting. Casting. Drilling Lead. Sand Moulds. Casting a Keel. Tables of Weights and their Uses. Finishing up a Fixing a Lead Keel. . 137 . 143 . 149 . 152 CHAPTER XV Rudders and Fittings. Deck-beams. Decks. Covering Boards. Hatches. ; CHAPTER XVI Painting and Varnishing. Lining a Deck . : : , CHAPTER XVII How to Fit the Braine Steering Gear. Vane Steering Gear . ; CHAPTER XVIII Spar Making. Hollow Masts. Calibrating a Boom. Spar Fittings. Spreaders, Jennys, Goosenecks, Jib Ferrules, Spinnaker Fittings. Deck Fittings: Mast Slides, Chainplates, Jib Racks, Horses, Gunwale Eyes, Spinnaker Sheet Hooks, Banspri Pings. Soldering and Siler Soldering . ; ; : . . CHAPTER XIX Rigging, Standing and Running. Standing Rigging. Running Rigging. Riggmg a Spinnaker. Kicking Straps. Beating Guys and Liverpool Boys. Making Rigging Hooks . Vill 164 XI ferent Points of Sailing. The Theoretical Angle for Trimming the Vindward. The Beating Guy, its Theory and Use. The Rudder Guy and ver pool Boy and its Use. Reaching. Jib Steering on a Close Reach. Running and Braine Gear. Retrimming. Mast Position and Tuning-up Using the Vane Gear 190 CHAPTER XXII h Vane Steering. ontrol. Using the Combined Braine-Vane Gear. The Possibilities of Radio General Notes on Handling 201 CHAPTER XXIII | e-and-Aft Rigs with their Salient Characteristics. Square Rigs . . . . 208 CHAPTER XXIV Advice to the Novice on the Selection of a Class to Build to. of Racing Rules. Race Organisation . . Formation of a New Club. ! . . : . ; . Summary . . 216 . . 220 : ~POSTSCRIPTUM . . ; . . “NOTES ON THE DESIGNS INCLUDED IN THIS BOOK “GLOSSARY OF NAUTICAL TERMS . . ix ; . . . . . 226 . . . . 228 zed, built nternational a = and skippered A-Class, 1950 si “ne F rontis piece hs – FACING PAGE 120 shea (D. al : : : . . A. Macdonald, Clapham MLY.C.). : : ; orber View of “ Yankee Doodle”’ in Frame . _ “olka Dot” under Construction, Stern View . . . Vane Steering Gear Set for Running ; ; . . . . . . ; ! wo Views of Completed Hull of “ Yankee Doodle” “ Claire”? (A-Class) Showing Hull Planking . . olka Dot” (American B-Class) under Construction : . ; . . . 120 . . . . ; . . . . 121 . 126 . 127 . 128 . J . 129 . . . 132 ; . 133 . 158 . 158 . 159 . “Esther,” View of Stern showing Vane Gear Installation . . . . Vane Steering Gear Set for Beating xd . Designed by H. B. Tucker, Winner : Championship for 36-inch Restricted Class, 1950 ankee Doodle’? (A-Class) in Frame | . ; . Lines of to-Rater Model “ Brilliant Lines of M-Class Model “* Emerald” III. Lines of A-Class Model “Amethyst” IV. Lines of 36-inch Restricted Class Model “ Gem” V. VI. VII. VIII. Fig. 25. The First Steps of the Design Fig. 26. The Design carried a Stage Further Fig. 27. The Canoe Body Completed . Fig. 28. The Design of the Hull Completed IX. Lines of 10-Rater Sharpie Model “ Diamond” X. XI. XI. Alternative Profile for “ Diamond”? for use with Vane Gear . Fig. 54. Method of Building a Bread-and-Butter Hull Fig. 55. Construction Plan showing System used in Rib-and-Plank Building . XII. Lines of ILY.R.U. 6-Metres Model “ Pearl” XIV. Alternative Profile for “ Pearl” for use with Vane Gear XV. XVI. XVII. XVII. Fig. 66. Deck Plan Figs. 67-71 Fig. 107. Rigging Details and Method of Bending Sails . Figs. 108-110 Xit INTRODUCTION HE origin of the sailing boat is wrapped in the mists of antiquity, but probably the first idea of sailing came when prehistoric man spread his skin cloak to the breeze and found that his log canoe blew along without labour at a more rapid rate than he could propel it with his crude paddle. Since the first dawn of early civilisation, model-making has possessed a fascination for mankind, but when and whete the first model sailing craft was fashioned we have no means of knowing. Certain it is, however, that models have been found in the ancient Egyptian tombs, and since these were of the craft in which the Egyptian went a-pleasuring on the Nile, we may safely style them model yachts. From the ancient Egyptians to the Middle the mutton on which the prisoners were fed, and by selling them the prisoners made a small revenue with which to buy little luxuries. In those days £5 or {10 was a good price to give for one of these little ships, which took months To-day good of patient work to execute. examples (after proper restoration of the rigging), fetch tremendous prices, as much as £1500 having been paid for a particularly fine specimen. The detail work in these little vessels is often most beautifully executed. The bone is laid on a wooden block, and in some of the smaller examples the rigging is done with human hair. Bone ships are amongst the most interesting and beautiful models extant, and are usually extremely accurate. pean models are mainly found in the. Medi- About 1840 steam began to take the place of sail in the Navy, and from that time models of warships lose their interest for the student of Ages is a long step, but then we find that there was much model making. These early Euro- terranean countries, and frequently take the sail; form of Church Ships. The sailor of those days, of sail was then just commencing, as but in merchantmen the golden age when starting out on a perilous voyage, or in onwards was the age of the clipper ships. 1840 moments of dire danger, would often vow to For about thirty-five years sail held its own give a ship to the Virgin or to his patron on the longer trade routes, but gradually steam saint, if he was spared to return safely. began to be used, especially for mails and fast Con- sequently Church Ships were usually the work cargo of sailors, not craftsmen, and are often crude relegated to less important routes, and services and inaccurate in proportions and details. where low freights were more important than We services. Sailing vessels were then must also remember that they were made to be fast passages. hung up before the Altar, and consequently viewed from below, which would naturally of the clippers had their sail spreads cut down and crews reduced. affect the perspective. was at that time of more importance than Ships cannot, historically Although these Church therefore, exact, their be regarded study is as of great Cargo-carrying capacity speed, and the big iron ships then had their day. Little by little, steam ousted these also, and to-day hardly a single sailing ship spreads interest. From the collector’s point of view, the best periods Under these conditions many are the seventeenth and eighteenth her lofty pyramids of canvas to the wind. There are still models of sailing ships to be found in centuries, when many magnificent models were out-of-the-way places. turned out by shipwrights and designers. made by sailormen to pass the time on long, Fine Many of these were examples of these can be seen in the Greenwich tedious Museum, builders and shipwrights. South Kensington Museum, the Louvre, the Dutch Museums, etc. During the Napoleonic wars, the French prisoners of war also made many beautiful model ships. M.S.C, These were made of bones from voyages. Others are the work of The latter are usu- ally better than the sailor-made models, as the hull lines are more accurate. In our fishing fleets and coastal craft, it is the same story, and steam and the ubiquitous B = ————_—_—_—_—_—_- MODEL motor have almost supplanted sail. SAILING CRAFT Soon the Model sailing craft can be divided into t yachting fleets will be the only representatives main categories—“ show ” models and work- of sail afloat. ing (Z.e., sailing) models. Here again the motor is gaining ground, so that the time may soon come when except for racers, sailing yachts are a rare sight. Even in yachting, alas, the war has gendered many changes. en- Gone is “ Britan- nia,” gone are the “‘ Endeavours ” and those lovely yachts of the large classes. Show models are of various types. There is the waterline model, which shows the ship as she appears above water, complete with spars and rigging. These are very decorative if well executed. ‘There are, Another type of model is the hull model, of course, the R.O.R.C. yachts and the handi- and many of these are museum pieces, showing cap classes, but the largest purely racing class the exact method of building employed. to-day is the 6-metres, and at present prices variant is the half-model, which is frequently even this comparatively small racer is beyond made by yacht and ship builders to show hulls the means of all but the wealthiest. as actually designed. In place of the open classes, we have now a number of one-design racing, classes. and These test helmsmen provide and good crews, but obviously restrict the chances of young de- The third type is the complete A model showing the entire ship from mast truck to keel, and this is perhaps the most interesting of all to the student of naval architecture. . signers, especially as almost the whole of this Any kind of sailing vessel from a lordly work is concentrated in the hands of half-a- full-rigged ship to a sailing dinghy may be dozen well-established naval architects. built as a show model. Hence the model sailing yacht (which could almost more accurately be described as a ““ miniature sailing yacht ”’) is the only vehicle left for an aspiring young designer to test his This aspect of model yachting is not always stressed. Yacht neither an art nor an exact combination of both. designing science, is but a For the professional naval architect, even if his work is mainly with power sailing model as well craft, experience and understanding of boats is invaluable. In consequence, yachting has a great educational value as being an absorbing hobby. * * the greatest accuracy should be employed down to the smallest detail, as the aim of these models should be to form a record. There is another class of show model which is usually styled a “‘ decorative ” model. These ideas and gain experience. sufficiently Whatever the subject, * * It is not within the scope of the present volume to give a detailed history of sailing craft or early models, and the student is referred to the many excellent books which have been wtitten on this subject. The foregoing brief survey, however, serves to show that model-making is a very ancient art, and the modeller of to-day, whether he makes his models as “‘ show” pieces or as actual miniature sailing vessels, is but one of a long line of craftsmen that stretches back to the days of the Pharaohs, and even before. are nearly akin to the Church Ships of early days. Decorators to-day model as an ornament. often use a ship The position in which these are set usually precludes close examina- tion and intricate detail would Broad effect is what is aimed at. be wasted. These ships are often of the style called ‘* conventional,” and have little or no interest to a serious student of naval architecture. Many ships made by silversmiths are conventional models, but occasionally some very fine examples of ship models in silver are seen. Several good treatises on making show models have been written, and nothing more need be said here on this subject, since the subject of our present book is the actual sailing model. * x * * Sailing models can be divided into tacing models and “‘ prototype” models. The latter term is used to imply non-racing craft, but would really apply with equal force to racing conditions of wind 3. schooner: many others. etch 3, It will he present volume to deal 1 these different types, so we elves to our real subject, 1odel racing yacht, but methods nature bestows on us. and sea that Many model sailors find much pleasure in sailing alone, whilst others prefer the excitement of racing. And, after all racing against boats of similar type and size is the supreme test of design and workmanship. Every boat appears to be minor performing well when she is sailing alone, 90d deal of attention has been devoted worthy rival that her true merit can be judged. ction s) and rigging (with apply to these also. subject of actual sailing, but there is no uilding a first-class sailing model unless and it is only when she is pitted against a * * 2 2 is able to handle her properly. Moreover, It has been the aim of the authors in compil- ydel yacht sailing is one of the most healthy ing the present treatise to explain every process d fascinating pastimes. Little by little as e’s skill grows, one finds the little craft is in the designing, building and sailing of model esponsive, tractable, able to perform almost e same evolutions as a real yacht except for he fact that her skipper is ashore instead of aboard. yachts in the clearest possible manner without leaving anything to the imagination. Every- thing has been detailed step by step, and all technical terms explained as they occur. If _ It is a great pleasure to watch the work of this book helps to smooth the way of the recruit and assist him to enjoy the fascinating one’s brain and hand threshing to windward and instructive sport of model yachting, it will in a gale or under the thousand and one have served its purpose and repaid its authors. CHAPTER I Yacht Racing and Model Yacht Racing. Why Rating Rules are Necessary. The 10-Rater Rule. The 6-Metres HE sport of model yacht racing has LY.R.U. Class The origin of the term “tonnage” (or much in common with yacht racing, “tunnage ’’) is rather curious, as it appears to even as the models themselves are akin have been derived from the number of tuns to their bigger sisters. ‘The differences between (casks) of wine a vessel’s hold would contain. the miniature and the full-size are attributable Thus a ship of 100 tons should have been able to to carry a cargo of 100 tuns of wine. one thing only, that the model has no skipper aboard, whilst the yacht has. In many ways the term “‘ miniature yacht ” is a better description than ‘‘ model yacht,”’ as the yachts. little ships are veritable miniature Moreover, the term “‘ model yacht ” ** * K *K Although model yacht racing has not as long a history as yacht racing, some of our oldest clubs can trace their origins back for eighty is applied indiscriminately to the toy boats years or more. sold in the shops, which even when they are men found the necessity of Rating Rules, and sufficiently well-made to sail at all, are at most these were mostly based on rules originating capable of reaching with wind abeam, whilst with full-sized craft. the real model yacht is able to perform credit- As with yachts, model yachts- The oldest class of models still in use is the ably on every point of sailing. to-rater to the Length and Sail Area Rule. In model racing, as in yacht racing, the best sport is between boats of the same class and type. In order to secure this it is necessary to yachts in 1887. This rule was invented by Dixon Kemp for It was a great improvement on previous systems of measurement and embod- have a system of measurement. These systems of measurement are known as “ Rating Rules,” and, naturally, in these the model has closely followed the prototype. In order to under- ied two entirely new features. stand the origin of these Rating Rules, it is necessary to look into the history of yacht taxed was now measured. racing. as well to deal generally with the factors which The history of full-size yacht racing in this country dates back to the reign of King Charles II., and the earliest race recorded was one from the Pool to Tilbury and back between the yachts of the King and the Duke of York. Owing to various causes very little progress was made for many years until the Royal Yacht Squadron came into being in 1815. In the early days of the “‘ Squadron” there govern the speed of a yacht. was no attempt to classify boats or handicap them, and consequently the largest yacht in the race almost invariably won. ‘This was dull work for all but the owners of the big boats, so in 1843 a scale of time allowances was adopted based on the tonnage of competitors and the length of the course. Hitherto the length taken for measurement had been length over all, but in this formula load water line was used, and sail which had formerly been unBefore discussing this formula, it might be In boxing a good big ’un will always beat a good little “un, and exactly the same applies to yachts. Of course, in boxing, men are classified by weights, but the problem of classifying yachts is by no means so simple. It is more or less possible to even things up by judicious handicapping, but the best sport will always be between vessels of equal class sailing on equal terms. The three main factors that govern the speed of a yacht are her length, displacement and sail area. Of these length is the most important and in this connection it is not the load water line length nor yet the length over all which counts, but the actual length used when sailing. One consideration which must govern the _ eee THE 10-RATER rating rules is that it is the designer’s e ago. Early 1o-raters measured 36-38 in. on to take full advantage of the rule to the L.W.L., with an overall length of about fastest Go in., and a displacement of 16-20 lb. possible boat. Hence any axed or lightly taxed dimension will lead to cess in that direction. For instance when ats are rated by length over all (L.O.A.), the esigner naturally produces a boat without modern 1o-R. is 48-52 in. L.W.L., A 66-72 L.O.A., and displaces anything up to 30 or even 32 lb. This increase in size is brought about partly by the different methods of sail Rule, Load Water Line (L.W.L.) was measured, measurement now used, and partly by the superiority of modern sailplans, which give greater driving power per square inch of can- so the designer naturally produced a boat with long overhangs to gain additional unmeasured can be regarded as a typical example of an sailing length. up-to-date 1o-rater, but the 1o-rater sharpie is overhangs. Under Dixon Kemp’s Length and Sail Area | CLASS Numerous classes of both yachts and models vas. One of the designs included in this book more unusual. have been built under this rule, but the only surviving class to-day is the 1o-rater model. Though this class is over sixty years old, it is Dixon Kemp’s Length and Sail Area rule to-day more popular than ever, and is the most was followed in real yachts by the two Linear numerous class in England, over a thousand Rating being included in the Model Yachting Asso- (international Yacht Racing Union) Rules of ciation’s Register. 1908 and 1920. L.W.L. (in inches) x S.A. (in square inches) _ 6,000 .@) came the J.Y.R.U. rin. = 1 ft. One club, the Model Yacht Sailing Association Round Pond, Kensington Gardens, built up a nice fleet of these little models, but The class has been brought up to date as taken in accordance with the latest ].Y.R.U. given later in this chapter). Only 85 per cent. of the fore-triangle is taken mainsail batten limits are optional. Then * Smith’s 18-footer class ona scale of of the regards sail area measurement, which is now in the computation of total sail area. Rules. * yachtsmen, but they did adopt Major Heckstall For the sake of reference the rule is given below in its model form:— (as * None of these rules was followed by model THE 10-RATER CLASS regulations * For the When they they did not take on elsewhere, and were eventually dropped. In 1933 the third I.Y.R.U. Rule was pro- mulgated, and was adopted for model use the following year. The first model class under it was the 12- metres (Scale 1 in. =1 ft.), but for various are adopted, the number of battens is limited reasons did not make a very successful model, to four equally spaced. and it has The length of the now died out except for a few upper and lower battens must not exceed 5 in. survivors in some of the Scottish clubs. and the intermediate ones 7 in. few 1o-m. models were also built but this class not exceeding 1 in. A headboard width is also allowed. again never became popular. A The last and By taking advantage of the batten limits and most successful 1.Y.R.U. model class to be headboard adopted was the 6-metres (Scale 12 in. = 1 ft.). concessions, a quite appreciable area of unmeasured sail can be gained. If It should be added that this class is not peculiar batten limits are not adopted, the total area of to Great Britain alone, but has been adopted by the sail is measured. the International Model Yacht Racing Union measuted in fresh Models of this class are water. They are not obliged to carry the same sized spars on small suits of sails as they do on their full suit. The modern to-rater is, however, a very different craft from that of even thirty years for one of the classes for International model yacht racing. In passing it should among real yachts this be mentioned that rule has now been superseded by a new rule for yachts above 6-m. “BRILLIANT” |O-RATER SAIL 79.75″ AREA FORE A 22 %!75 2.499 © 56.0″, LESS 15% 2 73 / 417 (195 MAIN-LUFF LEACH FOOT 44 [ 5 6 2 JIB—LUFF LEACH FOOT MAIN-LUFF LEACH 42.8″ 39.5″ (3.2″ 52.4″ 55. 2″ FOOT i‘ — —— =e | FORE A= 17.5″ SPINNAKER 54-0 X 56.5 X 29.0 a ee = oe oe 3.5″ 49. Sf” 16.5” So BASE SECOND S$ U 48. JIB- LUFF LEACH Lf — SAIL PLAN OF 10-RATER MODEL. Lines on Folding Plate I opposite. 19.2 | T Z === x | ea a — ee a : Iw wal a a2nr TABLE_OF_WEIGHTS eo DECK –H——_\ BAI & VARNISH nl FITTINGS > a VANE GEAR LEAD KEEL vi 10 a 1 1) 12 . 4 r, 13 : YA, J Ib, oz. i 8 n 8 8 15 6 2 26 O y WA eee eee —_ eee [To face page 6. | | “BRILLIANT” 1O-RATER 79.75″ | \ \ \ 56-0″ / = 73 LESS 15% 417 SECOND SUIT AA JIB- LUFF \ LEACH FOOT MAIN-LUFF LEACH FOOT \ MAIN O22 cee -778 | 1195 | \ | oa BASE \ | in =s FORE A ” ce} cle7B 4] 4 Al in O BYSS | ane rT) [A “ 0 Mrryop oF TAKING d MEASUREMENT. Taken on Both Sides of Yacht. OCA — OBA = d. XO = Freeboard Measurement. ending, plus the freeboard at the stern L The maximum freeboard to be used as a minus quantity in the formula when calculating the Rating shall be as per scale at foot.t Hollows in the Surface of the Hull. No hollow shall be allowed in the surface of the hull between the L.W.L. and the sheer line, except- ing in the profile of the stern forward of the Hollows in the surface of the hull at the stern immediately resulting from the hollow allowed in the stern profile are not prohibited by this clause. Draught. The maximum draught allowed shall be in accordance with the Tables given * Depth for d Measurement below L.W.L.—4:1 in. }, Freeboard, Maximum, to be used as Deduction.— 4°0 in. Maxinum Height of Sailplan. ‘The maximum height allowed, measured from the deck along the mast, shall be as per Table at foot.§ Maximum Height of Fore-Triangle. ‘The maximum height allowed, measured from the deck along the mast, shall be 75 per cent. of maximum height of sailplan.|| Battens in Mainsails. Restrictions point of measurement of L. Limitation on Minimum Beam. ‘The minimum beam measured at § of the measured ’midship freeboard above L.W.L. at the point of greatest beam on that line shall be as per scale at foot.t Any deficiency to be multiplied by 4 and added to L measurement. This rule does not apply to yachts built or building before September, 1937. station, plus the freeboard at the bow L ending; the sum to be divided by 3. less than the amount given in the Tables Jater in the chapter. Ifa yacht is less than the displacement required by the rule for her length on L.W.L., then the difference between the length on L.W.L. to which her displacement actually corresponds, and the actual length on L.W.L. will be doubled and added to the length measurement. N Fic. 2. Displacement shall not be ‘The number shall not be more than four and shall divide the after leach into approximately equal parts. The length of intermediate battens shall be as per Table at foot, upper and lower battens being one-fourth shorter. 4 Limit to Size of Spinnakers. ‘The maximum dimensions of a spinnaker shall not exceed the following :— Maximum length of luff and leach (which shall be of equal length, 80 per cent. of the t Minimum Greatest Beam Allowed.—10-o in. § Maximum Height of Sailplan.—71-1 in. || Maximum Height of Fore-Triangle.—5 3:3 in. «’ Batten Limits.—6-6 in. and 5:0 in. MODEL SAILING CRAF TABLE OF MINIMUM DISPLACEMENTS AND MAXIMUM DRAUGHTS 6 METREs (13 in. = 1 ft. o in.), L.WL. Min, Max. WL. 35°O | 17°78 | 8-33 3770 | 20°65 | 8-65 39°0 | 23°81 | 8:97 || 4I-c | 27°28 | 9:29 35°2 | 1805 8°37 37°2 | 20°95 8-69 39°2 | 24714 | gro A4I°2 | 27°64 | 9°32 | Min. Max. | Min, Max. Min Max. 3574 | 1833 | B4o | 37-4 | 21-25 | 8-72 || 39-4 | 24:47 | 9:04 || 41-4 | 28:00 | 9°35 35°G | 1861 | 8-43 37°6 | 21°56 | 875 39°O | 24°81 | 35°8 | 18:89 | 9:07 || 41°6 | 28:37 | 9°39 8°46 37°8 | 21°87 | 8-78 39°8 | 25°15 g:I0 36°0 | 19°18 | 41°38 | 28°75 | 9°42 8-49 38’O | 22°19 | 8-81 40°O | 25°50 | Q13 36°2 | 19°47 42°0 | 29°13 | 9°45 8°53 38-2 | 22°51 8°85 40°2 | 25°85 36-4 | 19°76 | 856 38-4 | 22°83 42°2 | 29°50 | 9°48 8°88 40°4 | 26:20 | 9:19 36°G | 20°05 | 42°4 | 29°89 | 9°51 859 38°G | 23°15 | 8-91 40°6 | 26°56 | 9:23 36°38 | 20°35 42°6 | 30°28 | 9°55 8-62 38:8 | 23°48 | 8-94 40°8 | 26-91 | 42°8 | 30°67 | 9°58 square root of (I squared plus J squared) plus the scale of 2:5 metres.* N.B.—I is the height of fore-triangle; J is the base of fore-triangle. In yachts of 6 metres the clew of the biggest jib shall not extend, when new, more than o-5 Rating, abaft the fore side of the mast measured head to wind. No jib shall have a club or other device for extending it to other than a triangular shape. Headsticks. Any dimension of headsticks to CREW WEIGHT The carrying of crew weight in this Class is entitely optional. If carried, it may be less, but shall not be mote, than 2 lb.§ It shall be fixed in the boat after measurement immediately over the centre of gravity of the yacht, and shall not afterwards be removed. Its weight shall be checked by the measurer and noted on the certificate. MEASUREMENT cent. of Rating.y This shall be carried out in salt water of a ‘These are permitted. Masts (Wood or Metal). 9°26 of lowest position of boom for measurement of sail area is as Table at foot. triangular mainsails shall not exceed 24 per Loose-footed Mainsails. 9°16 deck to the top of the black band marking top Sleeves or tubular pockets extending from Spinnakers are prohibited. Limit of Size of Balloon Jibs. | Permanently bent specific gravity of 1:025. Yachts may be masts, rotating masts, double luffed sails, and measured in fresh water, in which case theit similar contrivances are prohibited. ratings may be increased to the allowed limits. Booms. concave Yachts measured in fresh water may weigh A boom must not be permanently in a fore-and-aft direction. 1/36th less Per- than the weight given for the manently or mechanically bent booms, and corresponding L.W.L. taken in salt water. struts and outriggers on booms, are prohibited. adjustment is A jackstay or rail, if used, must be fixed in the Draughts. All the minimum displacements fore-and-aft line of the boom. and maximum draughts given in the Tables are The maximum height allowed from necessary in the Table No of to be taken as without crew. the t Maximum Height for Boom.—6-o1 in. § Crew Weight. Crew of 5 persons taken as 2 1b. 0 oz. * Scale of 2-5 Metres.—13-67 in. + Headstick Limits.—o:8 in. Io ‘OI”€ “OI’y ()PE PY —> (2)Aenauryjst} Dw \ a = =a ae ur 7 ey t a oe eee R(“E0P}S) ee we et ewe ~~ ew ee el lr ell El oe mm en ew eel el eee es an ewe . + pPrerygre) een A i Il MODEL SAILING CRAFT SAIL AREA MEASUREMENTS Lugsail. Noze.—All points of measurement of sails shall be marked on spars by a black band } in. To be measured the same as a gaff mainsail except as follows :— B and C. Forward end measured to black band at lower end of yard. D. Lower end measured to tack cringle of mainsail, if below top of boom, or for- wide. Gaff Mainsail, or Gunter Lug, whose head makes an angle with the luff. (See Fig. 3 (a) and 4 (¢).) ward of mast. A. Measured from the top of the extreme Triangular Mainsail. (See Fig. 4 (@).) A. The luff, measured from top of boom at after side of mast (or from tack cringle if below the boom) to the black band on the mast beyond which the headstick shall not be hoisted. B. Diagonal measured from the top of boom at black band at outboard end beyond which the sail may not be extended to the nearest point at the outboard end of the boom at the black band beyond which the sail may not be extended to the underside of the extreme outboard end of the gaff at the black band beyond which the sail may not be extended. B. Perpendicular to A, measured to the black band on the mast above which the throat cringle of the mainsail may not be hoisted. after side of the mast. C. Measured from the top of the boom at as the mast at the throat cringle. Restrictions. Headsails. (See Fig. 3 (a).) I. The hoist I to be measured from the deck up the foreside of the mast to the black band where the line of the luff of the foremost headsail cuts the mast. J. The base J shall be measured from the foreside of the mast to where the line of the luff of the foremost headsail, when extended, cuts the deck, bowsprit or other spar (excluding the club to which the sail may be laced) as the case may be. Where a mast slide is fitted, the centre of the mast must be marked on deck, and the distance from stemhead recorded on the certificate. The D. Perpendicular to C measured in to the mast in a line with the top of the boom, or to the tack cringle of the mainsail, if below the top of the boom. Yard Topsail. (See Fig. 3 (a) and (c).) E. Measured from the black band on the mast above which the throat of the mainsail may not be hoisted to the black band on the outer end of the gaff which extended; the sail may not be or to the black band on the outboard end of the jackyard. F. Headboard and battens may be used per tegulations given under the the lower end of A to black band on beyond Perpendicular to E, measured to black band at the lower end of yard. G. Length of yard between black bands. H. Perpendicular to G, measured to black band on outer end of gaff or jackyard. Jib Header. “a mast may be moved forward or aft not more than 3 in. from the marked position, provided limits of movement are marked on deck. The base of the foretriangle shall be marked on the deck, bowsprit or other spar. Should the the foreof mast be moved, the base triangle shall be adjusted so that the (See Fig. 3 (0).) K. Measured from the black band on the mast above which the throat of the mainsail may not be hoisted to black band on the topmast above which the measured base is not exceeded. sail shall not be hoisted. Limits of movement shall be marked on deck, L. Perpendicular to K, measured to black band at extreme outboard end of gaff bowsprit or other spar as the case may be. or jackyard. 12 = = — t=O SAIL AREA MEASUREMENTS dimensions of the fore-triangle for calculation ‘pinnakers. I. of area. The hoist I shall not be taken from the of luff to the centre fore-and-aft line In the case of a yacht carrying a square sail or square topsail, or raffee, together or separately, the actual areas of the same shall be computed; and if such area exceed the area of the fore-triangle, the excess shall be used in the total area for determining the rating. If a square sail is used, it must be set between the mast and headsail, or aftermost headsail if more than one is used. of mast. Foresail of Schooners. deck up the foreside of the mast to where the line of the luff of the spinnaker cuts the mast. J. The base J or length of perpendicular shall be found by setting the sail taut with the heel of boom pointing towards the mast, and measuring along the top of the boom where it is cut by the line A spinnaker may have a headstick or board not larger than one-twentieth (1/zoth) To be measured and calculated as mainsail of similar shape. the length of the spinnaker boom, but not a footyard, nor more than one sheet, nor any con- trivance for extending the sail to other than a CALCULATION OF SAIL AREAS triangular shape, and must not be so set as to Gaff Mainsail or Lug. increase the measured area of the fore-triangle. N.B.—The spinnaker sheet may be led round the luff of the foremost headsail. 3 (a) and 4 (¢)-) Multiply A by B and C by D; add the pro- ducts and divide by 2. The spinnaker boom shall not be used as a bowsprit by being tacked or fixed down at the Bermudian Mainsail and Stiding Gunter whose head is in the same -straight line as the outer end when the boom is right forward. A spinnaker may be set in the ordinary way as mast. a balloon jib by setting it as a bowsprit spin- (Fig. 4 (a).) Multiply A by B and divide by 2. naker on the bowsprit, or by tacking it at the Yard Topsail. ordinary place on deck. (See Figs. 3 (a) and (¢).) Multiply E by F and G by H; add the pro- The spinnaker boom must be shipped and used only on the opposite side to the mainboom. (See Figs. ducts and divide by 2. Jib-Header Topsail. A spinnaker must not be set without (Fig. 3 (b).) Multiply K by L and divide by 2. a boom. Headsails. No jib or spinnaker shall be sheeted on the (Fig. 3 (a).) Multiply I by J and divide by 2. main-boom. No contrivance such as an outtigger shall be used on the sheet of the spin- Multiply by 0-85 to find the area used for formula, Lugsails and Headsails. naker or any headsheet. No deduction is to be made from headsail In the case of a schooner, the base and hoist area on the score of any portion of the shall be measured on the foremast, but if the lugsail area before the mast. main spinnaker exceeds the before-mentioned Sails bounded by Curved Edges. measurements, this excess shall be added to (See Fig. 3 (@).) Except as provided in the case of the leach these for computation of area of the fore- of mainsail and in the case of the rounded triangle. In the case of a model yacht having no head- foot of a mainsail that is not laced to the sail but carrying a spinnaker, the area for the boom, any increase of sail area due to bent headsail shall be computed from the spinnaker or curved spars, or curved edges extended hoist and length of the spinnaker boom. Note.—Should the spinnaker hoist or boom by battens, shall be computed and added as measured exceed the dimensions of the fore- The base O shall be multiplied by two-thirds to calculations for rating. triangle, any such excess shall be added to the of the perpendicular P. 13 KI The measurements for headsails and spi naker shall be taken exactly the same as in the case of a vertical mast. Small suits of sails need not be the same shape as the full suit, provided that no dimension exceeds the limits of the full-sized suit. Spars for small suit sails shall be the same “The ends o marked by vertical marks § in. w high, having their outer edge at t ending. The ends of the measured lengt formula) are marked with similar marks. Upper and lower points of d measureme Class Rating below L.W.L.) with a round dot having its centre at 0-55 L.W.L. UNITS OF MEASUREMENT Upper points of bow and stern tax measure- Inches and decimal fractions of an ments (Z.e., -5 per cent. of rating above forward end of measured L, and covering board above Square inches and decimal fractions after end of L) with similar dots. inch. of square inches. Weight. band 4 in. wide. (7.e., on covering board and 12-5 per cent. o size as those used for the full suit. Sguare. be Hull, SMALL SUIT SAILS AND SPARS Linear. shall Pounds avoirdupois (lb.) and decimal fractions of a pound. All measurements beyond the second place of decimals shall be disregarded. Immersion marks at waterline at position of d and midship Freeboard measurement to be an inverted triangle having its apex on L.W.L. The lower angle to be a right angle and the top side of the triangle to be 2 in. long. CHAPTER II istory of Model Yachting as an Organised Sport, and its Influence on Rating Rules. International Racing, The A-class, The M-class (Marblehead). The 36-inch Restricted Class HE | classes dealt with in our last Model Yachting Association. It can fairly be said that this was the turning point in the chapter are to rules originating with full-sized yachts, but, in addition, there are other classes to rules that have never been used for anything except models. ‘These are the A-class, M-class, and 36-inch Restricted Class. As the origin of these is connected with the history of model yachting, it is advisable to commence by giving a short summary of history of the sport. Another great influence on model yachting has been the interest aroused by International Racing. The first international model yacht race was held at Enghein-les-Bains, near Paris, and was between three teams (each comprising three boats) this. Although model yacht clubs were in exist- representing France. Belgium, England and The yachts used were to the now extinct 80-cm. Class. ence over eighty years ago, there was no at national organisation. In fact, The English team consisted of Messrs. W. T. attempt every club had its own code of sailing rules and racing classes, with the result that interclub racing was practically impossible, and model yachtsmen rarely journeyed beyond the confines of their own ponds. The first Vines, W. J. Daniels and A. W. Johnson, and it successfully defeated the other nations. Mr. Daniels with the highest individual score, had the honour of winning a handsome Sevrés vase, presented by M. Poincaré, who was then President of the French Republic. attempt to organise a national authority was made by Mr. G. Colman Green, then Secretary of the Norfolk and Norwich Model Yacht Club. He started to form a British Model Yachting Association about 1900. This made a certain amount of headway but dropped when Mr. Green went abroad on business a * * * * The next international contest in 1922 was the result of a challenge issued by Mr. W. J. Daniels to any model yachtsman in the United States to meet him in a series of races. The few years later. conditions of the contest called for the use of Another important event which occurred about 1900 was the invention by the late Mr. models to the American B-class, and the races were sailed from skiffs. George Braine (a member of the Model Yacht Sailing Association, a famous club with headquarters at the Round Pond, Kensington), of the steering gear which bears his name, and Mr. Daniels built “Endeavour ” * for the event and took her to the States to meet the selected American model. His opponent was “ Polka Dot,” Mr. A. E. Bull. The American boat was successful in these races, but the effects were probably with its discovery model yacht racing became possible as a serious spott. In 1911 the Model Yacht Racing Association came into being. It was composed of about a dozen clubs, mainly in and around London, and catered principally for the io-rater class. It continued to function until the First World War started in 1914. more far-reaching than if “ Endeavour ” had won, as the series of international races that commenced in 1923 was the direct outcome of a promise to give him a return match. On his return from the States, Mr. Daniels interviewed Sir Edgar Mackay, who acquired the Yachting Monthly about this time, and the The war ended in 1918 and in due course * Twelve years later, in 1934, Mr. T. O. M. Sopwith also selected the name ‘‘ Endeavour ”’ for his Challenger for the “‘ America’s ”? Cup. the M.Y.R.A. was restarted, but in 1923 it was entirely re-organised and reconstituted as the T5 MODEL upshot was the offer of the first SAILING Yachting CRAFT winning yacht was designed by Mr. W. J. 7 Monthly Cup for international competition with Daniels, while Mr. Reg. Lance and Mr. Sam models to a new rating formula, which is now O. known as the A-class Rule. Daniels The first Yachting Berge have each skippered done the so winner twice. seven Mr. times, Monthly Cup was a Challenge Cup which could Mr. A. Jones three times, and Mr. R. Jurd and be won outright by three successive wins. Mr. Sam O. Berge twice each. A challenge having been received from the During this period two other international Royal Danish Yacht Club, the first contest for regattas were held. this handsome trophy was held at Gosport in Regatta of 1933. 1923. ‘““Dawn,” A selection Race was held to determine was The first was the Chicago The British representative, designed and sailed by her the British representative, and the honour was owner, Mr. W. H. Davey, of the Bourneville gained by “‘ Invader ” (owned by Mr. J. Scott M.Y.C. Freeman, Staines Model Yacht Club, designed A-class boats and skippers, and the race was built and skippered by Mr. W. J. Daniels). won by “ Bostonia II]” (J. Cawthra). the international event, In ‘‘ Invader”? had an She met the pick of the American The British boat finished seventh in a fleet of ten, of whom no less than nine were American. easy victory over her Danish opponent. When the Olympic The following year Denmark again chalThe British repre- Games were held in lenged with a new boat. Germany in 1936, the Deutches Segler Verband sentative was found by a Selection Race as (Modellsegel-Abteilung) before. Model Once more Mr. J. Scott Freeman was successful with a new boat, the well-known “‘ Crusader,” designed, built and skippered by staged Yachting Regatta at an Olympic Hamburg with races for the A-class and M-class. In the A- class race, two British, one American and two German models competed. Mr. Daniels. Again in the international contest the British boat won comfortably. In 1925 Denmark did not enter, but a new challenger appeared in “‘ Slipper,” designed, The winner was “* Busilier,” Lt.-Col. Jan Dennistoun, Britain, which was designed, built and skippered by Mr. W. J. Daniels. The other British yacht built and sailed by the veteran American model finished second, followed by the yachstman, Mr. Joe Weaver, of the Central Park Model Yacht Club, New York. As had now become customary, the British repre- and the two Germans. American In the M-class, the winner was “ Cheerioh,”’ Mr. John Black, America, which was designed, sentative was found by Selection Races, and for the second time “‘ Crusader ” proved the winner. In the International Races she again had an easy victory over her American rival, and by securing the Cup for the third time, Mr. Daniels won it outright for Mr. Scott Freeman. A new Cup was given in 1926 by the proprietors of the Yachting Monthly, but this is a perpetual Challenge Cup and cannot be won outright. This time instead of being a duel in built and skippered by her owner. competitors, two The other Germans, a British and a Danish boat, finished in the order named. When the second World War broke out, model yachting in this country came to an end as an organised sport, and it was not possible to organise any International Races until 1948, but during this time things had not altogether stood still, and in the States the use of Vane Steering Gear had become almost universal. the International Races there were three entrants besides Britain. The history of this and subsequent races can be seen from the Tables of International Results included in the Vane steering was used by the great American yacht designer, Nathaneal G. Herreshoff, on experimental models which he made as far back as 1875, and tentative experiments in its use had been made from time to time by various present chapter. An analysis of the results of the seventeen races that were held prior to the commencement of the Second World War reveals some On eight occasions the interesting facts. model yachtsmen. It was not until 1935, however, that a model fitted with this type of steering gear scored a major success in this country. In that year Mr. Sam Berge won the 16 | INTERNATIONAL RACING RESULTS OF INTERNATIONAL RACES, 1949-1951 1949 1950 1951 Winner Runner-up U.S.A, 1214 No Race U.S.A. 93 Britain 95 — Britain 6o Year Other Entrants Denmark 90 — — Yacht France 64 — — Owner and Club 1949 | “‘ Ranger ”” 1950 | No Race Skipper F. L. Pigeon, Boston, M.Y.C. . — 1951 | “ Ainslie ”’ When model yachting in this country was Second World War, the Designer W. Bithell — R, Ballantyne, Mill Pond M.Y.C. resumed after the Belgium 264 — — Carl Auberg — Owner Carl Auberg After a week’s strenuous racing, a boat often needs a complete overhaul. Morover, the hull Model Yachting Association did not feel that becomes water-sodden and needs a few days to the sport in this country was ready to stage an dry out thoroughly. International Race on the same scale as the racing is tiring, and skipper and mate also pre-war International Races for the Yachting would probably benefit from a few days’ rest. Monthly Cup. Likewise, a week’s hard So in 1948 an “ All Nations ” It is interesting to note that in this 1949 race, Regatta for A-class models was held at Gos- all of the competitors except Belgium used port in which boats representing Australia, vane steering pears. Belgium, Denmark, France, Portugal, U.S.A,, The winning American model “ Ranger ” England, Wales, Scotland and North Ireland is undoubtedly a very cleverly designed boat, competed. but an analysis of the score sheet showed that The winner was “‘ Ranger,” F. L. Pigeon, Boston U.S.A. She was designed specially to race M.Y.C., representing the under conditions likely to be found in this country by her, and representatives. the Danish Down wind, and British however, the Carl American boat was markedly superior to her Auberg, and skippered by W. G. Bithell. The rivals. was “Revanche.” well-known between designer, runner-up the in windward work there was little to choose Denmark The with English Kai boat Ipsen’s “ Tinker Thus, after nine previous efforts, the States were successful in taking the Yachting Monthly Bell” (R. Jurd, Gosport M.Y.C., designed by Challenge Cup to America. Admiral A. Turner) came third. American boat was not, as previously, selected The following year, 1949, the first post-war For this race the by holding Selection Races in the States, but race for the Yachting Monthly Cup was held at specially designed for British waters. Fleetwood. The States did not receive a return challenge from Britain until 1951, when the race was held The entrants represented Belgium, Denmark, France, U.S.A. and Britain. Britain was represented by the Alexanderdesigned “‘ Scamp,” built, at Boston, Mass. owned and skip- by a pered by L. K. Corroin, Fleetwood M.Y.C. As in the 1923-1939 series Committee appointed by the M.Y.A. of races, the “ Shalimar ” was built by her owner from a design by the late J. G. Feltwell, while the British representative was selected by strenuous Selection Races held the week prior to the international event. Special The British yacht was chosen American “ Ainslie” was a shortened edition of “ Ranger,” which was so successful in Britain Whilst this has many advantages and has always been done, it is in 1948 and 1949, but carried more canvas. very questionable whether it is always wise. As there were no other competitors, the 21 MODEL SAILING CRAFT match was a duel, and the British boat held her own until the end of the 19th heat, when her score was 46 to the American’s 49. The wind other running sail. Load Water Line Length (L.W.L.), is the distance in a straight line between the points the British farthest forward and aft in the plane of flotation in full racing trim. then fell very light, and in these conditions “ Ainslie” rapidly forged ahead, finishing an easy winner with 93 points to boat’s 60. We will now pass to the A-Class Rating Rule. Load Water Line Beam is the extreme breadth in the plane of flotation. THE INTERNATIONAL A-CLASS The original idea of this class was to be a model of a 6-m. yacht to the new rule pro- pounded for the Yachting Monthly Cup races on a scale of 2 in. = 1 ft., but as no allowance for crew weight was made, it was not a true scale model in the sense that the I.Y.R.U. 6-m. model is. In order to eliminate unnecessary complications for model yacht designers, the tule is now stated purely as a formula for models, and yachts of the A-class must not exceed 1 metre (39°37 in.) by the following formula :— L+tvVS LVS ae 127/D full racing trim with largest suit of sails, including spinnaker or Quarter Beam Measurement is the quarter beam length (Q.B.L.) measured in a line parallel with the middle fore-and-aft vertical plane (or centreline), at a distance from it equal to onequarter of the load water line beam, and onetenth of this breadth (L.W.L. beam) above L.W.L. Excess of Quarter Beam Measurement is the amount by which the Q.B.L. exceeds the length allowed without penalty. This length is equal to a percentage of the L.W.L. length found by subtracting the square root of half the load water line length in inches from 100. centage = 100 — = Rating. (Pet- Vi L.W.L.) Displacement in Cubic Inches is the weight of the model in pounds (pounds avoirdupois) divided by 0-037. Where L = Load water line length in inches plus $ any excess in Quarter Beam Measurement. 7 LIMITS in PENALTIES (2) There shall be no limit to the displace- The square root of the total sail area AND square inches measured ment of models, but the cube root of the dis- accordance with LY.R.U. placement (VD) as used in the measurement in regulations. formula shall never exceed one-fifth of L.W.L. The cube root of the displacement (in inches) -++ 1 but in the event of it being of the model in cubic inches, in less than one-fifth of L.W.L. (in inches) + 0-4, ———S 40°” Beam Water Line- —— . Load Water LineYOrter _—— _ Bo de*Bn= We Lyw – Quarter Beam Length. & > 4 , LE eosin Beam ——— SS a ‘Fic. 5. Centre Lire- METHOD OF MEASUREMENT FOR QUARTER BEAM LENGTH 22 a mount equal to the deficit up to the of WD shall be deducted from the actual ube root for use in the measurement formula. (4) The maximum draught shall not exceed L.W.L. X 0716+ 3:5 in. Any excess in draught shall be multiplied by 3 and added to rating. (c) Average freeboard (taken at centre and at forward and after ends of L.W.L. to top of deck below rail) shall not be less than /D x 0:28 +1. Sheer shall be a fair continuous concave curve. Any deficit in freeboard shall be added to rating. (d) Height of sailplan above deck shall not exceed 85:3 in. tating. Any excess shall be added to Height of fore-triangle above deck shall not exceed 64 in. (¢) No hollows are allowed in the surface of the hull between L.W.L. Stem and stern profiles and sheer line. must be fair easy curves. (7) Any local concave jog or notch in the plane measurement at either end of the L.W.L. shall be bridged by a straight line, and the L.W.L. taken to the intersection of such lines with the established L.W.L. plane. Booms. In the case of booms other than those round in section, half the depth in excess of 1 in. shall be added to sail area. Masts. If the section of a mast is greater in a fore-and-aft direction than athwartships, the difference shall be included in the area of mainsail, and of topsail. (&) Models must always sail with masts and spars as measured. (/) Hollow masts and spars are allowed. (m) ‘There are no restrictions as to scantlings or materials. (x) Models must be measured in salt water. The weight of sea water to be taken as 64 lb. to the cubic foot. UNITS AND MEASUREMENT All measurements shall be taken and recorded in inches, square inches, cubic inches All decimals beyond two places shall be disregarded except for the weight and displacement. straight line equal to one-third of the greatest load water line beam, placed equally above and below L.W.L. (g) The round of deck beams must not HULL AND SPAR MARKS The load water line shall be permanently marked at centre, and fore and after ends. exceed ,4, in. for every 2 in. of the beam. lee-boards area. and pounds avoirdupois. Any con- cavity in the stem line shall be bridged by a (2) Centre-plates, of the fore-triangle, whether the fore-triangle is less or equal to the maximum height allowed. (/) Any increase of sail area, obtained by the use of intentionally bent masts and spars, will be measured as a bow and included in the sail Each side mark shall consist of two equilateral and _ bilge- triangles whose apices touch at the established boards are prohibited. (7) The number of battens in the leach of the L.W.L. and whose bases are parallel to it. mainsail shall not exceed four, and they shall The total vertical height of each side mark be equally spaced. shall be } in. Intermediate battens shall Fore and aft marks shall be } in. not be longer than 7-87 in., and top and bottom long and 4 in. high, and be placed so that the battens bottom of them indicates the position of the 5:90 in. Headstick to a triangular mainsail shall not exceed 0-98 in., and any established sail with a longer headstick shall be measured with the model floating on an even keel in sea as a gaff sail. water of the usual density, both side marks The headstick of a spinnaker racing trim, measutement with a black band } in. wide. The length of luff and leach Where a mast slide is fitted, the fore side of the mast must be marked on deck and distance The maximum width of the spin- naker shall not exceed twice “J.” in All spars must be marked at the points of shall not exceed the height of the fore-triangle, plus 6 in. When must be cut by the surface of the water. must not exceed one-twentieth of the measured length of the spinnaker boom. Spinnakers. L.W.L. from stemhead recorded on certificate. The spin- Mast may be moved forward or aft not more than naker shall be set at a height not exceeding that = MODEL SAILING CRAFT 4 in. from marked position, provided limits of L.O.A., movement are marked on deck. between. The base of the fore triangle shall be marked on the deck, bowsprit or other spar. Should nor her L.W.L., but something For the sake of convenience this may be referred to as the “sailing length,” or “* sailing waterline.” As will be seen from the the mast be moved, the base of the fore triangle chapters must be adjusted so that the measured base is important factor for speed in a yacht, and not exceeded. Limits of movement of base consequently in a Rating Rule, it is essential to of fore triangle must also be marked on deck, have a method of measuring sailing length bowsprit or other spar. properly. The sail area is measured as under the on designing, length is the most There are only two methods of doing this. One is by taxing the girths at the L.W.L. 1.Y.R.U. Rule, as detailed in Chapter I. Rating certificates are valid for twenty-four endings and the other by quarter beam months from date of issue, provided no altera- measurement. tion to hull or sails has been made in the the I.Y.R.U. Rule. interim. has one undesirable effect, as it tends to make the designer cramp in his deckline in order to ‘The former method is used in It is a good method, but This rule has now been in use unchanged, pay as little as possible in the way of end taxes. except for a few minor details, since 1923. On the other hand, quarter beam measure- Boats differing greatly in type and dimensions ment, which is used in the A-class formula, have been built under it, but in every case may have a tendency to cause designers to competition has been keen between the leading make the after ends of their L.W. Lines a trifle yachts. lean. Models to-day are considerably larger than they were when the rule was first intro- Any excess in this direction would, however, be paid for dearly. duced, but this may be ascribed to the fact that In the consideration of any measurement designers did not at first realise the full pos- rule, it must be borne in mind that there are sibilities, rather than to any fault of the formula bound to be limits in certain directions, and itself. that these limits must invariably have a certain that are worthy of remark. There are a number of features in this rule In this the Ameri- cramping effect. The primary object of a Rating rule is to measure boats fairly, and so can system of quarter beam measurement is balance the elements of speed that close racing used. is ensured. Obviously, in a Rating Rule, if the only If the rule is such that success 1s measurement of length is length over all, de- attained by beauty of modelling and excellence signers will not give their boats any over- of form, it may be claimed to be a good rule. hangs; if, on the other hand, load water line This is done by both the A-class rule and the length any present J.Y.R.U. 6-metres formula, and there- method of checking the overhangs, designers fore both can be considered as good rules, and it is entirely a designer’s own fault if he does not produce a desirable boat under either. is taken into account without will give long overhangs in a desire to get unmeasured length which will come into play amount of overhang is desirable in a boat, Possibly, in some respects, the A-class formula is the better of the two, as many consider that generally speaking, as it gives reserve buoyancy, improves appearance, and avoids any the quarter beam measurement is a better method of measuring sailing length than end suspicion of clubbing the deckline in forward and chopping off at the stern. Therefore, taxes. when the vessel is sailing. Now a certain The quarter beam measurement is obtained in the following manner: a buttock is taken at the quarter beam width, in other words, midway between the centreline of the vessel and the point of her greatest waterline beam. This is known as the “ quarter beam buttock.” A. every good Rating Rule must contain some means by which the overhangs can be regulated. When any vessel having overhangs is sailing, she has a sailing waterline appropriate to her angle of heel. This is neither her 24 INTERNATIONAL M-CLASS though in reality it is far more difficult to design a yacht to a simple rule because the simple rule is bound to permit exaggerations which a more complicated formula checks. In order to meet this demand for a simple rule, Mr. Roy G. Clough, of the Marblehead terline is next struck above the L.W.L. at a height equal to one-tenth of the greatest waterline beam (7.e., one-fifth of the maximum half-beam). This is known as the “‘ 4,th beam waterline.” The points of intersection, for- ward and aft, of the quarter beam buttock and the 4th beam waterline are called the “‘ quarter beam spots.” M.Y.C., produced the formula which is now known as the M-class Rule. The distance in a direct fore-and- simple rule and possibly more even to its this class rapidly became very aft line between these quarter beam spots is the “quarter beam length” (Q.B.L.). Due partly to its Another handy size, way of stating this is to say that the Q.B.L. is popular in the States, where it now far out- the distance between the quarter beam spots numbers any other class. measured in the plane of the quarter beam taken up by the Ryde M.Y.C. (Isle of Wight) buttock, or their distance apart measured in and has made rapid progress in many parts of the plane of the th beam waterline. the country. It will, therefore, be seen that the Q.B. It became a recognised British class in due course, and is now recognised as buttock and 3,th beam waterline vary their an International class also. position in direct relation to the beam. The rule is:— The real novelty of the formula, however, is INTERNATIONAL M-CLASS that whereas other rules have a strong tendency in a certain direction, in this rule there are two Overall Length and Sail Area rule. strong forces pulling in different directions. Formula. Overall length of hull, fifty (50) As can be seen, the formula is divided into inches. two parts. (800) sq. inches. light The first directly displacement boat, encourages a whilst favours heavy displacement. the second allowed. Prohibited. an easy matter to effect by variation of the Centre-boards; its inception that no adjustment has proved boards; necessary during the number of years it has Model yachtsmen are as Ballast. This may be checked by use a race or series of races. Shifting ballast prohibited. is that many people find the models too heavy Bumpers are not included in overall length and they are also rather large for travelling. measurement, but are limited to one-half (4) Since, however, there are other classes which inch overhang. be No Restrictions on scantlings or materials. possible for every model yachtsman to select a No Limit to Displacement L.W.L., Beam, class which suits him. * Overhanging Weight of lead ballast must not be changed during In fact, the only possible objection to the rule * Bilge- midship section. any change will be made for a very long time. should (7) (5) of a disc 2 in. in diameter fitted to garboard at existed, and it is, therefore, most unlikely that it Bowsprits; one inch radius. proved themselves the best class that has ever smaller, (6) Lee-boards; Hollow of garboard shall not be less than a The A-class models have both lighter and (4) (3) rudders. well pleased with the rule to-day as they were are (1) Movable keels; (2) Metal fin keels or others without hollow garboard; So well was the rule balanced at in its first year. One-quarter (4) inch in excess of or less than 5o-in. overall measurement is adjustment considered necessary, it would be ‘been in existence. Sail Area not to exceed eight hundred Exception: The two parts are balanced against each other, and were any constants. In Britain it was first Draft, Freeboard, Tumble-home. * * SAIL Undoubtedly the demand for a simple rule AREA MEASUREMENT No fore-triangle measurement is taken, only will always exist amongst model yachtsmen, the actual sail area being measured. 25 MODEL SAILING CRAF Roach of sails shall zo¢ exceed 2 in. Rounded foot of loose-footed sails not measured. BATTEN cutved edges extended by battens, shal computed and added to calculations for rati LIMITS The battens allowed in mainsails shall not exceed four in number, and shall divide the after leach into approximately equal parts. Battens not to exceed 4 in. in length. The battens in headsails shall not exceed three in number, and shall divide the leach into approximately equal parts. Battens not to exceed 2 in. in length. No wire or other stiffening shall be put in head of sails. SAILS UNFAIRLY OR SET No contrivance such as an outrigger shall be used on any headsheet or upon the sheet of a spinnaker. The spinnaker boom shall not be used as a bowsprit by being tacked or fixed down at the outer end when the spinnaker boom is right forward. A spinnaker must not be set without a boom. Two mainsails may not be set at the same time. HEADSTICKS OR No HEADBOARDS Headsticks or headboards shall not exceed jib or spinnaker shall be sheeted onto the main boom. three quarters (3) of an inch across base. HEIGHT OF MASTS exceed 80 per cent. of the height of headboard of mainsail above deck. SPARS The greatest diameters of masts or spars are limited to three-quarters (#) of an inch. There are no restrictions on material, weight, or section, and no extra measurements entailed where not round. SPINNAKERS Hollow masts and spars are allowed. Spinnakers are allowed. Permanently bent masts or spars, rotating Spinnaker poles not to exceed fifteen (15) inches in length, measured from the centre of mast to outer end of pole. or bipod masts allowed. Any increase in sail area obtained by use of bent masts or spars shall be measured as a bow Spinnaker must not be hoisted higher than and added to sail area. point where jib-stay cuts the mast. Spars or masts not to be included in sail area The hoist shall be measured from the deck measurements. to forestay where it cuts the mast. Raking Masts. A spinnaker may have a headstick not larger Measurements taken exactly the same as in the case of vertical masts. than three quarters (#) of an inch across base. Alternate rigs are allowed provided sail area It must not be set with a footyard, or more does not exceed 800 sq. in. than one sheet, nor any contrivance for extending the sail to other than a triangular shape. THE 36-IN. RESTRICTED CLASS The spinnaker sheet may be led around the As a small simple class for waters which are luff of headsail or forestay. not big enough for the tIo-rater or 6-metres, Sleeves or tubular pockets prohibited. BOUNDED BY CURVED AND There shall be no limit to height of mast. RIG Height of jibstay above the deck shall not SAILS SHEETED and also for juvenile use, the M.Y.A. formu- lated the 36-in. Restricted Class with the fol- EDGES lowing limits :— Except as provided in the case of the leach of mainsail when Batten Limits are observed, and in the case of the rounded foot of a sail L.O.A. (extreme) . Beam » . – 95, not laced to boom, any increase of sail area Depth ‘ . . Il,, due to bent or curved mast or other spars, or Weight (maximum ~ I2_1b. 26 36 in. ntinent and in the United States. It is impossible to give particulars of all of these here, but typical examples are the Continental ., boats with forward ibited. Box measurement I-metre L.O.A. Class, and the American X-Class in which the sole restriction limits the be Sail Area to a maximum of 1,000 square inches. tting into a box with inside It is interesting to record that the British National Championships for ali classes recognised by the M.Y.A. have now been converted to British Open Championships. ‘Thus these events, instead of being confined to the ts 36 in. 36-in. X gin. Class X can 11 in. This ing the boat to get the utmost possible. yachts from British Clubs, are thrown open to boats of any nationality. All the classes dealt with in this and the pre- Whether this will result in less interest being ceding chapter are recognised by the M.Y.A. taken in the Yachting Monthly Cup races remains for racing in Great Britain, and three of them to be seen. li CHAPTER III Shipwrights, Ancient and Modern. An Explanation of the Lines used to Delineate a Yacht. Designing to a Rating Rule As model yachtsmen to whom the if it were longitudinally cut in half by a vertical magic, and the lines themselves are as meaningless as the signs of the Zodiac. In the olden days, when a shipwright designed a vessel, he took a block of wood and carved out a half-model. When he had faired this to a shape that satisfied him, he proceeded line.” to saw the block through and took off the sections he obtained. He then went to his mould loft and laid out the sections full size from his model. The section moulds were duly set up on the keel and faired up again with battens. He was then ready to build. Many a beautiful vessel was evolved in this way, and there is no doubt that many of these line. old fellows had a wonderful eye for a ship. Another point in their favour was that in fairing by batten they were obliged to get a natural curve. Even to-day many boats are ‘* designed ” in this manner, and some of the men who do so, still style themselves “‘ yacht and boat designers.” This method is, however, too hit-or-miss for these modern times, and increasing know- yacht is being treated as a half-model, the part PART from the cognoscenti, there are line from deck to keel. art of designing a yacht savours of black This line appears on the deckline, and is known as the “ centreWhat has to be considered is really the lines of a half-model. The same yacht is shown in elevation in Fig. 7. This plan is usually known as the “sheer plan,” and takes its name from the sheer, which is the side elevation of the deckA straight line will also be seen on this diagram, showing the line of the plane of flotation of the yacht. This is called the *“ load water line ” (L.W.L.). Treating the yacht as bilateral instead of as a half-model, and cutting her through hori- zontally on the L.W.L., a plane would be revealed shaped as Fig. 8. As, however, the that is shown as a dotted line can be dispensed with. Comparing Figs. 7 and 8, the L.W.L. appears on the sheer plan as a straight line, and in plan as a curve. In order to save space, the deckline and waterline are shown on the same plan as in Fig. 9. Other waterlines are struck at con- venient intervals above and below the L.W.L., ledge has made it possible to do on paper all the old shipwright did with his half-model as shown by the dotted lines on Fig. 7. and a great deal more besides. Even to-day a good eye for a vessel is an invaluable possession to a designer, even as a good ear is to a to avoid confusion they have not been inserted These are also shown on the “‘ waterline plan,”’ but on Fig. 9. Again considering our original deckline in musician, and just as a sheet of music is intelligible to a musician so are a yacht’s lines to a designer. So, nowadays, the old ship- plan, if a line is drawn parallel to the centre- wright’s procedure is exactly reversed, and instead of making the design from the model, the model is made from the design. tock line.” line, as in Fig. 10, the result is a plane shaped as in Fig. 11. This line is known as a “ but- In order to save space, this is shown on the sheer plan, as in Fig. 12. Other buttocks are taken out, being struck as shown by the dotted lines in Fig. 10. These also appear on the sheer plan, but for the sake of clarity, only one buttock has been shown in The first step in designing is to understand what the lines represent. In Fig. 6 the deckline of a yacht is shown, but as the two sides of a vessel are alike, there is no need to duplicate the work, and only one side is usually shown. The craft is, therefore, considered as the diagram. Once more, starting from our original deckline in plan, a line is struck at right angles to 28 Loap , WATER Line CENTRE Line mo ‘ . A – x ~ uw ~s a = -” – ~~ Fic. 8. DECH LINE, oe, | | FIG. 9. Fic. 10. 29 – – ad oo” ss MODEL SAILING CRAFT the centreline, as shown in Fig. 13. The boat on the section plan and plotted on the water- is again cut through, and we get a shape as in Fig. 14. line plan. As the boat is being shown as a half- Although not shown in the figures illus- model, only one half of this ‘‘ section” will trating this chapter, the deck camber can be appear on the plans. Other sections are taken shown on the sheer plan by means of a line out as shown by the dotted lines on Fig. 13. representing the centreline of the deck. These sections are plotted on the “ body plan ” line can be seen on the plans of racing class (or “ section plan ”’), as shown in Fig. 15. For This models included in this book and is just above the sake of clearness, only about half the full the sheer line. number of sections have been shown in the line at the stemhead, and in a canoe sterned diagram. boat also at the sternpost head. It will be noticed that on the water- This line runs into the sheer- line and sheer plans the sections appear as This completes the catalogue of what are straight lines, and as curves on the section plan. known as the “lines ” of a yacht, and as such Similarly, the buttocks, though not shown on represent her actual shape. Fig. 15, appear in the section plan as straight are certain other lines used in designing, which lines. are most important. The waterlines also appear as straight However, there These are the Curves of lines on the section plan, but only the L.W.L. Areas, which can be taken out when the vessel is shown in Fig. 15. The “‘ diagonals ”’ have next to be considered. is upright and also when she is heeled. These have a large part to play in the designing, but These lines are struck on the section plan in the explanation of this must come later in this the first instance at such angles and heights as treatise, as there are a number of other points the designer’s to be dealt with first. most useful. experience tells him will be The dotted lines in Fig. 15 show For the moment the above explanation of a one diagonal struck across the sections which yacht’s “ lines ’’ must suffice, and it will enable appear on either side of the centreline. the tyro to set out the full-size lines of any It may be mentioned in passing that in drawing the existing design he wishes to build to. section plan, if the boats’ bow points to the right, as in the present instance, the sections to the right of the centreline will be forward well to stress the point that the intersections of the various lines in the different plans must sections, and those to the left of the centreline, after sections. If the bow is to the left, the another. reverse will be the case. As will appear in the chapters on designing, the diagonals are the most important lines in the boat. The diagonals can be shown in three ways. The first is in plan in their own plane as shown in Fig. 16. This plan is usually shown on the opposite side of the centreline to the waterline plan. It is plotted by measuring on the section plan up the diagonal to the centreline on each section. The diagonals can also be shown in elevation on the sheer plan. In this case the vertical distances above and below L.W.L. are measured on the section plan and plotted on the sheer plan. The third way is to show the diagonals in plan. To do this, the distance the diagonal is horizontally away from the centre-line on each section is measured Before leaving the subject, it would be as coincide. In other words one plan checks If this were not so, each plan would show a different boat. It is, therefore, clear that one important part of the work of a designer consists of “‘ fairing ” his lines. There is, however, a great deal more in designing a boat than merely drawing the lines and making them fair in the different plans. If one is designing a boat that is not to a particular class, the sole considerations are to produce a healthy, well-balanced and satisfactory craft, but if the yacht is being designed as a class racer, there is the additional problem of producing the fastest possible boat to the rating. In the latter connection it becomes a matter of balancing the factors in the rule so as to get the most suitable boat for the conditions likely to be encountered. In most modern rating rules, sail area and hull dimensions both enter. 30 NOILD3S Fic. 12. Fic. 13. Fic. 15. DiA GONAL Fic. 16, 31 hy +) a v a sma or j u 3 Ora hes =aAVYV-WE 7 her putting a small sail area on an outsize hul e ‘The real skill lies in designing a boat that be warned iS gene will do consistently well under average con- to try to evade mode ditions. freak boat that evades t Modern sail plans give us greater efficiency per square inch of area, and can be done successfully but onl consequently enced designer can know when | under current rating rules, boats are larger be taken. than they were a few years ago under the same obtained by evolving a well-bala combining sweetness of form wi judgment in selecting the best dimensio fit the class for which the yacht is intended. rules. With larger hulls and smaller sail areas, it is not necessary to have as much natural stability in the shape of the hull, and in conse- Even then success can – 42 CHAPTER IV Drawing Requisites. Midship Sections. Calculation of Section Areas (Simpsons and Trapezoidal Rules). Co-efficients of Fineness. Raked Midsections. The First Steps in Drawing a Set of Lines. al Considerations in Designing. set out methods by which this desideratum can thrown out of her stride and stopped. She will also bury her ends and ship water on deck, making her a bad sea boat. Further, the sails will be constantly vibrated and prevented from doing their work efficiently, so that she loses be attained, it would perhaps be as well to speed through the water. enumerate some of the considerations which In making a design, the vessel is primarily considered in an upright position, as this is OW, whether the yacht is being built Ne a class or not, the aim of the de- signer must be to produce a satisfactory and well-balanced craft. Before proceeding to must guide the designer. The design of a steamer or motor ship is less complex than that of a sailing vessel, for whereas the former is propelled by a known force upon a more or less even keel, the latter is propelled by that intangible force, the wind, which varies continually, and except when the wind is dead astern, is constantly heeled to ever-changing angles. It must, therefore, be necessarily the basis of comparison in form. borne in mind that the immersed portion of a trim under every condition. sailing vessel’s hull alters with every different does this at every angle of heel, she will refuse angle of heeling and consequently her under- to hold a true course. water shape continually changes. As will be explained in due course, certain centres govern the fore-and-aft trim, and it is part of the designer’s work to compare their positions when the boat is heeled with their positions when she is on an even keel, and make such adjustments as may be necessary to ensure her retaining the same fore-and-aft Unless a yacht The importance of this point can easily be If follows that the design of the topsides and underwater understood if the body must form one harmonious whole, so that the craft is balanced in this particular fore-and-aft trim effects respect. the hull is parallel to the waterline. are of alterations considered. When of a vessel is on an even keel, the natural axis of This is, however, only one of the If on being many features that has to be studied before heeled she stoops by the head, the natural axis the yacht can be expected to perform ade- of the hull will no longer be parallel to the quately under all conditions. waterline, with the result that the hull will Moreover, the water cannot be considered want to run off the wind, and as the boat runs off the wind she increases her speed and angle as a plane surface, as it is in a state of constant disturbance, and the yacht’s form must be of heel. considered in relation to the ever-changing being out of parallel with the load waterline, motion of the waves. At the same time the plane of the fin, 4 358 XX 4 = 14°32 >> – 7 8 212 1726 X X 2 4 = = 4:24 5*04 > 9 o00 X T= 0:00 = 69:20 “2 » » 5 6 ae 277 X=? — X 4: =~ Multiplied by D The former is more generally used by naval accurate, which represented in the formula by D. 6:40 11:08 13840 architects, but the trapezoidal rule is almost equally are known as “‘ ordinates.” this is to count the squares, making allowance for parts of squares. and these lines Half-section Area = 4’613 MODEL SAILING CRAFT Stated in this way, the rule sounds a = little correct, whilst the error by Trapezoidal Rule complicated, but in reality it is quite simple to use. For the purposes of the naval architect it can safely be ignored, and, as the Trapezoidal is about 4 per cent. This error is so small that it is usual to set the calculation out in tabular form, as shown in the worked example, which Rule gives the calculation of area for the section recommended to the young designer. shown in Fig. 22. ordinates are It will be noted that the very worked example, shallow and the consequence. In close but curve a together the in section changes deeper this is very is easier and more convenient than Simpson’s Rule, the use of it can safely be Mention is made above of the planimeter, and the following explanation of its use is therefore included. rapidly in section a wider THE spacing might be used. It will be noticed that in this calculation of area, the canoe body only has to be taken. PLANIMETER There is also a method of arriving at the If area of any figure by the use of an ingenious the area of the hull including keel is needed, instrument known as the planimeter without the procedure is exactly similar. doing any calculation whatever, except multiplying or dividing, as requisite in order to THE TRAPEZOIDAL bring the result to the required scale. RULE This This rule may be used with any number of latter method is the one that is always employed ordinates, even or odd, whereas Simpson’s Rule by professional naval architects, as it is even can only be used with an odd number. To more accurate than calculation and saves a apply the rule, add together all the ordinates great deal of time. and subtract half of the sum of the first and last amateur designer’s point of view is the cost of ones. The result is multiplied by the common The drawback from the the instrument, which is in the region of £8, interval, which was described above as D. though a good second-hand one can often be The formula is illustrated by the example shown, which also shows the calculation of the picked up for about half this figure. area of the section shown in Fig. 22. like a pair of compasses with one leg longer It will In appearance the planimeter is somewhat be noticed that, as the curved side runs into the than the other. base line as the lowest point of the section, the leg and the short leg the movable one. ordinate there is represented by zero. short leg moves, a roller bears on the paper and actuates the dials. CALCULATION OF AREA OF A HALF-SECTION By Trapezoidal Rule ; Ordinate No. 1 » Length Multiplier 418 X O§= 2 4°07 X 3 383 X SK IT 2:09 4:07 IT = 3°83 The dials are situated stitute the index on which the readings are of Areas = As the close to the hinge between the legs, and con- Functions I The long leg is the stationary shown. ” 7 212 & I = 212 The method of employing the planimeter is to place the fixed point on the paper in such position that the pointer on the movable leg can ttavetse the periphery of the area to be » 8 126 X I = 1:26 » 9 000 X O5= 0-700 measured. >» » 4 3°§8 = 3°58 > 5 320 X I = 3°20 i, 6 277 X I = 2°77 before = Half-section Area = Actual Area by Planinreter Half-section Area = A 584 461 by Simpson’s Rule is whilst the pointer on the point is again reached, the index is read. In otder to be additionally sure, after reading It will, therefore, be seen that the area as measured starting, moving leg is at a predetermined starting point, such as the intersection of the centreline and load waterline. The outline of the figure is now followed round with the pointer in a clockwise direction. When the starting 22°92 Multiplied by D The index must be set at zero the index, the instrument can be run round the practically 42 CO-EFFICIENTS in in an anti-clockwise direction, e index should return to zero. * *K * * OF FINENESS tration of the processes of designing, works out at 242°76 cu. in., and as this equals 33-6 per cent. of the block, the Block Co-efficient is 0°34. with our 36-in. design and have decided to use The Prismatic Co-efficient is the ratio that the actual displacement bears to the volume of a solid block equal in length to the L.W.L., and having a transverse sectional area and form equal to that of the immersed midsection of the yacht. The block in this case would be 28 in. long, with a cross-sectional area of 16°64 sq. in., giving it a volume of 465-92 cu. a section similar to Fig. 21. in. It will be noticed that though the keel has been shown in the sections examined, it was not included in our calculation of area. The reason of this is that for present purposes the keel is regarded as an appendage to the canoe body of the hull proper. We will now assume that we are proceeding We accordingly The hull displacement is 242-76 cu. in., L.W.L. beam of 8-6 in. and a body depth of which is 54:2 per cent. of this, and the Prismatic Co-efficient is, therefore, 0-54. When the midship section has been drawn, it is advisable to ascertain whether this will 3 in., and by measurement we ascertain that produce a boat of the desired displacement on the half-section area is 8-32 sq. in. = 16°64 sq. the given L.W.L. length. in. for the whole section. displacement cannot be calculated until the draw this to the required size. We then have a section (or rather a half-section, as only one side of the boat is shown in a design) on a While the exact The next point to consider ts the relation of design is completed, it is possible to get a the area of the midship section to the displace- fairly close approximation for a boat of normal ment of the whole hull. form. For this purpose we can make use of the Co-efficients of Fineness. The formula for ascertaining the approxti- The further uses of these will be explained mate displacement of a hull from its immersed later, but for the moment we will consider midsection area is :— them solely as a means to estimate the displacement of a boat from the area of her mid- ship section. There are three Co-efficients of Fineness— the Midsection Co-efficient, the Block Co-efficient and the Prismatic Co-efficient. The Midsection Co-efficient is the comparison of the actual section area with a rectangle, the width of the L.W.L. beam and the height of the body depth. As the beam is 8-6 in. and the body depth 3 rectangle is in., the area of the 8-6 X 3 = 25:8 sq. in. The section area of 16-64 sq. in. is 64-1 per cent. of this, so the Midsection Co-efficient is 0°64. In calculating the Block Co-efficient the displacement of the hull in cubic inches is compared with that of a solid block having a length equal to the K.W.L. length, a breadth equal to the L.W.L. beam and a depth equal to the greatest body depth. In the present model the 28 x 8-6 X 3 = 722-4 block cu. in. would be Midsection Area x L.W.L. x Prism. Co-eff. = Displacement in cubic inches; or, alternatively to get the Displacement in pounds avoirdupois: Midsection Area X L.W.L. x Prism, Co-eff. — 27°65 = Weight. Before seeing how this works out for our present boat, it should be mentioned that the value taken for the Prismatic Co-efficient is one ascertained to be an average by experience from previous boats, and as an average figure 0-54 will be found satisfactory. It will be noticed that the divisor 27-65 is taken, this being the figure for fresh water. If we were designing to a rule which embodied sea water measurement the divisor would be 27. For our boat the calculation will, therefore, be :— 16:64 X 28 X 0-54 + 27°65 = approx. 9 Ib. As we shall ascertain later, the dis- This, of course, has only given us the dis- placement of the 36-in. boat, used as an illus- placement of the canoe body, and for the total 43 MODEL SAILING CR displacement due allowance must be made for the displacement of the keel appendage to the hull proper. In the case of an A-class model, an allowance of between 6} and 84 lb. must be The amount of rake given to the mid-sec is governed by the fore-and-aft balance of th made. This, however, varies according to the type and length of the keel, and in a little boat diagonals, which will be investigated in due of this kind the keel will displace from 1 lb. to exactly what a raking mid-section is, however, 15 lb., so from the midsection we have drawn it may be assumed that the greatest beam will we ought to get a displacement in the region of 10-108 lb. fall further aft than the G.B.D. An alternative use of this formula would be to work back from the required displacement in such a way that the greatest depth merges harmoniously into the greatest breadth, the and its position would be spoken of a the L.W.L. course. For the purposes of explaining ‘Therefore, in order that the section lines can be worked out oe a =a Oe 23 (a). FIG. RAKING Mipsrirs SECTION, RAKED IN PLAN (SEE TEXT). ——— ao _ 23 (b). Fic. to ascertain what area the midship section mid-section is so arranged that it will embrace should have to ensure this displacement. both these points. this So far the reader has only been introduced Obviously, in order that merging may be properly effected, the at section must be at such an angle to the centre- right angles to the centreline of the boat, but, line that the greatest breadth of each waterline as a matter of fact, in modern designing it 1s will fall on this mid-section, also the greatest found that the approved form of distribution depth of every buttock and the greatest width to the ordinary transverse mid-section of displacement can be more easily obtained of every diagonal. when upright and maintained when heeled, if know the lines are developed about what is termed a these points, and the rake of the section will ‘‘ raking midship section.” determine this. It is very important to the fore-and-aft position of each of From the above it will be seen that there are Now, the rake in the mid-section is brought about by the fact that the greatest body depth two ways in which a boat can be designed (G.B.D.) and greatest beam are-not in the same fore-and-aft position. It is usual to speak of the position of these two points in percentages of the length of the L.W.L. measured from the fore end. Thus, for, instance, the G.B.D. might come at the exact centre of the L.W.L. 44 about a mid-section. The mid-section can be the actual shape that will be used for the transverse mould (set at right angles to the centreline) on which the boat is planked up. In other words, the mid-section used in designing can be the actual one that appears on the of the vessel, and in that case beam may be astern of it or pos.B.D. may be ahead of it, and the waterline beams, greatest buttock more considered in an upright position at right angles to the centreline, keeping the bottom in position on the G.B.D. and the whole at right angles to the profile, the top is pths and greatest diagonal widths need not Alternatively it may be a inclined sternwards until the greatest beam point comes into its correct fore-and-aft section which only appears on the drawings during the working out of the lines and has no actual being as a mould in building. position. The section will then be raked in an up-and-down fashion instead of transversely across the boat. This is shown on the sheer The designer will be well advised to follow this latter method and use a raking mid-section, as not only will it help him to secure the best plan in Fig. 24 (a). t coincide with it. — Now, if the section is raked by the first of these methods, it is plain that the greatest 4 \ é Fic. 24 (a). RakinG Mipsuips SecTION, RAKED IN ELEVATION (SEE TExr). Fic. 24 (b). depths of the buttocks will be moved sharply aft, but the greatest waterline widths on the topsides will be kept more or less close together vertically. The effect of this in elevation is shown on the sheer plan in Fig. 23 (b). On the other hand, if the section is raked in distribution of displacement, but will also materially assist him, as it fixes his greatest breadths and depths, and thus materially assists in the designing of a fair and sightly hull. Returning to the consideration of the raking at right angles to the centreline (which in this an up-and-down fashion, the greatest depths of the buttock lines will be moved aft to a less degree, and the run of the vessel will be kept longer than under the first method, but, on the plan forms the profile of the yacht), it could be other hand, the greatest widths of the water- swung backward in the fashion of a door lines in the topsides will move aft very slowly opening until the outer point representing the in proportion to the greatest beam point, and greatest the correct unless the topsides have a large amount of fore-and-aft position, whilst the G.B.D. re- flare, an unsightly wall-sided craft may result mained time. unless a This would be shown in the waterline plan as made. ‘The effect of this is shown in plan in in Fig. 23 (a), where the G.B.D. and greatest Fig. 24 (b.) midship section, there are two ways in which this might be raked. If the section is con- sidered in the half-model as being set upright beam point correctly in arrived at position all the beam point are joined by a straight line. certain amount of adjustment 1s The first method by which the G.B.D. and On the other hand, if the section is once greatest beam are joined by a straight line on 4} MODEL SAILING CRAF the waterline plan is, therefore, recommended waterlines and will be used for designing the little boat Before proceeding, it must again be emphasi which is being used as an example. that the straight lines that form the basis of th This have been spaced 1 in. a section may be considered as the “‘ dominating design are almost more important than th section.” lines themselves. There is yet another method by which the dead true, and every right angle must be exact. raking mid-section is drawn as a curve on the waterline plan. It is, however, Every straight line must be The necessary instruments for drawing have considered been already mentioned, and there is no need advisable not to introduce the beginner to too for the list to be repeated here. Taking the many complications and therefore this straight- long batten, line method will be used. through the G.B.D. and L.W.L. endings. Now, having decided upon the mid-section of the boat and that it shall be a raking mid- must not be forced in any way, but allowed to section, the next step is to place it. curve round the G.B.D. being easy and not take its natural curve. In the too present instance the G.B.D. has been placed at the exact centre of the L.W.L. bend it gently until it passes sharp. The It This will ensure the ends beyond the L.W.L. endings forming the overhangs can carry out It is by no means certain that this is correct, and many the same curve. designers hold that it should be forward of this point. Successful yachts have been designer to get the ends of his boats low in designed both ways, and most modern racing yachts have their G.B.D. slightly forward of amidships. The beginner, however, will find the yacht is sailing, and, if necessary, the ends it easier if he places his G.B.D. at the centre of that the ends look dragged down or drawn out, . the L.W.L. but rather they must be kept so that the yacht The designer can now proceed to draw a tentative profile of the canoe body of the boat. To do this, three points have already been is a harmonious and compact whole. determined—the forward and after endings of the L.W.L. and the position of the G.B.D. A line representing the L.W.L. can now be drawn and these three points spotted in. The length of the boat has to be 36 in., and the L.W.L. is fixed at 28 in. There is, therefore, 8 in. to be divided between the forward and the overhangs. after overhangs. In order that a boat may look balanced, her overhangs should be the same It was accordingly length or nearly so. the angle of incidence of the above water decided to give 4 in. overhang at each end. It will be found convenient and assist in drawing the lines if the section lines and waterlines are struck on the sheer plan before attempting to draw the profile. On a larger boat it is usual to divide the waterline into ten equal parts, but in this little craft eight will be found sufficient. The sections will accordingly be spaced 34 in. apart. The waterlines also are represented by straight lines in the sheer plan, and the most convenient spacings are 2 in. or 1 in. In the present instance the It is the object of every order to gain as much length as possible when can be eased down a little afterwards. This should not be done to such an extent, however, Many yachts have their profiles dragged out to such an extent that they never use a great portion of This is a mistake, as it repre- sents unnecessary weight and windage, and renders a boat unsightly as well as less sea- worthy. The craft now under design is, how- ever, limited to 36 in. L.O.A. so the question of dragging the ends out does not arise. If the reader looks at Fig. 25, he will see that profile is steeper forward than aft, which is the case in almost every boat. Turning back to our body plan on which the mid-section has been drawn, strike in the main diagonal diagonal). (otherwise called the bilge The angle at which this is struck on the body plan is determined by the point where the mid-section turns from the topsides into the floor of the boat, and it should follow through similar points on the other sections. Thus in a shallow-bodied boat, the bilge diagonal can be carried out at a low angle that will keep the turn of the bilge low in the boat, and consequently the overhangs will be kept 46 ¢ = . , Dl 1 1 ) -L. be y \ os 6h 2a D t3 yy Va \ WL? AN + TM. VMS NaN ~~ Ww. L.6 os — ie-m Raking Midsection Fic. 25. THE Frrst STEPS OF THE DESIGN, Folding Plate V [To face page 46. MODEL SAILING CRAFT the waterline plan is, therefore, recommended waterlines and will be used for designing the little boat Before proceeding, it must again be emphasi which is being used as an example. that the straight lines that form the basis of t This have been spaced 1 in. a section may be considered as the “‘ dominating design are almost more important than the section.” lines themselves. There is yet another method by which the dead true, and every right angle must be exact. raking mid-section is drawn as a curve on the waterline plan. It is, however, Every straight line mast be The necessary instruments for drawing have been already mentioned, and there is no need considered advisable not to introduce the beginner to too for the list to be repeated here. many complications and therefore this straight- long line method will be used. through the G.B.D. and L.W.L. endings. batten, Taking the bend it gently until it passes It must not be forced in any way, but allowed to Now, having decided upon the mid-section of the boat and that it shall be a raking mid- take its natural curve. section, the next step is to place it. curve round the G.B.D. being easy and not In the too present instance the G.B.D. has been placed at the exact centre of the L.W.L. sharp. The This will ensure the ends beyond the L.W.L. endings forming the overhangs can carry out It is by no means certain that this 1s correct, and many the same curve, designers hold that it should be forward of this point. Successful yachts have been designed both ways, and most modern racing designer to get the ends of his boats low in the yacht is sailing, and, if necessary, the ends yachts have their G.B.D. slightly forward of can be eased down a amidships. It is the object of every order to gain as much length as possible when little afterwards. This should not be done to such an extent, however, The beginner, however, will find it easier if he places his G.B.D. at the centre of that the ends look dragged down or drawn out, . the L.W.L. but rather they must be kept so that the yacht The designer can now proceed to draw a is a harmonious and compact whole. Many tentative profile of the canoe body of the boat. To do this, three points have already been yachts have their profiles dragged out to such determined—the forward and after endings of the L.W.L. and the position of the G.B.D. A the overhangs. line representing the L.W.L. can now be drawn and these three points spotted in. The length of the boat has to be 36 in., and the L.W.L. is fixed at 28 in. There is, therefore, 8 in. to be divided between the forward and renders a boat unsightly as well as less sea- after overhangs. In order that a boat may look balanced, her overhangs should be the same It was accordingly length or nearly so. decided to give 4 in. overhang at each end. It will be found convenient and assist in drawing the lines if the section lines and waterlines are struck on the sheer plan before attempting to draw the profile. On a larger boat it is usual to divide the waterline into ten equal parts, but in this little craft eight will be found sufficient. The sections will accordingly be spaced 34 in. apart. The waterlines the angle of incidence of the above water also are represented by straight lines in the sheer plan, and the most convenient spacings are 3 in. or 1 in. In the present instance the an extent that they never use a great portion of This is a mistake, as it repre- sents unnecessary weight and windage, and worthy. The craft now under design is, how- ever, limited to 36 in. L.O.A. so the question of dragging the ends out does not arise. If the reader looks at Fig. 25, he will see that profile is steeper forward than aft, which is the case in almost every boat. Turning back to our body plan on which the mid-section has been drawn, strike in the main diagonal diagonal). (otherwise called the bilge ‘The angle at which this is struck on the body plan is determined by the point where the mid-section turns from the topsides into the floor of the boat, and it should follow through similar points on the other sections. Thus in a shallow-bodied boat, the bilge diagonal can be carried out at a low angle that will keep the turn of the bilge low in the boat, and consequently the overhangs will be kept 46 — ee: p ——— ee ~ ~~] eee 6 9 (Renee * ¢ D B . ” ~~. ae <= TL _ ~~ . fe L Son LW. t i W.L.9. ee) ! Se t ) 1 = Tr-~L tW.L. oy a \ ts3 \ a SC ee es - ah a ae iS, ta 2) te va Ny ‘\ a WL? \ Xn AY al WL W.L.6 S| “ORS ra ~~ Raking Midsection Balancing Points an Deckline — a’ LZ) kao aan — Fe a. = sagoret sr eot a ee,‘ ce 71m | -_-t7 me ~aS BuTrocu 2 TTT a wa Burtocw| ¢_ OFFS Ss Coad | “ bY v ‘ 2 Buyiork| B Buyer} 4 ra A i L. ‘ Po i 3 ~~ $ é ~~. 7 3S Te. Ue ee ae Fic. 25. THE First Steps oF THE Desion. Folding Plate V.] [Main Diagonal, _] [To face page 46, / AVA WL YZ \ |= 7 = Fic. 26. i THE DESIGN CARRIED A STAGE FURTHER. [To face page 47. | is, of course, identical in plan with the greatest a deeper-bodied boat, such as we t designing, the angle of the bilge nal will be considerably steeper. beam line. In order to draw the deckline, a baseline representing the centreline of the yacht is first drawn. The plan now being started is what is known as the “‘ waterline plan.” This was explained fully in the previous chapter. Before proceeding with the deckline, the It st always be borne in mind that if the boat is to be without disturbing influences at varying angles of heel, the overhangs must be a correct blend with the middle of the hull. The correct method of obtaining the angle for this main diagonal on the body plan is to draw a tangent to the periphery of the midsection at the exact point where the topsides section lines should be put in to correspond with those in the sheer plan. As already explained, the sections which, in the body plan, appear as curves, appear as straight lines on the sheer and waterline plans. The buttock On this tangent a metge into the floor. perpendicular is erected at its point of contact with the section and produced until it meets lines can also be ruled in parallel to the centre- the centreline. This diagonal must be repeated on the other side of the centreline. This diagonal gives another spot which guides the designer in drawing the profile of the after overhang of the boat. The after end of the boat’s profile should be continued beyond the stern until it comes to the height at which the diagonal meets the centreline on the body plan. The point where the profile reaches the height of the diagonal forward is subject to adjustment and cannot yet be determined. Before leaving the profile, the curve should be checked to see that it is even on each line. side of the G.B.D. plan as a Since the G.B.D. is at the The inner buttock is spaced 1 in. out from the centreline, and the others 1 in. apart. Great care must be taken to get all these lines correct, and all right angles in the plan exactly accurate, as the accuracy of the whole plan depends on them. It will facilitate drawing the greatest beam line if a straight line is drawn parallel to the centreline at a distance from its equal to half of the greatest beam. The greatest beam of this boat is to be 9 in., so this line will be 4:5 in. from the centreline. The transom will appear on the waterline straight line, but as eventually our exact centre of the L.W.L., this means that the transom will be raked, this really represents sections immediately fore and aft of it will be the upper edge of it. equidistant sections always considered in the first instance as being The depth at each section should be vertical, and is trimmed off as requisite when likewise. from it, and the next The transom is, however, checked accordingly, and any necessary adjust- finishing the design. ment made. During the drawing of all curves, the batten will, of course, be kept in place with must next be considered. weights. bear in mind the type of boat that is being The width of the transom In deciding the width for the transom of the yacht, one has to In many modern racing yachts, the G.B.D. designed. The present model is to be a fairly is placed forward of the exact centre of the full-bodied, able little craft, but the ends will L.W.L., and when this is done, obviously the cutve representing the bottom of the canoe not be over-full. body (z.e., the line of G.B.D.) will be steeper in novice the forward part than in the after part. which will help him to select suitable dimen- experience must guide the designer, but the The next line to draw is the deckline, or in sions. the case of a boat with tumble home, the great- est beam line. The expression In arriving at a decision, can usually examine similar designs In this instance the width of the tran- som was fixed at 3-8 in. ‘“‘ tumble A tentative deckline can now be drawn. home ” implies that the width on deck 1s less Taking the long batten and allowing it to than on one of the waterlines below it, and the assume a natural curve, bend it until it touches section consequently tumbles home on itself. the parallel line which has been drawn at the When there is no tumble home, the deckline distance of the greatest beam from the centreAT > 5 6 WwLId 7 8 9 ” Yeotative Transom Dp h S25 a £3 t I t wd == ‘ – bw 1 val tw | 7 \ _ wuy WL IBurteck 5 [Butireck A Pertpcn D ; == {puttocn ¢ ~ == Burrock B os 7 / g Burrock A, = ite, ab, – ~ ‘Tue DESIGN CARRIED A STAGE PURTHER. = 6 Folding Plate Vi. Dinca Coe [Main in Diagons bis l 7 e p [To face page 47. er-bodied boat, such as we esigning, the angle of the bilge will be considerably steeper. It ways be borne in mind that if the boat o be without disturbing influences at varying angles of heel, the overhangs must be a correct blend with the middle of the hull. The correct method of obtaining the angle for this main diagonal on the body plan is to draw a tangent to the periphery of the midsection at the exact point where the topsides On this tangent a merge into the floor. perpendicular is erected at its point of contact with the section and produced until it meets the centreline. This diagonal must be repeated on the other side of the centreline. This diagonal gives another spot which guides the designer in drawing the profile of the after overhang of the boat. ‘The after end of the boat’s profile should be continued beyond the stern until it comes to the height at which the diagonal meets the centreline on the body plan. The point where the profile reaches the height of the diagonal forward is subject to adjustment and cannot yet be deter- is, of course, identical in plan with the greatest beam line. In order to draw the deckline, a baseline representing the centreline of the yacht is first drawn. The plan now being started is what is known as the “‘ waterline plan.” This was explained fully in the previous chapter. Before proceeding with the deckline, the section lines should be put in to correspond with those in the sheer plan. As already explained, the sections which, in the body plan, appear as curves, appear as straight lines on the sheer and waterline plans. The buttock lines can also be ruled in parallel to the centreline. The inner buttock is spaced 1 in. out from the centreline, and the others 1 in. apart. Great care must be taken to get all these lines correct, and all right angles in the plan exactly accurate, as the accuracy of the whole plan depends on them. It will facilitate drawing the greatest beam line if a straight line is drawn parallel to the centreline at a distance from its equal to half of The greatest beam of this boat is to be 9 in., so this line will be 4-5 in. from the greatest beam. mined. Before leaving the profile, the curve should be checked to see that it is even on each side of the G.B.D. Since the G.B.D. is at the exact centre of the L.W.L., this means that the sections immediately fore and aft of it will be equidistant from it, and the next sections likewise. The depth at each section should be checked accordingly, and any necessary adjustment made. During the drawing of all curves, the batten will, of course, be kept in place with the centreline. weights. bear in mind the type of boat that is being The transom will appear on the waterline plan as a straight line, but as eventually our transom will be raked, this really represents the upper edge of it. The transom is, however, always considered in the first instance as being vertical, and is trimmed off as requisite when finishing the design. The width of the transom must next be considered. In deciding the width for the transom of the yacht, one has to In many modern racing yachts, the G.B.D. designed. The present model is to be a fairly is placed forward of the exact centre of the L.W.L., and when this is done, obviously the cutve representing the bottom of the canoe body (z.e., the line of G.B.D.) will be steeper in the forward part than in the after part. The next line to draw is the deckline, or in the case of a boat with tumble home, the greatest beam line. The expression ‘tumble home ” implies that the width on deck 1s less than on one of the waterlines below it, and the section consequently tumbles home on itself. full-bodied, able little craft, but the ends will When there is no tumble home, the deckline distance of the greatest beam from the centre- not be over-full. In arriving at a decision, experience must guide the designer, but the novice can usually examine similar designs which will help him to select suitable dimensions. In this instance the width of the tran- som was fixed at 3-8 in. A tentative deckline can now be drawn. Taking the long batten and allowing it to assume a natural curve, bend it until it touches the parallel line which has been drawn at the 47 MODEL SAILING CRAFT line. It is also known that the deckline must greatest join the centreline at the bow and that it must beamline, this curve is the most important part of the design, as it will govern pass through the point which has been fixed for the the corner of the transom. hull after the mid-section has been drawn. In drawing the deckline, it should be borne shape of every section throughout the Reference has already been made to the in mind that if this curve is to be satisfactory, importance it must be balanced about the baseline. The placement throughout the entire length of the highest point of this curve will be where the boat, and it is obvious that the character of the batten touches the parallel line. diagonals, particularly the main diagonal, is course, settle greatest beam. the This will, of fore-and-aft position of of correct distribution of dis- the best indication of how this distribution has In order that the deckline may been effected. As will be explained in a be balanced about the baseline, it is necessary subsequent chapter, the area of each section in that the breadths on either side of the greatest the boat is graphically plotted in the form of a beam point must be equal. curve, known as the “‘ curve of areas.” These can be As, checked with the dividers, 7.e., the breadth however, an infinite variety of sections could 3 in. forward of the greatest beam point must be drawn having any given area and with any be the same as that at 3 in. abaft it. given depth body and greatest beam, it is That at 6 in. forward of it must equal that at 6 in. abaft quite it, and so on. governs the actual shape of the sections themselves must be an even more reliable guide than the curve of areas. To give the reader some idea of the extent to which the main diagonal influences the distribution of displacement, it might be mentioned that if a diagonal is adopted that is a pure arc of a circle, the resultant distribution of displacement will give a slightly too fullended boat. It is, therefore, the practice to The after part of the deckline makes the shorter curve, and it is best to adjust the forward part to agree with it. In types of boats that have long overhangs, the ends are often drawn out, and the extreme ends of the deckline are allowed to straighten out considerably. The present boat is, however, a normal type, so that extreme overhangs have not to be considered. Some designers prefer to balance the highest waterline below the sheer line in certain types More is said in a later chapter there is often the mistaken idea that it is far easier to design a 1o-rater, because only one hull measurement has to be considered, than an A-class or I.Y.R.U. model. Actually the extreme type requires great care in balancing correctly coupled with great experience. The next line to receive attention is the main diagonal, which represents the bilge curve of Coupled with the bilge diagonal which curvature about the mid-section, but tends to straighten out towards the ends. How much this tendency is allowed to proceed is almost entirely dependent on the class of boat which is being designed. about these sharpies. In passing it may be remarked that a normal type of boat is far easier to design successfully than an extreme boat, and therefore it is a far easier problem for the novice to tackle the design of a boat under a rule that produces a normal type than a boat under a rule that produces an extreme type. Amongst beginners the boat. that make this diagonal of a form that has an easy of boat. This applies particularly to the design of a sharpie with a constant angle of flare to the topsides. clear the profile and 48 The bilge diagonal will first be drawn in its own plane. This is done on the opposite side of the centreline, which serves as base for the waterline plan. The first point to be found is the spot for the highest point of the curve. In order to do this, it is necessary to draw a straight line on the waterline plan to represent the raked mid-section. On the centreline find the position of the G.B.D., which was fixed at the exact centre of the L.W.L. This is then joined to the position of the greatest beam. Turning to the body plan, measure out from the centreline horizontally to the position where the main diagonal intersects the midsection, this being the widest point of the is point is found to be 3-91 in. the fore-and-aft position of the forward inter- reline, and the position at which est height which is exactly midway between section of the L.W.L. and the diagonal. Similarly the after point can be found. Transfer these positions to the elevation and also to the waterline plan. In the case of the waterline plan; at the correct fore-and-aft position it will be necessary to set off the actual width out from the centreline of the point of intersection, remembering that we are now drawing the diagonal in plan wot in its own plane. The distance has now to be measured on the section plan along the L.W.L. to the point of intersection with the diagonal. This gives the breadth of the L.W.L. at the point it intersects the diagonal, and, as we have already found the fore-and-aft positions, these two spots can be marked on the waterline plan. In a similar manner, the intersections with the buttock lines can be measured and set out on the plan of the diagonal in its own plane, thus finding the positions at which the buttocks intersect the diagonal. These positions can be transferred straight away to the straight lines representing the buttocks in the waterline plan, and by measuring the distance above ot below the L.W.L., the correct positions can be found and marked on the sheer plan. When all these positions have been marked, them. ‘The long’ batten is used to draw this the diagonal can be drawn through the spots. cutve and is gently bent into position, not The curves should fair exactly, and if there is any discrepancy, it will be necessary to check one plan with another and make the necessary corrections. It should be emphasised at this point that all intersections between the various lines in the different plans must absolutely coincide. For example, the main diagonal must cross the L.W.L. in exactly the same foreand-aft position in the sheer plan and waterline king mid-section is 3-91 in. wide is 7 in. abaft the G.B.D., and this position can _ now be marked on the waterline plan as being the fore-and-aft position of the greatest width of the main diagonal. Immediately opposite this, on the other side of the centreline, set out the greatest width of the main diagonal measured in its own plane. This is obtained by measuring from the centreline on the body plan down the diagonal to its greatest point. A simple method of transferring these various measurements is by using a strip of paper. From the sheer plan we can find the spot at which the after end of the diagonal produced would meet the profile produced. This is another way of saying where it would meet the centreline. This position must also be spotted in on the centreline on the plan, where we are now drawing the diagonal in its own plane. Measure from this point to the fore-and-aft position of the greatest width of the diagonal and set out a similar distance forward. This will give us three points—a forward ending and an after ending, also the position of great- being forced in any way, but allowed to take a natural curve. It is held in position with the weights and the line drawn in. This line must be checked up and carefully balanced on either side of the greatest width, as was done with the deckline. The next step is to draw the bilge curve in plan upon the waterline plan and in elevation upon the sheer plan. It will be seen that on the body plan the main diagonal cuts both waterlines and buttock lines diagonally, Whilst this gives the breadths and heights of these points of intersection, it does not give their fore-and-aft position. Starting with the L.W.L., measure the distance along the diagonal from the centreline to the point where the diagonal and L.W.L. intersect. The position forward where the diagonal is this width will immediately give plan, and so on. The forward profile of the boat can now be finally adjusted and completed, as it must pass through the point of the forward ending of the bilge diagonal, which has already been drawn in elevation on the sheer plan. Before proceeding further with the development of the body of the boat, the sheerline should be drawn in. Its curvature will be largely determined by the amount of freeboard that is decided on. The midship height has E MODEL been determined by the midship section, and fashion that she is geometrically c this point should be put in first. whole design will follow. The height at the stern and the character of the curve of the sheerline is very largely governed by the, type of boat that is being designed. Sufficient The design carr out to this point is shown in Fig. 25. Before leaving the subject of these governing lines, a word or two should be written about freeboard is necessary to keep the boat dry, the actual turn of the stem. and be strictly in keeping with the character of the a bold upstanding sheer forward is a This turn should characteristic of many craft that are intended midship section. to keep the seas in heavy weather. bilge should have a hard turn where the stem other hand, too much freeboard On the is useless turns upward. windage, tending to push the vessel to leeward, Thus a boat with a hard Conversely, a boat with a slack bilge requires a long gentle turn. Moreover, and can also make a boat look stumpy and the rake of the transom must match the for- unsightly. watd profile if the boat is to look balanced and The designer has, therefore, to balance one consideration with another and sightly. strike needs her transom more upright than one with the happy medium. Apart from any restrictions on freeboards, which form part of A boat with a hard turn to the stem a longer nose. various measurement rules, there are only two Yacht designing is both a science and an art. considerations that need govern the designer. The first of these is the purely utilitarian con- There are boats that sail well and yet have their appearance entirely ruined by an ugly sheer. sideration of keeping the deck dry, and the There are other boats that look pretty on the second is the zsthetic consideration of appear- water and are complete failures through lack of ance. balance. A badly planned ugly sheerline does A sailing craft under way is one of more to mar the appearance of a craft than the loveliest things ever devised by man. anything else. great designers have all been artists as well as Study should, therefore, be given to the sheerline of boats that have a men beautiful appearance on the water, and the alone will not win races, but it is something designer should endeavour to get an equally desirable line. worth striving for, so that our little yachts in their modest way may be things of beauty and Having completed the midship section, the of science. The Appearance above water a joy to the eye. The deckline, profile and main diagonal of the boat, embryo designer should, therefore, the design of the canoe body becomes prac- cultivate his eye. tically a matter of routine. themselves entirely govern the design, and if craft from the drawings, learn to distinguish those points that make for beauty of line, and they have been properly planned provided the he will gradually come to the conclusion that remainder of the design is carried out in such beauty and harmony are synonymous. These lines in 50 He should try to visualise ORS \ = + ~s NI 4 =“ – “DS iw _ ae 57 | Se r -7 dq ~ a a ~ >»: LC 4 ~ 6 W.L Heeled Waterline vsed for caleviation Heeled Waterline of inclined displacement. wero : A ian ~ Fic. 27. THE CANOE Bopy COMPLETED. |To face page 50. been determined by the midship section, and fashion that she is geom this point should be put in first. whole design will follow. The height at the stern and the character of the curve of the sheerline is very largely governed by the. type of boat that is being designed. Th out to this point is shown in Fig. 25 Before leaving the subject of these Sufficient lines, a word or two should be writte freeboard is necessary to keep the boat dry, the actual turn of the stem. and be strictly in keeping with the character of th a bold upstanding sheer forward is a This turn shoul characteristic of many craft that are intended midship section. to keep the seas in heavy weather. bilge should have a hard turn where the stem other hand, too much freeboard On the is useless turns upward. Thus a boat with a har Conversely, a boat with a slack windage, tending to push the vessel to leeward, bilge requires a long gentle turn. and can also make a boat look stumpy and the rake of the transom must match the for- unsightly. to ward profile if the boat is to look balanced and balance one consideration with another and sightly. A boat with a hard turn to the stem needs her transom more upright than one with The designer has, strike the happy medium. therefore, Apart from any restrictions on freeboards, which form part of various measurement rules, there are only two Moreover, a longer nose. Yacht designing is both a science and an art. considerations that need govern the designer. There are boats that sail well and yet have their The first of these is the purely utilitarian con- appearance entirely ruined by an ugly sheer. sideration of keeping the deck dry, and the There are other boats that look pretty on the second is the zsthetic consideration of appear- water and are complete failures through lack of ance. balance. A badly planned ugly sheerline does A sailing craft under way is one of more to mar the appearance of a craft than the loveliest things ever devised by man. anything else. great designers have all been artists as well as Study should, therefore, be of science. Appearance The given to the sheerline of boats that have a men beautiful appearance on the water, and the alone will not win races, but it is something above water designer should endeavour to get an equally worth striving for, so that our little yachts in desirable line. Having completed the midship section, the their modest way may be things of beauty and a joy to the eye. The deckline, profile and main diagonal of the boat, embryo designer should, therefore, the design of the canoe body becomes prac- cultivate his eye. tically a matter of routine. themselves entirely govern the design, and if craft from the drawings, learn to distinguish those points that make for beauty of line, and they have been properly planned provided the he will gradually come to the conclusion that remainder of the design is carried out in such beauty and harmony are synonymous. These lines in 50 He should try to visualise , W.L.10 NX N we IN NO a 3 Cc ) oe es \ \ oR oN _ ee W.L.6 § St ee U } eee SS Burrock C _————— IE Borrocuge e a ae, “Wits Cs So ee ee —— ° — ae Pa ~ —” aes -o? ee ~~ [_— W.L 6 used ~ . PN “2 = Fie. 27. THE Canor Bopy CompLerep. yj 7 ‘o/s oS] S. NX § ee ia <>“ Button A 4 _ ——*:CSBtoc B | a Heeled Waterline e _ ep “ a WL VO of inchined an rd SZ) Wo +77 | | al | JS 5 | a pees — Fr i a i pee Tentative. 8 aro |? ag ae ss ~A 7 ~ 4 a . * a > << ~ ~~ Piacoway ¥ ~ —— oe, SS re ~~ ~~GUAVE! of aneas or cance?”2 ae oo -f Basia x Ci 7 “Sup —| DIAGONAL W — Oe Folding Plate VIII,| in ee RS, ) “*, rhe i is rm | tN \Ny B WZ LL \ 5) N= A WAS 20 4 i /! — ne | (— NN I SU WLS Purtock B Butrock | Wi 6 SS[ Burrocn C Le Lot” | Wl a Butrock D aani = Lwe ==al\ sa pp} eA wid | yt9 = 1, eS Ne wt Lines OF 36-INCH MopgL YAcHT. a _ purrocn Y ff WLIO as eee —————— oe 8 ial 2 } Art |__Burtocn Bt ee ———ee _ ? 6 zs c3 pa AREAS aera —~ _ ipcLUrt Z “ ‘ ee = [To face page 51. CHAPTER V of the Canoe Body. Curves of Areas. The Colin Archer Theory. Calculation of Displacement and Centre of Buoyancy. Speed Factors. Tumble home. Deck Camber FTER the outline lines are accordingly drawn tentatively through the positions that have been found, and this gives the two further points that are required to draw the after end of the L.W.L. It must not, however, be overlooked that since this waterline ending is based on two points that of the hull design A been completed as detailed in our last chapter, it only remains to complete the lines. The work of the designer in this connection may really be considered as drawing within the length of boat at his disposal a series of sections that carry out the characteristics of have not been finally and definitely determined, the midship section that has been decided upon. it must be regarded as being a tentative line also. A tentative transom is now drawn. The manner in which the main diagonal has been plotted has already assured the design being fair throughout the bilge, and the waterlines and buttocks have now to be developed The transom ending of the boat is first treated as if it was going to be an upright one, situated at the extreme end of the deckline. When the after end of the boat has been completed, the transom is trimmed off to suit the profile and deckline of the yacht. The height of the top of the transom is known and its breadth on deck, also the lowest point which falls on the in a manner that will ensure the same result in respect of the underbody and topsides. The first line to receive attention must be the L.W.L. this. The We have already five points on forward and after endings are known, also the positions forward and aft where it crosses the main diagonal and the profile. point point can be ascertained by measuring the on the raking midsection where main it The point of its intersection with the diagonal is also known. The latter These points are height in the sheer plan, the beam in the water- sufficient to draw the entire L.W.L. with the line plan or the distance down the diagonal exception of the part lying between its after intersection with the main diagonal and the itself from after L.W.L. ending. Whichever of these is taken, the point found reaches its greatest breadth. the centreline taken drawing of the diagonal in its from the own plane. must be the same, provided the diagonal has In order to get the curve of this part of the L.W.L. correct, the points of intersection with been correctly drawn in the various plans. the two inner buttocks are needed, and to get tentative transom can now be drawn through A these two points, part of the buttocks will have these three points, preserving as far as possible to be drawn in tentatively on the sheer plan. the general characteristics of the midsection. Tentative sections can also be drawn at the The positions at which the main diagonal crosses these buttocks can be found in a fore- forward and after L.W.L. endings. and-aft direction from the waterline plan and forward section, we have the lowest point, the the heights can be taken from the body plan. deckline and its intersection with the main With this data these positions can be marked diagonal, and on the after one we have also on to the sheer plan, and one point has now the points of intersection with the two inner been definitely fixed on each of these two buttocks. Now it is obvious that if the character of the sections is to be maintained throughout the after-body, the inner buttock lines must be buttocks, as drawn in tentatively. practically parallel to the profile for distance above and below the L.W.L. For the After this the inner buttock must be drawn in. It should be observed that the profile is in reality a buttock line taken through the centre of the ship, and if the technique of some draughtsmanship These is correctly observed, the buttock lines of the topsides will be consistent 51 is z a MODEL SAILING CRAFT in character. In drawing lines such as this In order to guide us, we draw in a tentati buttock, it will possibly be of assistance to the section midway between the forward L.W.L. novice to observe the following procedure, ending and the fore-and-aft position of the which is almost identical to that recommended point of greatest body depth, which in this in drawing in the deckline. ‘The buttock has case is situated at the exact centre of the L.W.L. to attain its greatest depth at a given position The underwater part of this section is already on the fixed by the waterlines and buttocks that have lowest point, as plotted on the sheer plan, been finally settled, and we also know its width lightly pencil a horizontal line. on deck. the raking midsection. Through If the curve From this tentative section, the of the buttock ts correctly drawn through this point of intersection with the waterline above lowest point, the line must be a tangent to it. the L.W.L. is obtained, and this point will be a Aft of the lowest point the inner buttock runs guide to the character of the curve. practically parallel to the profile line for its has been faired up nicely with the forward full length. Forward it gradually comes away from the profile, but the character of the curve is the same, and the turn-up to the deckline completing the forward follows the stem. | When this sections, this in turn will give other points for buttocks. ends of the inner As we have the points of their intersections with the main diagonal and the The second buttock line is drawn in a similar manner, and then the first waterline below the L.W.L. can be developed. Starting from the forward end, we know its ending, where it points on the sheer, no difficulty should now crosses the two inner buttocks and the point on the raking midsection where it comes to its greatest width. If any difficulty is experienced in getting the waterline through the points of intersection with the buttocks, the necessary adjustment must be made to the buttock and upper waterline follow naturally. be experienced in getting all this part of the design nicely faired up. The intermediate sections have also to be drawn in. ‘The outer In the completion of the forward part of the boat, no difficulty should be experienced, as no further adjustment should be required, provided that the buttocks and waterlines have been correctly faired. In drawing these for- buttock lines until one plan fairs with the other perfectly. In a similar way the waterline is continued aft and similar adjustments are made ward sections, the depths of each buttock and breadths of every waterline are spotted on the as requisite. For this purpose a celluloid spline will be found body plan and a curve swept through them. In a like fashion the lowest waterline of the hull is developed. This gives us the complete underwater body of the yacht, as if fair curves have been drawn and the points of intersection tally in the sheer and waterline plans, the sections should fair without any further adjustment of any kind. The design developed to this point is shown in Fig. 26, Before proceeding with the topsides, the third buttock line should be put in. This will form a further check on the underwater body. Proceeding with the topsides, the first waterline above the L.W.L. has next to be very useful. This completes the forward part of the canoe body of the yacht, and an exactly similar procedure should be followed in the development of the after-body. In order to act as a further check upon the fairness of the hull, it 1s customary to take out further diagonals. These diagonals differ materially from the main diagonal, as they are obtained from sections that are already determined, whereas the main diagonal was a definite line laid down at the commencement of the design before any section other than the drawn. This will, of course, pass through its correct points at profile, diagonal and midsection. In addition to these five fixed points, we have also points on the tentative sections which have been drawn at the L.W.L. endings. midsection had been drawn. The curves formed by these diagonals should, however, be similar in character to the main diagonal. These additional diagonals should be arranged above and below the main diagonal, so as to §2 MODEL SAILING CRAFT form a curve round the hull, which shall be as and the greatest beam point on the L.W.L. nearly as possible intermediate between the This curve is shown on Fig. 27. run of the waterlines and buttock lines, or, in other words, Now a number of theories have been pro- at approximately an angle of mulgated as to the virtues of certain specific The line these diagonals make forms of Curves of Areas (or Displacement round the hull is very similar to the lay that Curves), and some authorities have gone so the planking will have to take, and therefore far as to lay down the axiom that the Curve of they give a good idea as to whether the boat Areas should be one of the first lines drawn for will be easy or difficult to plank up. the design, and the form of the hull modelled 45 degrees. The diagonals likewise approximate to the to fit this arbitarily determined curve. paths the water will take around the hull, and About the best known of these Displace- to the practised eye give an idea of the yacht’s ment Curve theories is that propounded by the speed potentialities. late Colin Archer, which is usually known as A further diagonal can, with advantage, be the “‘ wave-form”’ theory. This requires that taken out in the after part of the hull, following the Curve of Areas shall be in the form of a the turn of the bilge from the main diagonal waveline. To of curve of versed sines of a length of 60 per bilge will teach * diagonal into curve the primary the midsection on main as shown. the forebody the Curve the transom. plane, for this, position on the midsection up to the turn of This, when plotted in its own Areas accord with must be a cent. of the L.W.L., and the Curve for the afterbody a troichoidal curve of the remaining 40 per cent. This completes the draughtsmanship of the As a matter of interest, we can draw a pure canoe body of the vessel, which is shown on Wave-form Curve of Areas on the dimensions Fig. 27. of the little model we are designing. As the hull proper is now designed, This is it is advisable to prove the lines as far as we shown in the upper drawing in Fig. 29. have gone. the baseline BC of the same length as our In order to do this a Curve of Areas has to be drawn. underwater areas sections have methods L.W.L. first to this be calculated. have already The been Having tabulated these, the Curve (¢e., 28 in.). Place the point A at Go per cent. (16-8 in.) from the forward end, of each of the transverse of doing explained. For this purpose, the Draw thus giving the lengths of the fore-body and after-body according to the theory. At this point A erect a perpendicular 4:16 in. long to correspond with the area of Areas can be plotted. section. The usual method is to use the same base- of our half mid- This line becomes the diameter of a line as has been used for the diagonals, that is, circle which is on the other side of the centreline to the water- Circle.” known as the “‘ Generating be Dealing first with the fore-body which is to chosen to plot the section areas, which should have a curve of versed sines, divide the cir- be marked out at right angles to the centreline cumference of the forward semicircle into any on the respective section stations. convenient line plan. A convenient scale should The plans number of equal parts—in this for this 36-in. model were drawn full-size, and example four has been taken—at a, b, c. the scale chosen was 4 in. = 1 sq. in. divide the baseline AB into the same number In other of parts at a’, b’, c’. words the half-section areas were plotted fullsize. diculars at a’, b’, c’. For this Through the points of intersection draw the curve Bc” b” a” D, which purpose a somewhat slender batten will have to be used. Through a, d, ¢, draw lines parallel to the baseline AB, and erect perpen- A curve has to be drawn through these points to form the Curve of Areas. Next is the required curve of versed sines. This curve should reach its highest To describe the trochoid for the after-body, point somewhere between the point of G.B.D. the circumference of the semicircle is similarly divided at e, f, g, and the baseline at e’, f’, g’. * Teach = fair nicely into. 54 DISPLACEMENT CURVES Then through delivery sets up a system with its crest at the points e, f, g, dtaw lines parallel to the stern, and the boat herself runs in the trough. in the points e, f, gto A. Cg” f’ e’ D, which forms the required curve In other waves her bow runs on the back of the bow wave and the stern on the front of the stern wave. Colin Archer thought that the displacement should be distributed in such a way that the vessel fitted the trough between of the trochoid. the two waves. baseline. ‘Through e’ draw a line parallel to Ae, through f’ draw a line parallel to Af, and through g’ draw a line parallel to Ag. the points of intersection draw Through the curve Although The Curve of Areas which we have just many writers still place much drawn is absolutely in accordance with the faith in this wave-form theory, there is no Colin Archer theory, but in accordance with more modern practice the Curve of Areas of doubt that many highly successful yachts do not conform to it. Moreover, it must be our little boat has its highest point consider- remembered that the ably more forward than in a true Colin Archer represents the form of the hull, when the craft Curve of Areas only As 4 matter of interest, the wave-form is at rest, and owing to the fact she heels, this curve has been re-drawn in the lower diagram form is never present when under way, except of Fig. 29 with the generating circle placed at curve. An possibly when immediately before the wind in the lightest of breezes. been It is the considered opinion of the authors of This gives the reader the oppor- this book that no specific value attaches to any the highest point of the actual curve. additional added aft. curve of versed sines has tunity to compare the Curve of Areas of our particular set form of Displacement Curve. boat with a curve of versed sines forward, and It is, however, most essential that the curve curves of versed sines and trochoid aft. It will be seen that the forward part closely shall be fair and harmonious with an even rate approximates to the versed sines curve. The after part falls between the curves of versed delivery. sines and trochoid, but its nature partakes of been employed in drawing the little hull, by the former. starting with a balanced main diagonal prac- are displacement governing the entry and It may be added that the method, which has Curves of versed sines, or curves closely approximating to them, of much used for tically ensures a distribution of displacement which will be as nearly as possible correct. yacht Displacement Curves, though very fre- Actually the Curve of Areas of the canoe quently the fine endings are somewhat snubbed back. Power-boat designers often favour a body only is of very great use to the designer trochoidal curve both forward and aft. has drawn. as it enables him to estimate the type of hull he The inferences to be drawn are It should be mentioned that the area of a largely a matter of practice and experience, but versed sine curve is always equal to the pro- as a guide it may be mentioned that the hull duct of the baseline multiplied by the diameter of the generating circle divided by 2. should show a nice gradual rate in both entry and delivery without any sudden changes. In other words it has a prismatic co-efficient of +5. The trochoid has a varying co-efficient depending on the ratio of the diameter of the A little experience will teach us to make an generating approximate citcle to the baseline, the It will also be of use if at this point we take out the displacement of the canoe body for comparison with our intended displacement. co- efficient increasing with the ratio. The general idea behind the estimate of the additional placement of the keel appendage. dis- While we wave-form are doing this it is only a matter of a few more theory can be easily understood if one con- figures to ascertain the fore-and-aft position of siders the wave systems a hull sets up in its the Centre of Buoyancy of the canoe body. forward progress. ‘The entry creates a wave system having its crest at the bow, while the This will be of use when we design our keel as it will give a rough idea for placing the bulk of Dp) i EXAMPLES OF CALCULATION TO f FORE-AND-AFT POSITION OF CENTRE OF By Simpson’s Rule Areas Section of Half Simpson’s No. Sections Multipliers Functions of Areas By Trapeyoidal Rule Arm Moments I ooo X I = o070 X O09 =~ 0o-00 2 TIO xX 4 = 440 XxX I = 4°40 3 359 X 2 = FIO X 2 = 14:20 4 657 X 4 = 26:28 X 3 = 5 78:84 832 X 2 = 1664 XK 6 790 X 4 = 3160 X 4 = = 66°56 158-00 7 §Il X 2 = 1022 X 6 = 61°32 8 195 X 4 = $780 X 7 = 54:60 9 oo0o0 X I = ooo xX 8 = 000 5 104°04 section No. Areas of Half Sections Functions of Multipliers Areas Arm I ooo X05 = O00 X 0 = 2 TIo X TF => TI0 K I = 355 KX T= 3595 X 2 = 832 K 1 832 K 4 = 3 4 O57 6 7 790 §Tl 8 9 5 X 1 = O57 X X I FT = = F90 gir X Xk § 6 = = 95 xX T = 199 X FJ = o00 X05 = O0O X 8 = = 437°92 XK 3 = 34°59 Up to this point the figures used for the two calculations (Displacement and Centre of Buoyancy) are worked out by same methods, but in finding the Displacement only, the Moments are not required, so that the Functions of Areas are not multiplied by the Arm. It will be noticed in above calculation that as areas of end sections (Nos. 1 and 9) are o, the Functions of Areas are same as Half-Section Areas, and when this is so, some figures can be saved by eliminating the repetition. Displacement Displacement Sum of Functions of Ateas = 104’04 Multiplied by Spacing = 3°5 Sum of Functions of Areas = 34°50 Multiplied by Spacing = 3°5 52020 17250 31212 Divided by 10350 3)364:140 121°3 120’750 Displacement in cubic inches :— = 120’75 for Half Model. Displacement in cubic inches :— = 121°38 for Ha/f Model, 241-5 for Model. Displacement of vessel in fresh water:— or 242:76 for Model. 241°§ — 27°65 = 8-731 lb. If yacht is to be calculated out for Fresh Water, divide number of cubic inches displacement by 27-65 to get weight in pounds. For Sa/t Water, divide by 27. Centre of Buoyancy Sum Displacement of vessel in fresh water :— of Moments divided by Sum of 242°76 ~ 27°65 = 8-779 lb. Functions of Areas, and result multiplied by Centre of Buoyancy (145-0 + 34°5) X 3°5 = 4203 X 3°5 = 14-710. Spacing. C.B. Sum of Moments is divided by Sum of of canoe body is 14:71 in. abaft Section No. 1. Functions of Areas and result multiplied by Spacing. (437°92 + 104:04) X 3°5 = 4:209 X 3°55 = 14°731 Therefore C.B, of canoe body is 14:731 in. abaft Section No. 1. Note.—As the C.B. is the centre of gravity of the volume of water displaced by the vessel, the centre of gravity (C.G.) of a solid mass (¢.g., a lead keel) can be found by exactly similar methods, and its weight by similar methods to those used for calculation of displacement. 56 It is also The C.G. of any body can be calculated or the first steps in proving the either by Simpson’s Rule or the Trapezoidal cement of the keel (or fin). nee of the hull, as explained in a later chapter. In order to explain these calculations Rule. In either case the calculation is tabulated and the Functions of Areas ascertained. in turn, are multiplied by the Arm. it will be better to take them separately. It has been stated that a vessel floating in These, This Arm is the number of stations the section in question water displaces a volume of water having a is abaft of the foremost one. weight equal to her own weight. If, therefore, most section will have an arm of o, the second the volume of the boat is calculated up to the section an arm of 1, the third section an arm of L.W.L., it will give the volume of water dis- 2,and soon. placed. Sections which are summed. As the weight of water is quantity, it is a known quite an easy calculation to This gives the Moments of the Functions which is Interval between the stations. the weight of the The Sum of the Moments is then divided by the Sum of the ascertain the weight of the displaced water identical with Thus, the fore- of Areas and multiplied by the It should be mentioned that a simple and boat. In the calculation of Displacement, either accurate method of finding the C.B. without Simpson’s Rule or the Trapezoidal Rule can be calculation is by cutting out the shape of the used, as was explained in the last chapter, when Curve of Areas from thin card or stiff car- we were dealing with cross-sectional areas. tridge paper and balancing it on a pin-point. The latter have already been plotted in the If the beginner is working upon squared paper, form of a Curve of Areas. he can, accordingly, get his section areas by On this the ordi- nates represent square inches. It only remains coustting, and plot his Curves of Areas, and to calculate the volume of the Curve of Areas compare heeled and upright Centres of Buoy- to have the volume of the underwater body of ancy without putting a single calculation on the boat in cubic inches. paper. Displacement in Cubic This gives us the Inches, and The novice should be reminded that if the the body plan represents half-sections, so for weight is required, all that is necessary is to the heeled Curve of Areas, having measured divide the Displacement in Cubic Inches by the half of the section embodying the in-wedge, the number of cubic inches of water that go to he must take the other half that is minus the 1 lb. out-wedge from the same side of the centreline. In the case of fresh water this is 27°65 cu. in, and 27 cu. in. of salt water. The It should be added that a Curve of Areas can be measured with a planimeter above methods of ascertaining the position of the C.B. only give its fore-and-aft if desired, position, which is all we need for our present though this is usually calculated as the figures purposes. If its height is also needed, this can are required for calculation of the C.B. be found as detailed in a later chapter. Turning to the question of buoyancy and Before passing from the design of the canoe the C.B., the force of buoyancy can be regarded body of the hull, it might, however, be as well as being a force equal to the weight of the to investigate some of the features that make yacht that supports her from below, and if this for speed, as the qualities that govern this are force can be considered as concentrated and inherent to this part of the design. acting through a single central point, the Any consideration of the speed poten- reader will be able to realise exactly what the tialities of a yacht must be considered from the C.B. consists of. vessel displaces a volume of water equal in point of view of the inclusion of factors that make for speed and the exclusion of factors weight to her own weight, and therefore the that detract from it. Actually as mentioned, the C.B. is the Centre of Gravity of the displaced volume of water. Now in the comparison of a model with the In order to find the position prototype, or of a small yacht with a large one, of the C.B., the C.G. of the displaced volume of it must be remembered that the wind has the water has accordingly to be calculated. same force for all vessels, whether they are 57 MODEL small or large. smaller really striving to get the maximum sailing vessel reaches her maximum potential speed length possible, and the whole hull design sooner. resolves itself into that consideration as far as When Consequently this has been the SAILING CRAFT reached exceeded she becomes overdriven. yacht is, therefore, more driven than her larger The small frequently sister. and This speed is concerned. Undoubtedly, quite apart over- from any considerations of rating rules, the means necessity to get sailing length is the first con- that a relatively higher potential speed is even sideration of the designer who aims to produce more essential to the smaller yacht than it is to a speedy vessel, but other features have to be the larger, and further, that she requires to be studied, and it may be said that all naval proportionately more powerful, even if this architecture is a compromise. implies the sacrifice of something under very In arranging a design so as to get the longest light weather conditions. possible sailing length, not only the profile and In her forward motion through the water a the angle it makes at the L.W.L. endings have vessel creates a trough in which she is borne. to be considered. That is a wave system her overhangs is governed by her form, and in having a crest at her bow and another at her this connection the distribution of displace- stern. ment is most important, and also her actual to say, she creates The faster she moves the farther apart How far a yacht will use are these crests, until the boat reaches her shape. maximum potential speed. low-speed potentialities, as she will offer great resistance to forward motion. The fineness or otherwise of a vessel’s form can be judged This wave system is governed by the same laws as other waves. A boat with a coarse model will have The greater distance apart the crests (regardless of the depth of the by her Co-efficients of Fineness. In order to trough), the faster the waves travel, and the obtain any useful data, these must be calcu- speed of the boat is, therefore, governed by her lated on the canoe body without the keel abilitv to set up a long-wave system. appendage. This ability to set up a long-wave system is in turn, regulated by the actual length that the the Co-efficients of Fineness, and, in addition, The reader has already been introduced to to their use in estimating what a vessel’s dis- vessel herself is able to use. In this connection neither L.W.L. length nor L.O.A. count, and it is o#/y sailing length that matters. placement is likely to be from her midsection, but their main function is to enable the designer to judge the fineness or otherwise of a hull. This is merely another way of repeating the old adage that length means speed. This has been amply proven more than once in the case of steamships which have been lengthened to increase cargo-carrying capacity, and have gained an increase in speed whilst In order to obtain any useful data, these must be taken on the canoe body only without the keel appendage. The use of Co-efficients of Fineness is really only for purposes of comparison, and a great deal employing the same engines and boilers. All other things being equal, a longer and larger vessel should be faster than a smaller one. A common instance showing the difference in potential speed due to difference in length may be cited. If one tows a 9-ft. dinghy at 5 knots of experience become beginner is of any use to is, therefore, needed the before designer. advised to be they The very chary of their use, as without the necessary experience he may be led astray. Another feature that may detract from a behind a 25-ft. yacht, the yacht will slide through the water with hardly any disturbance, whilst the dinghy behind her creates a great fuss. In fact the dinghy is being overdriven whilst the yacht is maintaining her normal boat’s speed is skin friction. In this connection quality is of more importance than quantity. A comparatively small area of wetted surface that is not absolutely smooth may set up more skin friction than a larger surface of smooth skin. Provided the surface is really smooth, skin friction does not form a speed. The designer, in trying to get high speed, is 58 S OF to the design of a modern sailing yacht. Designers sometimes employ tumble-home to reduce the volume of the in-wedge, but as a proportion of the total resistance t low speeds, so the amount that can be is not sufficient to SPEED warrant any un- reasonable cutting away of surfaces. Useless wetted surface is, of course, to be avoided, as general rule it does not have any great effect in is the water when sailing and make full use of her overhangs depends on a correct distribution of displacement, so that she makes a trough in the water for herself. Another use of tumble-home in the case of a boat with rather a high freeboard, is to avoid any semblance of being wall-sided. The third and most practical use of tumble-home is to anything resistance. else that needlessly this respect. increases More will be said on this subject later in the book. Reference has been made to length in con- nection with wave-making, and also to the low speed potentialities of vessels having a coatse form. The connection between these facts should be explained. It was stated that For a boat to get well down in waves having the same length between their keep the decks dry. crests travel at the same speed, regardless of This is correct, but it should be added that the flatter the wave the less energy does it require Uffa Fox and Mr. Morgan Giles make a very to is best omitted. clever use of it for this purpose. the depth of the trough between them. propel at this maximum speed. In In racing dinghies, Mr. As far as small models are concerned, tumble-home serves no practical purpose and a In larger models such as an similar way a vessel with a fine form that makes A-class, it can be used to enhance the appear- a flat wave requires less energy to propel at her ance of the yacht, though it will not have much maximum speed. beneficial effect on her sailing qualities, unless Consequently the sweeter lined hull is easier driven, and reaches its maximum speed sooner, or alternatively it is requires less sail to enable it to attain this speed. heeled to a big angle. an infinitesimal reduction of windage surface on the weather side when the boat is This applies to the design of any boat, but, Deck camber is another point which might above all, is a consideration when a designer briefly be considered. is engaged on a class boat where the rating is a compound of hull and sail measurements. “round of beam” (.e., deck camber) is limited. Careful consideration is needed in this respect reason that a road is cambered, in order to in order to get the combination of hull and drain water off it. sail that will give the best result under the rule. not analogous with a road surface, as the deck The calculation of wetted surface is a matter cants with the heel of the vessel, and even if that, as a general rule, has little value from the the deck was dead flat, most water would run Under some rating rules, Nowa deck is cambered for exactly the same But a sailing yacht’s deck is model designer’s point of view, but in case it overboard as she heeled. is required the method of so doing is explained therefore, unnecessary, and as will be evident in a subsequent chapter. Reference has already been made to tumble when we come to the making of deck beams home. tional point of view. Excessive camber is, in a later chapter, inadvisable from a construc- Tumble home was very extensively In a model where the used in medizval ships, where it served many deck is usually made from one piece of wood, practical purposes, one of which was that it it is also inadvisable as the deck itself has to facilitated the efforts bend in two directions—with the sheer and boarders. of the crew to repel These considerations do not apply with the camber. 19 CHAPTER VI The Keel Appendage. and Rudder. Lateral Planes and the C.L.R. Forms of Keel Appendages. Drawing the Keel Comparison of Fore-and-Aft Position of Centre of Buoyancy when Vessel is Upright and Fleeled. Calculation of Lead Keels. HE canoe body of our boat is now is useless in yacht design, as it does not make complete and ready to receive its keel for success. appendage, means, and the secret is beauty of line, balance, but, before proceeding with this, a short digression should be made in order to discuss a few points that have to be borne in mind in making any design. Success is attained by the simplest and a correct estimation of the type and dimensions likely to be successful under any given rating rule. For the purposes of explaining the processes of design, it has been found necessary to divide of underwater profile for models, it would be the subject into different sections, and hull design and sail design are dealt with under a merely mechanical point of view as apart from Now, before considering the vexed question well to consider what the keel has to do from separate headings. It was also advisable to subdivide hull design into the canoe ‘body and the keel. If this procedure had not been have a big, powerful type of model. followed, the explanations would have been one hand is a large sailspread trying to heel the of necessity so involved that the student would not have a fair chance of grasping the different boat, and at the other extreme a heavy lead ptinciples. all its influence on performance. ‘Take the case of an A-class boat in a heavy wind. keel striving to keep her upright. Here we On the Shorn of Yet actually the canoe body and the keel are really parts of the same thing, and the hull, including the keel, must be considered language, what is happening? as a Single entity. ballast are two forces at opposite ends of a Again, keel design and sail technicalities of heeling and righting moments, and stated in the plainest possible ‘The sail and the design are intimately connected and bear the lever, and each is striving for mastery. strongest strain on the arms of the lever is, of course, relationship. For instance, it is The entirely useless to have the finest sail-plan in tremendous. the world if it is above a keel that is unsuitable. In fact, a yacht design must be treated as a and the chain plate must be of great strength. whole whilst each of the component parts is Moreover, the bar-taut shroud immediately In the case of the mast, the weather shroud takes the brunt, and both this considered not only in relation to itself, but in sets up a powerful downthrust on the mast, relation to the complete design. which in turn presses on the mast-step. This Again, in drawing the plans of a yacht, the puts a great strain on the weather side of the designer has always to bear in mind construc- boat, and, unless due precautions are taken, the tional difficulty. In this connection the model sheer may be pulled upward at the chain-plates, yacht designer, who has never built a planked with the result that the boat “‘ hogs ” (7.¢., the boat, may be misled, as it is possible to carve middle of the sheer is pulled upward and the out or build up features that would present the ends droop). greatest heavy craft, an internal stay is fitted from the building. difficulty If a of hull execution planks up in plank easily In order to obviate this in big, gunwale in the neighbourhood of the chain- and sweetly, it. follows that her /imes are easy and plates sweet, and in all probability she will prove a described in the chapters on building. good boat in consequence. if it passes over a spreader (or cross-tree), the shroud through the spreader arm imparts a Turns that are so abrupt that they present difficulty in planking, the keel under the mast-step, as Again powerful side thrust to the mast, which in turn is supported by the lower shroud. peculiar reverse twists and so forth should be avoided. to Striving after effect by these means Go From the real yacht builder’s point of view the flat-plate type of keel has the advantage that ther end of this lever arm is the lead naturally there is an even greater side on this part of the structure. It is it is easy and cheap to construct, especially on obvious, therefore, that the keel design must boats of a shallow type, and it is consequently give sufficient strength and rigidity. Cases have been known in real yachts fitted with bulb- used for craft such as Norfolk Broads yachts. fin type keels, where the metal fin has bent and would not amount to anything, and except in buckled under the strain. However, the saving in cost on a model yacht Apart from any models, such as a Sharpie, where such a keel 1s considerations of displacement gain or loss, the strictly in keeping with the design, the model bulb-fin type of keel is unsuitable for heavy designer will be well advised to eschew the displacement craft for constructional reasons. type altogether. On the other hand, the bulb-fin has certain In designing a boat, the object is to create a As hull that presents the minimum of resistance to will be explained a little later, the flat surface forward motion and the maximum of resistance of the plate is more efficient, area for area, from to sideways motion; in other words, the boat the point of view of lateral resistance, than a must make as keel presenting a convex surface. leeway as possible. advantages for light displacement craft. Also the much headway and as little actual angle between the plate and the canoe If a boat is at rest in the water and we try to body of the hull is not detrimental to lateral push her sideways, she will offer resistance. resistance, but rather the reverse, and, finally, This on a limited displacement this form enables the lateral plane. weight to be carried very low. this plane has equal value in resisting lateral Conversely, the filled-in garboard lateral resistance is derived from her Whilst the boat is at rest, all movement, but when the vessel starts to move gives greater displacement, and where it is desirable this is entirely altered. Before considering to have a greater displacement, this can be put what happens when the vessel starts to move, in the garboard and the lines of the hull fined it will be as well to explain what the Centre accordingly. of Lateral Resistance is. In this connection stability Now there are If a pole was taken and placed against the two kinds of stability that a boat can have— vessel’s side and used to push her sideways, natural stability from the form of the canoe somewhere towards the centre of the boat a body, spot could be found where she would balance so that, when pushed, she would move bodily comes under consideration. and ballast. A artificial beamy, stability given flat-floored, by the hard-bilged boat such as was shown in Fig. 18, has great initial stability, but loses If the pole were placed when heeled too near the bow, the bow would swing away. On the other hand, a narrow hull with an easy bilge will have very If too near the stern, the stern would swing away. At just this one spot the boat would small initial stability in her hull form and must move evenly sideways. depend on her ballast. Stability due to hull is, in fact, the centre of gravity of the plane form rapidly decreases to the vanishing point enclosed by the underwater profile of the vessel once the boat is heeled well over, whereas and the L.W.L. stability due to ballast gives a more powerful to any great angle. this and evenly sideways. This is the C.L.R. It further. The method by which this is calculated is exactly similar to that used for the calculation Again, the narrow, easy-bilged hull is easier of the C.B. from the Curve of Areas, and either to drive and has an easily-driven form, putting a good propor- Simpson’s Rule or the Trapezoidal Rule can be used. It should, however, be noted that as the figure formed by the underwater profile tion of displacement into the garboards and changes rapidly, the ordinates should be spaced rely mainly on ballast to give the necessary pretty closely together. stability. made in this calculation between the canoe body righting moment as the boat heels a higher potential speed. In designing it is therefore preferable to use GT No differentiation is MODEL SAILING CRAFT and the keel appendage, although, as will be seen shortly, there is a great difference in their is shown in Fig. 30. For the purpose of ca culating the C.L.R., this is divided into two values as lateral plane. parts on Section 15. Some designers do not take their rudders by taking 6-601. ! yj Cra #o., 6:40 l= 6.20 found ‘This will be perfectly clear to the i) COmeiNED ¢. | md moments. In the case of racing dinghies, C.L.R. a) take a portion. combined 5-95 |» The 6:80 [oe into calculation as lateral plane, others only 5 The C.L.R. of Sections o-15 is then found, also that of Sections 15-16. \ FIG. 30. NYSa CALCULATION OF CENTRE OF LATERAL ResisraNce (C.L.R.) oF FuLrt-KEEL YACHT. In this centre of part of lateral plane from Section o to Section 15 is calculated separately. The centre of part between Sections 15 and 16 is also found separately. The combined centre of these two parts is then found and is the C.L.R. where the larger part of the lateral area is reader after reference to the worked example represented by the centreboard and rudder, it shown in the next column. When the boat is of the fin-and-skeg type, is certainly essential to take the rudder into calculation. as shown in Fig. 31, it will be necessary to In the case of model yachts the rudder should be considered as forming part of further divide the lateral plane. the lateral area. shown in this diagram is that of the little 36-in. model which we are designing, and it This to a small extent com- plicates the calculation, as the shape to be ‘ CLR rel I The profile | | | CLR oF A 6B – c D c 13-37 20-72 22-86} abalt Sovward end of LWL Fic, 31. CALCULATION OF C.L.R, oF FIN-AND-SKEG YACHT. calculated becomes an irregular figure owing to the gap between the top of the rudder and Consequently the lateral plane the hull. bounded by the underwater profile of the yacht has to be divided up into suitable parts (See text.) will be seen that it has proved necessary to divide the lateral plane into the five parts A, B, C, D and E. The centre of lateral resistance and area of each part is then found separately, and the combined C.L.R. calculated which are separately calculated. The combined centre can then be found quite easily. The underwater profile of a full-keel yacht by taking moments. It will perhaps make the matter quite clear if it is mathematically stated as follows: 62 LCULATION C.L.R. moments, using distance aft of Station No. o ual area of part A and a the distance . is astern of the forward ending of .W.L. HE O as the Arm. Let B and @ likewise equal area Forward Part After Part distance for part B, C and ¢ for part C, D and d for part D, and E and e for part E. Area Arm Moment 109°66 & 15°98 = 175§2°37 o80 KX 27715 == = =21°72 . Then the combined C.L.R. equals 110°46 (A Xx a)+(Bxb)+(Cxe)+(Dxa+(Exe)] Therefore C.L.R. of whole Lateral Plane is = in. +(A4+B+C+4+D+E6E) abaft Station No. o = 16-06 in. Now let us work out the C.L.R. of the yacht shown in Fig. 30. A simple method of finding this combined centre, which is recommended as being quick and accurate, is to cut out the shape of the entire profile, including rudder, from cartridge CALCULATIONS OF THE FORE-AND-AFT POSITION oF C.L.R. Station Length of No. Ordinate Multiplier Functions Arm Moment Oo O00 K OF§ = OOO XK o = 0°00 1 o60 X I0 = o60 xX I = oo 2 rI7 xX %I0 = ITI7 xX ee es 4 paper and balance it on a pin-point. Unfortunately for the designer, the position of the C.L.R. only remains constant so long as 3 167 X %$ITo = 167 X 3 = 5°01 4 220 XX 10 = 2:20 X 4 = 8°80 § 302 xX 10 = 3°02 X 5 = I5§’Io 6 7 8 445 560 Go5 TM* xX xX 10 10 10 = = = 445 560 Gos xX xX xX 6 7 8 = = = 26-70 39°20 48-40 9 Io II 12 620 640 660 680 xX XX X XX To T0 tI0 10 = = = = 620 640 G60 G80 xX * %* %*% 9 I0 %«I1 12 = = = = 55°80 64:00 72:60 81°60 13,595 14 480 X TO = = $95 480 X 13 = 77°35 57°20 boat 15 230 % of = 15 XK 15 = 17°25 undisturbed * 10 62-66 % 14 = the boat remains motionless. In order to differentiate during the further discussion of this matter, we will refer to the true C.L.R. as the “ Actual C.L.R.” and the calculated C.L.R. as the “* Calculated C.L.R.” Firstly, let us consider the whole lateral plane as if it were a flat plate. moves forward water, it Now, as the constantly and meets consequently the resistance encountered by the forward part 571-95 of the boat is greater than that encountered The distance between the ordinates (7.e., their spacing) = 1774.09 by the after part, which meets water that is 1°75 in. already in motion. Therefore Area of Lateral Plane= 62°66 « 1°75 sq. in. = 109°66 sq. in. This increases the pressure at the bow and decreases it at the stern. Centre of Gravity of Lateral Plane (#.e., C.L.R.) is There- fore the resistance of the forward part of the – es a * 1°75 in. abaft Station No. o (forward lateral plane to sideways movement is greater L.W.L. ending) than that of the after part. = 15°98 in. moves, the greater this The faster the boat difference becomes. Now in that part of the lateral plane aft Whilst the boat was at rest the whole lateral of Station No. 15, owing to the sudden change plane was of equal value in resisting sideways in contour, the ordinates will have to be very thrust, but under way the forward part is the much more closely spaced to get its correct most valuable. area. An exact parallel may be drawn from aero- This portion of the lateral area (7.e., between Stations 15 and 16) is then worked out separately in a similar way. Its area is then found to be o-80 sq. in. and its C.L.R. is o-4 in. aft of Station No. 15. As Station No. 15 is 26:75 from fore end of L.W.L., centre of this part is 27-15 in. aft of it. The combined C.L.R. of the two parts of the lateral plane is now found by taking dynamics. The best illustration is to think of a leaf falling from a tree. ‘This never falls straight to the ground edgewise, but planes gently down from side to side. What actually happens is that the leaf has a natural tendency to keep its plane surface horizontal, and so it planes towards the ground, one edge being slightly lower than the other. 63 As it gathers MODEL §S speed in that direction the centre of pressure shifts towards the leading edge, which con- each design, there can be no specific in placing it at any given distance from t sequently develops more lift than the back forward end of the L.W.L. edge. It then of the position of the C.L.R. in percentages of the L.W.L. from the forward end. Thus, in a starts to fall again but with the other edge as 1oo-ft. waterline boat, if the C.L.R. was at 58 leading edge, when the process is repeated. per cent. L.W.L., it would be 58 ft. from the The front edge then tilts upward and the momentum of the leaf is arrested. Thus the leaf comes down with a gently planing motion that reverses from side to side. It is usual to speak forward L.W.L. ending. The Some designers pin their faith to given posi- movement of the pressure towards the leading tions for placing the C.L.R., but, as has been edge is known as the “‘ shift of the centre of shown, nothing definite can be based on such pressure data. towards the leading edge.” This torward shift of the centre of pressure is also The main use of the calculated C.L.R. is, therefore, to use as an assumed centre for a very important consideration in sail design, reference when the sail-plan is being designed but the designer has to remember that in this and placed over the hull. respect the design of keels and sails is Our next consideration is the shape of the analogous. Now it has C.L.R. moves lateral plane. It is a generally accepted theory been shown that the actual that the actual C.L.R. moves forward. forward, this is true as regards the C.L.R. of the canoe but there is also Whilst another consideration that must be taken into body and the keel appendage taken separately, account. it does not follow that the actual C.L.R. of the As has been pointed out, the lateral plane is in part the underwater body of the whole underwater hull moves forward. The hull proper, and in part the keel appendage. movement of the actual C.L.R. of the whole Of these the canoe body presents a more or less is governed by the area of the keel in propor- saucet-shaped surface to resist lateral move- tion to that of the canoe body, the position of ment. Obviously, quite apart from actual the former under the latter, and, above all, by area, this saucer will be easier to push sideways the contour of the leading edge. than the keel appendage, which is practically a flat surface, In the case of a yacht (Fig. 32, Diagram A), ‘This difference is marked even where the area of the canoe body is equal to that at rest, but directly the boat starts to travel of the keel, it is obvious that when the vessel is forward it becomes more marked, and the faster she travels the greater is the difference in power to resist side thrust. Now it is quite at rest the C.L.R. will fall on a line joining the feasible to calculate this difference for various becomes increasingly more efficient in relation separate centres of the canoe body and the keel, exactly midway between them. As the keel speeds, but, as the vessel does not maintain to the canoe body when the vessel travels any given speed, but constantly varies, this would not be very useful. Moreover, the resistance would depend on the shape of the profile, and as this constantly varies with the angle of heel, it can be seen that it is impossible forward, a tendency will be produced to drag to gain any reliable data from these calculations. Again, the actual C.L.R. is very much influenced by the type of hull and shape of the waterline plane, but these also vary. One is, therefore, forced to the conclusion that the actual C.L.R. moves about, and all that the calculated C.L.R. serves to show is the point from which its movement starts. Moreover, this forward shift in the keel takes place is the centre of the whole towards the C.L.R. of the keel. keel, On the other hand, the centre of the taken by itself, moves forward rapidly than that of the canoe body. more How fast entirely governed by the angle of the leading edge. If the forward edge of the fin was vertical when the boat was on an even keel, the forward shift would be much more violent than if it were a long raking line. The angle of incidence of the leading edge is, therefore, of great importance, and an angle of about 45 as the movement of the C.L.R. is different in 64 degrees will be found very suitable. It _ MOVEMENT OF C.L.R. is shown having approximately the same area required as well as its fore-and-aft position, it can easily be calculated by the following method. The whole lateral plane is first divided into two parts by a vertical line passing through the lowest point of the keel. It should be noted that, if necessary, more than two parts can be used. This vertical line forms the base- and C.L.R. The combined C.L.R. would be line for calculating the C.L.R. of the two parts the same as for Diagram A whilst the yacht separately. Divide the vertical line into any convenient number of equal parts and erect ordinates at these points. Incidentally, these ordinates will be parallel to the L.W.L. The ordinates are duly measured and the vertical position of the C.L.R. of each part that in this diagram the leading he fin is at approximately the angle mended. The skeg and rudder were omitted from this drawing in order not to complicate matters. In Fig. 32, Diagram B, another shape of fin was at rest. When, however, she started to move forward, the steep angle of the leading edge of the fin would cause a violent forward shift of the centre of lateral resistance of the appendage, and consequently of the actual =r DIAGRAM A a DIAGRAM B FIG. 32. (SEE TEXT.) CENTRE OF LATERAL RESISTANCE. C.L.R. of the whole lateral plane, which would move forward far faster than that of the yacht in Diagram A. The reader will have noticed that the instructions for finding the C.L.R. given earlier in this chapter only covered the method of determining its fore-and-aft position, whereas the exact position is used in the illustration just cited (Fig. 32). The use of the exact calculated by Simpson’s position was necessary to explain the manner proceed with our discussion about the angle in which the C.L.R. moves about. general of the leading edge of the keel, and how its rule it is unnecessary to calculate the exact area is to be placed under the canoe body of position of the C.L.R. unless it is being used the boat. for matters so that the tendency stability calculations, as Asa mentioned in The combined or the Trapezoidal C.L.R. is found by taking moments in exactly the same fashion as when finding the fore-and-aft position. Given the fore-and-aft position of the C.L.R. and its vertical height in relation to the L.W.L., its exact position can be plotted. However, all we need for present purposes is the fore-and-aft position, and we can now It must be our aim to arrange these of the actual C.L.R. to move towards the centre of the flat Chapter IX. If, however, the height of the C.L.R. is also M.S.C. Rule. keel is compensated by the drag of the leading 65 F MODEL SAILING CRAF edge. it is too far aft, the rig will have to be t of the keel at the correct distance aft of the centre of the area of the underwater body. This, unfortunately, is not a matter that can be cal- at all. tendency of the C.L.R. of any body is to shift culated, but largely a question of experience. towards the leading edge as forward progress Hence all that can be done is to give the novice is made through the water, and, further, that guidance as to the principles involved. a plane surface (such as the appendage to a It will be seen that the only method by which this can be done is by placing the centre Unfortunately, if the keel is incorrectly far aft in order to make her point to windw: Now it has already been shown that the yacht) increases its power more rapidly placed, steering tendencies will be introduced than the canoe body of the vessel. that in a model will prevent her ever performing to her owner’s satisfaction, and in a real therefore, possible to arrange the appendage yacht may be highly dangerous. of the appendage shifts towards the leading It must not It is, under the hull so that, although the C.L.R. be imagined, however, that this is the only edge whilst the C.L.R. of the canoe body moves cause of undesirable steering tendencies in a similarly, vessel. appendage in proportion to the power of the Another very prevalent cause is lack yet the increased power of the of hull balance and a movement of the C.B. in canoe body drags the combined C.L.R. of the a whole lateral plane either forward or aft in fore-and-aft direction various angles. when heeling to This was explained early in Chapter IV, and is again referred to later in this book. accordance with the relative positions of appendage and canoe body. In consideration of the relation of the Centre It can be said that the elimination of every- of Effort of the sail-plan to the C.L.R. of the thing that produces undesirable steering effects hull, it must be remembered that the C.E. also is about the most important part of a naval moves forward towards the leading edge. architect’s work. spite of this, however, it would be extremely A tendency to gripe into the In wind is bad, but a tendency to run off is far difficult to arrange the C.E. over the C.L.R. in worse. If this tendency to run off is present in such a manner that forward movement of the a large yacht, it may be very dangerous, as C.L.R. would be counterbalanced, but, even if under certain conditions it may develop to this was accomplished, it would not be an ideal such an extent that the rudder is powerless to arrangement by any means, as there would be counteract it. a conflict of opposing forces, and any such It was undoubtedly this feature that caused the roo-ft. L.W.L. yacht “ Satanita ” balance would be a compromise which would to ram and sink the “‘ Valkyrie ” on the Clyde result in loss of speed. many years ago. Weight Arm o8lb. 1-0 ,, 18-80 in. BRE… 15°04 2°25 O45 5, 077 LS on Moment 3°5 Ib. Item _ Below L.W.L. Weight peadwood, Skeg & Rudder °°5 Ib. SB WAI Fre. 36. 18-06 Arm 3*60in. 972 99 6°8 lb. Moment 48 Shown in Fig. 36 for our little 36-in. boat. 180 35°91 The C.B. can now be found either by cutting out the shape of the Displacement Curve and 37°71 balancing, or calculated by either Simpson’s or the Trapezoidal Rule. If calculated, the dis- C.G. below L.W.L, =22 27 SOT gr ‘>, Placement can be taken out at the same time 3°5 + 6°8 and will serve as a check on our calculation by means of the section areas. As an example we have worked out the vertical position of the C.B. of this boat (see page 76). Apart from anything else, two important lessons can be learned from this little calculation—the importance of minimising weight aloft and the necessity of getting the lead As the waterline spacing is x in., the Funcof Areas x Spacing = 13955 x I tions ballast as low as is practicable. * * 6 VerticaL Curve or Areas (or D1spiAceMENT CurVE). 139°55 cu.in. > There is a very small portion of the keel below W.L.1; its area can be calculated or it will be near enough if we estimate Ina previous chapter we have seen how to 7) MODEL it at 1 cu. in. SAILING The total displacement is, therefore, 140°55 cu. in. When we calculated CRAFT If it is desired to find the C.B. of a single section it is done in a similar way. this on the section areas we found it as 140°35 Another method of ascertaining the C.B. is cu. in. for the half-body, so this is quite near by the use of an instrument called an “ Inte- enough to pass. grator,” but as model yacht designers are very To find the C.B., the Moments are divided by the Functions of Areas multiplied by the Spacing. and 187:26 + 139°55 X 1 = 1°35. tion the result We, therefore, get of keel below W.L.1 these instruments this need not be gone into here. The small poris too * small to influence the result, so that C.B. is 1-35 in. below L.W.L. The unlikely to possess, or have the use of, one of * * * We can next consider the Metacentre, but let us start with the forces that act on a vessel’s transverse C.B., when the vessel is heeled, can be calculated, but this is a very complicated and laborious process, and Blom’s method, which is a purely mechanical one, is recommended. hull. Buoyancy can be considered as a sup- porting force upholding the vessel, with its vertical up-thrust concentrated at the C.B. Gravity can be considered as a depressing force with its down-pull acting vertically The shape of the underwater portions of downward through the C.G. the sections, taken up to the waterline at the Now it is obvious that when a vessel is on desired angle of heel, is pricked off on to thin an even keel, a line produced vertically upward through the C.B. coincides with the centreline. Directly she heels, the C.B. will automatically shift over to leeward. At the same time, since the in-wedge is larger than the out-wedge and the vessel does not increase her actual displacement, she rises bodily in the water until the in-wedge and out-wedge are exactly equal. cardboard from a tracing of the body plan. These sections are then cut out with scissors and pasted lightly together in their correct relative positions. Do not use more paste than necessary as the weight may interfere with the balancing. now to The common centre of gravity has be determined. This is done by suspending the bunch of sections from two or more points at the edge of the card and noting where the plumb lines from the points of suspension intersect. Points should be selected so that the plumb lines do not intersect at too acute an angle so as to get a good sharp cut. The point of intersection is the C.B. and its distance from the centreline can be measured in a direction parallel with the heeled water-line. CALCULATION OF VERTICAL C.B. W.L. Nos. LLW.L. 7 Areas of W.L.’s 82-70 §7722 6 23°24 5 4 3 2 I R250 316 449 496 255 Functions Multipliers XK Of = §722 ; Ll = = = 23724 B25 316 X 2= KX R= KX 4= 46-48 9°75 12:64 *% X & = IT = 1 o5g= 449 4:96 128 % § = X 6= X7= 22°45 29-76 8-96 139°55 FIG. 37. Arm Moments XO= 0:00 XX XX 1 KT 1 X = of Areas 41°35 % l= = This is shown in Fig. 37, where W’ represents the heeled waterline, G the C.G., B the upright C.B., and B’ the heeled C.B. If a vertical line is produced upward through B’ it meets the centreline (7.e., the original vertical through B) §7°22 at M, which is the Metacentre. 187-26 As the C.B. varies for every different angle 76 As an example of this calculation, our 36-in. model works out :— , possible ; pe such that the meta- Sect. Nos. Half-Breadths Cube I 0°00 0°00 for all normal angles of heel. called a ““ Metacentroid.” ‘There 2 1°50 3°37 lar virtue in this, however, and, 3 2°86 23°39 seen later, it is likely to be more 4 5 6 3°78 4°27 4°30 54°01 77°85 79°51 ental than otherwise for a racing yacht all events. 7 For small angles of heel (up to about 10 degrees) the height of the Metacentre (M/C) 8 remains practically constant. It can be calculated by the following formula:— The height of the transverse M/C above the C.B. is equal to the moment of inertia of the 9 3°92 60-24 0°00 0:00 3°02 27°54 Less $4 sum of first and last ordinates waterline plane about the centreline divided by 325°91 0-00 the volume of the displacement, or I BM=5 Multiplied by Station In- terval This entails the ability to calculate the Moment of Inertia of the waterline plane » 325°91 3°5 162°95 about the centreline, so we must digress to 977°73 explain how this is done. 1140-68 Moment of Inertia I104°68 X 2 = 760 We have found the Volume of Displacement of this boat to be 280-7 cu. in., so:— As we have found the C.B. is 1°35 in. below L.W.L., the M/C is 2-71 ~— 1°35 = 1°36 in. above L.W.L. We have also found that the C.G. is 1-91 in. Fic, To obtain the Moment waterline plane about its measure the below the L.W.L. 38. half-breadths The M/C height GM is, therefore, 1-91 in. plus 1°36 in. = 3:27 in. of Inertia In Fig. 38 we have the usual M/C diagram of a in which @ = the angle of heel and a (which is longitudinal axis, at each the distance between B’ and G in a direction section parallel to the heeled waterline) is the righting station, cube these and apply the Trapezoidal Rule to the cubes, the result being multiplied Arm. by 2. If the drawing is not full-size the halfbreadth widths should be scaled up first. Displacement multiplied The Righting Moment of the boat is Otherwise the sum of the cubes must be multiplied by the cube of the inverted scale (¢.e., if the drawing is half-size the sum must be above C.G.). by Righting Arm. The M/C Height is GM (7.e., Height of M/C The actual formula for calculation of the Righting Arm is:— multiplied by 8). GM sin 0 = Righting Arm, 77 and that for Stability :— D x GM sin 0 = Righting Moment. As an example, let us work these out for our 36-in. boat :— We know that GM = 3:27 in., and let us assume that @ the angle of heel is 20 degrees, then :— 3°27 sin 0 = 3:27 X +3420 in. 1°11834 in. — = Righting Arm. We also know that D is 10-3 lb., so:— 10*3 X 1°11834 = 11°5189 inch-lbs. 184°32 inch-oz. = Righting Moment. This is not a difficult calculation, but entails the use of logarithmic tables. Something will be said about its uses in a later chapter. At the same time model yachts require very ample stability. Hence the model designer usually relies on experience and omits these calcula- tions. Another way of finding the Righting Arm is to find the C.B. of the hull in a heeled FIG. 39. VESSEL IN CONDITION OF STABLE EQUILIBRIUM. is shown rolling heavily in Fig. 39, and she is assumed to have a heavy cargo below hatches and alight deck cargo. The force of buoyancy thrusting upward through B’ and the force of gravity pulling downward through G, both combine to give the vessel a strong righting position by Blom’s method, and plot it and measure. Obviously the greater the distance the C.G. is below the M/C the greater will be the sta- bility of the vessel for any given angle of heel. It is also evident that two considerations enter into the stability of the hull—its form as affecting the position of the C.B., and the weight and its disposition as affecting the position of the C.G. As long as the C.G. is below the M/C the stability is positive and the hull will return to an upright position. When the C.G. coincides with the M/C the stability is said to Fic. 40, be neutral, but when the C.G. is above the M/C the stability is negative and the vessel will capsize. It is not necessary for the C.G. to be below the C.B. for her to be stable, but moment. VESSEL IN CONDITION OF UNSTABLE EQUILIBRIUM, In Fig. 4o the same steamer is shown, but this time she has a heavy deck cargo and a light cargo below hatches. The desirable to have the C.G. as low as possible C.G. is now above the M/C, and the force of buoyancy and the force of gravity are combining to capsize her. While this instance does to have a powerful righting moment and thus not concern the model yacht designer, it is enable the vessel to carry her sail. included to enable him to get a grasp of the it must always be lower than the M/C or she becomes unstable. In a sailing vessel it is influence of sails, the vessel is apt to have a whole principle of stability and the M/C. It will have been noticed that when we jerky motion if the C.G, is too low. compared the fore-and-aft positions In a steamer which has not the steadying A steamer of the e hull on an even keel and heeled, nce was made for the hull rising the in- and out-wedges were equal, as all normal angles of heel, and it is possible to design a Metacentroid with either a low M/C or a high M/C. Probably, for reasons of shown in the M/C diagram above. Fortunately for the designer, when a vessel is stability, she would be designed with a high sailing she tends to settle deeper in the water, due partly to the downthrust of the wind in disadvantage in light winds, when opposed. to her sails and partly to the arrangement of dis- under these conditions to her sailing angle, placement in the design. and yet has It is, therefore, suffi- M/C, and such a boat would be at a great a well-designed hull that heels plenty of power to readily carry her ciently near if we consider the heeled L.W.L. sail in heavier winds. as passing through the intersection of the only be attained by designing a hull in which upright L.W.L. and the centreline. the M/C alters its height to suit prevailing con- Another point is that in making these tests ditions. This desideratum can This applies to racing yachts particu- the extreme effective angle of heel (varying larly, but as cruisers Metacentroids might be with the yacht herself) is taken for purposes of comparison with the upright hull, since if suitable, particularly in types which are designed to sail as upright as possible and not the hull is balanced upright, and at this extreme to be pressed to extreme angles of heel. angle of heel, she will be balanced at all inter- * mediate angles. * * 2K If the reader will take the trouble to draw a Much has been heard in recent years about few sections of different types and take out Admiral A. Turner’s system of balancing a their M/C at various angles of heel, he will find the M/C a very useful and reliable guide as to hull, but very few yachtsmen or model yachts- performance. men have really understood it. This, we It will immediately be apparent believe, is due to the fact that it has been that beam has an immense influence on the described as the “‘ M/C Shelf” system, whereas position of the M/C. For instance, the beamy it is simply a method of checking the distribu- scow has a very high M/C at low angles of heel, but once a certain angle is exceeded, her M/C tion of displacement in the hull by balancing begins to fall very rapidly. Buoyancy. This indicates Moments of Buoyancy about the Mean Axis of The modus operandi is as follows :— great initial stability, but increasing tenderness Find the C.B. for each individual section of once a certain angle of heel is exceeded. On the other hand, a boat with a deeper, narrower section has a comparatively low M/C at small angle of heel, but the M/C rises rapidly as the angle of heel increases. This indicates that the the boat for the full L.W.L. length when heeled to the same angle as was used for the Vol- umetric Balance calculations. Also find the transverse C.B. for the whole boat at the same angle. Do this by Blom’s method as pre- boat will heel readily to her sailing angle in light breezes, and become increasingly stiff as viously described. her extreme boat in its heeled position on the body plan instance of this type is the ‘* plank-on-edge.” draw a line perpendicular to the heeled water- and though it is not desirable to go to this line. extreme for many reasons, it is through angle of heel increases. The Through the transverse C.B. of the whole a distinct This represents a vertical plane passing the boat’s C.B. The M/C shelf advantage for a racing yacht to have a low balance has to be plotted about this vertical initial stability that increases rapidly as the heel increases. In this way a yacht readily lengthens her sailing waterline in light winds and yet has plenty of sail-carrying power without any tendency to rise on her bilges. plane, and for the purpose drawa straight line of the same length as the L.W.L. This line forms the Mean Longitudinal Axis of Buoyancy for the vessel’s angle of heel. The C.B. of each individual section has now to be plotted in its. correct position in relation to the Mean Axis As previously mentioned, a Metacentroid is of Buoyancy. a vessel with a constant Metacentric Height at 79 ‘To do this measure on each MODEL SAILING CRAFT heeled section the distance it is to windward or and the Moments of Buoyancy are correctly leeward of the vertical plane. balanced. It is possible for one ot more of these individual Centres of It should be observed that in a racing yacht Buoyancy to fall on the Mean Axis of Buoyancy. with a bulky keel the Centres of Buoyancy of A line is then run through the points we have the sections in the centre of the boat in the just found, and this forms the Actual Axis of way of the keel will lie to windward of the Mean Axis of Buoyancy. In a boat with a plate keel or a cruiser with a small keel, the reverse will be the case. The ends of the boat should Joth fall on the opposite side of the Buoyancy of the boat. If the Centres of Buoyancy lie in a straight line along the Mean Axis of Buoyancy, the Actual Axts of Buoyancy will cotncide with it, a OF BUOYANCY Fic. 41 (2). { 4 7 Moments or BuoyANCY CORRECTLY BALANCED. ght 0 1. Cc sean » NT b Cy Rbe MEAN AXIS. oF BUOYANCY Fic. 41 (8). MoMENTS OF BUOYANCY INCORRECTLY BALANCED. je-—OC wer ~ MEAN AXIS OF BUOYANCY, Fic. 41 (¢). BuoyaNey Moments of BuoyANCY VERY BADLY BALANCED. and the balance is satisfied. This will be obvious when it is explained how the Moments of Buoyancy are balanced, since when the Actual Axis of Buoyancy coincides with the Mean Axis of Buoyancy, the arm of the Moments of Buoyancy is o, and consequently all the Moments of Buoyancy also equal o. It is not necessary for the Axis of Buoyancy to coincide with the Mean Axis of Buoyancy, and a hull can also be balanced when the Axis of Buoyancy is curved, provided it is regularly disposed about the Mean Axis of Buoyancy, Mean Axis of Buoyancy to the centre of the boat. If the reader will refer to Fig. 41 (a) he will see the Axis of Buoyancy shown as a broken line. Moments of Buoyancy are taken (Area of Section multiplied by difference between C.B. of section and Mean Axis of Buoyancy), and plotted. Now since the Curve of Moments is plotted about the Mean Axis of Buoyancy, the parts to windward must of necessity equal those to leeward (7.e., the areas 4 + ¢ = b, where a represents the fore-body, ¢ the after-body, 80 HULL BALANCE it must be designed not to interfere with this middle-body), and if the fore-body ces the after-body, the area 2 = the area ¢. balance. The whole idea of the system is that in a This method of balance is supplementary balanced boat the Moments of Buoyancy of to the usual checks on the fore-and-aft posi- the fore-body must fall on the same side of the tions of the upright and heeled Centres of Mean Axis of Buoyancy as those of the after- Buoyancy, which must o#” no account be omitted. The routine inspection of the upright and heeled Curves of Areas must also be carried out. As a matter of fact a boat that gives satisfactory results when tested by these body and be equal to them. It should be added that in order to make the theory clear, Fig. 41 (2) shows a theoretical Axis of Buoyancy and Curve of Moments rather than those of an actual yacht, since those of two methods, is unlikely to show up badly by Admiral Turner’s further test of the “ M/C Shelf.” This system of balance has been accepted by some well-known designers and rejected by actual yachts do not usually exactly agree with the absolute ideal, and though they may be near enough balance, for all theoretical practical curves purposes make of better examples for illustrating the theory. others. Whether it is correct to test a vessel’s Now Fig. 41 (4) shows the Moments of static balance in this way, and whether a static Buoyancy correctly balanced, but in Fig. 41 (0) balance of this kind gives any useful indication and (¢) we have common forms of incorrect of the vessel’s dynamic balance, or whether balance. In Fig. 41 (0), although both ends of the boat, a and ¢, fall on the same side of the Mean Axis of Buoyancy, there is a considerable difference in their areas. In such a boat the ends need re-designing, @ being increased and ¢ decreased. ‘This may necessitate alteration the radius of gyration about the C.B. should be considered, are points upon which divergent opinions are held. From the way the theory has been presented, the reader will be able to understand it and the reasoning that prompted Admiral Turner to formulate it, and therefore to form his own estimate of its value. of areas of the sections, or more likely in this case alteration of beam, or both. It should be added that though it is equally possible for a to be greater than ¢, the fault is not so common. In Fig. 41 (¢) still more serious faults are Boats designed specially to comply with this system of balance have done very well in open competition, but, on the other hand, any revealed, since the two ends of the boat are on reasonably well designed yacht complies pretty closely with its requirements whether opposite sides of the Mean Axis of Buoyancy. designed with this intention or not. Such a boat requires complete re-designing. It is, however, certain that this sytem of The faults shown in Fig. 41 (4) or (¢) will have balance is not a panacea for all evils, and a obvious steering effects. yacht’s behaviour is governed by many dif- It is sometimes suggested that to cure faults ferent things, all of which must receive due of this kind the keel should be shifted forward consideration by the designer. or aft, or made thinner or thicker. recommended that this be left alone and atten- Finally it should be said that balance in itself, however perfect, will not make a prize-winner, and a yacht to be fast must also be designed tion be given to the design of the canoe body. with due regard to the factors that make for able keel has Ifa reason- been designed, it is strongly The first essential of a well designed boat is speed. On the other hand, especially in a for the hull proper (¢.e., the canoe body) to be model, absence of balance will make a boat un- balanced. controllable, and prevent her being successful. M.S.C. When the keel appendage is added, 81 CHAPTER VIII Designing the Sail-plan. General Considerations. and Height to Breadth. Selection of Rig. Calculation of C.E. and Position of Rig over Hull N designing a sail-plan, the first things to seresmin are the rig and area that are to be adopted. Proportions of Headsail to Aftersai. model, and, further, the single sail does not give the greatest efficiency. In full-size yachts the rig is Recent experiments in aerodynamics have mainly determined by questions of utility in shown that two aerofoils working in conjunc- consideration of the work that the yacht is tion are infinitely superior to a single aerofoil expected of their combined area. to perform. For example, in a The principle in- cruising yacht, the considerations will be the volved is that of the overlapping wings of number of hands available and whether the insects, and there is also a less pronounced vessel is required for coastal work or ocean form in the wing of the eagle. voyages. It is obvious It would that the more any require another book to deal fully with this given area is subdivided, the more easily can subject, and those who wish to probe the each sail be handled. matter Further, if the yacht is further are advised to obtain Dr. required for ocean cruising, any reduction in Manfred Curry’s books on the aero-dynamics weight of spars will tend towards more com- of yacht sails. fortable conditions for the crew. If, however, the yacht under consideration is a racer, the The best rig, therefore, to adopt for a model yacht is the Bermuda sloop with a single jib sole consideration must be to make the most and mainsail. efficient use of the sail area that she is permitted under a rule that embodies both hull and sail to carry under her class. measurements, the question of the proportion Recent discoveries in aerodynamics have In designing a racing model of hull to sail is one that requires the closest shown that a sail set on a wire stay is the most consideration. This matter has been pre- efficient aerofoil for any given area, provided viously referred to, and the best guide for the that the stay is kept rigid and the sail is cor- novice is to study the proportions of successful rectly sheeted. It is, however, essential to have boats under the class to which he is designing. a mast to support the sails, and the triangular This is not a very scientific method of tackling mainsail is the most efficient form of main- the problem, but it is certainly the best for the sail. amateur designer to follow until he has gained enough experience to form his own judgment. Again, if the length of masthead required to set a gaffsail is taken into consideration, area Having decided upon the rig and area, the for area, the triangular mainsail requires less next considerations are the proportion of head- length other. sail to aftersail, and the proportion of height to Obviously also the gear required for a triangular sail is less than that required to set an breadth in each of these sails. When the position of the keel appendage ordinary gaff mainsail. was being discussed, reference was made to the of spars to set it than any The question of area from the point of view shift of the centre of pressure towards the of handling does not trouble the model yachtsman, but, on the other hand, in order to gain efficiency during races he must reduce his gear to a mimimum. It might be suggested leading edge, as exemplified by the falling leaf. In deciding the proportions of sails this that this, coupled with the fact that the sail would not be divided, would point to the adoption of the una rig. Actually, however, a tendency is for the pressure to become mote concentrated at the leading edge, and this has the effect of dragging the centre of pressure single-sail rig is most difficult to balance in a forward. principle must also be borne in mind. wind 82 speed across the sails As the increases, the This forward travel will be in pro- e breadth of each sail, and their limits as to how far this may be carried with SUCCESS. centre of pressure will also be uenced by their relative areas, If, there- When a yacht is close-hauled, what actually happens is that the wind impinges upon the luff of the sail first and spills away across the sail, finally escaping at the leach. This escaping wind from the luff has its free passage across the sail impeded by the wind which strikes upon the after-part of the sail, with the result that a choke occurs and pressure develops. The highest pressure is naturally at the luff, ote, an excessive amount of sail is placed forwatd of the mast, the forward travel of the centre of pressure will be so great that the boat’s head is forced off the wind as the latter increases in strength, and she will refuse to point up. A certain amount of forward travel is necessary to keep the boat full and bye. However perfect a hull is, there is just one sail-plan and position for it over the hull that The amount of this choke, and the pressure produced thereby, therefore, entirely depends will give the best results. This differs with on the efficiency of the after-part of the sail. Now this area of maximum pressure 1s more or each boat, but average modern sail-plans have from 274 to 35 per cent. of headsail. This is actual area, not sail area as measured for rating purposes. A little experiment may, however, prove necessary before the best combination less proportionate to the width of the sail, and it follows that if the total width of the sail is unduly reduced, the width of the most efficient part will likewise be reduced, and its efficiency per square inch of surface will also suffer by is arrived at. With regard to the aspect ratio (proportion of height to breadth) of sails, wind tunnel tests show that for windward work a proportion of reduction in pressure: 9 to 1 gives the best results, and dead before in mind in connection with narrow sails is the the wind a proportion of 1 to 1. It would, question of the spiral flow that manifests itself therefore, appear that the best proportion for to a certain extent in all sails, but increases to an excessive extent when the sail is too high in proportion to the width, with the result that all-round work lies about half-way between. At the same time this data must be regarded with some suspicion when it comes to its application to yacht sails, as these tests were made with aeorplane wings, and there is an essential difference between a rigid aerofoil like a wing and a flexible aerofoil like a yacht’s Another consideration which has to be borne the sail is very difficult to control and is con- sequently ineffective, especially off the wind. A particularly difficult sail to control in this respect is a schooner’s foresail, which is a high narrow sail, and unless great precautions are taken the gaff will swing outboard. ‘The skipper sails. Actually, sails with an Aspect Ratio (Height: is then faced with the dilemma that he must Breadth) of as high as 4:1 have been used, either have his sail so closely sheeted that the but such sails have to be very well made. lower part is too close-hauled to be efficient, or Further, their trim is very critical, both as ease off and trim the lower part, with the result regards that the upper part spills. strap.” * the sheets and on the “ kicking Undoubtedly higher aspect ratios A further difficulty arises from the fact that can be used on large models than on smaller, the length of the keel appendage and the base but the novice is advised to start with a lower of the sail-plan are directly related, so that a aspect ratio on his first boats. long keel requires a wide base to the sail-plan Actually it has been found that the back of the sail does more work than the front, and it has been proved also that the old saying that “an inch in the luff is worth two in the leach (or foot)” is well founded, but there are and a short keel a narrow base. In a model, if the keel appendage and base of the sail-plan are too long, the boat will be sluggish and not pay off quickly, whilst if they are too short the boat will be tricky and difficult to control. As in all things connected with yacht design, the * The “ Kicking Strap ” is explained later in the book. happy medium is the only correct course, as 83 G2 ESIGNING problem from the point of view of sheeting, if asserted that under the I.Y.R.U. system of sail measurement the area of the fore triangle is increased by raking the mast, but a glance at Diagram D will show that this is not so, and this sail is designed too high and narrow the that raking the mast decreases the actual area. same problem will arise in getting the head of feature will lose its virtue if carried O excess. Whilst the headsail is not such a difficult the sail to draw properly. If the jib is designed In the case of a jib Or triangular mainsail, of which it is desired to find the actual area, the in such a manner that the sail has to be strapped usual procedure it to take the luff * of the sail down in order to get the head of the sail to as representing the base of the triangle and the draw properly, the lower part of the sail will clew * as its apex. not be able to do its work efficiently. Pri- marily a jib is a lifting sail, but if it is too closely sheeted it becomes a depressing sail. > ,, 55 4» Hardener GP3o0 14 hours 2} 4 7s I2-14 29 > os ,, Hardener B50: 2 hours 3 23 I2-I4 ,, 4, 6 8s, The above are maximum times, and no attempt must be made to use the mixture after it has started to gel (#.e., become stringy and lumpy). Times for setting aregiven in a separate table, not quoted here. MOISTURE TIMBER is équivalent to the humidity of the surrounding free from traces of paint or varnish, the joint after it is set, can be painted or atmosphere. As wood absorbs or emits surfaces open for a period to air-dry before the moisture, it swells or shrinks. Now if a very dry piece of wood is glued to a very wet piece of wood, it is obvious that the very dry piece will absorb moisture from the air and swell, while the very wet piece will emit moisture and shrink. This is bound to cause warping, twisting and splitting, so it becomes an axiom for laminated construction that pieces of wood of widely different moisture content must never joint is assembled, but this is a relic of the first be glued together. resin glues and entirely unnecessary with a to thick pieces of wood, as for example the modern glue, such as any of those cited above. layers of a bread-and-butter hull built up of Makers also advise roughening surfaces, but 1-inch timber. In consideration of this point, it must be varnished over the glue-line. No a/kali of any ‘kind must come into contact with resin, hardener, or mixture. Mixing vessels may be glass, china or iron, but must not be brass or copper. Resins can be kept in a pot or tin, but hardeners should be kept in glass or china containers, as they contain acid. Makers sometimes advise leaving the spread this also is unnecessary unless the wood sur- This applies particularly It remembered that wood is mainly cellulose and can do no harm, but its importance can be lignin, the wood substance being practically overstressed. face is glazed, when it can be glasspapered. spreading the same for every kind of timber. Swelling is caused by absorption of water into the wood implements must be thoroughly cleaned in hot substance itself, and it is only when the fibre water before the glue has set, and preferably before it has gel-led too much. saturation point is reached (usually when the moisture content has risen to about 28 per Certain very simple precautions are neces- cent.) that the pores commence to fill with After use, mixing vessels sary in using these glues. and The hands should water. Swelling takes place as the fibres be thoroughly washed before and after glueing. absorb water, but the pores do not expand. Any cuts or wounds on the hands should be Hence the water taken into the pores causes no covered. expansion whatsoever, though it adds to the Glue should not be allowed to dry on the skin. The arms are more tender than sodden condition of the wood and increases the hands, and people with very tender skins its weight. should keep their sleeves down. contrary One advantage possessed by these glues is to From this it is apparent (though what one dense heavy woods would expect), swell more that than light their very low moisture content, which means porous timbers, because they contain a higher that laminated constructions made with them proportionate volume of wood substance. are less liable to distort than those made with A plank does not increase in length as it other adhesives. absorbs moisture, because the wood fibres do The moisture content of timber used for not stretch in length. It increases in width laminated constructions influences the liability and thickness, to distortion, but since the scientific facilities fibres swell as they become saturated. Another point to bear in mind is that for any given percentage of increase in moisture content the required to determine moisture content are very unlikely to be available to any model yacht builder, all that can be done is to select however, because the wood dry, well-seasoned timber, and carefully to increase in width of otherwise exactly similar planks will depend on how they have been cut seal with paint or varnish all faces other than from the log. those which form part of a glued joint. grain must never be glued to a tangentially- Wood has not only the property of absorbing Hence a board with a radial moisture from immersion in water, but out of cut one, since unequal swelling will ensue if there is an appreciable change in moisture water it will either absorb moisture from the air content. or give out moisture until its moisture content In plywood the grains of the plies run in 29 H 2 | MODEL SAILING CRAFT different directions, but on the other hand the atea of the glued surfaces is large compared with the thickness of the plies. We mentioned tabulated data from the repeated experi shows that with only two plies a bend has strong tendency to straighten out after removal plywood at this juncture in case the reader from the jig. wonders why this is made with the grains of the plies running in opposite directions and if less than half that with two. With four or more practically this is liable to cause unsatisfactory bonding between the laminations. However, having vanishing point, and in some cases a slight is appropriate in model yacht building. mended to avoid possibility of fracture. With three plies the tendency is plies this is decreased to tendency to move inward is found. For most raised the subject of plywood, it should be ‘ purposes, therefore, three plies should be added that provided this is Pheno/ Bonded it is a regarded as an absolute minimum. For very highly satisfactory material to use wherever it sharp bends, pre-bending treatment is recom- The commonest use is, of coutse, for decks which can be much thinner than those of ordinary wood, while being stronger and less prone to splitting. Laminated bent constructions in any case should long under One little hint on the use of these glues iis to Another use would be for the skin of a sharpie model. be left about twice as pressure as ordinaryjoints. On the other hand, it would not be satisfactory to cut the frames of use a sheet of newspaper to obviate the work a planked model from a sheet of plywood as the fastenings would then be in the edges, and to Pieces, liable to force the laminations apart. needed, cellophane can be used. sticking to anything it is not intended to stick (as for instance—jigs, etc.). Where cramps, something packing thinner is An alter- In cramping up joints made with synthetic native form of protection is afforded by var- resin glues, only sufficient pressure is needed nishing jigs, etc., with special Anti-Adhesive to keep the parts of the assembly in their cor- Lacquer. rect be one very suitable for model work is made by applied by means of cramps, by weighting, by Messrs. Stanley Smith & Co., Worple Road, screwing, or in any other fashion that happens Isleworth. relative positions. Pressure can to be convenient for the job in hand. There are several makes of this, but On the A good deal has been written about these other hand, if greater pressure can be applied, glues, but much of this applies to the use of a thinner glue-line will result, and in certain any glue. instances this is highly desirable, as for example Actually resin glues are just as when glueing the layers of a bread-and-butter simple to use as casein glue, and quicker in use, once the technique has been mastered. It hull together, since thick glue-lines ‘materially is only necessary to go slowly and carefully to distort the design. More is said about this in work for the first few times, and above all to the chapter on bread-and-butter building, so follow implicitly the maker’s instructions. After a few trials the worker will appreciate the great possibilities and advantages of synthetic it will suffice to add that when a thin glue-line is wanted, the resin should be applied in a thin coat, but when it is desired to take full advan- resin glues. There is one apparent disadvantage in the tage of its gap-filling properties, a thicker use of these glues, but that has lately been over- layer of resin should be used. Synthetic resin glues are very suitable for making laminated bent constructions, and something is said later in the book on the possibilities of multi-skinned hulls. One point which can be mentioned now is that the number of laminations has great influence on the stability ofa bend. ‘This question has been thoroughly investigated by the Forest Products Research Laboratory, and their published come. All synthetic resin glues have a rather short “‘shelf life,’ that is to say they only remain usable for a comparatively short period even if kept in an air-tight lever top tin. The usual shelf life is 3-6 months, varying with the different makes of glue. Packages are usually stamped with a date after which they must not be used, just as photographic films are marked. TOO Actually it is should be well protected from water to avoid rust. Apart from keel fastenings, all fastenings containers. evelopments, resins can now a dehydrated form, when they powder. They are re-constituted , just like dehydrated eggs. It is not reconstituted that the shelf life of the commences, and it then has its normal shelf life of 3-6 months. | A good example of used in model yacht building should be brass, copper or yellow metal. pins, nails and screws. This applies to all With chromium-plated deck fittings, chromium plated screws should be used. The ordinary commercial C.P. screws are frequently plated on iron screws, this type of resin is Aerolite 300 which, when but our screws should be C.P. on brass. If the model builder is making his own reconstituted, fittings, he can have his brass screws plated at becomes the normal Aerolite 306F, and is used in exactly the same way.* the same time as the fittings. The Beetle Company have also a good resin in being obtained from one of the firms who powder form and so do several other makers. specialise in model yachts and components, * 6 *K C.P. screws can be purchased at the same time 2 As will be seen when we deal with keel-bolts as the fittings. for our lead ballast keels, these are best made from motor cycle spokes. One reason for not using brass keel bolts is that brass, copper and other yellow metals immersed in water are subject to galvanic action which gradually eats them away. Also if the holes, in which the heads are sunk, are properly filled up, there should be no fear of rust. If the fittings are Likewise any loca- ing pins, dowels or screws used in lead keels are best made of steel or iron, but their heads * See Aerolite 306F, page 98. IolI * * * 2k If the reader will digest the above carefully, it will be unnecessary for us to do more than mention that parts should be glued. Likewise it will be understood that when we refer to pins, nails or screws, these are to be of non-ferrous metal. This explanations. will save time and simplify . After these preliminary remarks we can now turn to the various kinds of yachts and methods of building them. CHAPTER XI Punts, Barges and Sharpies. Building a 10-Rater Sharpie HE simplest form of sailing boat is the sailing punt. The punt is a flatbottomed craft, the floor being straight bottom can be put on in one piece, but other- wise the construction is similar to that of a model sharpie, except for the fact that the punt across from chime to chime, but rockered in a has a forward transom. fore-and-aft direction. mote difficult to build than either a punt or barge, because of its V-bottom, but is an The punt also has a transom forward as well as aft. A punt must not, however, be confused A sharpie is slightly infinitely better boat. with a pram, which is a round-bottomed boat with a forward transom. In a full-sized sailing punt, a centre-board is used and the crew act as ballast; but in a model A sharpie is a V-bottomed craft with a pointed bow and a chime (or chine). The chime is the angle formed by the sides and floors of a punt, barge or sharpie. Sharpies are punt, a plate keel with a lead bulb is usually popular amongst American yachtsmen, but it fitted. must be admitted that there is a certain amount A barge has a pointed bow, and a flat bottom, running straight across from chime to BARGE a round-bottomed one, and where this is not TYPE sO, non-success is attributable to inferior design and not to any fault inherent in the 4 type. Probably the most numerous and successful one-design in the world is the American ‘* Star’? Class. This was designed by the celebrated American designer, the late Mr. William Gardiner, and inaugurated over forty years ago. To-day, the class numbers literally hundreds of boats. This proves that a well designed sharpie is as capable as any ordinary yacht of her own size, besides being cheap and 4 SHARPIE of prejudice against the type in Britain. Actually a sharpie can be just as good a boat as SECTIONS easy to construct. There are a number of different varieties of sharpie. Some early variants were built with straight sides and bottoms that had a curve across the rise in floor from keel to chime = Cc) (see Fig. 47 (a)). Others had their floors straight from keel to chime, but curved top- Cd) Fic. 47. SECTIONS OF Harp CHIME CRAFT: BARGE AND SHARPIE TYPES. (2) (4) (¢) (¢@) Sharpie Sharpie Sharpie Double with straight sides and rounded floors. with rounded sides and straight floors. of ordinary V-type. chime Sharpie. chime, but the keel is rockered in a fore-and-aft direction (see Fig. 47). In building a model punt or barge, the sides (see Fig. 47 (#)). These two varieties were not, however, exactly true to sharpie type, which has a flat bottom with a rise in floor from keel to chime, and flat sides, usually flaring in section (see Fig. 47 (¢) ). Many early sharpies, though true to type, yet had an angle of rise of floor that altered, particularly in the bow sections where it became steeper, and also topsides that varied 102 SHARPIE DESIGN rater rule, however, and a number of very successful sharpies have been built to this class from time to time. Hence it is very The first advance was when some- ody conceived the idea of making the angle of flare constant throughout the length of the evident that the sharpie can compete success- boat, thus simplifying building and effecting considerable economy of time and material in planking. This was finally taken a step further when not only was the angle of the flare of the topsides kept constant, but also the fully with “‘ round-bottomed ” types when the rating rule permits their employment. The model builder is, therefore, advised not to build a punt or sharpie except as a Io-rater or angle of rise of the floor throughout the length ** free-lance ” sailing model. of the boat. The designs of a 10-rater V-bottom sharpie of the single-chime, constant chime-angle type are included in this chapter. Whilst this is the easiest possible type of model to build, it As far as the floor is concerned, this means that the planking goes straight on with a simple fore-and-aft bend instead of having to bend in two directions. This makes is by no means the easiest to design. The hull balance has to be every bit as exact as for a normal boat, and to attain this means a very careful adjustment of the chime line, line of for great economy, both of labour and material as it eliminates the necessity to taper and fit planks, as there is no sny, and the planks are the same width from end toend. sharpie is This type of G.B.D., and line of Greatest Beam. described as a “constant chime- angle sharpie.” Now, if the reader will examine the sharpie Its advantages to the model builder are very obvious, since the whole hull design given in this chapter, he will observe can be planked up with four pieces of thin ply- that by reason of the stem being higher than the stern, the actual amount of flare in the bow wood, and the fitting entailed is of the simplest sections is greater than in the stern sections. nature. Actually, sharpies can be either single- or If we simply draw a balanced deck-line as we double-chime (see Fig. 47 (d)), and many of did when designing our 36-in. model in an the larger sharpie cruisers in the States are of earlier chapter, we will have a balanced deck- the latter type, as in a big yacht at all events, it line, may section. method used to balance the line of Greatest Rither a single or double-chime sharpie can be Beam in this design was to draw a waterline a designed with a constant chime-angle. All sharpies are V-bottomed, and this is the main suitable height above L.W.L. (in this design give a more advantageous and an unbalanced chime line. The 2 in. was used) and balance the line of greatest difference between a “‘ barge yacht ”’ which has beam at this height. a flat bottom from chime to chime and a section was produced to the height of the sheer. sharpie. People often speak of a ‘“‘ V-bot- The upper part of the In this design the greatest body depth was tomed sharpie,” but from its nature a sharpie placed forward of midships. must always have a V-bottom. Unfortunately, if the model builder decides balanced Greatest Beam Having drawn a line, and a mid- section (or master section), a tentative line of to build a model sharpie, most classes are G.B.D. was struck. closed against him. In the 36-in. Restricted fixed the angle of rise of the floor and angle of Class, the Maximum Beam restriction means flare of the topsides, the whole of the sections Since our master section that sufficient flare cannot be given to the top- could then be drawn tentatively on the body sides unless the boat is made unduly narrow on plan. the had not only to fair on the body plan but also L.W.L. Beam, carrying power. thereby sacrificing sail- In the M-class the restriction This in turn gave a chime line, which on the profile and beam plan. It will be noticed on hollow garboards goes against the sharpie, that we have not called this the “‘ Waterline while the methods of measurement used for Plan ”’ but the “‘ Beam Plan.” With a sharpie, the 6-metres and A-class, preclude the design- there is no need, and it is not customary, to ing of a successful sharpie to either of them. take out waterlines or diagonals. There are no such limitations under the 1o- In 103 order to fair the boat’s chime line, SHARPIE IO-RATER “DIAMOND” _—— SAIL Fore A+ AREA 72 Mainsarl « 62:5×17: 2 Less 15 %o : Spinnaker Luff 64″ Leach 64″, Foot SMALL 2nd Suit Mainsail Jib 3rd Suit Mainsail Jib Luff SUITS Leach Foot 64:75″ 66-5″ [8-0″ 54:0″ 49°’5″ 14-75″ 57:5″ §9:0° 16-0” 48:0″ 44-0″ 13-0″ Foreside from T rn — SAIL PLAN OF SHARPIE 10-RATER. Lines of this model appear on Folding Plate IX opposite. 104 34% Mast Bow . 33-0 LINE DATUM L.W.L. TABLE Hull Paint Deck L WEIGHTS Ib. 92. 4 | | & Varnish Rig Line Trimming Ballast Lead Keel Rabbet and roken shown as ebove | B 4 6 4 Sundries NB. After side of Stem also O B Fittings ’ + OF 17 26 6 8 12 Lines in | a ee oe | .—. .-—~ The lead iine shown aboveis suitable for use with Braine Steering Gear. An alternative lead line, also alternative Skeg and Rudder for use with Vane Steering are given on back of this plate. [To face page 104. SHARPIE !1O-RATER “DIAMOND” SS SATE Mainsarl = “2 Fore AA* 62-5x 17-75 | : — Less Spinnaker = 15 So Suit | Luft 64″ Leach Foot 34° SMALL ond = Luff SUITS Leach Foot Mainsail 64:75°665° {[8-O” Jib 54:0″ 49-5″ 14-75″ Mainsail 57-5″ 59-0″ 16-0″ Jib 48:0″ 44-0* 13-0″ Foreside Mast from SAIL PLAN OF SHARPIE 10-RATER, Lines of this model appear on Folding Plate IX opposite. 104 Bow 33-0″ 5 DATUM LINE 8910 11 12 Tr O19. ry 56 DATUM , Approx. Position LINE for Mast a : i L.W.L. fc & aL . ‘ / (rei L.Wit., DIMENSIONS ere Displacement ee | oo nner Transom rane |__| a poe ee See . ee Chine | rN\o2 Deckbeams cut to are same ; | La Top of | Keel 5 ee 7 Se WLS TABLE HUN a SSG ——————— === sf showing Cheek in way of Fin to se WEIGHTS nish — 4 rn 1 ittings trimming Ballast shown a8 ee OF Rig. above ES ae Nel yanten eiaereiersms ize Lead Keel Rabbet and @Searding Lines SS / WLI 9 6 8 a 17 1D8 56 broken lines in | — \ arc. ~~ Deck fo) Top! of Skeq 27° WL.4 oS WL3 ww wid 7 == | proper WLB a cred Line f*wisg : 2″ Cheek, | 7 so es W.L.7 L / Lead Line-—~ ” Pa a Bottom Lilne Canoe Body | += Ze a L.W.L. ji == fk 52:5 x 1140 +6000 = 9-98 be a vy co | Tg! 261bi20z RATING All LINE 4 Sail Area 140 sq.ins. 5ect.O from Stem 4-375″ NOTE. DATUM q 12 1 10 9 pW LB 8 7 6 5 a ie 3 | oO oO 658 Scale : One-sixth of full-size, Folding Plate [X.] SHARPIE IO-RATER “DIAMOND” N.B.–The leadiine shown above is suitable for use with Braine Steering Gear. An alternative lead line, also altesnative Skeg and Rudder for use with Vane Steering are given on back of this plate. [To face page 104. ALTERNATIVE FOR SKEG ALSO LEAD USE WITH VANE AND RUDDER LINE STEERING GEAR f Lead Keel is reduced to 17 lb. 2 oz. on account of Vane Steering Gear. [To face page 105. > B.D. line e e case, it might even be htly to adjust the Greatest Beam this should be avoided if possible, nds to alter the character of the sections. garboards are the angle is more gain than detriment, as it makes for weatherliness. The plate type of keel is also correct technique, as would also be a fin and bulb. It will also be noticed that the centreline of the deck has no rocker but is dead straight. By using the same arc for all the deckbeams, the deck can conveniently be made out of a single sheet of plywood, as this form of design gives a simple thwartships bend to the deck camber, instead ships of a double bend—thwart- and fore-and-aft to a rockered deck BOARD centreline. By reason of the different beam at each of the section stations a pleasing sheerline 1s obtained. given a transom with a forward rake. BUILOING It will be noticed that the boat has been This serves no practical purpose but is purely for the of appearance. The transom is well T-SECTION sake above the waterline and will never be immersed as it would be in a square sterned boat, so one can be swayed by purely esthetic considerations, and with this design, the transom shown will make for a lighter and more graceful appearance. The yacht is moderately light displacement for a 10-rater, but the methods of construction employed will enable the hull to be built very lightly and a high proportion of the total displacement to be concentrated in the lead keel, which will make for stiffness. Owing to the long L.W.L., the sail area is small so the sail plan is designed to get every available ounce of driving power from the amount permitted. The mainsail has a high aspect ratio, and there is a large proportion of headsail. The sail plan shows an ordinary boom jib, which is simple to rig and use. With such a.big headsail, a radial jib club might be 105 (C) Floors. unfilled (B) Moulds. completely (A) Crosspieces on Building Board. The correct technique for a sharpie, and actually KEEL IN POSITION. ends of the boat. Fic. 48. necessaty, it should only be in the extreme Mou.ps FOR SHARPIE I0-RATER ERECTED ON BUILDING BoARD WITH STEM, TRANSOM, KELSON AND any alteration in the Greatest Beam line 1s L.W.L. en ee oe > — ~~, Outside EE os — B ar f ‘ % SS SSS = SS X x ~~, (oat Meriop or Burtpinc a Breap-anp-Burrer Hutt. [To face page 116. hd 2 a Lar ; “ _ p. ; | ey re ° a . s | RuPpeER bed WASHER | a Pin and packing pieces at stern as required to fix on to building board. | | | fair curve, check the measurements carefully. The inside of the layer has next to be marked for cutting out. The layer which is decided shall be taken from the centre of the largest . to the boat’s depth, disesign and throwing the yacht out g. Consequently, good contact between surfaces is necessary. Accordingly the wood must be planed dead flat and smooth. one must then be marked in the same manner. In each case the largest layer that will come out comfortably should be selected. This inner layer will have to be marked out in a similar Unless the builder has a good jack-plane and can use it well, it is advisable to have the wood planed to thickness at the sawmills. This costs very little extra and is worth while to manner. save time and labour. measute over several thicknesses, since any After the largest layer has been marked out, together with those that come out of its middle, the next layer down will have to be attended to. The inside of this layer is again used for smaller layers, and the remainder of the layers are likewise marked out. The more or less V-shaped piece required error will then be multiplied and show up for the half layer Z (see Fig. 53), that forms readily. the sheer forward, can be arranged to come When ordering, specify for the wood to be planed to the exact thickness required and stress the need of accuracy. When taking delivery, check the thickness carefully to see your instructions have been carried out. In checking, it is a good plan to out of the board that forms about the third or The first thing to do is to mark out the layers. foutth layer down by taking it from the end piece of the board forward of the actual layer. When all the layers are marked out, they can be sawn. If this is being done at home, the best tool to use is a bow-saw. Failing this, a compass (ot keyhole saw) can be used, but Square up the edges of the board and accurately strike a centre line on both sides. The buttock lines and section lines must then be put in, and the latter squared off right round the plank to make sure they coincide on both sides. Starting with the largest complete layer, which is marked A in Figs. 53 and 54, proceed the bow saw will be found far easier work. to mark in the half-breadths on each side of the centreline. Also spot in the intersections of the waterlines and buttocks. If there is a steam fretsawing works near and time is an object, it should not be an Only the expensive matter to get the layers cut. Ask larger of the two waterlines which represent the sawyer to make sure that the saw is cutting the faces of the layer need be marked in. absolutely If there is a tumble-home a slightly different pro- perpendicular to the table, and instruct him to cut about } in. outside the lines. cedure will be needed. After the layers have been cut, they must The term ’’ tumble-home ” is used when the be prepared for glueing up. The first thing to width of the hull at deck level is less than at one do is to trim the larger face of each layer down of the lower waterlines. absolutely sharp to the pencilled waterline. If the hull that is A under construction has any tumble-home, the sharp chisel and a finely-set small plane should extra width for this must be allowed when the be used for the purpose. wood is cut. Any part that is wider on the When this has been done, the smallest layer lower waterline than the upper one must be can be used to mark the waterline of the lower drawn in on the top face of the layer as well as face of the layer above it. the waterline that belongs there by rights. continued until each layer is marked on both Having put in all the spots for the half- breadths and buttock intersections, a line must be drawn in with a fine hard pencil. faces. This procedure is This will give the outside shape of all the joints. This is It is now necessary to draw on the bottom done with a spline, which can be held in posi- face of each layer a line to represent the inside tion with tacks or weights during the opera- of the glued joints. tion. was explained how to set off the thickness Be careful that this intersects all the spots exactly, and if any part does not make a Earlier in the chapter it requisite at the ends. 117 This is done on the ‘ aS Sr iere LEFT ON DaTum STEMMEAD LINE | Kupper Packing ey a WASHER ell 4 i ( f i TL Locating Pin wig CONSTRUCTION AT Bow, Mipsnip & STERN SECTIONS — + o l | eee \ LocaTiInG Fin Fic. 55. ConsrrucTION PLAN SHOWING SYSTEM USED IN Rrp-AND-PLANK BUILDING. Backbone of model yacht showing method of building up in three partsavith fashion piece attached. Backbone is shown with fin built up and lead keel bolted into place, also piece left on stemhead and packing pieces at stern as required to f Mast step (mounted on chock screwed to backbone) and rudder tube are shown in position, though the latter is not fitted until shell of boat is completed, as described in text. BP , te Oe The “ Datum Line ” shown represents the building board which can be considered as the stocks on which the craft is built upside down. The smaller diagram shows three sections at various stations in the boa:, and illustrates the way the ribs are checked into slots in the keelson, and the manner planking is fitted into rabbet. to buildi Omi oibui aoe ees. c ~,* <> + Folding ing Plate Plate XII. XII.) c {To face page 117. . ! | ING THE LAYERS fair curve, check the measurements carefully. The inside of the layer has next to be marked for cutting out. The layer which is decided shall be taken from the centre of the largest one must then be marked in the same manner. In each case the largest layer that will come out comfottably should be selected. This inner layer will have to be marked out in a similar 4 in. to the boat’s depth, dis- design and throwing the yacht out ng. Consequently, good contact be- en surfaces is necessary. Accordingly the wood must be planed dead flat and smooth. Unless the builder has a good jack-plane and can use it well, it is advisable to have the wood planed to thickness at the sawmills. This costs very little extra and is worth while to save time and labour. When ordering, specify manner. After the largest layer has been marked out, together with those that come out of its middle, the next layer down will have to be attended to. The inside of this layer is again for the wood to be planed to the exact thickness required and stress the need of accuracy. When taking delivery, check the thickness to mark in the half-breadths on each side of used for smaller layers, and the remainder of the layers are likewise marked out. The more or less V-shaped piece required for the half layer Z (see Fig. 53), that forms the sheer forward, can be arranged to come out of the board that forms about the third or fourth layer down by taking it from the end piece of the board forward of the actual layer. When all the layers are marked out, they can be sawn. If this is being done at home, the best tool to use is a bow-saw. Failing this, a compass (or keyhole saw) can be used, but the bow saw will be found far easier work. If there is a steam fretsawing works near the centreline. and time is an object, it should not be an carefully to see your instructions have been catried out. In checking, it is a good plan to measure over several thicknesses, since any error will then be multiplied and show up readily. The first thing to do is to mark out the layers. Square up the edges of the board and accurately strike a centre line on both sides. The buttock lines and section lines must then be put in, and the latter squared off right round the plank to make sure they coincide on both sides. Starting with the largest complete layer, which is marked A in Figs. 53 and 54, proceed Also spot in the intersections under construction has any tumble-home, the expensive matter to get the layers cut. Ask the sawyer to make sure that the saw is cutting absolutely perpendicular to the table, and instruct him to cut about 4 in. outside the lines. After the layers have been cut, they must be prepared for glueing up. The first thing to do is to trim the larger face of each layer down absolutely sharp to the pencilled waterline. A sharp chisel and a finely-set small plane should extra width for this must be allowed when the be used for the purpose. of the waterlines and buttocks. Only the larger of the two waterlines which represent the faces of the layer need be marked in. If there is a tumble-home a slightly different pro- cedure will be needed. The term “’ tumble-home ” is used when the width of the hull at deck level is less than at one of the lower waterlines. wood is cut. If the hull that is Any part that is wider on the When this has been done, the smallest layer lower waterline than the upper one must be can be used to mark the waterline of the lower drawn in on the top face of the layer as well as face of the layer above it. the waterline that belongs there by rights. continued until each layer is marked on both Having put in all the spots for the half- breadths and buttock intersections, a line must be drawn in with a fine hard pencil. faces. This procedure ts This will give the outside shape of all the joints. This is It is now necessary to draw on the bottom done with a spline, which can be held in posi- face of each layer a line to represent the inside tion with tacks or weights during the opera- of the glued joints. tion. was explained how to set off the thickness Be careful that this intersects all the spots exactly, and if any part does not make a Earlier in the chapter it requisite at the ends. 117 ‘This is done on the MODEL SAILING CRAFT centreline at the ends, and also on the mid- they have been cut away, as these lines are ship section for the sides. used in setting the layers in their correct rela- A very simple dodge for marking the inside of the joint after tive positions. these points have been found is to use the lining-up is correctly done as otherwise the next smallest layer. boat will be all out of shape. Place this in position on It is most essential that this The layers are now the underside of the layer to be marked, and ready to be glued draw it back diagonally until the spot at the together, and the question of cramping up end and the spot at the midship section are has to be considered. Ordinary G cramps are not much use for this purpose, but special cramps can be made up fora few pence. These are shown in Fig. 56. The bottom bar of the cramp is a piece of hardwood 2 in. X 1 in., uncovered, and run a pencil round the edge through the spots. This is repeated for the other three-quarters of the layer. om gin J ob eee = a ome — —— as ee “ee Fic. 56. fe oe — a — we ae i oo The next step is to cut a small groove round THe Giurinc-up Cramp IN USE. N.B.—Bolts are not shown full-length. each layer on the line which shows the inside of the joint. This is best done with a small sharp V-chisel. Having cut the groove, the surface of the wood inside should be carved down sufficiently to avoid contact. By this means, contact will only be made on the parts which will form the finished joint. ‘This gives full pressure on the right spot when glueing up, and also permits the air to get to the joint, which facilitates the glue setting. Another advantage of the groove is that it will act as a guide as to the thickness remaining when carving down the inside of the hull. This is clearly shown in Figs. 53 and 54. The section lines and centreline should now be squared round the edges of the layers where x = Packing pieces. and the top a piece 1 in. square. The bars are 4 in. wider than the greatest beam of the boat, and have the holes for the studding 1 in. from the ends. Studding is iron or brass rod threaded all along its length, and is a standard product obtainable from any good ironmonger. For these cramps +} in. studding is used and the lengths should give the cramp an opening sufficient to take the full depth of the canoe body of the boat, the keel being made up separately as explained later. For a 36-in. boat four of these cramps would suffice, but ten would be necessary for an A-class. The first layers to be glued up are the bottom two of the canoe body of the hull. In Fig. 53 this would be layers H and G. The 118 GLUEING UP THE LAYERS rocess of glueing was described earlier in the ook, so there is no need to repeat it here, this joint, as the contour is always affected by the next layer. The reason for finishing the except to remind the reader that in lining-up, fin before fixing to the hull is to get the pattern the centreline and section lines must register for the lead keel. In order to hold the fin securely during the exactly, The layers are cramped up with the Put one at each end of operation of shaping, a spare piece of wood the layers first, and the others in between. can be fixed to it, the whole being held together Be careful to screw down evenly, not one side by the keel bolts. cramps just described. first. Before screwing down firmly, verify the The spare piece of wood can be held in the vice in a convenient position. position of the layers again in case they have leaving both hands free for the work. In shifted while the cramps were being adjusted. carving down, chisel, gouge and small plane Finally, screw down firmly and givea final look are all used until about 7 in. from the water- to the alignment. lines. ‘Then set aside to dry. The next layer to be added will be F. Coarse glass-paper finishing off with fine. Now is then used, During the rubbing the pressure is required on the joint between down the glass-paper should be wrapped round layers a piece of thin wood. Gand F. If the cramps are put across When the fin is shaped, the lead-line must the bottom of layer H, pressure will be put on the wrong spot, and this will also tend to be marked in from the design. distort layer G. Packing pieces are cut from pattern was cut off exactly on this line, the Now if the some of the waste wood left over from the width of the saw cut would be lost and the layers, and placed between the cramps and lead would not fit properly. layer G to bring the pressure on to the right obviate this, a line should be marked } in. spot. below the lead line. The pattern is sawn off, running the saw cut between the two lines. This is shown in Fig. 56. The remaining layers of the canoe body are added in similar fashion. the glueing process, On no account hurry trimmed dead down to the marked lines. but see every layer is Take a piece of wood a full } in. thick and each glue joint to dry thoroughly. are built up order to The pattern and the residue of the fin are aligned correctly and allow sufficient time for The fin layers In glue a strip along the top of the pattern for the in a similar lead keel to compensate for the wood cut away. manner, but these have to be drilled for the This strip should be a keel-bolts before glueing up. The positions casting itself will be a little full, which will for the keel bolts should be accurately marked permit the lead to be trimmed up before fitting off on both faces of each layer. to the keel. The best method of drilling these is to drill about half- little full so that the It may be pointed out that a good pattern is way through from the top and then drill the essential other half of the way from the underface. smoother the surface the better. The best things to use for keel-bolts are motor- to get a good casting, and the The pattern should, therefore, be glass-papered to a high cycle spokes, but cycle spokes will be suffi- finish and varnished. ciently strong for small boats. and their finishing is dealt with in a subsequent If the builder does not possess a die to thread these, the chapter. The casting of lead keels When the lead keel is ready, it must cycle dealer should be asked to put 14 in. of be fitted to the remainder of the keel, but not thread on them. finally fixed in position. Two or three keel-bolts will be sufficient for a small boat and four for an A-class. In order to minimise the chance of The spokes which form the keel bolts will have to be cut to the right length. At the the keel wringing, it is better to have the keel- bottom end allow about 4 in. more than will bolts well spaced out. be required to come flush with the keel, and When the fin is glued up, it must be shaped bend back to form a loop. This serves as a before the final joint is made between it and stop to prevent it being drawn through, and a the hull. hole will have to be made in the lead to It is not wise to finish quite up to 119 MODEL accommodate the loop. On the top SAILING CRAFT now be made, using the keel bolts to cramp it end which goes through to the inside of the boat up tight. allow about 2 in. more than will be required to accommodate the full length of the nipple. skeg If the boat is of the fin-and-skeg type, the Before inserting the spokes they should be thoroughly greased with tallow. = should be also fitted and carefully squared up in a similar way. The loop to big boats, such as the A-class, and the pro- The boat will be easier to handle during carving if the lead keel is taken off, and in any case it will have to be removed when the inside is carved out. Screw the spoke nipples back until they are just above the top of the bolt Take a punch (or drift) and using a light hammer, tap out until the point when the nipple touches the wood. Unscrew further, cedure in that case is somewhat different. and repeat until you are able to withdraw the must be punched well home below the surface of the lead and the hole soldered over. When screwing the nipple on, it should be put on with the base (or bigger end) downward, and this also should be well greased. Some builders prefer to fit a removable keel The advantages of a removable keel are that in rail- bolts easily, but take care not to bend them. way travelling the weight of a boat governs the amount paid on it. The hull can now be set up for carving. On long journeys the Two pieces of wood, about 3 in. wide and 1 in. difference in freight between 11 or 12 lb. and thick, are screwed on top of the gunwales. say These pieces should be about a foot longer 5o lb. is quite appreciable. Again, in travelling, the hull without keel is a far easier than the width of the boat. The boat is then thing to handle on a crowded railway platform, turned upside down and the pieces of wood and is less liable to strain through jarring. screwed to the table or bench on which the The disadvantages of the removable keel are work is being done. that, unless well made, it is apt to get out of that the hull comes just outside the table-top. truth, and that it 1s more trouble to Most of the hull can be carved away without con- moving her, but it will be necessary to reverse struct. her for the gunwale on the side near the table. This holds the boat steady and permits both hands to be used comfortably during the work. In parenthesis it may be observed that it is Whichever form of keel is adopted, it cannot be too strongly emphasised that the keel must be absolutely true in a fore-and-aft direction, and perpendicular to the designed waterline of the yacht. The boat is arranged so very unwise to try to hold a boat with one hand and carve with the other. Not only is The slightest inaccuracy in this respect will make the boat perform differently bad work likely, on the two tacks, and cause the skipper endless trouble when he comes to sail the boat. have occurred through tools slipping. Using gouge, plane and paring chisel, the hull of the boat can now be trimmed down The method of fitting a removable keel is given at the end of this chapter. but many accidents When build- ing a yacht by the bread-and-butter method, it is advisable to make the fin before carving the outside of the hull proper, so that advantage may be taken of the “ steps ” to square up the keel. This applies equally whether the keel is removable or not. The method of doing this is the same with either a fixed or removable keel. A set-square is used in conjunction with the centreline. The square is placed on the hull and the centre- line at each end of the fin carefully checked and adjusted if necessary. The glued joint between the fin and the body of the boat can to within about 7 in. of the finished shape. The fairing is accomplished by means of glass- paper wrapped round a thin piece of flexible wood. The final rubbing down should be done with fine glass-paper. It is most important to see that there are no flats or hollows in the surface. This can be tested with a straightedge, and the hull should be looked at from every angle, both close up and at a little distance, during the final rubbing down. ‘The better the finish that is got on the bare hull, the better will be the result when painted. It I20 Hutt Gruep Up REApy To Carve, Note the “‘ steps ” inside and outside. THE OursIDE FINISHED. The next step will be to hollow and cut the sheer. The lead keel has been temporarily bolted into position. |To face page 120, : DB ‘ CS 2 Mipet, gp iioee ts RWIS ing PO” gps 7 nn i 7 PBs _ ; “. eS Says eg bia bein re eee i ti aay 3 – . “ QUACKY IE” (D. A. MACDONALD, CLAPHAM M.Y.C.). Designed by H. B. Tucker. Winner : M.Y.A, National Championship for 36-inch Restricted Class, 1950. [To face page 121, LOWI The operations are, however, described sepa- lying on paint to cover up rough rately for the sake of clarity. should be emphasised that glass ering should be done in the direction of the diagonals and across the grain. The inside has now to be carved out. In order to support the deck, it is necessary to leave a greater thickness along the gunwale A good result will not be obtained by rubbing down the glue joints will appear almost as fine as (see Fig. 53). If the deck is being fixed on top of the sides the hull should be left about 2 in. thick at this point, and this thicker part should, hair lines. extend downward for about #in. in the direction of the grain. When the hull is properly rubbed down, After shaping, the section marks If, however, the deck is being dropped in, this extra thick- will still be visible on the top of the sheer. Using the uppermost waterline (as represented ness will have to be increased to about 4 in. by the glue joint) as a base, measure off on the and extend downward for about ~ in. sections the height of the sheer. extra thickness that has to be left down the If the deck is to be dropped in, the height will be exactly as stem, shown on the plan. rudderpost, has already been referred to. If, on the other hand, it the thickness of the deck must step and round the In hollowing out, the wood can be gouged is decided to lay it right across on top of the sheer, under the mast The away until down to the grooves. be At this deducted from the height on each section. point a small round-bottomed fiddle-plane is Through the spots on each section the sheer the best tool to use, and with this the hull is line is now drawn in, using a spline. finished down to any required thickness. It is then cut down with a chisel and finished with glasspaper. If the boat is built of pine, the distance from the outside can be judged by holding her up to The glass-paper should be wrapped round a piece of wood longer than the breadth the light. of the boat, but only round the endinuse. have still plenty of wood left. As the wood resting the wood across the boat during the gets yellower and operation of glass-papering down, the top of brighter. the gunwale will be absolutely square across fear of going through the hull. the yacht. By If it appears very faint and red, you thinner the light shows If care is taken, there should be no It is very important to fair the But if you have the misfortune to go through sheer up properly, as nothing is more unsightly the hull, the pieces can be glued in place, ora than a sheer that is not a fair curve. suitable piece of wood let in. To cut the sheer and shape the inside com- Chips can be glued on to fill in a thin place. fortably, the boat is removed from the two In the case of a big boat, such as an A-class, pieces of wood that were screwed across the which has a very heavy keel, some builders fit gunwales. floor timbers extending from bilge to bilge, These pieces of wood are then well wrapped round with pieces of old cloth, to to take the weight of the keel. In the case of prevent marking the outside of the boat, and a hull which has been built exceptionally light, again screwed down to the table. Padding particularly if it is fitted with a removable keel, should also be placed between the boat and it might be an advantage to fit two to take the the edge of the table. main keel bolts. The boat will then lie This is, however, certainly in them as in a cradle, with her fin between the unnecessary in any smaller boat. pieces of wood. floors are glued and screwed through. The hull can be held down by a piece of webbing placed across the end 2k that is not being worked on. 2K If fitted, the 2k * The operations of cutting the sheer and Some builders use the alternative method of hollowing out are carried out more or less building bread-and-butter fashion on the but- simultaneously. tocks instead of on the waterlines. A good deal of the super- This, of fluous wood from the inside of the upper course, applies to the canoe body only, and the Jayets is fin keel is built up bread-and-butter on the cut away before the sheer is cut. After the sheer is cut, the inside is finished off. waterlines as usual. Bal MODEL SAILING CRAFT For building on the buttocks, the latter must be spaced not more than 1 in. apart, and, if necessary, buttocks will have to be taken out at suitable intervals. In any case, however, the centre layer must be arranged so as not to have a joint up the centreline of the ship, as this would be bad engineering, since the bolts carrying the heavy lead keel would then fall on a joint. Thus, if the layers were being made 1 in. thick, the buttocks would fall at $ in, 14 in., 24 in., 34 in., etc., cut from the centreline. As this is a bit awkward, it is a better plan to make the centre layer double thickness (2 in.) so that the other buttocks are more conveniently spaced. The advantages of this system are vety great economy of wood, and the fact that the backbone of the yacht is in one piece. Against this, the hull is somewhat more difficult to shape, and the beginner will probably find it easier to \ i laAAm build on the waterlines. If a 2 in. centre layer is used, considerable INTERNAL BRACE TO TAKE PULL OF THE SHROUDS. FIG. 57. economy might be effected by building up the centre layer in three pieces, rather after the fashion used to build the backbone of a planked is to use a wire instead of the strip brass. model (see Fig. 55). This will make a considerably stronger job also, as the grain of the lighter (see Fig. 57). Either is equally efficacious, and the wire is wood up the stem will run correctly instead of * being an end grain as in any other form of * * 2 The deck-beams must now be fitted, also bread-and-butter hull. * * * the rudder-tube, as explained in due course. * The inside of the hull must receive three coats of varnish. The down-thrust of the mast in an A-class Of these, the first coat should be boat is very considerable, and unless precautions are taken to counteract this, trouble is almost certain to follow. An internal stay (or varnish and turpentine mixed in equal parts. brace) must, therefore, be fitted from the kelson, under the mast step, to the gunwales, to take the pull of the shrouds. For this purpose some builders use a piece of }-in. half-round brass strip. This is let into the kelson under the mast-step and firmly screwed down. ‘The ends are carried to the gunwales, into the top of which they are sunk and screwed. The ends of the strap are bent over sharply to lie flat on top of the gunwale, and the screws When the hull is dry, the mast step is fitted driven straight downwards. The strap is bedded into the hull with white-lead paint. Another method of effecting the same result of the yacht. This causes it to sink well into the wood. The second and third coats are pure varnish. into position. In order to facilitate carrying, a handle is fitted to the bottom of the boat, immediately under the hatch. This can conveniently be made of stout leather, and can be held into place by the nipples on the keel bolts. The handle should be sufficiently large to allow of a comfortable grip, and should be arranged to come immediately over the centre of gravity harder to A badly-balanced boat is far carry. Another point which is worthy of consideration is that if the handle I22 DETACHABLE KEELS fort, and a handle coming just under the hatch keel-bolt cut off accordingly. The two faces of the keel at the joint will have to be brass, but this will be put on later. The first step will be to get the keel made and assembled with the lead. The holes that are bored through the hull will have to have is very convenient. a brass or copper tube through them of an is too low in the boat, the edge of the hatchway will take against the wrist in carrying. In a small boat this is a matter of no moment, but in a boat weighing nearly 4 cwt., it makes a considerable difference to the skipper’s com‘This is easily arranged by using a wooden handle of suitable size to internal bore that just clears a jg-in. rod. If fit the hand and fixing the ends by stout floors are to be fitted in the boat, the tube copper wire, using several strands. The wire should be left sufficiently long to allow for the is made fast to the top of the keel-bolts by tube reaching through the floors. the nipples, and, being flexible, allows the forming the keel-bolts should be left of such a handle to be pushed aside to bail the boat, or length that they will protrude about ? in. for any other purpose when it is in the way. through the tubes into the boat. If a leather handle is used, this must be renewed every two or three years. The rods The top ends of the keel-boats have to be threaded down about 1 Leather in. and brass butterfly nuts under the action of water, particularly salt fitted. water, rots in time, as the oil and dressing dry put a piece of wood with a hole to act as a up. washer and prevent the tubes being withdrawn Do not wait until the handle actually Until the floors are fitted it is wise to breaks as the boat may be dropped and badly by the weight of the keel. damaged, but inspect the handle occasionally temporarily inserted at first, and can be with- and renew at the first sign of perishing. drawn during the operation of cleaning up *K *K * the inside of the boat. * The tubes are only When all is ready, inside and out, and the floors (if any) in posi- If it is desired to fit a detachable keel, this must be arranged for early in the building. tion, the fitting of the brass keel faces can be If attended to. Two strips of brass are cut, and possible, the keel should be arranged to take two holes bored of the right size to clear off straight across the boat at a waterline just the keel-bolt tubes in the upper one and the below the hull itself. keel-bolts in the lower one. This will enable the The hull is now hull to be handled conveniently and stand level turned upside down, and the upper face put when it is put down. into place temporarily. If the boat is of the fin- and-skeg type, the joint should be below the The lower face is then put into place and two pieces of rod passed bottom of the rudder, if possible, to avoid through the holes into the tubes to make sure injury to that important part. it registers exactly. In order to take off parallel with the L.W.L., part of the The next step is to fit a stud at each end of deadwood will have to come away with the the keel to prevent it wringing. lead. ance Instead of using four keel-bolts, two of a much stouter gauge will be required. The of stressed. keel alignment has The import- already been It will, therefore, be sufficient to say that the fitting at this point must be extremely keel-bolts will be made from };-in. brass rod. In order to keep the lead and the removable carefully done. part of the deadwood together, a stop must be perfectly, remove the lower face, and with a braised, or hard soldered, to the rod at such a scriber lightly mark in a centreline. level that it will just come below the surface of suitable distance from each end, which will the deadwood at the joint. entirely depend on the thickness of the keel, The bottom end After making sure that the two faces register At a of the bolt is threaded up for about 4 in. and make a punch mark on this centreline. fitted with a nut. place the face, and using the punch marks, drill right through the two faces and about 3% in. The keel is recessed so that, when screwed home, the nut will be just below the surface of the lead, and the bottom of the into the wood of the hull. 123 Re- Both faces are now Brass Se Face Plates Prass Face Plates Fic. 58. 124 be tested, and if all has been accurately carried twice the thickness of the out, should fit exactly. face is now replaced and If necessary, the holes for the studs in the with a scriber and cut just out- hull can be eased in the wood, provided the The face is now replaced on the brass remains a good fit; but if it is necessary ing bedded in white lead. The tubes ilarly bedded and put finally into posi- to do this, the brass should be removed whilst .. The brass face is drilled and fastened with brass screws to the hull. The face can be now trimmed down with a fine file. The inner end of the tube should be slightly belled outward, to fix it firmly into the bottom of the boat or floor, as the case may be. The bottom face has now to be attended to. Place the bottom face in position on the detachable portion of the keel and drill holes into the wood to take the studs. Mark round with a scriber, remove and cut to shape. As the thickness of the brass has been allowed-for the holes in the detachable part of the keel, . so doing. The studs remain permanently in and can be bedded there in white lead. In order to protect the wood in the upper part, the holes should be well doused with oil, which will soak into the wood. The bolts and studs should themselves be well oiled before putting together, to obviate sticking. the butterfly nuts Under a leather washer with a metal washer on top will obviate any leakage. The handle can be put on to the keel bolts if desired, but this will mean that with the keel off there is no handle to carry the boat. Alter- already, there will be no need to remove more natively, it can be secured to the bottom of the wood. ‘Two pieces of brass rod are needed to make the studs. These should be 3 in. long and of a size to fit the holes in the face plate. These should be hard-soldered into the face hull and well screwed down. plate with 4 in. below the plate and ¢ in. so as to be out of the way when it is desired to adjust the keel-bolt nuts. The whole arrangement is above. The upper ends can be rounded off slightly, but not down to the plate. The face is now replaced and fixed into position. It is in Fig. 58. then trimmed off exactly. butter model with a full keel. The keel can now 125 In that case it is best to have the handle between the keel-bolts, shown clearly The top drawing in this figure represents a planked model with a fin-and- skeg keel, and the lower one a bread-and- CHAPTER XIII The Construction of Planked Yachts. Setting Up. Various Systems Explained. Planking Up. Making the Moulds and Muiti-skinned Hulls Tin methods of planking a model yacht In building a large wooden vessel, the prac- in the main follow real yacht practice, tice is to lay the planks with a slight gap but, naturally, there are certain minor differences due to the difference in size. Yachts are built either on cut timbers or between, into which caulking is forced with with bent ribs, or a combination of both. said to “ take up ” until she becomes tight. caulking chisel and mallet. This allows for the wood swelling as it gets wet, and a vessel is The In cut timbers in a real yacht are formed from smaller constructions, a single thread of caulk- natural crooks (or bends), and in the old days ing cotton is laid between each plank during a shipwright used to set great store by his stock of oak crooks. To-day, the use of cut timbers is almost entirely confined to fishing- the building. boat work. the good fit of their planking. In smaller work still, nothing is put between the planks. Canoes and simi- larly finely-finished light craft rely entirely on In models, bends are not available, and therefore this form of construction would In models, which can be adequately protected against the be very weak, owing to the fact that some part damp reaching the wood, and kept entirely of the cut timber (or frame) would be across the tigid so that they do not work, the best plan grain. is to make the planks a good fit and glue them To get the necessary strength, very heavy frames would have to be used, so that edge-to-edge. the method cannot be recommended. model one piece of wood from gunwale to Its one This practically makes the advantage is that it dispenses with the use of gunwale. moulds, as the frames answer the purpose of varnish, and put the planks on with their edges moulds also. luted with this. Some model builders use three- Some builders prefer to use thick ply, or even five-ply, to make their frames, but Whichever system is to be employed, the this is very bad engineering, as the fastenings first step is to get out a full-size profile and are put edgewise into the plywood in such section plan of the yacht. a way as to tend to force the layers apart. this was explained in a previous chapter. It is, therefore, best to use bent It will now be necessary to decide how far timbers down the planking is to be carried. throughout. There are two main systems of building with bent timbers. The method of doing The first is to bend the timbers on to the moulds and plank up on these. Some builders treat these timbers, which are bent Some builders like to plank down nearly to the lead, in imitation of the real yacht, but this is unnecessary labour, from which nothing is gained. ‘The real yacht is, of course, hollow on to the moulds, as main ribs, and when the right down to the kelson, but if a model were boat is planked up, bend additional ribs of hollowed down proportionately low, it would be impossible to dry her out. lighter scantling into the boat in between. The first thing to decide is, therefore, how Others do not put any extra timbers into the boat, but trust to those originally put in. The second method of planking on bent timbers is to build a former over the moulds and bend very small timbers over this at close intervals and plank up on these. This is the best method of planking, as a stronger and lighter hull will result. It takes slightly longer, but the result is well worth while. far down the hull is to be planked, and below this point the fin (or keel) will be built in layers bread-and-butter fashion. Thus the top layer of the bread-and-butter keel forms the kelson. A study of Fig. 55 * will make this clear. In deciding how far down the planking is to 126 * See Folding Plate XII facing page 117. “YANKEE DOODLE” (A-CLASS), BUILT BY A. E. BULL, U.S.A. Cag ap Rear : ~~ THe Boat IN FRAME. Note the planking rabbet down the stem and the sheer strake tacked into position. ‘The building board used by Mr. Bull is wider than that suggested in this book, but there is no great advantage either way except that the narrower board uses less wood and ts possibly easier to handle. The excellent photos of “ Yankee Doodle,” “ Polka Dot” and “ Claire” which illustrate this chapter were supplied by Mr. A. E. Bull, the well-known American builder and model-yachtsman, [To face page 126, LAASA ‘ “3 a ANOTHER VIEW OF “S YANKEE DooDLE” IN FRAME. The completed boat is shown in the photographs facing page 132. [To face page 127. : SETTING UP A PLANKED HULL nd, a point to remember is that the reverse of the yacht to plank, but the real deciding After putting in the backbone on the profile drawing, a datum line must be struck on the plan to show the building-board. This should factor is the width across the sections in this be about an inch above the stemhead, and part of the boat. parallel to the L.W.L. turn of the garboard is the most difficult part Having decided where the kelson is to The construction of a T-shape building backbone can be of pine, cedar or mahogany, board was fully explained in Chapter XI, so need not be repeated here. The moulds have next to be prepared. The but the two former are preferable on the score full-sized section plan is laid over a sheet of of weight. fairly stout cartridge paper and the section come, it will be necessary to draw the back- bone in on the full-sized profile. The fin and Ifit is intended to paint the boat all over or up to the waterline, pine is preferable pricked through. for the fin. waterlines must also be marked in. If she is to be varnished on the Centreline, buttocks and The half section so found will have to be drawn in with lower part, it must be cedar or mahogany. The forward part of the backbone will have a flexible spline and a sharp pencil. By folding the stem incorporated with it, and on the score the paper up the centreline and cutting out of strength, mahogany is best. the double thickness, the whole section will be The after part of the backbone can be of pine, mahogany. govern the The same choice cedar or considerations of material, as for will the obtained and both sides will be alike. The shape can be checked after cutting by laying it on top of the full-sized section plan. kelson. Obviously, if the moulds were made the The forward part of the backbone for an size of the sections, the boat would be increased A-class model will be made of 1-in. wood, by the thickness of the ribs and planking. and its depth (or moulding) will depend on will, therefore, be necessary to reduce the paper the size of the boat and the shape of the bow template from which the mould is to be made waterlines at the particular point. by an amount equivalent to the thickness of The actual It stemhead of a boat of this size will require to the be about 3 in. from back to front. It must be method of building over a former is being remembered that a boat of the A-class weighs used, the thickness of the battens which com- anything up to 56 lb., and in the case of a pose the former will also have to be taken into collision the force of the blow on the stemhead account. is very considerable. be 4 in., and the ribs are to be } in., the The after part of the backbone can be cut planking and ribs. If the alternative For example, if the planking is to amount to be taken off will be + in. If the from 1I-in. wood, but need not be made so method of building on a former is being used, strong, and also the shape of the forward water- the planking might be } in., the ribs yg in., and lines is more acute than those aft. About an the battens in the former } in., so that the inch will be enough for the siding and 3 in. for amount to be taken off in this case would be the moulding of most of this afterpart. je in. It must Lines will have to be drawn parallel be borne in mind that there must always be a to the outer skin, and the size of the paper sufficient depth of wood from side to side to patterns fasten the planks and take the two rabbets in which the plank-ends are housed. The wood method of doing this is to use a small pair of which is left must also be sufficient to ensure to the required distance. a reasonable margin of strength. largely govern how far the are carried out at the ends, and the construction of this part of the boat requires to be carefully considered. Ina keel-type boat, this will apply particularly at the after end of the keel. accordingly. The best dividers, preferably a spring bow, and set them This will garboards reduced As the fin will be built up solid, the moulds in the centre part of the boat will only be required to come down to the kelson. At the ends, it will be necessary to carry the patterns down the full depth and then slot them in the centre to receive the backbone. 127 MODEL SAILING CRAFT ——— The top of the paper patterns should be carried right up to the datum line, as method. the On the waterline plan draw a line representing the width of the stem parallel with moulds are to be mounted on the building- the centreline. board which this represents. each waterline is the position of the rabbet-line Similar paper patterns, complete with on this particular waterline. buttocks and waterlines, are made for every section. pieces Now if the water- lines have been put on the stem, when marking They are then pasted on to suitable of whitewood, + in. The point this line intersects out for cutting, it is an easy matter to transfer thick, and the these points to the stem. A line is now run moulds cut out just outside the paper, and through them following the contour of the trimmed down sharp to the outline. stem. The boat is to be built upside down on the For the bearding-line set the dividers to the building board, and the next step is to set up the thickness of the skin planking, and find from moulds. This is done exactly as was described the Waterline plan the spot on each waterline in Chapter XI, except that the sharpie moulds where the planking runs to the surface of the are in two parts (the floor and the mould stem. proper), and those for a planked hull are not Next with the marking gauge put a centre- divided as the whole mould is removed when line down the foreside of stem. planking is complete. marking gauge put in two more lines 7 in. In order to prevent the moulds shifting, a With the on either side of the centreline and parallel to couple of battens are lightly tacked along each it. side of the boat. wood between the rabbet-line and the cut- The next step is to prepare the backbone. This gives a cutwater 4 in. wide, and if the water is carved away, the forepart of the stem This is made up in several parts, as shown in Figure 55.* The middle part, which consists of the kelson, is laid off from the waterlines, as will be correct to shape. explained in the chapter on Bread-and-butter Construction. After this has been marked out on both faces, it is cut out and carefully carved to shape. The forward part of the backbone is now marked out from the plans. The stem- for the depth. be cut out. The rabbet can now It will facilitate this operation if a slip of the planking wood is used as a gauge The after patt of the backbone is similarly cut out and shaped, and the rabbet cut. endings are not so acute an angle as those fotward, the method of marking the rabbet-line head must be made long enough to reach to the building-board, and in order to facilitate screwing to this during building operations, a tab of wood should be left on the foreside of the upper continuation. This is shown in the as detailed for the stem does not apply, but the builder will not find any great difficulty on this score. It will be noticed that on the Con- struction Plan (Fig. 55) the after part of the backbone butts on to the centre part. diagram. Now the planking of the yacht has to be rabbeted into the stem. The rabbet (or groove in which the plank-ends lie) is the full depth of the thickness of the planking at its forward edge, and gets shallower until the point where it comes to the surface and the planks leave the groove. The front edge of the groove on It should be noted that as the after waterline The object of this is to leave sufficient wood to carve away when the skeg is fitted, and thus obviate a hard angle at the junction of these parts of the structures and permit the round of the garboard to be continued up to the rudder tube. The skeg should now be fitted. It will be noted that an alternative method of the stem is known as the “ rabbet-line,”’ and the point where the groove comes to the surface as the “‘ bearding-line.” Both of these can be determined from the plans by the following fitting the skeg was given on Folding Plate X inserted in Chapter XI. able to using screws. This is really preferThese parts are now carefully glued and screwed into position on the kelson. The greatest accuracy is needed to get these correctly aligned, as if they are the * See Folding Plate XII facing page 117. 1238 : . B-CLASS), BUILT By A. E. BULL. ml = metat 4 . + we The stern view of this celebrated model during construction shows the builder’s system of planking with closely spaced ribs. [To face page 128. “PotKka Dor a5 PARTIALLY PLANKED Up, Note the tissue paper between the ribs and th e former, [Vo face pave 129. THE FASHION-PIECE most important thing in building a planked hull, as otherwise a twisted hull will result. If the rabbet for the garboard has not been cut along the kelson, this must now be done. st bit out, the boat will be out of truth and sail differently on the two tacks. The fashion-piece has now to be made. Taking a piece of cedar or mahogany of the As the kelson is already shaped, there will correct size, draw a centreline in the direction of the grain. On this top face set out the deck- The fashion-piece be no difficulty in doing this, especially if a slip of the wood for the planking 1s taken for a gauge of the depth. The slots to house the ends of the ribs must also be cut in the kelson. As the planking has to lie flush in the rabbet, the slot must be sufficiently deep to permit the rib to drop down level with the bottom of the rabbet. Provision has to be made for the for an A-class boat will have to be the fore- rib to have a good holding on the kelson, and line at this point. For the benefit of the tyro it may be explained that the “ fashion-piece ” is the extreme stern of a boat with a counter. The board across the end is known as the “transom.” The centreline must be carried right round the block of wood that is being used for the fashion-piece. and-aft distance covered by the rake of the the slot should allow the rib to come at least transom plus 1 in. 2 in. on to the kelson. Upon the forward vertical face of the wood lay off the section of the boat The planking should extend below the ends of the ribs, so that the at that point, and upon its after face the section rabbet-line will have to be at least 4 in. below that would have been made the upper face of the kelson. had the boat finished with a vertical transom. Up to this point the procedure is exactly Care must be taken to give the deck the proper camber similar, but if the boat is to be built over a on the after end. Starting with the bottom face, the block is now carved to shape. A former, it will now be necessary to make this. The former (or jig) is made of strips of wood rabbet has next to be cut to allow the planking Finally, a slot must be cut to about 4 in. wide and exactly } in. thick. to lie flush. thickness is a matter of moment, as it must be The allow the backbone to be checked into it, and the same as allowed when taking the thickness two slots to house the ends of the inwales. off the patterns for the moulds. The fashion-piece is now fitted to the back- importance that these battens should be in one bone with glue and two brass screws which are placed in the rabbet, where they will eventually be hidden by the planking. By referring to the profile plan, it will be seen that the fashion-piece will not reach the length from end to end of the boat. building-board. A suitable piece of wood must be cut and screwed to the top of the fashion-piece to pack it up to the correct dis- turn of the garboard the strips should be fairly to the moulds, it will be found that they only tance from the building-board. touch the forward moulds on their forward The backbone is now ready to be dropped into place in the slots along the moulds. The stem and stern are secured with screws to the building-board. Before proceeding any further, again carefully check over all the moulds, and see by the buttocks and waterlines that they are in perfect alignment. The importance must also be stressed of getting the various parts of the backbone in perfect alignment, and setting up the backbone dead square to the building-board. The proper alignment of the backbone and moulds is the M.S C. It is not of any Their sole purpose is to form a frame over which the ribs can be bent to shape. On the sides where the section is more or less vertical, larger gaps can be left, but round the bilges and in the reverse close together. edges. When these strips are offered Similarly, on the after moulds, the strips will only touch the after edges. The moulds will, therefore, have to be rubbed down till the strips take properly right across each mould. At this point it can be seen that all the curves are fair. If anything requires adjusting, this must be done now. The strips should take on every mould without having any flats or humps, and, if necessary, any section mould must be padded out or reduced. Ifa properly- drawn design (such as those that accompany this book), has been used, and care taken in 129 K MODEL SAILING CRAFT its enlargement and laying off, little or no If the model is not being built on a former, adjustment of any kind should be required. the inwale (or shelf) must be put into place This adjustment is called “ fairing-up.” When before the ribs are set up, and the upper ends everything is nicely faired-up, the strips should The distance between the of the ribs glued and screwed to it. The shelf will render it a matter of difficulty to remove strips can vary from 4 in. to $ in., according to the moulds from the boat unless due precau- which part of the boat is being covered. tions are taken beforehand. be nailed in place. The It is a very good strips are fastened to the moulds with brads. plan to make the moulds in two halves. Before the ribs are set up, the former must be order to keep these together, a piece of wood covered with tissue paper, or better still, with can be screwed across near the top asa tie. The cellophane. second tie, which is put lower down, can be The object of this is to prevent the ribs and planking sticking to the former nailed instead of screwed. In It will be quite easy and causing great difficulty when the time to reach the upper tie to remove the screws, comes for the boat to be removed from the and the lower tie can be levered off with a screwdriver when the moulds are taken apart to facilitate removal. In the case of a model built on a former, it would be a matter of the very greatest difficulty to get the boat off the former if the shelf was put into position, and it should not be put in moulds. If a former is not being used, the fairing-up process must be carried out after putting the ribs into position. Any necessary packing up can be done by putting a chip or slip of paper between the ribs and the moulds. If necessary, the mould itself may be eased, but any minor adjustment can be done by rasping the rib until later. itself off. thoroughly, the boat is ready for planking-up. In a big yacht it is customary to start planking at the bottom, the garboard being the first strake to be laid, and the sheer strake the last. In canoes and light craft, very frequently planking is started both at the top and bottom. The last plank put on is a “shutter ” plank somewhere on the turn of the bilge, which fills the gap between the top and bottom planking, and completes it. Many model makers consider that it is easier to start with the sheer strake. One reason for this preference is that one will thus be working upwards instead of downwards. The main disadvantage is that when it comes to the garboard strake there will be two edges to fit at once. This can be got As The ribs themselves will have to have their forward or after edges, as the case may be, rubbed off, to permit the planking to take evenly across them. The best implement to use for rubbing down the ribs is a sheet of glass-paper wrapped round a flexible slip of wood. This will rest across the ribs and ensure their being faired properly. The ribs themselves can be made of white oak, American elm or Italian walnut. The last- named wood is not generally used for this purpose, but will be found very suitable, as it is reliable and easy to work. It is particularly good when the boat is being close ribbed over a former. The wood must be cut into suitable strips for the ribs and boiled for a couple of hours to make it pliable. The ribs can then be bent over the moulds or former, being lightly secured into position with brads or panel pins. The lower ends are fixed securely into their slots with glue and brass screws. If the boat is not being built on a former, the size rib to use for an A-class model will be 3 in. by } in., and they should be spaced about 3-in. centres. In building on a former, the ribs can be 2 in. by 7 in., spaced 14-in. centres. soon as the ribs have dried out over to a certain extent by adjusting the rabbet a little if required. In the present description of the methods employed, it will be assumed that the model is being built on a former and planked from the sheer strake upward. If the reader wishes to start his planking with the garboard strake, or is not using a former, he will easily be able to deduce the small alterations of method necessary as he goes along. The planking of a model is not as difficult 130 PLANKING A HULL might appear, and the main qualities called for are care and patience. Before starting, it must be emphasised that o# no account must the planks be forced up at the ends, as this will cause the yacht to hog (7.e., the ends to drop), immediately she is taken off the moulds. The object of the builder should be to make the planking lay naturally from end to end of the boat without forcing it edgewise at any point. Before starting to plank, it must be con- sidered whether the deck is to be dropped in real yacht fashion, or laid across on top of the sheer strake. Whilst it is quite satisfactory to adopt the latter plan for a bread-and-butter boat, it is not so suitable for a planked yacht. In the case of a varnished boat, the deck, if not Roughly, the planks that start at the turn of the stem should be about on the bilge on the midship section, and finish at the junction of A batten the backbone and fashion-piece. should be bent round the moulds through these points and adjusted until it makes a fair The intermediate sections can be curve. marked accordingly. This line will give the bottom edge of about the seventh or eighth plank down on an A-class model. For a boat of this class, the planks on the topsides will be about # in. wide on the midship section. It is customary to make the sheer strake a trifle wider than the other planks, and not so tapered totheends. This is entirely a matter of appearance. With a pair of dividers, set out In any case, in a planked boat, whether the requisite number of planks on each section, and then transfer the markings to the other painted or varnished, the builder will be well side of the model, checking the marks for the advised to drop the deck in. of this method as being more like a real yacht bottom plank with the batten. Divide the distance below this plank to the than fixing the deck across the top of the sheer, garboard rabbet into three parts, and proceed dropped in, will show a line along the sheer strake. We have spoken but actually ina real yacht a “‘ covering board ” to set out the rest of the planking in groups. is used. It will be seen that the planks change gradually and, as mentioned above, the garboards are ‘The ribs are carried up level with the top of the sheer strake. The covering board is put on top of the sheer plank, ribs and shelf right round the vessel and thus forms an edge to the deck planking proper. In a model yacht, however, it would not be feasible to wider at the ends than at the middle. The experienced builder will not require to divide his sections up in this manner, but the novice will find it a great assistance. fasten a covering board to the top of }-inch There are several methods of arriving at the planking, and the deck is accordingly dropped correct shape of the planks, but the easiest is in and rests on the inwales. to use a “ spilling plank ” (or “ trying plank ’’). When this is done, the sheer will have to A piece of wood similar to what is being used be carried to the full height shown on the plan, for planking up is cut about 3 in. wide and a but the ribs will have to be cut off level with suitable length. the inwale, which will be lower than the top of It will be found that when the centre is in the sheer by the thickness of the deck. Now, in This is offered to the boat. position on the midships section the ends are order to make the planks lay properly, they have to be cut to varying shapes away, so that the correct plank will have to be concave. Tack the trying plank into position, and breadths, so as to cover each section pro- arranging matters so that the gap at each end portionately. is alike. It will be found that the planks below the bilge are wider at the ends than in Mark on the plank the position of each section. ‘Take a pair of dividers, and the middle, and those above the bilge wider setting them about } in. wider than the gap, in the middle than at the ends. prick The curvature that each plank is cut to is known as the “ sny.” The first thing to do is to divide up the sections into widths, representing groups of planks. The diagonals on many designs give a idea good of the lay of the planking. 131 off each section. The hull can now be removed from the former, and the shelves (or inwales) fitted. The shelf is a very important part of the structure of a yacht, and it is a mistake to make these too light. For an A-class model In an A-class, or other big boat, especially when a detachable keel is fitted, it is advisable to fit two floors across the boat from bilge to bilge in the way of the main keel-bolts. These are best of mahogany, and can be cut from #-in. wood. ‘Their depth should be about 2 in. where they cross the kelson. The fitting of the keel, braces for the shroud a suitable size would be } in. wide by # in. deep. plates, The greatest strength is needed at the rudder-tube, mast-step, etc., are ex- plained elsewhere in this book. shrouds and in the middle of the boat, and these could with advantage be tapered down If the boat is of the fin-and-skeg type, the to $ in. deep at the bow, and # in. at the skeg should have been fitted when the back- stern. the bone was assembled. If the keel is fixed, this could also have been bolted to the backbone The height of before setting up, though many builders do Suitable slots are cut in the stem and fashion-piece to house the ends, shelves sprung into position. and the shelves is governed by whether the deck not do so for the sake of convenience. is being dropped in or not. case it should have been made and carefully The best material tested for alignment with the backbone before for the shelves is pine or cedar. the boat was set up for building. Before finally fitting the shelves, check the beam of the boat and, if necessary, adjust this It has been mentioned that when a boat is built on ribs spaced at the sections, it is often before inserting them. It will be seen that when the shelves are in desirable to fit extra ribs in between the main position, there are gaps between the shelves and the sides In any between the ribs. ribs. There is no difficulty about bending Packing these additional ribs into the hull after removal These are from the moulds, but the slots in the kelson made from slips of pine, and are arranged the and backbone to receive the ends will have same height as the top of the shelves. to be cut before planking is started. pieces have to be fitted into these. ‘The The ribs packing pieces are fixed into position with must also be put into position before glue and pinned through from the outside. packing pieces are fitted along the shelves. It would be possible to use a thicker shelf and the The hull is given three good coats of var- notch it for the ribs, but were this done, a nish inside. series of bends and flats would result, instead varnish and half turpentine, to sink well into of a true curve. the wood. The first of these should be half Should there be any places where The beam of the yacht should again be care- the light shines through the seams, care should fully checked to make sure that she has not be taken to work the varnish well into these sprung, and two or three temporary ties put to act as caulking. At the same time, if a gap- across her until such time as the deck beams filling glue has been used, there should be no are made and fitted. seams that require caulking. The pins are now replaced and driven home, using a light hammer and a pin punch. The ends are turned over inside the boat. The 2k * * ok For many years, craft with double and triple best method is to turn these downwards and skins have been built punch the point in flush with the grain of the where especially strong and water-tight hulls tib. were ‘The use of a cupped-head punch of suitable size for driving the pins home can be recommended. It avoids any chance required, a for special good example purposes, being the R.N.L.I. lifeboat. of The usual method of building these hulls bruising the wood with the hammer, and the was to lay the first skin at an angle of 45° to the cupped point prevents the punch slipping and keel with the strakes raking forward. scarring the strakes. second skin was laid raking aft, and between 133 The MODEL SAILING CRAFT the skins was a layer of silk or cotton material. set These hulls needed very few ribs or frames, between the moulds are nearly filled with and were often built with none at all. scrumpled newspaper and then filled up with This up on the building-board form of construction was known as “ double- plaster of Paris. diagonal,” faired up with coarse glasspaper. In “‘ triple-skin ” hulls a third skin was laid, which usually ran fore-and-aft like normal necessary system of boat-building In this a double skin is used with both skins raking aft, the seams in the lower skin being covered by the strakes of the upper skin. When resin glues were introduced, laminated hull construction became a practical pro- position. Two wartime examples .were the dinghies carried by Motor Torpedo Boats and the Air Sea Rescue lifeboats dropped from of course, were weight. The batten method is, The backbone of the hull must be-constructed in the same way as for an ordinary cost involved, but later Mr. Herbert J. Ash- These, The object however, recommended by the authors. yacht work because of the extra labour and planes. When dry, the plaster is is to economise plaster and also avoid un- Neither of these systems was much used for which bears his name. spaces of partly filling in the spaces with newspapers planking. croft invented the the planked hull, and the rabbet cut similarly. If the model is to have a heavy lead keel, it will be advisable to fit floors. These can either be made and fitted after the skin is finished and the boat off the former, or they can be made and fixed to the backbone beforehand and the boat built onto them. Probably most builders will prefer the latter, but in such case provision will have to be made for the floors when the former is being made up. repetition Having made the former and put the back- jobs, made with hot setting glues and requiring elaborate plant for their manufacture. However, simpler methods have now been evolved that are suitable for the use of ordinary boatbuilders, and these can be modified to suit model yacht builders. The first step is to build a former in the manner described earlier in this chapter, but bone in position, the former must be covered with cellophane or coated with anti-adhesive lacquer. The latter will probably be found more convenient in the subsequent work. since ribs are not necessary in hulls built by this form of laminated construction, the amount by which the sections have to be decreased in making the moulds will be the skin thickness plus the thickness of the battens. It was explained in Chapter X that in making laminated bent constructions, a minimum of three lamina should be used. So we will assume that our hull is to be made with three skins of veneer ay in. thick. That gives us #, in. and as we shall have two glue lines also, we can call the total skin thickness 4 in. The best wood to use is probably mahogany, but in this form of construction it does not make much difference, so long as the veneers are of dry wood. An alternative method of making a former for this form of building is to make the moulds full size less only skin thickness. When The object is, of course, to obviate any chance of the boat becoming stuck to the former. Before the first skin is laid, we have to decide how the skins are to run. There are two alternatives. These are:— (2) The first skin is laid diagonally, raked with the gunwale end of the strake forward; the second skin rakes the reverse way with the gunwale end aft; the third (outer) skin is laid fore-and-aft following the lay of ordinary planking. This is ornamental in a varnished boat but has no advantages otherwise, and the strakes are much more difficult to shape and cut into a great deal of veneer with much waste, (b) ‘The first skin is laid at right angles to the keel ; the second skin is laid diagonally raked with the gunwale end forward; the third skin (outer) is laid diagonally the reverse way with the gunwale end aft. This method is recom- mended. In ordinary double skin diagonal planking, the strakes were laid at an angle of 45° to the 134 Te = = a LAMINATED CONSTRUCTION strips tapered, but this will be seen when he gets down to the actual work. Great care is needed to get the skin down to the former all over and see it does not “ blow” (#., lift off 1, but for this laminated three-ply construc- tion, 60° has been found better and easier. The veneer is so thin it can be cut with scissors or a razor blade into strips. The width of the former) anywhere. the strips will depend on the size of the boat, The second skin is easier to lay than the first, its design, and the part of the boat that is being dealt with. 86«=«hldh However, for an experi- mental first strip, try one 14 in. wide. Offer since there is now something to glue it to. Again start in the centre, but this time the this to the boat amidships, fitting the end into strakes are laid diagonally. the keel rabbet. fitting is just the same, but care must be taken The strip should be long The process of enough to overlap the gunwale by about $ in. not to cut into the first skin. If you happen to possess a few of those glass- in doubt about this, he can mark with a sharp headed drawing pins that were sold to hang up It will be seen that the edges want peticil instead of cutting straight away with the razor blade. As the builder, in the course of fitting and glueing on the second skin, comes to the tacks holding the first skin to the mould, these must be taken out. In glueing, the separate application method should be used, the resin being put on the first skin and the hardener on the second. This gives a firm surface on which to spread the resin. The second skin is papered in the same way as the first, and it is also tacked to the former as required. It should be mentioned that it is not shaping to make the strips lie snugly alongside a matter of any great importance if there are each other. “ stealers *? * in a laminated hull, though they photographic films to dry, they will be ideal for use during the operation of fitting the strakes. Failing these, use very fine nails to tack the strip of veneer in place. Now ob- viously the strips will not be the same width throughout their length, but widest on the turn of the bilge and narrowest in the garboard. Cut a second experimental strip of veneer and offer it to the boat alongside the first, also keeping this at right angles to the keel. Let the second strip overlap the first so that no gap shows and tack in place. If the builder is are very bad practice in a planked boat. Take a razor blade and using the edge of the In this glueing a fairly fast hardener can be second strip as a guide, trim the edge of the used as all that is wanted is the time to put the first one. fitted strake in position and tack it down. The Remove the surplus bit of wood Strakes are worker is reminded that the resin should be put on either side of the boat alternately, and the two strips should then fit. thinly and evenly applied, because it is not working first forward and then aft. possible to get a cramp on the work. As each Hence if strake is fitted, it is glued into the keel rabbet. there is a heavy coat of glue, a thick glue line The seams between the strips are “ papered ” will result. as made and the strips are tacked to the former, ever, be used, and this will also stop all the A gap-filling glue should, how- the pins being driven only half-home to facili- tack holes in the inner skin. As was explained tate removal. in glues The term “papering”’ means Chapter X, gap-filling only need that a narrow strip of light brown paper is sufficient pressure to ensure the surfaces being gummed down the seam. This should not be brought into good contact, but the worker more than about 4 in. wide, and need not should press the second skin down as hard as necessarily be in one piece. he can using a cloth wrapped round a piece of The gummed brown paper strip sold for doing up parcels wood of suitable shape. would be very suitable for this job. When the second skin is dry, the brown In most boats it will suffice to have one shaped edge to each strake, with paper tape should be damped and taken off. the sole It was left on the first skin, but we are now exception of the centre one which will have two shaped edges. The builder may find it more convenient and economical to cut his 135 * A “stealer ” is a short strake inserted to filla gap between full length strakes. MODEL approaching the outside of the boat. SAILING CRAFT The boat can now be removed from the When this has been done, the boat should be well former, glass-papered until it is absolutely smooth and These should be prepared before the boat is there are no ridges. and the inwales glued into place. taken off the former, leaving just the final The third skin rakes the reverse way, but fitting (z.e., the chamfering off the fore end to otherwise is fitted and glued in place in ex- fit against the stem, and cutting to length) to be actly the same way as the second. ‘The tack done now. This is desirable as the hull should holes in the first and second skins have been not stand too long off the former without filled up by the glue, but those in the third inwales. skin will have to be stopped by hand, so only the skin should be tacked to them along the as gunwale. The beam should now be checked, and if necessary corrected, as was explained for many tacks should be used. as are absolutely necessary Most of the tacking can be Immediately the inwales are in place, avoided, except along the garboards, by bind- a planked boat, and a temporary tie put on ing right round boat and former with surgical from gunwale to gunwale, being screwed to bandage. If this is done, cellophane should be put between the skin and the bandage to avoid sticking. Along the keel rabbet and stem and the inwales. stern rabbets, also across the floors, the tacks used can be the same little copper nails that are used for ordinary planking, and they can be No ribs are necessary, but at least two floors are highly desirable, especially in a big heavy boat. If these have not been built into the hull, they must now be fitted. In a large model, it might also be advisable driven right home as they will be left per- to fit a bilge stringer. manently in the boat. this could be } in. thick by 8 in. deep at the centre, tapered off to 3 in. at each end. These laminated hulls are watertight, light When the third skin is dry, remove the tacks and stop the holes left with plastic wood, or white lead stopping made with gold size, and the hull set aside until the stopping is thoroughly dry. The brown paper tape has also to be removed. The skin is then glasspapered until all ridges disappear and the sur- face is brought to a fine finish ready for painting. The next step is to mark the sheer line on each side of the boat. This is done by measuring up from the building board on each section station. When these spots have been found, a line is drawn through them using a batten. For an A-class model, and strong, and also economical in material. There is one caution that must be given about laminated hulls. The double-skinned hull has a considerable tendency to hog * when taken off the former, but the triple-skinned is better in this respect. In either case it is advisable to make the backbone of a laminated hull about 15 per cent. heavier than for a planked model of similar size, also to check the hull carefully before putting the deck on. * A vessel is said to “ hog”? when the ends drop somewhat and the sheer flattens out. 136 CHAPTER XIV Lead Keels. Making Plaster Moulds for Casting. Casting. Drilling Lead. Sand Moulds. Casting a Keel. Tables of Weights and their Uses. Finishing up a Fixing a Lead Keel. HE casting of a lead keel is a task which 15 in. diameter. the builder may well be excused for not thirds full of clean cold water and plaster 1s attempting, as it is by no means an easy poured into the centre of the bowl until it The bow] is filled about two- matter, especially with the resources that the shows above water. amateur is is taken and the plaster is stirred until all the likely to have at his command. A large clean iron spoon Moreover, the cost of getting a casting made lumps have disappeared. at a foundry is very little more than what must the consistency of thick cream and be gradually be paid for the actual metal. thickening. If, however, the amateur builder has not a It should then be of Pour the mixture into the box until it is full, The wooden pattern is now foundry near, or wishes to do everything for pressed firmly into the centre of the plaster himself, there are two methods that can be until it is half submerged. used, as the mould can be made of plaster or have become very thick by this time, so with sand. an old knife smooth the top surface over. Probably the amateur will find it easier ‘The plaster will It to cast in a plaster mould, but both methods is not necessary to get this mathematically are given here, and the builder can take his level, but there should be no lips on the sur- choice. face, otherwise the other half of the pattern Whether the keel is to be cast at a foundry will not part from it easily. Any airholes or at home, the first essential is a good pattern. showing on the surface should be filled in with Fvery plaster. little irregularity of surface in the In a short while the plaster will be set and pattern will be multiplied in the casting, and it is, therefore, imperative to rub the pattern can be further trimmed up, and any loose down until it is absolutely smooth. plaster moulders also recommend Some that the pattern should be wiped off. Before the plaster gets too hard, a pyramid-shaped hole should be varnished and rubbed down again should be made in each corner about 2 in. afterwards. from the outer edge. For making a plaster of Paris mould, the about $ in. across. These holes can be The object of them is to ordinary plaster, as used by plasterers, is not act as keys to keep the two halves of the mould to be recommended, as it is too coarse to get in their respective positions during casting. the best results. found excellent. Ash’s Dental Plaster will be The quantity required The bowl must be cleaned out before mixing the plaster for the second half of the to make a keel of about 4o lb. for an A-class mould. model will be roughly 22 lb. has set hard, the bowl] should be placed under In order to make the first half of the mould, a shallow, lidless box is required. running water and knocked with the spoon. This should The plaster will then come off in lumps. Before making the second half, the first half be about 3 in. deep and about 2 in. larger than the pattern all round. As soon as the balance left in the bowl A stout cardboard box must be given a coat of clay wash. A brush will answer the purpose, or a rough wooden is dipped in water and then rubbed in soft clay box can be knocked up. and liberally applied to the surface. The wooden pattern must be well greased The plaster for the second half-mould is all over in preparation for making the mould. mixed in a similar manner, but this time a layer Vaseline is best for this purpose. ‘The plaster must be poured over the top surface of the first for the first half of the mould can now be mixed. half and the pattern whilst the plaster is still This can be done in an enamelled bowl about quite thin. 137 As the plaster thickens, the re- MODEL SAILING CRAFT mainder is gradually applied until the pattern is covered with a layer at least an inch thick. The second half can now be worked up and This box has a bottom but no lid, and the depth should be about three times that of the pattern. trimmed off. For the top half of the mould a framework The whole thing should now be set aside and allowed to set properly hard. If the plaster has been mixed correctly, this will take half an hour or so. is needed. This is exactly the same size as the box for the lower part, but has neither bottom not lid. Four pieces of wood are nailed on to the sides of the frame for the upper part, in The mould can now be removed from the such fashion that they project over the lower container and the edges trimmed up with the old knife until the joint between the two halves shows as a hair-line. To part the joint, put the mould edgewise under a AX slowly- running tap and slightly assist the parting with a thin knife. The two halves should now come apatt without any difficulty, and the pattern can be removed. If the cores for the Lolts have been left in place in the pattern and care taken that the first half-mould comes exactly these, it will save a lot of trouble. halfway \ up The pieces of spoke left over from making the bolts will serve admirably as cores. keel- If this has not been done, small grooves must be cut in the correct places and the cores set into position with clay. Fic. 59. The pouring hole and vents must now be cut. The pouring-hole should be at the highest part of the keel, and small holes should be THE Mouipinc Box. part and keep the top portion from sliding about. This is shown in Fig. 59. If the keel To make the sand mould, the sand is damped has a thin end, a small vent about an inch long and put into the box little by little, and rammed should be cut at this point to allow all air to down as it is put in, until it is absolutely firm. escape. When about + in. from the top the box is filled provided at either side as air vents. When complete, the mould should be well right up and the pattern inserted. Push it in blackleaded all over the surfaces and the two until it is half covered, and lies flat with the halves tightly bound together with stout cord other half sticking up. or wire. It should then be set aside to dry for * * * rounding sand very firmly and level off to the edge of the box. about a fortnight before being used. Ram down the sur- Parting sand must now be sprinkled over the surface of the sand mould. * The upper frame is now fitted on to the box. The alternative method of making a sand Continue filling up with sand little by little, mould is considerably cheaper, as all that is ramming it down firmly all the time. required is some moulding sand and a able tool (such as the end of a mallet head) can parting sand. little Moulding sand is rather of a Any suit- be used as a tammet. In the moulding shop of a brass foundry loamy natute, whilst the parting sand is fine and sharp. the bench is low, being about 2 ft. from the In order to make the lower part of the mould, a wooden box is required. This should be ground at most. about 2 in. larger than the pattern all round. mounts the bench and with his feet rams the From the roof ropes depend. Taking the rope in his hands, the moulder 138 ING A LEAD of the sand down, using all his weight. te isa knack of doing this, and it has been described as the moulder’s “‘ War-Dance.” It is not to be expected that the amateur will do this, but it is mentioned to show how important it is to get the sand properly rammed home. In making the mould for casting a large yacht’s keel, hot irons are used in ramming KEEL In order to pour the lead into the mould, a funnel made of sand is necessary. A small, round tin is obtained, and a hole is made in the bottom the same size as the pouring-hole in the mould. The tin is then tightly packed inside the sand with a funnel-shaped hole through it. The funnel is also baked hard, and set in position over the hole in the mould. Everything is now ready to cast the keel. down the sand. When the top part is full and tight, it can be carefully lifted off, when the sand it contains will come with the frame. The wood |Wm. pattern has now to be removed from the mould Fic. 60. For melting the lead, a Primus stove or furnace will be found useful, but the builder will have to use whatever is available in this tespect. The lead can be melted in an old iron saucepan, or similar strong receptacle. The pot should be absolutely clean, and a big old spoon or ladle is requited for skimming and removing dross. One and a half times the amount of lead required for the keel should be provided as a minimum. If the keel is a large one it 1s advisable to melt this in two or three small pans instead of one big one, because it will not only avoid cooling, but be easier to pour. As the keel must be cast in one attempt, it is essential to have an ample amount of lead ready. Thoroughly melt the lead and skim off all THe SAND FUNNEL. without disturbing the sand. * * * * This can be dirt, dross and foreign matter. The lead two halves of the mould can be smoothed with should be poured in as fast as possible, so that the first part will not have cooled off by the time the rest arrives. After a little while lead an old spoon or similar implement. will appear at the hole in the small end of the done by using two gimlets, which are screwed into the pattern. The impression left in the A hole must now be drilled straight through the sand in the upper half of the mould at the deepest part of the impression left by the keel pattern. This hole should be about 1 in. in diameter. ‘Iwo rather smaller holes must also be made to act as ait vents. mould. Continue to pour, as the lead will contract as it cools, and more is needed. Fill the mould right up to the top of the funnel and if necessary keep the pouring hole clear with a stick. These second holes are also made in the upper half-mould, Set aside to cool. The keel should be cool enough to handle in about an hour. Separate the two halves of and should be in the shallowest part of the the mould and remove the casting. impression. lead contracts as it cools off, it is a good plan The two halves of the mould must now be baked thoroughly dry and hard. to remove the cores (which have been cast in The upper for the bolt-holes) before the lead is cold. half is now replaced in position on top of the It might be mentioned that it will facilitate lower part, and the two clamped firmly together, in order to prevent the mould lifting when the lead is poured in. As the the withdrawal of the cores for the bolt- holes if the cores ate lightly greased before A good being put in position in the mould. 139 MODEL SAILING CRAFT way of doing this is to smoke them in a candle flame. A caution should be given not to do the casting on a cold stone floor, or to let the molten lead come near anything damp or cold, at the same time not altering the lead-line by planing lead from the casting, this can be done by drilling holes downwards from the top face. These can be filled with sealing wax to prevent them becoming full of water. as it will “ shoot.” Splashes of molten lead are nasty, and for one who is not used to handling it, it is not a bad plan to protect the hands with with a brass band or the bottom with a brass an old pair of gloves. small brass screws. Great care should also be taken to keep the face and eyes away from the danger of splashes. If the fore edge of the keel is to be fitted shoe, the best method of attachment is with A hole is drilled just a size too small to clear the screw. An iton screw is then passed into the hole, and cuts It is desirable to have the keel-bolt cores the thread as it is screwed home. The iron slightly full, as this will ensure their being screw is then withdrawn and a brass screw of easily withdrawable. exactly the same size substituted. Also the keel pattern The reason should be a little full, as it allows for trimming for using the iron screw first is that the brass up, and it is far easier to take a little off than to screws are apt to twist off and break inside the add weight. lead. In cleaning up a keel casting, various tools can be used. If the lead is an awkward shape, locating Ordinary files soon clog up and pins or screws can be used in the extreme ends become useless, but a Dreadnought file can to prevent bending and secure these parts of be relied on. the keel to the deadwood. A small iron plane is also useful, Such locating pins and a plumber’s shavehook cuts lead down or screws are, of course, additional to the rapidly. normal keel-bolts. If it is necessary to shoot the top of the lead keel, this can be done with an iron jackplane. fine as Es The edge should not be quite as that required for hardwoods. The ** ** cass Before the keel is finally bolted in position, plane sole and lead should be liberally lubri- it has to be tested for correct fore-and-aft cated balance as well as weight. with turpentine, and the should be set to take a fine shaving. plane iron Designers usually In shoot- allow a small margin in striking their lead lines ing the top of a keel, care must be taken to get as if it is the least bit out, the keel will be out and compiling a Table of Weights, because they cannot know the method of building which will be employed, or the specific of truth and the yacht will behave differently gravity of the timber available, or just how on the two tacks. lightly the individual builder will produce his this absolutely true in a thwartships direction, A blowhole in the casting can be stopped with solder if required; but if the keel is to be painted, a stopping can be made of equal boat. A Table of Weights is usually provided, however, and the builder should copy this on parts of red and white lead, with a little gold a sheet of paper and pin on the workshop wall. size to bind it. As each part of the boat is finished, the actual weight can be noted on this, and the builder will then be able to check his progress. The point is that if certain parts of the boat are overweight, the ballast keel will have to be reduced This stopping can be used, if necessary, to build up a slight flat on a casting. It sets quickly, and should only be made up as wanted. If it is necessary to drill holes in lead, this can be done with an ordinary twist bit. The bit should be kept freely lubricated, turpentine again being used, and lifted and cleared frequently to avoid binding. If the balance of the lead keel is out, or it is desired to slightly reduce the weight, whilst accordingly. There are two points the designer can determine absolutely—his total weight and the fore-and-aft position of the C.B. Now we correctly, trim to is boat the if that have seen the C.G. must fall in the same vertical line as 140 will have to be reduced, he s connection the builder is reminded that cast lead weighs between 6 and 6-36 oz. per cu. inch. Any reduction must be made alance can be tested, and any without disturbing the fore-and-aft C.G. of the boat and so should if possible be made in the same vertical line. It is wise for the ent made to the lead keel. builder, especially if a novice, to keep a few 1 respectively. After that A ounces in hand at this stage of the proceedings, In as it is easier to put in a few ounces of internal becoming water ballast to complete the designed weight than d from the top face downward. to avoid these holes 1 mts, they can be filled with wax. Ordinary sealing wax is quite suitable. Having got the fore-and-aft balance correct, the total weight must be checked. You have now got to take the lead off again and be obliged to re-paint the yacht. When this has been done the keel can be fixed. Give the face of wood and lead a the exact weight of the hull, which is the main priming coat of paint. item outside the ballast keel, and by the aid of both faces a thick coat of white lead paint and your Table of Weights can form a very close put together wet. When this is dry, give The keel bolts should be estimate of how your finished boat will com- well greased before insertion, and then drawn pare with the designed weight. up tight. If necessary, 141 =_— = 1.Y.R.U.6-M_ MODEL “PEARL” Second. Suit luff leach foot Jib 45:75″ 41-75″ 12-75″ Main 60-75″ 63-0″ 18-57 Third Suit Jib Main luff leach foot 40-45″ 37:25″ 11-25″ 54:0″ 56:0″ 16:5″ Fore a. 2325Ru ‘ 53-25″ 4 \ / Less 15% \ eee \ (O83 \ 1 6:0) Spinnaker-64-0″ x 64:0″ x 380″ 7 \ \ \ \ \ \ \ o- 6″ \ \ \ \ ie \ \ 70:0″ \ \ 20-5″ 4 F Sam. PLAN oF 6-MeErres MopeEL.. Hull Lines on Folding Plate XIII opposite. 142 68:39! Mains’t. 67:= 205.692 \ 67-5″ 459 W.L.1, W.L.| . WLAL wo LW j |_Y.R.U. G6-M. Model “PEARL” ” Note.—The Lead Line given above is for use with Braine Steering Gear and is for a Lead Keel of 17 Ib 14 02 Rudder and Skeg are also suitable for Braine Steering. Alternative Lead Line and Profile for use with Vane Steering are given on Folding Plate X. EE SS i. \E CN ‘A [To face page 142. || LY.R.U.6-M MODEL “PEARL” ———————— — Second. Suit luff Jib Matn leach 60-75″ 63:0″ Third Suit Jib Main foot 45-75″ 41°75″ 12-75″ luff jieach Fore 2. 5325×1728 18-5″ foot 40-45″ 37-25″ 1/25″ = \ 53-25″ , ——— 54:0″ 56-0″ 16-5″ L 459 Less (Slo \ 68 +} Mains’l. 67:5 ; 205 692. \ ee \ 1083, \ = A oe Spinnaker-64-0″x 64-0″ 2 x 380″ \ \ \ \ \ \ \ a oo) \ \ \ \ eS 67-5″ \ ‘ 70-0″ \ nt ‘ \ \ \ \ \ \ \ \ \ \ 20:5″ SAIL PLAN OF 6-MErRES MODEL. Hull Lines on Folding Plate XIII opposite. 142 \ : bs \ \ \ W.L2 ee WLI W.LA3 \ NN \ 1 Oo 3 2 9 omnes ne Tia 1312108 wo WALAL KIN . N <= wt \WK NEN AEE cae aa Payal LEA AY Ay GEeaey GZ, WL8TONNaN we A 10a SS W.L6 IN Sd W.L.5 NY zz = \ i | Se [| n / he xa ee oS. ee ee oa a | Ol ee es | ian =: |2 | | / 13 14 VA. — lal Aa eee i \ Xa _ oS SS — woe Nee TABLE OF WEIGHTS | Ib. oz, Hull Deck Paint & Varnish Lead \ wy 1O 9 W.L.2 4 8 | 12 [| 12 1 12 IO gs Trimming W.L.2 , Mast al ai wae N Vane Gear \\ ae wis tL Rig Mies | || L. WL6 8 for ; = Fittin W.L.4 j NN SS W.L.8 :i : : —--— oR PS 6 §.4 L.W.L. Ke | ES L.W.L, TT \ AY . SS W.L.13 Approx. Position Keel Crew Werght DIMENSIONS L.O.A. © {7 8B 2 O 30 41-0" Max Beam p2-5" Draught g Waterlines spaced 4 ; 60:6 LW.L. 6 Ballast SS) Buttocks spaced Sections Spaced LYR.U. 9-0" Model “PEAR L' u [t-O” |-O" 4-|% 6-M. Note.—The Lead Line given above is for use with Braine Steeri Line and Profile for use with Wane Steering are given on 8 Folding Plate X. — ee ee ee (ee mae eee W.L8 ee ee ee a eT ee tN NS SR Ko ea Paras Scale : One-quarter of full-size. Folding Plate XIIT.] a 0 Pa ea , ae ee | {wal ee Np ON PSS ss NK I \ \ N A \ | [To face page 142. — Bs » IYRU. 6-M. MODEL “PEARL” [To face page 143. —— _ CHAPTER XV Rudders and Fittings. Decks. Deck-beams. Covering Boards. Hatches ITH the sole exception of the old- When purchasing the tube for the ruddertube, a piece of brass tube for the rudder-post rudder, all steering gears function above deck. The rudder is composed of two parts—the flat part, known as the “ blade,” should also be obtained. The rudder-post must be a very easy fit in the rudder-tube, and show no sign of binding. and the stem, which is called the “ rudder- The lower part of the rudder-tube can be W fashioned and inefficient weighted post.” The top of the rudder-post is known as the “ rudder-head.”’ cut away with a hacksaw and finished up with a file. It is by no means easy to file this strip down without breaking or In order to accommodate the steering gear, bending it. A it is, therefore, essential to carry the rudder- piece of rough wood is taken and set in the head above the deck. vice. The wood rudder-tube. A accommodate the quite easy to hold In the case of a square- sterned yacht, with the rudder hung on the transom, the rudder-post passes outside the boat, but in the ordinary counter-sterned should be as long as the groove is cut in it to tube. This will make it the tube whilst filing down vessel it will be necessary to fit a “ rudder- and drilling the necessary holes for the screws tube ” to accommodate the rudder-post. to hold it to the stern-post. “‘ Stern-post ” is In order that the rudder may be a snug fit, the name given to the after edge of the keel it is customary to make a groove down the hollowed out with a small rat-tail file, and is or skeg which carries the rudder. Starting at the bottom of the strip, about 2 in. from the end, drill holes every inch and faced with brass, the facing being formed from countersink them. after end of the keel or skeg. This groove is The holes should be large enough to clear a No. 1 brass screw. the continuation of the rudder-tube. For the rudder-tube of an A-class model, a The greatest care must be taken not to bend the piece of 7g-inch light-gauge brass tube will be rudder-tube or rudder-post. A hole must now suitable. be drilled in the hull to accommodate the The length must be sufficient to reach from the pintle to a point about } in. rudder-tube. above the centre of the deck. and fall so that it covers the groove in the The actual rudder-tube is, of course, composed of the part that actually passes through the This must be at the exact angle, stern-post. hull. The rudder-tube must now be temporarily Below the hull, the tube will be cut away until put into place, and the top screw should be only a strip the exact width of the after edge of inserted to keep it in position. the keel or skeg is left. post can now be tried to see that all is aligned The width at this point will be found to be about Fin. Actually right, and that it is a good fit. the thickness of the after edge of the skeg or keel is the same as the diameter of the rudderpost. The thickness of the blade of the rudder is, of course, the same also. ‘Thus it all fairs in without interfering with the water-stream. The size of the rudder-post will vary with the size of the boat, but it is best to err on the The rudder- A rectangular plate must now be cut from thin sheet brass. An oval hole is cut in this so that it passes over the rudder-tube and lies flat on the keelson. Four screw holes are made in this to clear a No. 1 screw. The plate is soldered to the rudder-tube, and, in order been lost by reason of the rudder-post twist- to get this at exactly the correct angle, the soldering should be done in position in the boat. The rudder-tube, complete with plate, ing, and the size of the rudder-tube is governed is side of strength at this point. by the size of the rudder-post. Many a race has now removed and properly fitted, the wood behind the brass being luted with 143 O 3 9 10 7 n 12 13 Wi.i3 \ C WL. SN W.LA2 — WLIO 14 a (3s L.W.L. W.L,8 — W.L.7 WL60 ——— wis oN \ wi wis \ wL2 WL JS \ \ \ aM \ \ ~) \ ae \YRU. 6-M. MODEL “PEARL Lead Line ALTERNATIVE RUDDER AND SKEG, ALSO Leap Line FOR USE WITH VANE STEERING GEAR. Folding Plate XIV] [To face page 143. CHAPTER XV Rudders and Fittings. Decks. Deck-beams. and inefficient rudder, all steering gears above deck. tube, a piece of brass tube for the rudder-post weighted should also be function The rudder is composed of two Hatches When purchasing the tube for the rudder- ITH the sole exception of the old- fashioned Covering Boards. obtained. The rudder-post must be a very easy fit in the rudder-tube, and parts—the flat part, known as the “ blade,” show no sign of binding. and the stem, which is called the “ rudder- The lower part of the rudder-tube can be cut away with a hacksaw and finished up with a file. It is by no means easy to file this strip down without breaking or bending it. A piece of rough wood is taken and set in the post.” The top of the rudder-post is known as the “* rudder-head.”’ In order to accommodate the steering gear, it is, therefore, essential to carry the rudder- outside the vice. The wood should be as long as the rudder-tube. A groove is cut in it to accommodate the tube. This will make it counter-sterned quite easy to hold the tube whilst filing down vessel it will be necessary to fit a “ rudder- and drilling the necessary holes for the screws tube ” to accommodate the rudder-post. to hold it to the stern-post. head above the deck. In the case of a square- sterned yacht, with the rudder hung on the transom, the rudder-post passes boat, but in the ordinary In order that the rudder may be a snug fit, it is customary to make a groove down the “‘ Stern-post ”’ is the name given to the after edge of the keel or skeg which carries the rudder. This groove is Starting at the bottom of the strip, about hollowed out with a small rat-tail file, and is 2 in. from the end, drill holes every inch and faced with brass, the facing being formed from countersink them. after end of the keel or skeg. enough to clear a No. 1 brass screw. the continuation of the rudder-tube. For the rudder-tube of an A-class model, a piece of 7°g-inch light-gauge brass tube will be suitable. The holes should be large The length must be sufficient to The greatest care must be taken not to bend the rudder-tube or rudder-post. be drilled in the hull to A hole must now accommodate the reach from the pintle to a point about } in. rudder-tube. above the centre of the deck. and fall so that it covers the groove in the The actual rudder-tube is, of course, composed of the This must be at the exact angle, stern-post. hull. The rudder-tube must now be temporarily Below the hull, the tube will be cut away until put into place, and the top screw should be only a strip the exact width of the after edge of inserted to keep it in position. the keel or skeg is left. post can now be tried to see that all is aligned part that actually passes through the The width at this point will be found to be about $ in. Actually The rudder- right, and that it is a good fit. the thickness of the after edge of the skeg or A rectangular plate must now be cut from keel is the same as the diameter of the rudder- thin sheet brass. post. so that it passes over the rudder-tube and lies The thickness of the blade of the rudder is, of course, the same also. Thus it all fairs in without interfering with the water-stream. flat on the keelson. Four screw holes made in this to clear a No. 1 screw. The size of the rudder-post will vary with the size of the boat, but it is best to err on the side of strength at this point. An oval hole is cut in this Many a race has are The plate is soldered to the rudder;tube, and, in order to get this at exactly the correct angle, the been lost by reason of the rudder-post twist- soldering should be done in position in the boat. The rudder-tube, complete with plate, ing, and the size of the rudder-tube is governed is by the size of the rudder-post. wood 143 now removed behind the and properly brass being fitted, luted the with MODEL SAILING CRAFT white-lead paint. This is clearly shown in keel sometimes comes below the rudder heel Fig. G1. (see Fig. 63). AA deck beam can be fitted to hold the upper end firmly in position. made into the lead to take the brass strip. The rudder itself can now be made. The This strip is then grooved to prevent it moving sideways, and driven into the saw cut and first procedure is to see that the rudder-post is an easy fit in the tube. If not, it must be eased down with emery cloth. soldered over. It should be noted that where this is done, the rudder must be shipped before the lead keel is finally fixed in place. * A brass plug must be sweated into the lower end of the tube which is to form the rudderpost. In this case a saw-cut must be *k * * 7 To do this, clean the inside of the tube well, also clean and tin the plug. Put some flux into the tube, insert the plug, and heat until A hole } in. deep should now be drilled into the plug from the bottom to take the pintle on which the rudder TUBE the solder runs. hangs. The rudder-post should next be cut to length, allowing sufficient to project an inch above A plug about an inch long has then RUDDER the deck. to be sweated into the upper end. The wooden blade of the rudder must be cut out next. purpose. Mahogany is best for this A groove must be cut down the forward edge of the blade to accommodate the rudder-post. do this. RECTANGULAR *Prare A rat-tail file can be used to Holes an inch apart are drilled through the rudder-post and countersunk for the screws holding the post and blade together. should be #-in. No. 1 These brass screws. The lowest screw should come above the hole in the plug in the bottom of the rudder-post. The blade is fixed to the post with white-lead paint as bedding. Except for fitting the steering gear, the rudder is now complete. The construction of the rudder is shown in Fig. 62. The only other rudder fitting required is the pintle which supports the heel. This consists of a strong strip of brass the same width as the skeg. ‘This has two holes for the screws that fix it to the skeg, and a pin for the rudder to pivot on. The pin (or “ rudder pintle ”’) is just a trifle longer than the depth of the hole This in the bottom of the rudder-post. pintle, the on resting rudder the ensures and not on the strip of metal (see Fig. i full-keel boats the bottom of the lead 61). 4 sceaai, Pinte HeeL PLATE _— Fic. 61. THE RUDDER-TUBE AND PINTLE AS FITTED TO A BOAT WITH FIN-AND-SKEG TYPE OF KEEL, 144 of orm transverse ucture. heir consequently a great importance. The deck of a yacht is cambered, and, conse- quently, the deck-beams are arched. However, their under side cannot be hollowed, but must be straight from side to side. If they were hollowed, the beams would soon flatten out and the sides of the yacht be pushed apart. For the beams of an A-class boat the scantling can be 4 in. wide by 4 in. deep at the ends. beam in The depth of the the middle will be + in. plus the amount of rise of deck at that particular point. In cutting out the deckbeams, it may not be correct to use a fixed radius and depend on the lesser breadth of deck reducing the height as required at the various stations. The height must be taken from the drawing at each point and the beams marked accordingly. As in the case of ribs, it is better to have a greater number of deck-beams of light scantling rather than a lesser number of heavy scantling. The beams can be made of pine. In fitting deck-beams, allowance must be made if the deck is to be dropped in. Otherwise they will be set level with the gunwale. the The best way to fit deck-beams is to mortise them in, as shown in Fig. 64. This method keys the beams in place. The ends of the beams should be glued and screwed Soup PLu “~~ G J into position. The spacing of deck-beams is a matter for some con- sideration. It should be arranged that one beam rudder-tube. t, Hore at the Beams should also come fore and aft of the mastFoR Pinte Fic. 62. M.S.C. comes hole. METHOD OF MAKING RUDDER. 145 Some mast-partners. builders also fit These are foreL MODEL SAILING CRAFT i and-aft beams between the deck-beams on each side of the mast-hole. Beams should also come absolutely straight. Then put newspaper down exactly under the coamings of the hatchway. edges. on a board to prevent sticking, and glue both Panel pins can be driven through the outer portions that will be cut off when the deck is shaped up. Along the centre seam weights must be put to keep the edges firmly together. Paper should be put under the weights to prevent them sticking to the wood. DeADwoop/ If this is carefully done, an excellent joint should result. When the glue is set, the deck will have to be planed down. be very sharp and set fine. The plane must The deck is after- wards glass-papered well until a good finish is obtained. / On the upper side, mark out the hatch opening, the mast-hole and the hole for L the rudder-tube. — PINTLE On the underside at these points glue suitable pieces of material. Brass HEEL PLATE tings of sailcloth are admirable for this purpose. CARRYING PINTLE This will prevent splitting. ; Fic, 63. MerrHop oF Firrinc RuDDER PINTLE IN A FULL-KEEL MoDEL WHERE LEAD EXTENDS TO HEEL oF STERN-POST. Here again some builders fit “carlines” (longitu- dinal deck-beams). Mast-partners and hatch carlines are really unnecessary, smaller sizes of boats. particularly in Whether these are fitted or not is a point on which every builder must please himself. It is Cut- Draw a centreline along the underside of deck in pencil, if in one piece. Another excellent material for decks is the I mm. waterproof three-ply used in aeroplane work. The deck can now be offered to the boat. Get it exactly into position and mark out the shape with a sharp pencil. a good thing to arrange If the deck is not Ma that beams come under the main deck fittings, such as the two horses, the ends of the jib- rack, steering-gear pulleys, etc. The deck- beams on an A-class boat should not be more 5 than about 6 in. apart if they are the scantling mentioned above, and of pine. Heavier beams of mahogany might be as far apart as Ln 9 in. When the beams have been fitted and varnished, the deck can be made and fitted. Pine Fic. 64. is the best materia] for this. Holly is a very white wood, but is inclined to buckle when exposed to damp. If there is any difficulty in getting a piece of wood wide enough for the deck, two pieces can be joined together down the middle. The deck of an A-class boat can be }-in. pine, or even a trifle lighter, if plenty of deck-beams are fitted. The method of joining two pieces of wood to form a deck is as follows: the edges to be joined must be shot C = MerHyop oF MorrtrisING END OF DECK-BEAM INTO SHELF. being dropped in, it can now be cut out about 1 in. outside the line. If the deck is being dropped in, it can be cut exactly on the line and eased until it drops into place. In the case of a let-in deck, if the chamber in the fashionpiece and rebate in the top of the stemhead to receive the deck have not been cut, these must now be attended to. 146 properly in it, and it is necessary The deck, whether dropped in or not, should have three good coats of varnish on reinforcement pieces on the underside the underside, and be put into place with white the lightness of the deck, screws rever a fitting comes unless there is a deck- beam at this point. can be slips lead and brass pins. The reinforcement pieces of }-in. mahogany or Many builders prefer to screw their decks, as in case of an accident #-in. necessitating the removal of the deck this can then be done without fear of injury to it. pine. The opening for the hatch has now to be fitted with a coaming. In a model which has the deck dropped in, it This opening is best is necessary to fit a “‘ covering board.”’ of an oblong shape, and 5 in. by 34 in. is a good size for an A-class boat. Earlier in the book we explained exactly how this is The hatchway is done in real yacht building, and the essential fitted with coamings made from }-in. maho- difference due to size between this and model gany, and about 3 in. wide. building. These coamings Now a real yacht’s deck (including oF OD in danger of going overboard. oe bulwarks are fitted, varying in height with the oe size and class of vessel. oe the bulwarks may be nothing more than a ow covering board) is flush, and if there were nothing round the edge the crew would be footrail a few inches high, and in a small Gee ew racing boat it may mahogany beading. Accordingly, In a racing yacht even be a_half-round The part of the bulwarks eo that goes across the stern of the ship is known = as the taftrail. oe Actually speaking the covering board of a PP model yacht with a dropped-in deck, more or ess less combines the two functions of the cover- ow ing board and rail round the deck, as it covers the joint between the deck and sheer strake, \ ep ew SW \ 62 and prevents the water penetrating round the deck-edge. In an A-class model this would be $ in. thick and about 2 in. wide. Ina real eas ew gany is the best for this purpose in a model. ew In a model with a deck that is not dropped aw yacht, teak is usually used for this, but maho- in, a covering board is not necessary, and as some builders make a practice of carrying the paint up over the deck-edge for a correspond- Tor View oF Harceu Cover. ing distance, and thus saving weight. The addition of a beading (or rail) is, however, a nice finish to the deck. ZZ The covering board (or rail as the case may be) can be cut straight and sprung into position. ENpD View or HarcH Cover. side as well as the top. Fic. 65. The best method of fitting is with copper pins. are glued to the deck. It should not be glued, but must be varnished on the under Owing to the camber of the deck, it may be best to put these in place after the deck is fitted. If the heads of these are nipped off before the pin is driven home, they will be practically invisible. The deck should be finished up and varnished two 147 L 2 plac The | put over everything. Before varnishing the deck, the lining re senting the planks will have to be put on. The method of doing this is detailed in the next iN skylgn n senting skyligh chapter. cork should obviously be a goox Actually it is easier to line the deck after it has been cut out but before it is finally opening. anc It will add to the < fixed in position. ‘This was not previously the hatch cover is made about 4. mentioned wished than the hatchway coaming all roun as we to preserve the continuity of our explanation about covering parts of the hatch cover that repres boards, etc. can be left in the white of the pine, The hatch is the next consideration. ‘The best and simplest form of hatch is an oblong parts one with a hatch cover consisting of a piece of hatch cover is shown in Fig. 65. that represent the wooden a ' fra: stained dark to match the king plank. 148 T CHAPTER XVI Painting and Varnishing. There are three essentials for good results in painting and varnishing—a smooth surface to work on, good brushes and good materials. In order to get a good surface, plenty of work must be put into glass-papering the surface beforehand. The final rubbing should be done with “flour” glass-paper. Good I: cannot be sufficiently emphasised that in the case of a racing model yacht a smooth surface may make all the difference between success and failure. Lining a Deck Moreover, every model yachtsman wishes his craft to look smart, and a good finish adds immensely to the appearance of the boat. brushes are necessary, and are by no means In the desire to show their work, builders of planked models often varnish yachts all cheap. over, but this is not at all pretty. looking after. If two Once bought, they are well worth Brushes must be scrupulously boats from the same design are built, and one clean, and must always be thoroughly washed is varnished all over and the other painted to The reason of out after use. New brushes should be well soaked in cold water before use to make the hair swell and prevent it coming out. After this is that the waterline gives a break to the use, brushes can be cleaned with turpentine eye, which makes the boat look slimmer and or paraffin. the waterline, the varnished boat will look clumsy alongside her sister. more graceful. Even a painted One of the great difficulties in painting and waterline will improve the look of a varnished boat varnishing is that dust settles on the work, immensely. and care should be taken to avoid leaving the are never bottom, As a matter of fact, real yachts varnished all over. narrow boot-top work in a dusty place during drying. A _ painted (the stripe along So much importance is attached to this that at a certain not large firm of Continental yacht builders, where only looks well, but is like a real varnished a very fine finish is put on all work turned out, the waterline) yacht. and varnished top-sides The practice of planking in light and dark woods alternately is barbarous, makes a yacht look like a mandoline. and there is an airtight room for varnishing. Before work is done in this, the place is sprayed to Bread- keep down any dust. and butter models should always be painted As regards the paint used, the priming coats to protect the joints, as well as for the sake of can be of white lead ground in oil, mixed with appearance. turpentine, and a little varnish. The colours usually employed on a real After the priming, a couple of coats of good white lead yacht below the waterline are light green, Or zinc paint can be given. dark green, red, red-brown, dark grey, black should be a first-rate brand, and can be pre- and bronze, and those who aim at being true ceded by a couple of coats of whatever under- to the prototype can stick to these. Top- coating is recommended by the manufacturers. sides can be any colour, but light colours make Any varnish used should be one of the best the boat look larger. yacht varnishes. Actually, black and dark blue top sides become shabby far more quickly than white or light colours. A boot-top The enamel used Before starting to paint, the hull should be carefully gone over and stopped wherever should be narrow, or it will look like a bull’s necessary. eye when the boat heels over. Enamel must should, however, be very little need for this. be used for white or light colours, but the White lead putty can be used for stopping or, Ifa good job has been made, there builder can please himself whether he uses better still, a stopping can be made of white- enamel for darker shades, or finishes by var- lead powder mixed with gold size. nishing over flat colours. waterline falls on one of the joints of a bread149 If the MODEL SAILIN and-butter boat, a series of dots an inch apart should be made round this, using a sharppointed copying pencil. These dots will show through the paint, and will serve to mark the waterline. The first priming coat can now be applied, colours is to stick slips of paper a waterline so that the paint can be easily carried right up to the edge of the paper without fear of over-running the division. be and the paint for this can be “sharp.” The paper slips are put on with paste or gum, so that they can readily washed off when finished with. The term “sharp” is used by painters to denote a After getting the.gum paper into position, it paint that has little or no oil in it and dries part of the yacht right off. quickly. soaked off and a fresh lot put into position for The paint should be thin, to pene- saves trouble to go right ahead and finish one trate well into the wood and form a key for the other part of the boat. subsequent coats. coats are put on, the After the priming coat is The paper is then As the different boat is well rubbed dry, the hull should be gone over again, and down, using finer grades of the Wet-or-dry any place that has not been properly stopped paper. should be attended to. The hull can now be tubbed down again, using a medium grade of ““ Wet-or-dry ” paper. This is a special kind of flint paper made for high-class painting. used wet. The paper is dipped in before applying to the work. Two coats of enamel are given. first, the yacht is rubbed down with the finest possible Wet-or-dry paper, and the last coat is It is water applied. By way of finishing off, the enamel is rubbed down with a damp chamois leather and very finely-ground whiting. This prevents If the model has been well rubbed down it picking up the paint, and gives a much smoother finish. After the The secret of using this iis to between coats and the paint applied in thin coats, the finished result should be something keep the work wet all the time. After rubbing down, another coat of priming to be proud of. is given, and the boat again rubbed down. Care In varnishing a boat, the first coat should must be taken that each coat of paint is thoroughly hard before any rubbing down is attempted or another coat applied. be half turpentine mixed with the varnish. This will sink well into the wood and act as a filler. Two coats of white lead or zinc are now given, the boat being rubbed down after each. Between each coat the spots representing the waterline should be gone over with the pencil. If the boat is planked, or the water- After this the boat is rubbed down with the Wet-or-dry paper. In a varnished boat, any stopping used should be carefully coloured to match the wood. Cabinet makers use a wax that can be bought in sticks like sealing wax. This is melted with a hot iron and run line does not fall on any of the joints, the best method of getting the waterline level is to carefully chock the boat up on a smooth table. Be sure that she is dead level, and then, using a sctibing block, put in the waterline. If the builder has not got a scribing block, it is nota into the place to be filled. will answer the purpose. brushed in one direction only, so¢ backwards and forwards. The old saying was “ Paint thin and varnish difficult matter to improvise something that The undercoatings have now to be applied. As it is necessary to use different colours for the top-sides and bottom, preparation must be made to keep these apart. If the yacht has a boot-top, it is best to put this in at this point, and the width of the boot-top will then serve to keep the top-sides and bottom apart. The method of getting a sharp edge to the This is quite satis- factory for stopping a small place, like a wormhole in mahogany, but should not be used for anything big. At least three coats of varnish should be given, preferably four. The brush should be used in the same way as when working enamel. That is to say, it should be thick.”” Whilst the first part is correct, the second is misleading. Coats of varnish should only be just thick enough to flow evenly. If put on too thick, varnish runs in waves, and then it requires endless rubbing down to make it come anything like right. 150 ~ Fic. 67. SECTION THROUG Il —- L————" _————} Fic. 68. _—— HoLtow Spar MAKING, SHOWING Sp Fic. 69. MerrTHop < Fic. 7o. Fic. 71. CA THE BrEst The above figures are fully explained in Chapter XVIII, in which methods o Folding Plate XVI] MODEL SAILING CRAFT and-butter boat, a series of dots an inch apart should be made round this, using a sharp- colours is to stick slips of paper along pointed copying pencil. These dots will show right up to the edge of the paper without fear through the paint, and will serve to mark the waterline. are put on with paste or gum, so that they can The first priming coat can now be applied, and the paint for this can be “sharp.’? waterline so that the paint can be easily carrie of over-running the division. be The The paper slips readily washed off when finished with. After getting the gum paper into position, it term “sharp ”’ is used by painters to denote a saves trouble to go right ahead and finish one paint that has little or no oil in it and dries part of the yacht right off. quickly. soaked off and a fresh lot put into position for The paint should be thin, to pene- trate well into the wood and form a key for the other part of the boat. subsequent coats. coats are put on, the After the priming coat is The paper is then As the different boat is well rubbed dry, the hull should be gone over again, and down, using finer grades of the Wet-or-dry any place that has not been properly stopped paper. should be attended to. The hull can now be rubbed down again, using a medium grade of ““Wet-or-dry ” paper. This is a special kind of flint paper made for high-class painting. used wet. The paper is dipped in before applying to the work. It is water This prevents Two coats of enamel are given. first, the yacht is rubbed down with the finest possible Wet-or-dry paper, and the last coat is The secret of using this is to applied. By way of finishing off, the enamel is rubbed down with a damp chamois leather and very finely-ground whiting. If the model has been well rubbed down it picking up the paint, and gives a much smoother finish. After the between coats and the paint applied in thin coats, the finished result should be something keep the work wet all the time. After rubbing down, another coat of priming to be proud of. is given, and the boat again rubbed down. Care In varnishing a boat, the first coat should must be taken that each coat of paint is thoroughly hard before any rubbing down is attempted or another coat applied. This will sink well into the wood and act as a be half turpentine mixed with the varnish. filler. Two coats of white lead or zinc are now given, the boat being rubbed down after each. Between each coat the spots representing the waterline should be gone over with the pencil. If the boat is planked, or the water- line does not fall on any of the joints, the best method of getting the waterline level is to carefully chock the boat up on a smooth table. Be sure that she is dead level, and then, using a scribing block, put in the waterline. If the builder has not got a scribing block, it 1s not a difficult matter to improvise something that will answer the purpose. The undercoatings have now to be applied. As it is necessary to use different colours for the top-sides and bottom, preparation must be made to keep these apart. If the yacht has a boot-top, it is best to put this in at this point, and the width of the boot-top will then serve to keep the top-sides and bottom apart. The method of getting a sharp edge to the After this the boat is rubbed down with the Wet-or-dry paper. In a varnished boat, any stopping used should be carefully coloured to match the wood. Cabinet makers use a wax that can be bought in sticks like sealing wax. This is melted with a hot iron and run into the place to be filled. This is quite satis- factory for stopping a small place, like a worm- hole in mahogany, but should not be used for anything big. At least three coats of varnish should be given, preferably four. The brush should be used in the same way as when working enamel. That is to say, it should be brushed in one direction only, not backwards and forwards. The old saying was “‘ Paint thin and varnish thick.”” Whilst the first part is correct, the second is misleading. Coats of varnish should only be just thick enough to flow evenly. If put on too thick, varnish runs in waves, and then it requires endless rubbing down to make it come anything like right. 150 — — ee J ee K Fro. 66. oO Decx Pian. Starboard Side (R.H. side looking forward), Shows method oflining the deck to represent planking. The black edge to the deck is the mahogany rail, the part going across round the deck just inside this represents the covering board, the stern being the taffrail, The black part up the centre of the deck ic the king-plank , and the black edge to the hatchway shows the hatch coamings. Port Side (LH, side looking forward). Shows arrangement of the deck fittings, including the hatch cover, the portion of the hatch coaming that shows round the cover being shown in black. The broad plank all PRS OO The othez fittings are ; Jib-rack. Fore Horse. Jib Steering Block.* Mast Slide. Main Steering Block.* Quadrant.* Tension Stide.* Main Hozse, Gurwale Eye (for Spinnaker Boom Hook). Guiwale Eye (for Shrouds). Spinnaker Shect Hook. Gunwale Eye (for Beating Gye and Spinnaker Back-haul), * These fittings are only used when Braine Steering is employed. Folding Plate XV] [To fare page 150, LLOW SPAR SHOWING THE WEBS. —7 —] —— | 12 13 J4 [5 |6 17° [8 So wr oF = o [es) ao =f an uw hb yy DGED INTO JIG DURING GLUEING-UP OF Two HALVES, » 4 V5 6 li | he WS We —) SE TION FOR Jis-CLus. = | (OD OF MAKING SPREADERS. making and calibration, also construction and fixing of spreaders, are fully detailed. |To face page 151. t of varnish, the chamois edge as a guide, the planks can then be put in without any undue difficulty. When a deck is laid in this manner it has a king plank running odel yachtsmen “ Simonize ” their down the centre. Ina real yacht this is usually made of teak or mahogany, which furnishes a contrast to the pine of the remainder of the nd whiting can be used for using the well-known wax polish made motor-cars, and it certainly gives a wonder- fully glassy surface. In preparation for lining, deck. Fig. 66 will make this quite clear. In the model the centre of the deck, which represents the king plank, can be stained to match the mahogany covering board or rail. This is shown in the diagram, where the king plank, rail and hatch coaming are shown in black. After the deck is lined, it should have a the deck is given a couple of coats of clear size, coat of varnish to prevent the lining being to prevent the Indian ink (with which the lining marred during subsequent operations. is done) from running. reinforcement pieces and coamings can then * * * * If the yacht is a new one, the lining is best put on to the deck before it is fitted, and in fact before the reinforcement pieces are put on to the underside. It is then rubbed down very lightly with fine glass-paper. be fitted and the underside varnished. The lines are put in with a draughtsman’s ruling pen. After the deck has been fitted, the covering There are two systems of lining. board should be put on and the deck should The first is with parallel straight fore-and-aft lines, but this is not used for best work. The receive two more good coats of varnish. The If it is required to line out the deck in posi- best decks are laid in narrow planks, running tion on the model, this can be done in the same parallel with the deck-line. way. These curved lines It is not quite so convenient as doing are very difficult to put in nicely unless the the job before the deck is put into place, but proper method is employed. with a steady hand should present no great A marking gauge is arranged to hold the pen, and, using the deck difficulty. 151 / Fic, 67. — =, = C—O Hortow Spar MakING, sHOWING SPAR WEDGED INTO JIG DURING GLUEING-UP OF Two HaALves, wW nA oa | ce ite) man) Fic. 68. Ly = SECTION THROUGH HoLLow SPAR SHOWING THE WEBS. z ! Fic. 69. " [* FE i" E 5 [F [é is Ho i} ua Ws fa ys 6 17 |] p) Mrruop oF CALiprATING A Main Boom. > LE FEREEP PEELE ES == Fre. 70. CALI3RATION FOR J1B-CLup. : 9 ) Fic. 71. ay —_— THe Best MerHop oF MAKING SPREADERS. The above figures are fully explained in Chapter XVIII, in which methods of spar making and calibration, also construction and fixing of spreadets, are fully detailed, Folding Plate XVI] |To face dage 151. guide, the planks can then be put in without any undue difficulty. When a deck is laid in this manner it has a king plank running down the centre. Ina real yacht this is usually made of teak or mahogany, which furnishes a contrast to the pine of the remainder of the deck. Fig. 66 will make this quite clear. In the model the centre of the deck, which represents the king plank, can be stained to match yacht is a new one, the lining is best on to the deck before it is fitted, and in fact before the reinforcement pieces are put on to the underside. In preparation for lining, the deck is given a couple of coats of clear size, the mahogany covering board or rail. This is shown in the diagram, where the king plank, rail and hatch coaming are shown in black. After the deck is lined, it should have a to prevent the Indian ink (with which the lining coat of varnish to prevent the lining being marred during subsequent operations. The is done) from running. reinforcement pieces and coamings can then It is then rubbed down be fitted and the underside varnished. very lightly with fine glass-paper. The lines are put in with a draughtsman’s ruling pen. There are two systems of lining. The first is with parallel straight fore-and-aft lines, but this is not used for best work. After the deck has been fitted, the covering board should be put on and the deck should receive two more good coats of varnish. The If it is required to line out the deck in posi- best decks are laid in narrow planks, running tion on the model, this can be done in the same parallel with the deck-line. way. These curved lines are very difficult to put in nicely unless the proper method is employed. A marking gauge is arranged to hold the pen, and, using the deck It is not quite so convenient as doing the job before the deck is put into place, but with a steady hand should present no great difficulty. 15 HE earliest model yachts had no steering gear whatsoever, and consequently variation in the wind is anticipatec that the yacht keeps a dead-straig were unable to sail a good course when the wind was anywhere abaft the beam. The first steering gears to come into use were weighted rudders, and though these were who sails the straightest course is goi gain much ground on his rivals. Enp View SHOWING ON LOOP UNDERSIDE. re HoLe FOR RUBBER SCREW SET RUDDERFOST. HROUGH HOLE > FOR RUBBER JJ FIG, 72. BRAINE QUADRANT. better than nothing at all, it was not until 1906 It would, therefore, seem to be an abso- that the first efficient steering gear was in- lutely correct principle in models to make the vented. very factor that tends to throw the yacht off With its invention model yachting at one stride advanced from being a more or less her course actuate the rudder to keep her childish pastime to a sport calling for great straight. skill and accuracy. this, and in 1906 Mr. George Braine of Ken- Now, in theory the main function of the Several attempts were made to do sington evolved the steering gear for models rudder is not to hold a yacht on her course, which bears his name. but to steer her back to her course when she of the rudder can be made to vary in exact is thrown off it by a puffof wind. Actually, in ratio to the pressure of the wind on the sail. practice, the helm does hold the boat on her During the years that have elapsed since its course, introduction, minor improvements have been. and with a good helmsman every 1§2 By this gear, the angle —_——_ = = BRAINE STEERING GEAR de in the pattern of the quadrant and by this chapter, and their arrangement on the the substitution of a slide for the pinrack with deck can be seen in Fig. 66. which early gears were fitted. tioned that the set of gear shown in Figs. 72, of the gear, however, The principle remains absolutely 73, 74 and 75 It may be men- is drawn relatively to scale, unchanged. The method of using this gear will be found in the chapter on Sailing, and we are here con- cerned mainly with the way to make it and fit it up. At the same time some little explana- tion at this point may be of assistance to the builder in making and fitting the gear correctly. The principle is briefly that as the wind freshens the yacht tends to head up towards the wind. In a full-sized vessel the helmsman Fic. 73. PUuLLey. corrects this by giving the yacht weather helm. In the model the pressure of the wind on the being half size for a Braine gear for an A-class sail causes it to pull on the sheet, which is model. attached to the helm and thus operates the The quadrant of an A-class boat (see Fig. 72) will measure about 4 in. from back to front, and about 5 in. across. It will be smaller proportionately for the smaller classes. The radius of the curve of the forward part is approximately 44 in., and the holes for the hooks are spaced 3,-in. centres. A wire loop is hard soldered on the underside of the tail to take the rubber centering line as shown in the end view given in the diagram. In order rudder. ‘There is an elastic centering line to bring the rudder back amidships. As the pull of the sail must operate through the weather sheet, the steering lines are accordingly crossed. The gear itself consists of a quadrant attached to the rudder-head, a pair of pulleys, a tension slide, and an elastic centering line. The first essential of any steering gear is that the rudder shall move freely. To ensure this, i pa oa J = SIDE VIEW HOLE FOR RUBBER SLIDER son OF TENSION Stipe ONLY. PLAN View of TRACK Fic. 74. © END VIEW SHOWING TRACK 2) WITH IN SLIDER POSITION, THE TENSION SLIDE. the pintle must be properly made and fitted, to take the rudder-post, the quadrant carries a as described in Chapter XV., and the rudder- sleeve 8 in. long. post must not bind in the rudder-tube. quadrant, and has about half its length below Care This is hard soldered to the should be taken that no paint or varnish gets it. inside the ruddet-tube, as nothing will cause a rudder-head. rudder to bind more. Another point of the utmost importance is that the pulley blocks must tun very freely and that the steering quadrant from wringing round. lines must render easily through them. The various parts of the Braine gear are shown in detail in the diagrams illustrating The sleeve must be a close fit for the sleeve and A set screw passes rudder-head, and through prevents the It is essential that the rudder and quadrant be very carefully lined up when drilling the hole for the setscrew, as if the rudder is the least fraction out of central the boat will not sail properly. 153 MODEL SAILING CRAFT It will be noticed that the quadrant illusside webs. Although these are trated has advisable in a large quadrant such as fitted to an A-class model, they can be dispensed with for smaller sizes. The construction of the pulleys can be seen from Fig. 73, and it is sufficient to add that they must be of ample size to take the cord used for steering lines, and also use is not to be recommended to novices, however. In a Braine gear for a square-sterned boat the tail for the centering line will be ahead of the rudder, as shown in Fig. 75. The quadrant in this case is set higher than the tail with the set-screw that goes through the rudder head in between them. run very The hooks for the steering lines are shown freely. in Fig. 76. The slide consists of a base piece with the edges turned up, as shown, to form a track, and facilitate quick adjustment. the slider. rudder is put central and a screw-eye put into The slider must move easily, and SIpE ra View. When This form of hook is used to the quadrant has the deck abaft the rudder. Enp View been fitted, the ‘This screw-eye should be opened up to form a hook for the _ rudder centering line. A suitable length of Ly QUADRANT HOLE Sipe FOR 7 RvVABER ~ Ns Gates Fic. 76. : View Toe View. Hook For RUNNING Linz. rubber cord is now cut off to form the centering line. ; For an A-class model this will be #;-in. diameter. O: The rubber is used double. The ends are lashed together, and the cord middled and hooked on at the stern. It is then passed through the eye in the quadrant, and one part passed on each side of the rudder post under the quadrant. ° L t Fic. 75. have to be taken off whilst this is being done. * QUADRANT USED ON SQUARE-STERNED Boar. yet not so freely that it will shift of its own accord. The method of making this should be quite clear from Fig. 74. The quadrant will In the end view, the slider is shaded black for the sake of clearness. Some skippers fit a double slide. This consists of two tracks and two sliders. ‘The rubber cord passes between these, and when they are level in a fore-and-aft direction the cord cannot escape from between them. ‘They have the advantage that a different tension and adjustment can be given on each side. They are also useful for trick sailing round the corner of a pond, as the rubber can be slipped to one side to give a permanent helm. Their A cord with a bowser is fastened to the forward end of the centering line to allow for its adjustment. Carefully line up and put a screw-eye into the deck to take the forward end of the centering line. to be put in place. The slides have now In the case of a single slide, the rubber passes through the hole in the slider, but in the case of double slides it passes between them. In putting the slides into position, great care must be taken that they do not give the rudder bias either way. The slides should be so placed that when in the most forward position the slide is within +; in. of the tail of the quadrant. The steering pulleys have now to be fixed. These should be sufficiently far apart to ensure 154 gether, but it makes a rather neater job to do so. required. of tension slides enables oses These should be long enough to go through both bridges without touching dispensed with, many skipe in addition. To complete the fitting, two pins are the deck. Moreover, for ‘To avoid loss, the pins should be secured by short lanyards (see Fig. 77). they are very convenient. this is a very simple fitting to make. This completes the gear required for Braine aterial required is two strips of brass steering, unless it is wanted to make pro- in. wide. Bend the first to form a bridge vision for jib steering as well as mainsail. over the tail of the steering quadrant, and just In such case, an extra pair of pulleys and two more MEMBER LOWER UPPER MEMBER LOWER MEMBER Fic. 77. PINRACK. clearing it comfortably. Bend the second to form a corresponding bridge under the quadtant, about half way between the tail and the quadrant hooks are needed. bridges to clear a -in. No. 1 screw. on Sailing a Model. The fitting up of running lines is detailed in our chapter on Rigging. * As the two bridges are screwed down to the deck together, the holes must register. The uses of jib steering are fully explained in a later chapter deck. The length of these bridges will vary between 2 in. and 3} in. according to the size of the boat. Drill holes in the ends of the —_— — ae —s — ele = ee a PINS * * > When a model is fitted with Braine steering, Screw both the steering is out of action when she is close parts down together on a spare piece of wood. hauled, and she relies entirely on the trim of Starting at the exact centre, right across at #-in. intervals. length when we are dealing with the handling drill pinholes Since the two bridges are screwed down to the deck together, it is unnecessary to sweat them to- her sails. Although this will be discussed at of a model yacht, it must briefly be referred to here. 55 MODEL SAILING CRAFT Since a vessel cannot sail against the wind, her balance and sail trim, must “ find her own she has to work to windward in a series of “ tacks,” pointing first to one side of her goal and then to the other. To gain ground to head”? in heading puffs. devices such as the Liverpool Boy, the unsteered model must be at some disadvantage. windward, tacks must be sailed at an angle of less than 90° to the wind, and a close-winded yacht will sail at about 45°. Hence, in spite of In consequence, the model search for improvement in steering gears goes A boat’s course is on continually, and the latest type of gear is determined largely by her sail trim, and some boats “ point” higher than others. If a boat is sailed too close, she will not “ foot ” (move the self-tacking Vane gear. The Vane Gear in its non-tacking form was invented as long ago as 1875 by the renowned ta te s Pres Run without Spinnaker Main Boom to Starboard sure on Rudder to balance Water Pressure on Rudder Fic. 78. yachtsman’s on Rudder A StmpLe Form oF VANE GEar. Upper diagram: Setting for running without spinnaker. Lower diagram: Setting for beating to windward. smartly through the water), but lose speed. Sailing to windward becomes, therefore, a compromise between pointing and footing, so as to get the boat the greatest possible distance to windward in the shortest possible American yacht designer, Nathanael G, Herreschoff, when experimenting with sailing models time. pivots, counterpoise weight for vane, etc. Many model yachtsmen since have experi- When a full-sized yacht is being sailed to windward, her skipper takes advantage of every free puff to edge his craft further to windward, and he has always to be on his guard against heading puffs. A model, sailing to windward unsteered, and relying solely on of double-hulled craft. He made several patterns of these gears, which included many features used to-day, such as watch-pintle mented with various types of vane gear, but it was not until 1935 that it was successfully employed in an important race. In that year, Mr. Sam O. Berge of Norway won the International 156 A-class Races with his “ Prince VANE STEERING GEAR angles of heel. The degree of helm which was considered to give the best results varied up to about 5° ot so when the yacht was heeled to rming JI,” fitted with non-tacking vane steering. He repeated this success in 1937 using the same model and gear. model yachtsmen generally were of opinion het coveting board. When sailing to windward every yacht makes a certain amount of lee- that this form of steering gear had more dis- way, but according to these tests this was advantages than advantages. In spite of Mr. Berge’s successes, British was necessary to tack right across the lake, the teduced by about 10 per cent., when the yacht was carrying this amount of helm. Further, because of the improved hydrofoil action this yacht had to be stopped and the vane setting slight reversed by hand every time she came ashote, models in the tank tests had an appreciably decreased amount of head resistance, which, of coutse, made for higher speed through the water. While it does not of necessity follow that results obtained in a tank where the As mentioned, this gear was not self-tacking. So, when it which involved loss of time. Before dealing with modern vane gears, it might be self-tacking helpful to those unfamiliar with this type of steering, briefly to amount of weather helm gave, the of a vane (or “‘ feather?) mounted on an arm. models are mechanically towed, will be borne out in actual practice with an actual sailing craft depending on the wind for its motive power, the data obtained by these tank tests deserves very serious consideration. In view of these tests some designers, both This arm is carried on a disc with a projecting of full size and model yachts, have deliberately explain the principle on which it works, using as illustration a simple form of non-auto- matic (or non-self-tacking) gear such as was used on “ Prince Charming IJ.” This is illus- trated in Fig. 78, and as will be seen, it consists lever, which actuates the steering tiller. designed unbalanced hulls. Since ‘This, however, is the tiller is aft of the rudder-head, the tiller a very grave error and under all conditions a movement coincides with the actual rudder well balanced hull is highly desirable. ‘To make a yacht require a small amount of movement. The steering property of the gear arises weather helm in order to hold her course and from the fact that as the vessel slews off her not luff up, is a very simple matter, and merely course, a question of the fore-and-aft position of the craft’s the vane centerline changes its and actuates angle the to the rudder sail plan, coupled with the trim of the sheets. accordingly. Every helmsman of a full-size craft, knows A simple adjustment enables the angle of that all yachts appear to carry a certain amount the vane to be varied to suit the course it is of weather helm even when the tiller is amid- desired to sail. ships. The length ratio between the The reason of this is water pressure in actuating arm and tiller is an important factor the lee garboard. in the functioning of the gear, and a further “easy adjustment is furnished in the pivot between mouthed,” but this is simply a matter of hull them which can be moved as requisite. balance. on the Of course, some yachts are helm” and others “ hard- Very obviously a well balanced boat In assessing the rival merits of Braine and that is easy to steer and responsive will be Vane steering gears, one has to consider not a pleasanter craft to handle and easier to get only the technical merits of each but also ease the best results out of than her badly balanced of handling and actual performance on the sister. various points of sailing. If a yacht with Braine steering is pitted When the American yacht “‘ Ranger” was against a Vane steered model to windward, it being designed to defend the “ America’s ” will be found that the latter has the advantage Cup, a large number of tank tests were made. of following wind variations mote quickly, One conclusion that was drawn was that a but this is not all that has to be considered. slight amount of weather helm improves a Since the Braine steered boat is sailed to wind- yacht’s ward unsteered, the sail trim must be varied windward work, especially at big 157 MODEL SAILING CRAFT slightly from the optimum to ensure her paying off if the wind heads her, and under such auxiliary gybing line, or some similar device. conditions, though she may put up a very good performance, she cannot be expected to give of her absolute best. On the other hand, the vane On the other hand, the sensitivity of the often keeps a big balloon spinnaker drawing full when the Braine gear fails to do so, yacht steered by vane can be given just the amount of helm she requires to keep her sailing at her best, and the gear will vary this as and many a leeward board is gained thereby. It might be explained that self-tacking properties are only required to windward, so necessitated by variations of wind direction and strength. all self-tacking vane gears have a lock that converts them to non-self-tacking gears when Nevertheless, a well-designed model in the the yacht is being sailed off the wind. hands of an expert skipper can put up a performance to windward without the aid of gears was a big advance, it was not a very steering gear, which is little inferior to any- difficult mechanical problem to solve. thing that can be done with the vane gear. Hence until the self-tacking vane gear made that was required was a toggle joint between its appearance, most British skippers preferred This was first done in the States, but it was not the Braine gear. long before British experimenters had similar Although the introduction of self-tacking All the vane arm and the tiller operating motion. One thing the vane gear has done is some- geats. what to level down the difference between a To-day in serious racing, boats fitted with perfectly balanced boat and one that is not vane gears out-number those that still rely on quite so well balanced. Braine steering, and it seems probable that Likewise, it has some- what levelled out the advantage the expert very soon the vane will be the recognised skipper has over a less experienced yachtsman. method of control in almost all classes. In spite of this, provided other conditions are The sole exception seems likely to be the equal, the best boat and the best skipper will M.Y.A. 36-inch Restricted Class. finish at the head of the fleet. remembered Off the wind, each gear has its advantages that sail area It will be in this class is unlimited, so naturally the designer gives his The power of the Braine model every inch of canvas she will carry. gear is furnished by the direct pull of the sails, gently round in a complete circle, much as a Hence we have big sailplans over small hulls which are strictly limited in overall length, and there is no deck space left for the erection of vane steering gears. In the M-class, there is greater L.O.A. and a sail area limited to 800 sq. inches. Hence with a reasonably high plan on a Marblehead, there is sufficient deck space aft to mount a vane gear. There is plenty of room for a vane in all the larger classes, which generally speaking err on the side of being under-canvassed in comparison full-sized vessel might “stay round ” instead with the size of the hulls. of gybing ina gale, when it would be dangerous When a yacht is sailing, she has always a tendency to make leeway. Hence the water flowing along the leeward garboard is always under pressure, so that even when the rudder is amidships there is a certain amount of pressure on its lee side. Therefore in sailing to windward, the vane has to be set at an angle where sufficient wind pressure is exercised on and disadvantages. so in hard puffs the boat gets more helm. On this score it has the advantage over the vane, which operates solely on wind angle. On the other hand the advantage lies with the vane if the yacht broaches somewhat. The biggest (whether disadvantage self-tacking or to vane otherwise) disability to gybe the boat quickly. gears is the Instead of gybing, the vane gear makes the boat sail to gybe her over. Thus a model with a vane cannot recover quickly if she is accidently gybed by a flaw in the wind. Likewise, if she gets to windward of her course, she cannot be got off the shore by gybing the mainsail as is done with a Braine steered model. The only way to overcome this disability is to fit an 158 VANE STEERING GEAR. As fitted to “‘ EsrHer ”’ A-class. Upper photo—W ith Schismatic Motion locked for running. Loner photo-—With Schismatic Motion unlocked for beating. [To face page 158. « EsruHe|er,” VIEW OF STERN SHOWING VANE GEAR INSTALLATION. The above photograph shows a slightly different pattern of Vane Steering Gear to the preceding illustrations. It will be seen that this gear is also being used in conjunction with Braine steering, and a combined tiller and quadrant is fitted accordingly. The gear is shown set for beating to windward with the rubber centring line unhooked and the schismatic self-tacking motion unlocked. The end of the mainboom will be noticed on the left of the picture, also the main horse and various deck fittings. [To face page 159. more important with a vane gear than with Braine steering. A good deal has been written on the subject of specially shaped rudders and unteract the water pressure on r (see Fig. 78). In running, similar itions prevail except that the wind has to extreme vulnerability in the event of an acci- skegs for use with the vane gear, but in practice there is very little in these ideas. Experience has shown that with the Braine gear, the fin-and-skeg gives better all-round results than the full-keel model. On the other hand at least one full-keel A-class yacht has been converted to vane steering with most satisfactory results, and her performance is now as good as that of her fin-and-skeg sisters. It would, therefore, seem that the vane gear brings the full-keel model into the dental carry field of practical politics. vane be on the windward side of the feather. The above explanation should enable the reader to grasp the general principles on which the vane gear operates. The niceties of its use and adjustment must be left until we come to the subject of sailing a model. It will, however, be desirable briefly to refer to one or two points as we progress, in order to explain why certain adjustments must be provided. One point against collision, and vane many gears is their skippers anew model, the builder will, no doubt, With a fin-and-skeg boat, it appears that only a very slight modification is needed from the type of skeg and rudder used with a Braine gear. The rudder itself requires much the same area ratio to lateral plane area, but can with advantage be somewhat deeper and narrower. The type of barn-door rudder with upper edge almost touching the yacht’s backbone has still the disadvantage of trapping the water in the lee garboard, thus setting up give this point consideration during construc- back pressure, slowing the yacht and pro- tion. ducing steering effects for the steering gear to spare vanes (or even complete spare gears) when competing in an important race. If a vane gear is being fitted to an existing boat that has previously been sailed with a Braine gear, some adjustment will be necessary in her ballasting, as not only will the weight (anything up to 5 or 6 oz.) of the gear so far aft affect the fore-and-aft trim, but it is likely to put the model out of rating. case of In the To illustrate this, it can be mentioned that the C.G. ofan A-class yacht’s keel weighing counter. 38 lb. has to be placed 3 in. further forward on windward without steering, very great care has a boat with a vane gear than if she carried a to be used to avoid any possible vice in the hull Braine gear. which would steer her off the wind. Hence it is advisable to make the leading edge of the The reader can easily check this for himself by taking moments. In order to cut down weight as much as skeg Asa model with Braine gear sails to nearly horizontal. With the vane, possible, some vane gears have been made of greater liberty can be taken in this respect. wire, but this has been found unsatisfactory, With a view to increasing the steering effects of the vane gear, some designers have as wires bend too easily. been made of various Other gears have alloys, used curiously shaped keel appendages, such including some that are specially recommended aluminium as the so-called “‘Finless Fin,” the “ Prog- for sea-water use, but unfortunately none of nathous Keel,” etc. these light metals has given satisfaction in ing efficiency at the sacrifice of lateral plane vane gears, and chrome plated brass is, in the area, and cut down lateral resistance below the authors’ opinion, the best material to use, in minimum spite of it being an ounce or two heavier. Actually, For a vane gear to function properly, it ‘These seek to gain steer- requisite for resort to all-round these efficiency. abominations can only be ascribed to defeatism, arising from must not only be of good design, correctly failure proportioned, and well-made, but it must also steering ability. Owing to the difference in density of air and be installed correctly. In Chapter XV, it was stressed that the rudder must move freely, and this is, if possible, even to design yachts with reasonable water, the area of the vane feather has to be greater than that of the rudder. 159 The usually MODEL SAILING CRAFT 4, — accepted ratio is about 3:1. of an A-class yacht Thus the vane might measure Likewise, an adjustment is provided on the about “setting screw” on the toggle which forms 14 in. long by 34 in. wide. the self-tacking motion. This serves to limit the range of angle from one tack to another, when the self-tacking motion is in operation. If Fig. 79 is studied it will be seen that when The importance of having a freely moving rudder has already been referred to, but it is equally important for the gear itself to move freely on its pivot. Not only must this be well the stop (L) is dropped into position, the self- made, but in mounting the gear on the deck, . c J gin I H A WIND VANE i . L | ; U ® a Oc i ls a= = 3 UJ G DECK ; FEATHER G.~PIVOT B. FRICTION BAR H_TILLER C..FRICTION SCREW 1.SLEEVE D. COUNTERPOISE EW ACTUATING F.RANGE OF central J qip | F 3. K | = tacking movement is locked in its WEIGHT Fic. 79. ON J_ PIVOTS OF K. SETTING LEVER ACTION MOUNTED ON SCREW L. STOP DECK PLATE RUDDERHEAD SCHISMATIC MOTION SCREW LOCK GENERAL VIEW OF SELF-TACKING VANE STEERING GEAR. care has to be taken to get the pivot absolutely position. vertical. counterpoise The feather must be balanced so that neither The whole weight, assembly and of feather, schismatic pivots then become a single unit mounted on the weather nor lee helm is given when the yacht friction bar (B). heels. On the one hand the wooden blade of a rudder may tend to float upward on heeling, any desired angle to the actuating lever and is or the weight of the tiller may affect the gear. by means of the friction screw (C). This unit can be turned to held in place by friction, which can be varied To enable an exact balance to be attained, the The mechanism of the gear and its action counterpoise weight is made adjustable on its should now be clear to the reader, and its arm. installation The length ratio between the tiller and the difficulty. should not present any great It is, however, essential that the operating lever is also important, so the posi- gear should be the correct size for the boat. tion of the connecting screw (known as the “ range of action screw ”) is made adjustable. The vane should have an area of at least three times that of the rudder. 160 The steering tiller VANE STEERING GEARS d be at least twice as long as the steering steering gear or any part of it to be below rm, and under certain circumstances may be deck, this is now allowed, provided the gear is readily inspectable. If desired, therefore, the whole mechanism (except the feather) could be hidden away in a well with a removable hatch. Balsa wood is undoubtedly the best material considerably longer, especially when a combination of Vane and Braine gears is being used. As a rough guide for sizes, the vane lever on an A-class model will be about 24 to 3 in. long for the feather on account of weight. On the other hand, one or two skippers have not only placed the gear mechanism below deck but use a transparent perspex feather. This has to be reinforced either by a wooden spar or light metal stiffener down the leading edge. Vane feathers vary somewhat in shape, but a common shape is shown in Fig. 80. The size of the feather is governed by the size of the yacht and its rudder area. BALSA For reasons that will be explained in our WOOD chapter on handling model yachts, some ex- perienced skippers prefer a combination of Braine and Vane gears Braine or Vane gear. to either a ‘This is simple very easily arranged by the addition of a quadrant to the steering tiller. When this is done, a longer tiller is required, and it may even be found desirable to make the length as much as four times that of the steering arm. The exact ratio of tiller length to steering arm varies with every boat and can only be found by experi- ment. Hence the above ratios must be con- sidered as being approximate, and should more or less represent the central position for the range of action screw, room for adjust- ment being allowed either way. Fic. 80. It is quite a difficult matter to make one of Norma TypE OF VANE FEATHER. these gears as it calls for the skill of a pro- Size is in proportion to the size of yacht. fessional instrument maker. Most model These yachtsmen will, therefore, obtain their Vane lengths are measured when the range of action gears from one of the model yacht fittings sctew is approximately in its middle position. makers, but for the benefit of any reader who For smaller boats these lengths will be proportionately reduced. possesses the necessary skill, detail drawings of the various component parts are given in while the tiller will be about 6 in. Vane gears are by no means an ornamental addition to a yacht, and many skippers consider they spoil a yacht’s appearance. In addition they are liable to be damaged in an accidental collision. Fig. 81. In order to facilitate matters, the same lettering is used for the various parts in Figs. 79 and 81. It should be explained It should be added that there are a number that whereas it was formerly forbidden under of different patterns of vane gears, but they all Model Yachting Association Rules for the work on the M.S.C. 161 same principle, and the one M 40ONIMDVL-37aS ) 73 a‘Olye“1gTINiVL0l,a7]uoOpveAsdUxCJS“BuNrI9qO2V]-eAsTE”WaLS \ OG = 7 © ,| < -~ — E U °© 162 _ld as well as highly susceptible to amage. A slight knock or minor collisionis sufficient to disable them. gotten tters at the Round tdens) for his own use. Pond, This tions of light alloy clock wheels ismatic motion, and is extremely that these gears considerable stresses, Nor must it be for- have to withstand especially on a large, heavy modelin a iat blow. It is not an easy problem to solve, but these gears require to be strengthened and simplified, without being made too heavy. The main difficulty is to obtain sufficient power from the ion and construction at length. Hence we vane to operate the rudder under all condi- have confined ourselves to a single pattern that tions, bearing in mind that the vane and the can be relied on to give excellent service, once rudder function in different elements, of which the skipper has mastered its correct use. water has approximately 400 times the density Even better results can be obtained by combining of air. this gear with the Braine gear, as explained in Possible lines of improvement lie in getting a later chapter, and this is simply a matter of the main components of the gear below deck, fitting a quadrant to the tiller, and providing in improving leverage to get the utmost power Braine running sheets and pulleys. from the vane, in the use of gear wheels for Although vane steering has now become almost universal, improvement. the gear itself still needs Present patterns are clumsy the schismatic motion, and if possible, the elimination of the counterweight and substitution of a light spring or elastic. the CHAPTER XVIII Spar Making. Hollow Masts. Calibrating a Boom. Jib Ferrules, Spinnaker Fittings. Spar Fittings : Deck Fittings : Horses, Gunwale Eyes, Spinnaker Sheet Hooks. Spreaders, Jenneys, Goosenecks, Mast Slides, Chainplates, Jib Racks, Bowsprit Fittings. ~ Soldering and Silver Soldering which is to be the after side of the mast, the SPAR MAKING N spar making, the first consideration is [e material. For models there is nothing thickness is then set off on the edges, which better than a well-selected piece of pine. If a curve is struck through these points, the This should have a nice long even grain, and be clear and free from knots or waves in the spar can then be planed down, and will be grain, centreline is will eventually be the port and starboard sides. correct in profile as seen from the side. Having selected the wood, it should be cut to a square and planed up true. A struck with a marking gauge down the fore side of the mast and also down the after side. Many models The taper is marked from have unnecessarily heavy spars, and, provided this centre line and the faces planed down. the mast is well stayed, the thickest part of a The spar should now be square in section mast for an A-class boat need not be more throughout. than # in. making the mast octagonal. A hollow spar will require to be a trifle larger in diameter. The corners are next planed off The spar is then For an A-class boat, rubbed down with coarse glass-paper until it $ in. will be suitable. The part of a mast below deck receives very little side strain It should be noted that when marking the and therefore can be quite light. square for planing a small allowance must be strain comes about half-way becomes The greatest up from the round and finished off with fine. made for the glass-papering, as otherwise the deck, and the mast should be at its thickest spar may come out less than the required at this point. dimensions. The thickness at the deck will be about the same as that two-thirds of the HOLLOW SPARS way up, and below and above these points it will taper away to about 3 in. at the heel and 34 in. at the truck. In order that the sail may The weight of a solid mast for an A-class model is about 15 oz., and that of a hollow set properly, the after side of the mast must be mast about 9 oz. straight, so all the taper will be on the fore that a hollow mast will save 6 oz. side. Similarly, the boom is straight along its top side and the taper given on the underside. The thickest part of the boom will be about seem very little in comparison with the total weight of a boat of this class, but it must be the middle, and the same applies to the jib- it a great leverage, and an ounce saved aloft ts club. as good as several ounces of lead in the keel The term “jib-boom ” is often applied It will, therefore, be seen This may remembered that the height of the mast gives to the spar which runs along the foot of the from the point of view of stability. Against jib, but the jib-boom is more properly the boom which forms a continuation of the bowsprit in a square-rigged ship on which the jibs are set. The term “ jib-club ” is, therefore, this must be set the fact that it has to be of A-class boat would be about 4 in. more correct. whole, the advantages may be said to out- The first step in making a spar from the square piece of wood is to mark on the sides the thickness from the straight side. In other words, if the spar is a mast, having determined weigh the disadvantages slightly greater diameter to have the necessary strength. The increase in the mast of an On the considerably, pro- vided the builder is prepared to go to the extra trouble involved. The question of a hollow boom is an altogether different matter 164 MAKING HOLLOW MASTS - about # in. thick for an A-class, and +; in. for a 6-m. Section of a hollow spar showing the webs is shown in Fig. 67.* For glueing up the mast, a suitable arrange- ing to the fact that the boom is low and further, many authorities do not consider an abnormally light boom to be advantageous, as it rises too easily. This must not be taken as an advocation of an over-heavy boom, but simply an expression of opinion that a hollow ment will have to be made to clamp the two halves together. To make the jig for glueing up the two parts of the mast, a piece of wood mast and a solid boom are the best combination to use under normal circumstances. The best and easiest method of making a the length of the mast and 4 or 5 in. wide is required. Along each edge screw a batten about an inch square. The distance between hoilow mast for a model yacht is to build it from two pieces of wood. Two pieces of pine a little thicker than half the thickness of the finished spar and of slightly more than the breadth are required. These are planed up glued together and laid in the trough between ready for marking. Before commencing, it in the jig through any glue running out of the must be mentioned that the joint between the two halves of the mast is going to be fore- joint under pressure, the trough should be lined with paper before-hand. The mast is and-aft on the centre line of the yacht. then wedged firmly together. The the battens should be about 2 in. The mast is the battens and against one of them. In order to obviate any possibility of the mast sticking taper is marked out on each half for the fore are used side of the mast, and they are clamped together As a guide for the hollow- These are placed every 8 in. or so. The arrangement is clearly shown in Fig. 68.* The ing out, the faces of the two halves can be mast will, of course, be put into the jig with and planed down. so as Pairs of wedges to exert an even pressure. marked with the taper the spar will eventually the straight back downward and the shaped have, but the hollowing out must be done foreside upper-most. before any further shaping is done on the oughly set, the mast can be removed from the After the glue is thor- jig and the shaping proceeded with as if the outside. The mast will not be hollowed out from end to end, but at intervals solid pieces are left mast was solid. somewhat after the fashion of the knots in Metal Masts. Masts for models can also be made of duralumin and steel. Owing to the a bamboo. These solid portions are known nature of the metal, it is necessary to make the as ““ webs.” ‘The top 5 or 6 inches of the mast duralumin masts of thicker gauge than the will also be left solid, and the bottom portion steel, so that there is little or nothing to choose up to the gooseneck. between them as regards weight. It must be arranged that webs fall wherever a fitting has to come on the mast. The principle places are the spreaders, the jib halliards and the hounds for the lower shrouds. of a metal mast is about the same as a hollow wooden mast, but the metal mast is a decided advantage in some respects. ‘These places should be carefully marked out. The intermediate webs can be about 5 in. apart. Before starting to The weight A metal mast has much less windage surface than a hollow stronger. wooden mast, and is also On the other hand, it is beyond the hollow out the inside, the inner faces of the two power of an amateur builder to make a metal parts of the mast must be carefully marked mast, and these must be purchased. out with the thickness to be left for the Duralumin masts are made up of several walls. The inside is now hollowed out with a the suitable sized gouge, and the inside can be solder and special materials have to be used, smoothed and therefore the collars for the mast fittings down with round a piece of stick. glass-paper wrapped The two halves are now ready to be glued together. different diameters of tube jointed one into are other. usually Aluminium arranged to alloys fall at are hard one In hollow- ing out, the walls of the mast should be left * See back of folding plate facing page 151. 165 to of the i MODEL SAILING CRAFT joins between the different diameters of tube used. On the other hand, steel masts can be had nicely tapered, and there is no difficulty in sweating the collars for the fittings to the mast in any desired position. The sole disadvantage of steel masts is their liability to rust, and they should be kept well painted. The usual place where a steel mast rusts through is at the mast slide, where it chafes against the metal of this fitting and removes the paint. This can be avoided by the use of a little piece of rubber SPREADER and revolve it with the left hand whilst holding the pen firmly against the spar with the right. The boom is thus revolved as if it was in a primitive form of lathe whilst the marks are put in for the calibrations. As soon as these are dry, the necessary figures are put in with an etching pen. The figures should appear on each side of the spar rather above the middle, so that they can easily be seen. ARM SPREADER = Fic. 82. to be put on with Indian ink and a draug man’s ruling pen. The method is to push th end of the spar against the point of the screw ARM Socn ET a SOCKET The . 3 FERRULE FOR JOINTED MASr EMBODYING SOCKETS FOR SPREADER ARMS. THE DOTTED LINES SHOW BAND USED TO CARRY SPREADER ARMS WHEN MAST IS NOT JOINTED. tube slipped on to the mast at this point, or it after end of a main boom showing the cali- can be protected with adhesive tape. bration is shown in Fig. 69 * and a jib-club in Calibrating a Boom. It is customary calibrate the booms of racing models. to Fig. 7o.* The SPAR object of this is that having found the correct After making the spars, it is necessary to sail trim it can be repeated with certainty as make the fittings. many times as required. The spar to be calibrated must be prepared by giving a couple of coats The intervals Rigging. of clear size, should first Their arrangement will be seen in the figures illustrating the chapter on Spreaders, rubbing down lightly after each with very fine glass-paper. FITTINGS be ‘There are several ways of making and fitting these. rule. When the mast is in one length, the simplest A piece of wood of suitable size is then fixed and best method is to make the spreaders as at one end of the bench. shown in Fig. 71.* marked on the spar in pencil from a Into this a screw is driven with its point coming through the wood and projecting. The calibrations have A suitable piece of } in. * See back of folding plate facing page 151. 166 ited. In this bore a hole ‘mast at the required spot. iced from the plan view of the that they do not extend right round , but the ring is broken on the after When the spreaders are shaped, Alternatively a notch can be cut for This is particularly appropriate when the mast is made to take into two parts for travelling. In this case it can be incorporated with the tube which forms the joint. This is illustrated in Fig. 82. a small hole is drilled in each end for the wire shrouds. arms. Jennys. The jenny is the short strut forward of the mast which extends the jumper stay. The jumper stay is the stay which prevents the topmast from bending aft and also keeps the PAWN) HOLE MAST FOR IN mast from being bent forward by the forestay END or jib halliards. WIRE JUMPER STAY — There are several methods a| jenny. of fitting the One method which is not to be recom- mended is to make the jenny from a piece of small brass rod and socket the end into a hole yoy, Fic. 83. in the mast. flattened a little and has a hole bored through it to accommodate the jumper stay. METHOD OF MAKING 4 JENny (see Text). In order to prevent the spreaders, splitting the a small screw is put into the spreaders at the inner The notches can be } in. end of each notch. deep. A suitable length for the spreaders of an A-class model is about 1o in. A second method is to have a metal collar round the the shrouds at each end. wires The outer end in this pattern is mast with a metal jenny hard soldered to it. A third method is to have a socket on the collar and use a wooden jenny. Of these methods the second is by far the neatest (see Fig. 83). over all. Goosenecks. The gooseneck is the hinge on ie MAST eae PW Fic, 84. THE PROTOTYPE FORM OF GOOSENECK. When the spreaders are finished and have been which the boom swings. varnished, they can be put into position on the mast. A small screw can be put through the fore side into the mast. The spreaders are then gooseneck proper is the fitting on the end of the boom. It consists of a ball-shaped joint, firmly seized into position with stout linen thread. When the seizing is finished, it is well boom is held between two plates which are varnished to preserve it from the water. Another method is to have a collar round the mast with suitable sockets for the spreader In a real yacht the allowing the boom to swing upwards. screwed firmly to the boom. The The gooseneck has a round rod like a bolt with a nut on the bottom. This goes through a socket on the mast-band and permits the boom to swing 167 MODEL SAILING CRAFT sideways also. Fig. 84. This arrangement is shown in for the jib (see Fig. 87). For prototype models this is a very the merit of It used to be cus- tomary to have the tack-hook some distance suitable arrangement and has back from the actual tack of the sail. exactly following the original. of this was to keep the sail flat by preventing The best form of gooseneck for use in heavy models like an A-class is shown in Fig. 85. the clew from lifting. An The idea Actually this prevents the sail taking its natural curve and takes all eee eee ee @ Fic. 85. GOOSENECK USED ON LARGE Racinc Mops ts, alternative form of gooseneck, as Fig. 86, is the power out of it. easier to make and quite efficient for smaller a lifting sail to a pressing sail. racing models. One of these two types is tack-hook is only the least bit back from the recommended for all models except those that fore end of the boom, and the pulling power 7 TACK Hoow a BOOM HOLE Fic. 86. To-day the es = (Q) ALTERNATIVE ForM OF GOOSENECK FOR SMALLER SAILING MODELS. aim at being true to the prototype in every of the sail is greatly enhanced accordingly. detail, and these should follow Fig. 84. Jib Ferrules. It also converts it from An alternative, which is far simpler, is to The jib ferrule consists of a use a short length of light gauge brass tube. metal cone with an eye hard soldered into its This is put on the fore end of the jib-club, and tip. a hole drilled through tube and spar from top The tack of the jib is made fast to this, also the forestay. A second eye is fitted on the underside of the ferrule to take the tack-hook to bottom. A piece of german-silver wire is passed through the hole and turned into eyes 168 SPAR FITTINGS end. Many model yachtsmen nowadays uralumin tube for their jib-clubs. In as less liable to become foul in cases of col- lision. h case a hole is drilled through the spar and wire eyes made as described above. Spinnaker Fittings. In a real yacht the spinnaker boom has a gooseneck similar to The ferrule described above is suitable for that on the main boom, but is only shipped the ordinary type of jib-club along the foot of as needed. the sail. boom the mast has a second mastband of a There is another method of using a jib-club as a “ radial boom.” By this method smaller size above the main mastband. Owing to the fact that such small spinnakers only the clew of the jib is made fast to the boom. The tack of the jib is hooked directly To accommodate the spinnaker as can be used on even the largest size model have a tendency to sky (balloon up to the masthead, lifting the boom), another method of setting the spinnaker has been found for racing models. FERRULE FOR JrB-CLus. DECK on to an eye in the deck, whilst the fore end of the boom is pivoted on the deck slightly aft of The foot of the sail is As it is brought inboard, the reverse takes place, and when the sail is sheeted close in, the This gives the advantage of more adjustment of the rig in a fore-and-aft direc- tion, it is usual to fit a racing model with a mast slide. The advantage of this arrangement is that it permits the yacht to be tuned up A kicking strap Jf under the boom is advisable with a jib of high aspect ratio. For a radial boom, the eye in the ern NN MAST bottom of the ferrule is unnecessary, and the SSA eye at the end hooks on to an eye in the deck. An illustration will be found in Fig. 108, which, taken in conjunction with the above, should MAST make the principle of the radial boom clear Fic. 88. and also show the fittings required. Main Boom Ferrules. In order to permit of fine In order to make a STEP (Sipe wew) SS becomes looser and allows the sail more flow. Mast Slides. SARS RAN that as the sail is eased off, the foot of the jib racing sloop. RSS than that of the foot of the sail, it is obvious gives a suitable lay-out for the deck of a model WRAAN of the circle described by the boom is shorter flow in the sail off the wind. Their arrangement will be clearly seen on reference to Fig. 66, which then longer than the boom, and as the radius foot is taut. From the spar fittings we next proceed to the deck fittings. GSS the tack of the sail. FITTINGS ASS Fic. 87. This is fully explained in the chapter on Rigging. STEP (Pcan) Mast Srep FOR USE IN CONJUNCTION WITH Mast S.irpeE (see Text). neat finish to the boom; most builders fit a to a very fine pitch of sailing. ferrule to the outboard end. ‘This carries two the mast is moved at the deck level, the heel If the two-eye pattern is used below must also be moved, and the adjustable mast slide requires an adjustable step to correspond. The mast step, which is used with an adjustable mast slide, is made of a piece of brass tube of a square section. If the mast slide moves by eighths of an inch, the step will or four eyes. the small upper eye takes the clew outhaul and the larger lower one the jackline, the beating guy being hooked into the lower also when required. The four-eye pattern has all the eyes the same size and the beating guy hooks into the side eyes. This pattern is illustrated on the end of the boom in Fig. 109. The two-eye pattern is, however, recommended Obviously, if have to be made with slots across it } in. apart. The lower face of the brass square is 169 MODEL SAILING CRAFT left about } in. longer each end than the others, range of movement in a fore-and-aft direction. to permit of holes being made to take the The edges of this plate are turned over so as screws that hold it to the kelson (see Fig. 88). to form a slide in which the plate carrying the In order to fit this step, the foot of the mast has a notch cut in it. mast tube moves. The moving part of the A brass collar fits round slide consists of a plate with a hole through it the mast heel, and a screw is put through from of a size to accommodate the mast tube, which is hard soldered into it. mast slide in any desired position, two holes ‘PLAN e Fic. 89. A series of holes are drilled in each side of the sliding plate so as to register with the two holes in the deck plate. StreEw USED desired position. As PIN SIDE deck. By inserting a pin, the sliding plate can be locked into any BRASS VEEL Qa are drilled right through the deck plate and MAST fe MAST In order to fix the View ee MAST HEEL END The holes in the sliding plate are spaced 4 in. apart to correspond with At. the slots in the mast step. view It will be noticed in the drawing that the holes on one side of the Mast Heet apaprep To Fit Mast STEP ILLUSTRATED IN Fic. 88. sliding plate are spaced midway between those on the opposite side. This permits the whole side to side to ride in the slots in the step. mast to be moved by eighths of an inch, and, The slots in question should be just sufficiently at the same time, provides a fine adjustment to wide to accommodate the screw comfortably. the rake. This arrangement can be clearly seen in Fig. 89. shown in Fig. go, and its uses should be quite The mast slide itself consists of a plate The slide, slide plate and pin are clear. @o@eaeaeeeees¢+¢e8e HOLES HoLeS 7 oes FOR FOR PIN FIN e@eteeewe7enredée#e#¢ SLIDE le zi 2 | @ 2 EH u 3 < wy Hore MAST FoR a ais | @ Wy? CounTERSUNK @ | Pin 5 SLIDE A = FIG. 90. ® PLATE Screw Hores, Be Pin Hores ApjusTaBLE Mast SLIDE, USED IN CONJUNCTION WITH MAST STEP ILLUSTRATED IN FIG, 88. screwed to the deck. This has a hole through it of a width sufficient to clear the mast at this point. The length of the hole gives the Chainplates. In small models the strain on the shrouds is not very great, but when it comes to a big heavy model, such as an A-class, 170 in turnbuckles) are used to tighten up the wire heavy iderable. Most builders rigging that is used on large racing models. (see Fig. 96) in lieu of a These fittings are made in three parts, as shown n account of the neat effect of in Fig. 92. The upper and lower parts have Admittedly, it is not altogether a tight and left-hand thread respectively, so ineering practice to pull endwise on that the wire is tightened by turning the body. Jib Racks. ews which hold the eye in place, as In order to permit the jib tack rything depends on the thread cut by the screw inthe wood. There is no shearing strain on the screws, and therefore they need not be of large diameter, but they must be as long as possible, bearing in mind the depth of the shelf. Provided good screws are used, no (09900000000000) @ ® © SiIpE View © ® [(S.___ S____ 8} TOP © VIEW —| y END Fic. 91, VIEW Form or CHarnpLarte (see Text). trouble need be anticipated from their pulling out. Fic. 92. Another form of fitting used is more like the chainplates used on a real yacht, but it is not nearly so neat. This consists of a metal RiGcGiInGc Screw (oR TURNBUCKLE). This is shown on larger scale than other fittings, being full-size for an A-class model. It will be noticed to be adjusted in accordance with the position that this has two straps down the side of the of the mast, it is customary to fit a jib rack on fitting, as shown in Fig. 91. yacht. This is really a stronger form of racing models. ‘This T section consists (see Fig. of a 93). rail of fitting, and the row of holes provide an addi- inverted This is tional advantage in that the shrouds can be screwed to the deck and has a number of holes adjusted according to the position and rake of in it to hook the jib tack on to. It should have the mast. a sufficient length to not only permit the jib to not be hooked out when the mast is in its furthest strictly speaking deck fittings, they can be position forward, but also to permit the smaller considered as such as they hook into the gun- jibs to be hooked in towards the mast when wale eyes (or chain plates). sail is reduced in heavy weather. Rigging Screws. Although these are Rigging screws (or 171 MODEL SAILING CRAFT ae The horses are bars on which the shrouds are frequently made fast to gunwale sheets travel from side to side of the yacht. Horses. eyes, and they are also used to take spinnaker- Their length is a matter of great importance, boom hooks, spinnaker backhauls, and beating and affects the sit of the sails on the wind. guy. A plain horse is shown in Fig. 94. Spinnaker Sheet-hooks. On racing models it is more usual to fit a ‘These consist of a plate with a hook, as illustrated, screwed to ODOO0000C 0000 ScREews OVO000 invo be ee SIDE FIG. 137. ““ WISHBONE’? KeErcH wirH Detar. oF WISHBONE SPAR, 213 MODEL SAILING square topsail, and such craft are still found in the Eastern Mediterranean and other places. The topsail CR economy of working became essential competition, the later clippers had thei schooner, although usually classified as a fore-and-aft rigged vessel, is, for sails divided into upper and lower tops In some cases the topgallants were similarl the purposes of this book, included with the square-rigged vessels. divided. In our description of fore-and-aft rigs and also that of the square riggers which follow, headsails Dealing ’ with the fore-and-aft sails, the (when these ate three in number) are the outer jib, inner jib and fore staysail. no attempt has been made to classify the rigs of ancient vessels or describe them, as this would gaff-headed sail set on the after mast is known appear to be outside the scope of the present as the “spanker” (or “ driver”). volume. hermaphrodite rigs, gaff-headed sails are set * * * A flying jib is also used in some ships. The In some on other masts, and are known as “ spencers ” *K (e.g., the main spencer). The staysails set Before giving a catalogue of the various between the masts bear the names of their square rigs, it is as well to describe the masts respective stays, as the main staysail, mizzen and sails, as an understanding of these will topmast staysail, etc. simplify the explanation of the various rigs. The above will enable the reader to follow As will have been seen previously, vessels the definitions of the various rigs. such as the yawl and ketch have two masts, of The Topsail Schooner—This vessel is rigged which the forward mast is greater than the exactly like an ordinary fore-and-aft schooner, after mast, and these are known respectively with the addition of square topsails on her as the mainmast and mizzen. foremast. But in vessels having their after mast greater than the for- or more masts. ward one, these are known as the foremast and mainmast respectively. The topsail schooner can have two Brigantine—This is a two-masted square-rigged (including the course) When a vessel has vessel, on the three masts, these are foremast, mainmast and foremast and fore-and-aft rigged on the main- mizzen. When a fourth mast is added, this is called the jiggermast, and in a five-master, the masts are the foremast, mainmast, mizzen, mast. jigger and pusher. sail. Brig.—This vessel is square-rigged on each of her two masts, and carries a boom main- The lowest squaresail on any mast is the Barkentine (or Barquentine).—This is a vessel course, and the lowest squaresails are known collectively as the “courses” or “ lowers.” The course on the foremast 1s known as the “fore-course’”’ or ‘“‘foresail,’ that on the mainmast as the ‘‘ main-course,” ofr more generally the “ mainsail,” and that on the mizzen is known as the “crossjack”’ (pronounced cro’jack) when there are three masts. with three or four masts, and is square-rigged on the foremast and fore-and-aft rigged on the others. Bark (or Barque).—There are three, four, and occasionally five-masted barques. This rig is square-rigged on all the masts except the after one. The ill-fated “ Kobenhaven” was an example of a five-masted barque. The cro’jack is always the lower on the after Ship.—The ship is a vessel with three or mast. four masts, all being square-rigged. The squaresails above the lowers are the topsails, and these take their names from their hermaphrodite rigs, but the above are the respective masts. Above the topsails are the topgallants, which are similarly identified by their masts. Above these are the royals, and For conabove these again the skysails. venience in handling, particularly when In addition to these, there are one or two main categories of square-rigged vessels. If the reader is desirous of rigging a show- case model of a square-rigger, he is referred to such works as Kipping’s “‘ Masting”’ or “ Saifing Ship Rigs and Rigging” by H. A. Underhill, 214 l, it is advised that a single be chosen and nothing above masts. The masts are fitted in round sockets, so that they can be rotated as desired. The lowers are fitted with booms, which necessitates the shrouds being carried well aft. The e fitted. a square-rigged model, the cross- yards are fixed to the masts with brackets. est kept clewed up, and as a matter of forward of the masts, so that for beating when the sails are trimmed round, the centre of , it was rarely set on later ships. Other modifications that can with advantage be made on a sailing model are to omit These brackets carry the yards about ? in. effort of the whole sail-plan is moved The spanker sheet is made to aft. operate the the sheets for the squaresails and make these . rudder. In order to take the eyes for the staysail fast at the yardarms, and to make all the lifts, including the lowers, non-working. The halliards, sheets, etc., loose collars are fitted to the masts. It is necessary for the sails on the braces can also be modified with advantage. The lines of a real ship do not give suffi- foremast to be trimmed a shade closer than cient displacement to get the necessary stability, those on the main and mizzen, and consequently the brackets carrying the yards are not and the lateral plane also is insufficient. quite so long. Readers who have studied previous chapters The braces are carried from the yardarms on on design will appreciate that this is due to the scale on which the ship has to be reproduced, one mast to those on another. and that the best way to overcome this diffi- braces are the sole exception, and these are culty is to increase the sections bodily so as to led to the quarters of the ship. give greater length. displacement on ‘the desired Additional stability and lateral plane The main- It will be seen that by trimming the mainbraces, all the yards are swung and trimmed simultaneously. can also be gained by the addition of a false Whilst this method of trimming is not keel, which, if desired, can be made to unscrew absolutely perfect, it is the nearest thing that when the ship is not being used for sailing. can be got on the model unless the skipper A good method to rig a sailing model of a ship is as follows: In order to facilitate trimming, the yards are firmly clamped to the wishes to spend a good half-hour trimming braces and sheets every time the ship is put about. 215 | CHAPTER XXIV Advice to the Novice on the Selection of a Class to Build to. Racing Rules. Summary of Race Organisation [es thing to consider is the purpose for N the selection of a class to build to, the which the boat is to be used. Formation of a new Club. nucleus of model yachtsmen. A letter in the local paper will often produce good results in If she is this respect. As soon as six or eight enthu- intended solely for cruising, the builder can siasts have been found, a meeting should be follow his own inclination as to size and type, called at some convenient place. but if she is to be used for racing, it is a differ- there is no choice of sailing waters, but if there ent matter. is, select the most open and suitable one. The best plan is to find out whether Probably there is a club in the vicinity and inquire from In the selection of a lake, the requirements the secretary the terms of membership and the for the ideal sailing water should be borne in mind. Possibly the selected water will not classes of boats used. Unless the pond whete one intends to sail is come up to this ideal in every respect, but the very small, it is a mistake to build too small a model. nearer it does the better. At the same time, the owner must The consider the distance that he will ‘have to ideal sailing lake should have its carry the boat, the facilities at his command longitudinal axis in the direction of the prevailing winds, so as to give as much beating to for building, windward as possible. and what he is prepared to spend. There should be no trees or buildings to break the wind from any The character of the water must also be considered. quarter. Above all, they should not interrupt the course of the prevailing wind. It is useless to have a very large boat for a very small pond, and equaily futile The lake should be as large as possible within reason. go have a very smali boat for a large sheet of There should be a good depth of water in the water. middle and the water should shallow somewhat If the model cannot be handled from the bank, but has to be sailed from a skiff, towards the sides. this must also be taken into account, as a very there should be about 18 in. to 2 ft. of water big and powerful model is not easy to handle tight to the edge. or keep up with unless a special skiffis available. Whatever class is selected, if the novice edge is dangerous for children. are to be handled from the bank, the pond intends to go in for racing, he is strongly should have a concrete walk all round. advised to select the Bermuda sloop rig. boats are handled from the water by wearing Be- If there is a sheer side,