Model Maker: Volume 1, Issue 6 – May 1951

i ey ce LAAs AAS ; | MODEL MAKER 20 62 FESTIVE PART I OF A NEW SERIES BY THAT FAMOUS W. J. STEP DESIGNER DANIELS, AND GIVING INSTRUCTIONS SKIPPER STEP-BY- FOR’ THE BUILDING OF HIS LATEST MARBLEHEAD “FESTIVE” PRODUCED FOR EXCLUSIVELY “MODEL MAKER”. THE YACHT IS BEING BUILT IN OUR OWN WORKSHOPS UNDER’ THE SUPERVISION OF OUR STAFF EXPERT A. G. PALMER IBLE FOR OUR MODEL WHO WAS RESPONS.- SERIES SAILING OF SCALE CRAFT. THE (Marblehead Model is one of the classes catered for by the Model Yacht Association and is perhaps the most popular for the reason that they are easy to transport, and if correctly designed and built, will give quite as much sport as the larger classes. The class had its origin in the United States of America, and was started at the town of Marblehead, near Boston, Mass. The main demands of the class is that they shall not exceed 50 in. deck length and that the actual measured sail area shall not be more than 800 sq. in. There are other slight restrictions with regard to bottoms in sails and the arc at the junction of fin and hull, but as these have been complied within the design we are dealing with, it is not necessary to enumerate them. There are several methods of building a model yacht, and as long as the design is strictly adhered to and good workmanship is employed, one method is as good as another, but at these times when materials are very difficult to obtain, we must make use of the best we can get. The most economical method of building at the present moment is the orthodox method employed in the construction of full-size small yachts, and this is to be described in this article. 330 May 1951 A building board must first be made upon which to erect the boat. This should be of two pieces of seasoned timber each of 54 in. in length, and 1 in. thick. One should be 4 in. wide, the other 2 in. They should each be planed dead straight on all surfaces, care being taken to see that they are not winding. If you do not possess a trying plane a saw mill will shoot them for you for a small charge. A line must now be marked down the centre of each face of the 4 in. piece, and along one edge of the 2 in. piece. The 2 in. piece is then screwed to the centre of the 4 in. piece by drilling holes through the face of the latter of such size that the screws are an easy fit at intervals of 6 in. Place the narrow piece on edge on the face of the wider board and screw it, care being taken to.set it central. This will form a T-girder and will be our base for the erection of the model. Lines should now be squared off on the face of the building board drawing, taking care centre (approx. 29 in. board). This will leave at the intervals shown on the that section No. 6 is in the from the stern end of building 2 in. each end beyond the hull. Heading : The author (in cap) with his mate and one of the many world famous International A-Class winners with which his name will always be associated. Below left : Cutting out a half in pairs on the treadle fretsaw. mould Above, top : T-girder building board in vice with moulds erected, and backbone being tried for fit before adding cheekpieces and carving to shape. Centre, right: Close-up of transom. Instead of extending this piece to the building board and cutting away later it has been made to size and a temporary tab added. Bottom, right : Shows how moulds face stern and bow to enable bevel to be cut thereon. Note also the cutting away of slots for the inwhale. Two right-hand moulds have not yet been trimmed to take the backbone cheek-pieces. 331 MODEL MAKER FESTIVE MARBLEHEAD DESIGN 50/800 DESIGNED BY W.J. DANIELS. COPYRIGHT 3 OF LINE THE MODEL MAKER AERODROME, STANBRIDGE, bese na NR LEIGHTON DATUM BUZZARD, AT RAG BEDS LINE 7 esa ee ] poets Gas Ls = vi SOLID KEEL COMMENCES———y DATA LOA, SAIL AREA. DISPLACEMENT @ 20 800 SQ INS LBS, LEAD KEEL 12% 8S (12LBS 202 IF VANE) KEEL HULL | PAINT LINE ee DOTTED 3 LBS & FITTINGS 86 O2, VARNISH ETC FOR DECK ILB, VANE GEAR, WITH RIG HATCH & FIRM LINE FOR BRAINE 12 02S SPINAKER ILB 4 OF. {LB = aad Mepee ace A suitable wood that is obtainable at the moment is obechi. This, like any other timber, varies in qual5 Cross-section of mould, showing ; rib rebated into backbone, plank- eee ity, but as most retailers of this timber cater for the ing overlapping this rebate, and siot cut for inwhale. model men, it can be generally relied upon. We first have to make the section moulds or patterns of the Li 1/7) ne 7 Typical centre mould, with backbone to which cheekpiece has been added. Keel will be added below after planking has been completed. > shape of the model as shown on the design. These should be made in two halves and screwed together by a cross-piece as illustrated. The necessity of this is for their easy removal after the boat is planked. We intend to make the planking ¢ in. thick, and the ribs 5 in. It will therefore be necessary to make our moulds 7% in. smaller than shown on the design. The transom will, of course, only be less the thickness of the planking. All the section moulds should be marked so as to extend them to the datum line. Carefully mark off the position of the deck on each cross section, mould and recess it to receive the inwhale. This should be cut from a board + in. thick to the sheer, as shown. 332 patti THE aa { Ts | | | May 1951 MID DECK SHEER me Lh – fo is ” w TRANSOM ee eee It will be seen that the inwhale must be set lower than the rail line by the thickness of the deck so that when the latter is fitted it will give the correct freeboard as shown in the design. Having made the cross-section moulds it is now necessary to prepare the backbone of the model. This should be marked out as shown and cut from 1 in. board. First mark out the profile down to third waterline below the load water line. Carefully mark the position of the section stations and also the water lines. On your design draw a line parallel to the centre line of boat 4 in. away from it. If on the wood you mark a spot where the 4 in. line crosses each waterline you will find that you can draw a curve through these spots and this will give you the correct level to pare the stern and stem to in order to conform to the design. The transom will, of course, be left in the boat, and this must be 4 in. thick. It will be reduced by only the thickness of the planking. It will be noted that as the inner face of the tran- som is larger than the extreme end allowance must be made for the bevel if the planking is to seat properly. It will be seen also that the moulds over which the ribs are to be bent must also be bevelled for the same reason as the transom. In order to fix the moulds to the building board, cross-pieces must be fitted across the board to attach the moulds. In the case of the forward sections the other face must be over the section position and aft of the largest section the forward face must be fitted. The cross-pieces must be screwed from the underside of the building board as otherwise it would not be possible to remove the boat when finished. These must be placed aft of the section forward and forward of the section aft. This will then bring the mould into position to allow the bevel to be made. Before erecting, the moulds however, they must be recessed – to allow the backbone to take its correct seating, and also for the inwhale let in. Having erected the moulds (Continued on page 384) 333 “TN May 1951 History & Development of Model Yachts PAR T-1 NTERNATIONAL “M’CLASS| } 50/800 MARBLEHEAD j | ~ BERNARD REEVE . : [ sé’aesraicteo cuss class | : R. GIVES DETAILS M.S.N. ~ OF SOME INTERNATIONAL EVENTS SUMMARY AND OF A THE USUAL CLASSES S model yachting became more popular so more clubs were formed, and with increasing membership designers and builders began to apply more scientific principles to the design of their craft. Interest in international events began to awaken and in 1922 Mr. W. J. Daniels, the well-known designer and builder of model yachts, issued a singlehanded challenge to the model yachtsmen of Ameri- ca. Ho took his boat Endeavour to the States to meet the American defender, Mr. Bull’s Polka Dot. Mr. Daniels’ model put up a strenuous fight but was eventually beaten. Daniels who this time was successful. 1924 saw another win for Mr. Scott Freeman with Mr. Daniels once more acting as skipper, this time with another new boat called Crusader. In 1925 the States sent a challenge, a boat called Slipper, but Crusader proved to be the better craft. By his third win Mr. Freeman won the cup outright. The proprietors of Yachting Monthly very gener- ously put up another 100 guinea challenge cup which, in 1931, was made over by a deed of gift to the Model Yachting Association who nominated a Committee of Control chosen to represent International Model Yacht Racing and to decide the conditions under So much interest was aroused that the proprietors of Yachting Monthly put up a 100 guinea challenge cup for future races, and a special formula was evolved for these contests by the then editor Major B. Heckstall Smith. Thus international model yacht Returning to the yearly competitions we find in 1926 entries from America, Denmark and France. Captain F. N. Lazell won for Great Britain with man named Jnvader was entered skippered by Mr. 1927 saw entrants from America, France, Germany and Sweden. On this occasion the winner of the selection race in England was Mr. R. Jurd with Gertrude. This was the most exciting of all the international races to date as, after a terrific struggle Gertrude managed to beat the American boat Bostonia II by one point only. races could be said to be successfully launched. The next year, 1924, a challenge was received from The Royal Danish Yacht Club, and in order to find the most suitable defender for the cup a series of eliminating contests were held between club members in this country which resulted in Mr. Daniels being chosen. A new boat owned by Mr. Scott Free- which the cup would be competed for. Defiance. 361 MODEL MAKER It was during this event that the International Model Yacht Racing Association (I.M.Y.R.A.) was formed and the “International A Class” was selected as the principal class for international racing. So much for the events which lead up to the establishment of model yacht racing upon a firm footing. Today the governing body of the sport is the Model Yachting Association (M.Y.A.) to which all clubs must affiliate. Formed in 1911 its objects are to promote, organise, control and encourage the sport of model yachting within the British Empire. The M.Y.A. keep a register of all class model yachts, and issue registration numbers to such yachts, these numbers being of a predetermined size must be stencilled upon the main sail. They draw up the rules governing racing and the measurement of yachts; organise National Regattas and International Regattas. The principal classes recognised by the M.Y.A. are as follows: A Class, 12 metres, 6 metres, 10 Rater M (Marblehead 50/800) and the 36 in. (Re- stricted) Class. Fig. 1 is a comparative drawing showing typical profile of the four most popular classes. These profiles are not put forward as specific designs, but merely to illustrate the salient features and differences of each model. The metre classes have been omitted, the 12’s because they closely approximate to the A Class and are chiefly used by Scottish Clubs, the 6’s because their numbers are rather small. They are, however, included in the undermentioned description of each class which gives the chief characteristics of each model. Rating formulae of the “A” and metre classes are somewhat complex and are too lengthy to be included in this article. Those of my readers who desire precise information should write to the M.Y.A. Publicity Secretary, Mr. C. V. Hooper. 4 Freke Road, Battersea, S.W.11, for booklets dealing with the subject, price 1/6 each. Rating rules for the other classes being more simple can be quoted almost in their entirety. I have set out below a table showing the various racing classes of model yachts as now recognised by the M.Y.A. Maximum and minimum measurements are given where applicable as for example in the “A” and Metre classes, where any difference in measurement is taken care of in the rating formula. L.O.A. Classes inches L.W.L. inches F | Beam inches International “A” Class — 617. International LY.R.U. 6 Metre — 609. International I.Y.R.U. 12 Metre — 270. British 10 Rater — 1134. International “M” Class — 382. British 36 in. — 660. Let me elaborate on the bare statistics given above. 1. The International “A” Class This is the largest class and its weight usually calls for two men to handle and transport it. Its rating rule is a complex one and too lengthy for quoting in full, but as I have stated earlier full details are available from the M.Y.A. Publicity Secretary. The formula is as follows:— Lt (Weight) 123VD in Quarter Beam Measurement. VS = The square root of the total Sail Area in square inches measured Intl A | }Intlh M |36in. Res.| 70 56 70 \” to 51/| max. 50 47 max. 36 | 34 38 50 to to 50; 36′ 15 to 17} 11 11 9 to max. with the International D = The cube root of the displacement of the model 2. The International I.Y.R.U. 6 Metre Class These are scale models of full-sized craft at a scale of 1.2/3 inches to the foot. Lighter than the ‘‘A” Class but excellent sailers. A typical example would be:— L.O.A. 60 in., L.W.L. 40 in., Beam 10 in., Weight 26/29 Ib., Sail area 1,100 sq. in. variable). They are rated under the I.Y.R.U. Rule which again is a complex one. The formula is as L+2d+vVS—F under :— = Rating mot Where :— L = Length in linear inches. d Girth difference in linear in. VS = Sail Area in sq. inches. F. Freeboard in linear inches. 3. The International L.Y.R.U. 12 Metre Class This class is also rated under the I.Y.R.U. Rule and they are scale models of the full-sized boats built down to a scale of 1 in. = 1 ft. As shown in the table above there are only 260 registered with the M.Y.A., but a typical example would measure 70 in. overall, 48 L.W.L., 114 in. displacement 40 1b., with a sail area of 1,800 sq. in. beam, 4. The 10 Rater This is one of the oldest classes (1887) and the rating formula is a simple one being L x SA where L equals 6,000 the length on the water line and SA the sail area; referring to table above we get the equation 50 x 1,200 + 6,000 = 10, in. i.e. a ten rater. There are no restrictions as to Centre-boards, Bilge-boards, or Lee-boards and Bulb Keels. There is no limit to height of (Rig, or Fore Triangle hoist above deck. 48 to 52| 1800/1900 22 to 24 27 to 30 accordance in cubic inches, in full racing trim with the largest suit of sails, including spinnaker or other running sail. There are many limits and penalties which space prevents quoting as already stated. 1b. Intl. 6m /10 Rater in Yacht Racing (I.Y.R.U.) regulations Sail Area sq. +L VS = Rating Where L = Load Water Line in inches plus half any excess Displace- ment VS 1100 1200 Batten limits for mainsail are restricted to four, the upper and lower ones must not exceed 5 in. in length, and the intermediate ones 7 in. 10/16 to 20) 800 max. 9 max. 12 ‘ 8200/1000 As already mentioned the M.Y.A. keep a Register of all yachts owned by members of affiliated clubs, and at the end of 1950 these numbers were: — There are no restrictions as to materials or weight of spars, and bent masts, rotating or bi-pod masts are allowed. This briefly sets out the salient points of the 10 Rater rating rule. – 362 May 1922 The bar dividing the letters and numbers to be 5. The “M” Class (50/800 Marblehead) 4 in. thick. This class is steadily gaining popularity in this country. Originally designed at Marblehead in the U.S.A., this model gives a certain amount of scope or latitude to the designer as the rating formula is: Hull not to exceed 50 in. in length; Sail Area not to exceed a total area of 800 sq. in., thus Selecting a Model My advice to the prospective model yachtsman is to join a progressive club and learn all you can by “crewing” or acting as mate to an experienced skipper, before actually buying or building a model. You will find that practically all model yachtsmen :— 50/800. The following are prohibited Bilge Boards © Movable Keels Bowsprits Metal Fin Keels Overhanging Rudders Centre Boards Movable Ballast. Lee Boards Sail battens are limited to four and must not exceed 4 in. in length. Apart from these restrictions the rest of the rating rules closely follow those of the 10 Rater Class. are only too willing to do all they can to help a new member and even the raw novice will gain much valuable experience in watching a skipper and mate in action. When you have learned the rudiments of model yachting and handling ask a fellow member 6. The 36 in. (Restricted) Class to take you on as mate not for an important competition but during a tuning-up trial. Keep your eyes This is the smallest class registered by the M.Y-A., and is for use on restricted waters or for juvenile use. Nevertheless it is a fine model and in spite of its size is capable of putting up a really excellent performance. Its method of measurement was proposed by Mr. field Hicks some thirty years ago, and was known “Cuboid Rule”. This rule is one of the simplest rating formula: the dimensions shall not exceed a and ears open, do as you are told quickly and without question, and you will soon be welcome to the “crewing pool”. Stansas the of all length When practical experience has been gained it is time to think about acquiring a boat of your own. I suggest you put yourself in the hands of one of your club mates and take advantage of his knowledge and experience in helping you to select a suitable craft. If your club caters for the 36 in. class you should – consider acquiring one of these boats for a start. If you want something a little heavier there is the M 50/800 or the 10 rater, but do not buy a boat overall—including bowsprit if fitted—of 36 in. Beam 9 in.; Depth 11 in.; and total weight in full racing trim, including the largest suit of sails, spars, spinnaker and rudder, 12 Ib. As will be seen this rule allows great freedom of design and although a forward transom is prohibited the modern 36 in. hull is usually designed so that the L.W.L. is approximately the same length as the overall length; reference to Fig. 1 will show a boat of this type. which, as a class, is not raced by your club. Personally, I consider the I.Y.R.U. classes and the “A” International quite unsuitable for the beginner. True they are magnificent craft and are a joy to handle, but they are for the experienced man so keep off Distinguishing Marks on Sails The M.Y.A. allot a Registered Number to all models registered and this, together with a Class Mark, must be stencilled on both sides of the main sail in black. The position shall be mid-way between luff and leach at about two-thirds of the height from boom to peak. Owing to the transparency of the sail the marks shall be at different heights to avoid showing upon each other. In LY.R.U. and International A and M Classes the Registered Number must be preceded by the distinguishing National Letter “K”, but the 10 Rater and 36 in. Class do not carry this letter. These class letters and numbers are of a predetermined size and the M.Y.A. have stipulated in their regulations that these sizes shall be as follows: — Width of Class A. Marks 10R. 6M Height lin. Ace ti each item Thickness 3in. xin. them for the present. There is nothing against a second-hand boat pro- vided she is sound and has no vices. You will get an awful kick out of repainting the hull and overhauling the gear during the winter, so don’t worry about appearances if the model has a reputation for good sailing. To buy a boat with a wrung keel or other builtin fault will soon disgust you with the sport for such a craft can never perform satisfactorily, hence my advice to put yourself in the hands of a fellow club man and really heed his advice. Chromium plate and pony enamel does not make a sailer out of a dud ull. | Spaced tin. M between | item Registered Numbers A. 10R. 6M M | 3in. 2in. 4in. sin. between | 2%in, 13in gin. sin. between figures figures 36in.“Class 14in. high for number; fin. high for class mark. : Example: K.620 6m K.610 12m K.280 M K.380 10r 1150 | – Building Your Boat If you are a man of average skill and can use simple wood working tools there is no reason why you should not build your own model. Select one of the lighter classes for a first effort and buy a design from the board of a designer of repute. There are not many such designers but their boats can sail. Daniels, Littlejohn and Tansley can be relied upon to produce first class designs, to mention but three of our leading men. (Part III will cover some of thé author’s own ideas on future design and thoughts on radio control for model yachts.) 36in 700 363