- A New Model Yacht Class. By Vic Smeed
- Tucker’s Topical Talks, The Key to Successful Design. By H.B. Tucker
The Cabin Scale Electric or 30in. Barge—a Royal Cruiser Diesel for Power : Cosmic Checkers—3D Game : Lola Simple Outboard Conversion Unit for home workshop Construction : Electric Motor Review—First of a New Series : Table Top Car Racing Track : Airscrew Driven Racing Car : New Junior Class for Model Yachts : Prototype Parade—Vauxhall 30/98 : All Metal Steam Launch : Model Cars for Beginners Readers Letters Vi y2 BY VIC SMEED Whether you like small boats or not, if you are interested in the health of the movement as model a_ yachting whole, this article concerns you T HE thing that strikes most visitors to essential thing, the idea that he has a racing established model yacht clubs is the model, is missing when other boats to the same specifications are unlikely to be encountered. extraordinarily low percentage of young memThe answer is, we feel, a new, smaller class. bers. With a sea-faring reputation as a nation. and with the knowledge that few youngsters Oh, yes, smaller boats are less efficient, have reach maturity without the desire to possess a a lower potential speed, etc., etc. BUT they yacht, this state of affairs seems quite astonish- can be built simply, cheaply, and quickly and ing, and has occupied the editorial thoughts they can be raced on equal terms. Most important, they can act as a stepping stone to Conversations with expert for some time. bigger and better things—a stepping stone yachtsmen—including some connected with which has been noticeably missing for years. boys’ schools and clubs—bear out our idea Further thought and consultation led us to that the troubles are (a) cost, and (b) time. the size and rating. With the growing popuNovices wanting to go in for model yachting (novices, that is, of all ages and types) are _larity and the international acceptance of the 50/800 rule, we felt that halving this rule confronted with the necessity of building at would form an excellent basis for a new class. least a 36in. boat if they wish to race, since this is the smallest accepted class. Nowadays, Some simplification seemed desirable to make measurement easier, and to compensate a little an expert builder making all his own parts might expect to produce such a model for for wind gradient, surface effect, etc., it was around the 50s. mark; for the tyro, £4-£5 is thought expedient to allow a slight increase in sail area—up to 14sq.ft. or 216 sq. in. likely to be involved, plus a great many hours of quite skilled work calling for some tools instead of the 200 given by geometric scaling down. The result is the Half-Marblehead or which are not likely to be found in the normal 4M, or, to borrow from our American cousins’ No wonder, then, household tool drawer. that the schoolboy cannot seriously look at a idea of avoiding confusion with fractions, the model, and that the adult who would like to MM Class, the full specifications for which are given in the top right panel. try his hand at yachting (and is thus a potential Advantages for this class are (a) low cost, club member) feels that he is called upon for too great an outlay to try something he doesn’t (b) low building time, (c) easier building techniques, (d) opportunity for inexpensive know if he’ll really pursue. There are, of experimentation and home designing, (e) course, smaller models to build, but the 698 DECEMBER, 1954 encouragement of juniors (and fathers), (f) portability (what about proxy postal races?). Disadvantages are the lowered comWe parative efficiency and—what else? invite pros and cons in our Readers Write feature. Remember, the aim is to give an inexpensive introduction to would-be enthusiasts, with the opportunity of competitive sailing—a general whetting of the appetite, L.O.A. MM CLASS RATING RULE 25in. 4in. tolerance allowed. SAIL AREA Not to exceed I} sq. ft. (216 sq. in.). HULL Hollow garboard not less than jin. radius. checked with halfpenny.) (Can be BALLAST Movable ballast prohibited. Weight of ballast must not be altered during a race or series of races. BUMPER (or FENDERS) Not included in L.O.A., but must not exceed j{in. overhang. SCANTLINGS AND MATERIALS as it were. No restriction. Now, a new class can best be considered by producing a boat or two to the rule. This month, we are presenting Water Baby, a conventional round-bilge design which has received favourable comment from several experts, and which is fitted with a very simple vane gear we have evolved, so that training in the use of a vane can be had. Next month we shall publish Sea Urchin, a hard-chine boat of simple construction, with a new ultra-simple steering gear. Later, we hope to publish other designs and articles to widen the field. We have reason to believe that if reaction to this MM Class continues as favourable as it has proved up to now, the M.Y.A. might consider its adoption as an official class, providing that a resolution for its adoption is forthcoming from an affiliated club. With this in mind, we intend to open a register of boats; you build your boat, and on completion submit details to us, when, if the boat fits the rule, we will allocate a sail number. When fifty boats have been registered, we will put up a trophy for annual competition, and, should the M.Y.A. eventually adopt the class, the register will be handed over, when official acceptance of the boats will merely entail their submission to a club official for checks. Well, there is our proposition. We feel sure that readers will have much to say about it, and we cordially invite your views. Meanwhile, to give you an idea of the practical application of the rule, here is the first boat No limit to L.W.L. beam, draught, freeboard, tumble- home, or displacement. PROHIBITED Movable keels, metal fin keels, or others without Centre boards, lee boards, bilge hollow garboard. boards, bowsprits, and overhanging rudders. S.A. MEASUREMENT Is taken as a simple triangle between head, tack, and clew; roach, bow, etc., are not measured. SAIL BATTENS Jib or foresail—not exceeding | in. in length or three in number, dividing the leach into approximately equal parts. Mainsail—not exceeding 2in. in length or four in number, dividing the leach into approximately four equal parts. No wire or other stiffening permitted in headsails. HEADBOARDS Shall not exceed { in. along the base. HEIGHT OF RIG The jib shall not be attached to the mast at a height above the deck which exceeds 80% of the height of the mainsail headboard above the deck. SPINNAKERS Are allowed; boom must not be. more than 7} in. in length, measured from the centre line of the mast to the outer end of the boom. Spinnaker must not be hoisted higher than point where jib stay cuts mast, hoist to be measured from where forestay cuts mast down to deck. Spinnaker headboard or stick not to exceed 1 in. across base. A spinnaker may not be set with a footyard or more than one sheet, nor any arrangement to spread the sail to other than a triangular shape. The sheet may be led round the luff of the fore- stay. Sleeves and tubular pockets not allowed. MAST AND SPARS No limit to height of mast. Material, weight, and section are not restricted and no additional measure- ments for area are required when other than a circular section is used. Hollow masts and spars are permitted, as are permanently bent ones and rotating or bipod masts. Masts and spars are not included in measurement of sail area. Measurements for sail are taken in exactly the same way for raking or vertical masts. ALTERNATE RIGS Allowed provided S.A. does not exceed 216 sq. in. SHEETING OR SET OF SAILS No contrivances or gadgets, e.g. outriggers may be used on headsai!ls or spinnaker. The spinnaker boom may not be taken forward to act as a bowsprit. A spinnaker may not be set without a boom. A jib or spinnaker may not be sheeted on to the main boom. Two mainsails may not be used at the same time. designed to it. Water Baby Conventional in design, except for the relatively small overall dimensions, Water Baby scores by offering at least five different methods of construction. Firstly, the two normal processes, bread-and-buttering in obechi or rib-and-planking in ply and mahogany; secondly, either of these methods in balsa, with a solid paint finish or a glass fibre skin; thirdly, all glass fibre. Of these methods, we particularly recommend the obechi bread-and-butter system (as our original hull) and the balsa planking with glass fibre The one-ounce simplified vane gear evolved for this class—an easy job for anyone able to hold a soldering iron. 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O 3 ¥ 0 5 “ t + a = 0suypa!ji1e0+S3BAgL»UsNOp9u4ieVIy\‘xj3d5“AHOSLuB1Ni0SpY8sn“q4e3sg0KtnWOiAlBXYaDZNjVBIqG4weSu4nH0LavsueRsr1TicS3‘E*oUEjm=!.5-2nB”aO}tNrny4esW%0pA93d1iN)3odsu4‘SYOvMuCrieBjVsdyIJnHao(oy=lA:UpOe7>YnfaDa|IjeilsMe=*S4Ay—“eHaaSrn“jInd9vOr4wiMd=3iBT10o$1S>asN‘vuAp4a03djNAesLSFi,w3VeE4ezShG\1U7s85l7agr‘masVrPS-E/WWSRLIsCN:jiueswapY|o)A.7gSO6oa2uv3itee8;NL4x91d03GnBN¥4Vqs9E‘UoI43D>SNue}Sg4NLU0t3EOY‘HWGdMQOD3DaNvU\{cIyES\n37VoA4A19JmH9aTSI3H0GAS0ge¥OeIBTLdMU‘WOTORBYP1Lg8W1NNgd‘SMiOGMDAXa3eYcH9i,0Nv7|es4W>/”4oO4W9FVLw101T‘3/r2S#P’uIA2SR3UOM8Y0|O|R9*dY-T:AaOejSOhvk-BeIAN]PNi—mDsaD3woOG”0E MODEL MAKER n Pas DECEMBER, skin. However, two separate drawings are available, the first covering bread-and-butter and all-glass fibre construction, and _ the second rib-and-plank building in hardwood or balsa. This step is taken to avoid the inclusion of confusing parts and naturally results in two low-price plans rather than one unnecessarily expensive one. Water Baby is designed for all-round performance and easy construction. To the latter end there is no deck sheer, the sections are very easy, and the lead is designed to cast a little overweight so that trimming holes can be drilled and plugged with dowel. As mentioned above, the lines were approved by several experienced yachtsmen, and as an additional safety measure, we had the hull carved by Arthur Levison so that any faults which might have appeared would have been directly attributable to the design. The only criticism we received was not directed at the boat, but rather at the class; it was felt that a 6-71b. displacement on an 8in. beam would be called for. Well, time will tell on this. The drawings are self-explanatory, but the following brief notes may assist would-be builders to make their choice of plan. Pian “A” (MM.354) Obechi Bread-and-butter construction. All planks are shown full-size and need only be cut to shape and glued up in a set of cramps, using a resin glue such as Aerolite 300 or Casco “One Shot”. Carve to shape using the templates given. Balsa/glass fibre construction. The hull is built in exactly the same way as above, but the planks are fitted each side of a central ply keel through which the lead bolts. Finish can be paint—apply three coats of a 50-50 turps and goldsize mixture as a base, rubbing to facilitate this. Ply ribs are added, after fitting the keel, and planking carried out from the inwale. 3/32in. mahogany is. adequate for planking. After removal from the jig the shadows are removed, deck beams added, etc. Balsa Rib-and-plank construction. The shadows (3 balsa) are set up in the jig, the keel fitted, and tin. balsa planking cemented directly to the shadows, which remain permanently in position. No deck-beams are required. Finish is as for the balsa hull, described above. The only difficulty for the average builder will be the casting of the lead, but we hope that castings will shortly be made available for purchase, ready fitted with studding for screwing into place.. The tube for the mast is available from H. Rollett Chesham Place, S.W.1. obtained. Reinforcing items, fin, etc., can be “glued” in place with more resin. The result is unbelievably strong. Pian “B” (MM.355) Hardwood Rib-and- plank construction. Here the ply shadows are cut out and erected on a building board. The design has no sheer, & Co., Ltd., 6 Research into the question of a simple vane gear eventually led to the | oz. unit illustrated. This baby gear provides all the usual features a little simplified and can be built by anyone able to wield a soldering iron. Construction throughout is of brass tubes and brazing wire, plus scraps of rod and three small screws. One minor fault is the ability of the vane arm to pivot when the adjusting screw is slacked off; this could be overcome by doubling the wire and elongating the slot through which it moves. The vane is locked for running by drawing the arm out to its full extent, compensating on the tiller adjustment if required. A series of articles on the use of the vane gear will commence next month, and an article covering in full the rigging of both Water Baby and Sea Urchin will appear in our February _ issue. down well—or for maximum wear one layer of glass cloth brushed on with resin in the usual way. Glass fibre construction. This entails making either a male or a female mould. The ideal way is to carve a hull as above, paint it well, grease it, and make a plaster-of-paris mould from it. The resin and glass cloth shell is then built up inside this mould (grease it well !) and a superb finish can easily be 1954 Water Baby afioat is a lively and surprisboat—a fast ingly real miniature racing wave Good yacht. form is just discernible in this photograph 701 MM| @ Ge # | | | ; } MAKE IT FOR JUNIOR A JET BOAT Ling BY ay ci S uJ SSN Ty H. A. ROBINSON ms come out from it a small hole (4) is drilled s in the lid near the top. The lamp (5) is a flat tin with two holes in = the lid: Inside is cotton wool and tufts of ~ this are drawn out through the holes. Filled with methylated spirits this kind of lamp burns quite well, giving off a good smoke less heat. Supports (6) are two angles of tin of sufficient height to clear the flat tin and tuft wicks and give a little space for the flame. A hole is drilled through the feet of the angle s and each is held with a screw to the “deck”. The tops of the uprights are cut out to the same curva- HIS toy ship is sent through its native element by a steam jet set in the stern, and the reaction that this sets up. The first thing required is the cylindrical tin (1). This should have a tight-fittin g top. It is reinforced by the length of tin (2), which is a strip so cut that it goes right round the tin with turned-up ends (3) that come about } in. apart. ture as the “boiler” which will lie quite safely in these without further fastening if they are sufficiently deep. Now we come to the hull. In relation to the boiler and the lamp this must be of the size shown. Point the prow and shape the top as shown to suggest a turtle deck. Also make the little rudder (7) and fix it stiffly at the middle back with a small model-maker’s pin. The short mast (8) in front helps the general Drill a hole in each of these turns and pass through a small bolt which when drawn up pulls the strip and the lid tight. This tin is the boiler. Its position on the pontoon is horizontal and to allow a “jet” to ASSEMBLY appearance, this being merely a thin spill of wood bedded in a hole in the deck. At the top the flag (9), which should be bright red or some other brilliant colour, is first cut to an elongated diamond, this then being glued on its inside and wrapped round the top of the wood. A good finishing touch is the funnel (10). It is a piece of suitable diameter dowelling curved on its underside to sit on the hull and secured to the strip of tin (11) which in its turn catches under the band (2). All is now ready for the run. Loosen the band (2), take off the lid and half-fi ll the tin with fairly warm water. (Note the boiler is never fastened down but merel y lies on the supports.) The band (2) when loosened will slip off, its replacing and tightening being but the work of a moment. Fill the lamp container, light the wick and wait. As the temperature rises steam will come out of the hole and as the tempe rature gets ” WITH COTTON WOOL really high the force will be sufficient to move the boat forward—a perfect demonstrat ion of reactive propulsion. 704 DECEMBER, 1954 supplemented by special tanks in which waterstreams UCKER’S TOPICAL TALKS round the hull can be observed. Thus such establishments as the Stevens Institute at Hoboken have THE KEY managed to obtain incontrovertible data about hull TO forms, and these results have been published. I remember an old yacht builder, wth whom I was SUCCESSFUL friendly as a young man, disccursing on yacht design. DESIGN ? NZ A IN recent correspondence with a friend, I tried to analyse the ingredients of a successful design for a I came to the conclusion these model racing yacht. were:— (i) Correct Hull Balance and Freedom from Vice. (ii) Hull form. (iii) Good selection of dimensions under the rating rule in cuestion with due regard to weather conditions likely to be encountered, etc. Dealing with these in turn, freedom from vice em- braces many things in addition to hull balance. Hull balance is, of course, the first essential, but this alone will not ensure freedom from unwanted steering effects. For example, a fin with an oversteep or unduly thick leading edge will make a boat hardheaded and prone to gripe into the wind. Hence, it is the des’gner’s business to eliminate every feature that is liable to have a detrimental effect on the yacht’s behaviour. On any given dimensions the best hull form is obtained by shaping the lines in accordance with the princinles of speed and reduction of resistance to forward motion, always bearing in mind the necessity of providing adequate lateral resistance, etc. In general, it appears to me that the influence of the transverse sections is mainly to govern the boats stability, and the angle of heel she will take in various weights of wind, while the longitudinal lines (W.L.’s, Buttocks and Diagonals) mainly affect her speed through the water. When the old shipwright drew his moulds on the mould-loft floor, he usvally described the turn round his bilge with compasses, and ran in his floor as a tangent. If he was laying down a ship of the line, weight carrving and steadiness as a gun platform were primary object’ves, so he put the bilge turn low and made his floors almost horizontal. If on the other hand, he was building a blockade-runner or a privateer, and speed was all-important, he placed his bilge turn higher and gave his floors a good angle of rise. We do exactly the same thing to-day. If we are designing a cruising yacht, we want her to sail reasonably upright for the sake of comfort; but if our boat is to be a racing yacht, we want her to come to her sailing angle as easily as possible, and then become increasingly stiff so as to obtain power to carry sail. As our old shipwright found, this is a matter of the angle of rise of our floors and the position of our bilge turn. To-day, we phrase things rather differently, and talk about Metacentric Heights, Righting Arms, etc., but it all ccmes to the same th’ng, and in the long run science has confirmed what actual experience has taught. The principal feature that makes for speed is length, but there are many considerations which can affect the sailing length a yacht employs. Before modern testing tanks were brought into use, we had largely to derend cn guesswork and intuition. The first tests instituted, as far as I know, were towing tests recording the resistance to forward motion offered by various forms of hull, but these are now He said to me: “Water abominates hollows, such as a hollow bow. Likewise it does not like straight lines or abrupt corners, such as a sharp turn round the midship section. Long sweeping lines make a sweet hull, fast and sea-kindly.” Now these tank tests exactly bear out this dictum, and we know why certain features make for speed, while others detract from it. So far, yacht design can be considered as a matter of technique and perseverence in perf~cting the details of our design, but when we come to the selec‘ion of dimensions under the Rating Rule to suit conditions likely to be encountered, we are faced with the designer’s most difficult problem. The only Rating Rule which automaticallv settles main dimensions for the hull are limited while S.A. is unrestricted, we naturally make our hull as large to as the rule permits and then canvas our boat the limit. Since this eliminates all selecticn of dimensions. this rule is the best of all our Rating Rules : as a test of the designer’s technique. Under other rules it is possible for a boat with this question is the 36 in. Restricted Class. Since our a good selection of dimensions to good balance and has less wellbeat a better designed boat which selected dimensions. Hence I would. recommend a test. to designer, who hes theories about design to in this trv these in a 36in. yacht. If it succeedsones. Class. it is worth trying out in the larger Since boats have been bvilt for thousands of atyears, one almost every feature of design has been tried have been embodied time or another. Good ideas but unin the recognised techniques of the art, a successful exper’ments have been rejected. When be to a bright idea, his first step should in repeat hoary old fallacy. There is no sense. mistakes, and really new and valuable ideas are few designer has ascertain whether he is provosing to resurrect some ing and far between. ber, I made I see that in my “ Tovics” of Novem onal amount additi the of ng speaki when slin a slight of terylene. use the by able obtain roach il mainsa of 4 inches, to limited h is roac of width s A-clas the In but there is no limit on tablings. the use of The main point, however, about l is used for a terylene is that when this materiapart the after mainsail, the roach in the upper| even ofwithin the sed increa y greatl be can leach n on roach, limits, when the rule includes a limitatio and by this means many very valuable square inches can be gained just where they are most efficient, arly thereby increasing the drive of the sail, particul es larger in light winds. As a corollary, this postulat boats. is MODEL MAKER COMPETITIONS Prizes value £10 are being sent out before Christmas in respect of our glass fibre contest. Winners’ names will be published in January issue. Entries for the ‘Crested Goods” 0-gauge loco contest must be sent in by 31st March, 1955—again for a £10 prize. Deta‘ls of send’ng-in arrangements will appear in our February issue.
