Model Maker: Volume 4, Issue 40 – March 1954

VOLUME 4 MARCH NUMBER 40 1954 A Simple R/C Mercedes-Benz Car Mode! New Marblehead Yacht Design “Fury” 4ft. Powered Steering Launch “One Evening Jobs” for 00 Gauge Layouts More Hints and Tips for the HomeWorkshop 1904 Darracq Model “Genevieve” Completed Human Figures Add Interest to the Layout 0 Gauge Steam Tender Loco 0-6-0 ‘Crested Goods’ Lighthearted Model Car Passenger A simple Model Car Racing Memories Association Racing Calendar Rolling Stock Planimeter in at TT Low Stability of Model Planing DE Gauge Cost Hulls MmOoeEL MAKER er Gites Belle yy es towards the after edge. A theory has it that greater efficiency is achieved and although I have not been able to measure any improvement, I am equally certain it can do no harm. To return to the front end, it will be seen that an extra section has been drawn plan, spaced lin. from the bow. illustrate the curious flare and angle of this design. One of the difficulties A NEW MARBLEHEAD DESIGN stemmed boat is in providing sufficient reserve buoyancy to prevent plunging, particularly when BY “3 JOHN A. LEWIS sailing down wind. There are four contributory factors which play their part in avoiding this evil and any one of these can spoil an otherwise good boat. (1) The design of the sail plan; (2) The builder of the boat; (3) The skipper of the boat. (4) The design of the bow. Taking these in order and considering firstly the sail plan, I have noticed that the ratio of mainsail to jib has some bearing on the subject. J FROM the designers’ point of view, the “Marblehead” rule is remarkably free from restrictions. However, any rule that limits the overall length is bound to produce a particular type of hull. It is reasonable to suggest that with an overall limit of 50 in. between perpendiculars, the choice of load waterline length should be as close to 50 in. as possible. The use of well designed overhangs to increase sailing length, sea hardiness and stability, is denied us and the SQ/BOO ~MARBLEHEAD YACHT. \ CR, ) von’ Lems. (9/6) lal (My TONGA BELLE SIGNED BY is fast plumb ended racing machine is going to be a wet boat indeed. This fact accepted, let us examine the new design illustrating this article. It will be seen that the load waterline length is 49.55in., but this would have been 50 in. if it weren’t for the fact that a vertical stem always looks as though it is leaning backwards. This =. = . 5 COPYRIGHT OF MODEL MAKER PLANS SERVICE 38. CLARENDON RD. WATFORD. ¢| HERTS ° would look hideous and in. of rake will be just enough to counter this effect. The overall length is 50.25 in., which is the limit allowed by the rule and may as well be fully used. The extra }in. is utilised in the after end to form a duck’s tail, which will help in leaving a clean and undisturbed wake. The shape of the after sections are such that very little immersion of section No. 10 takes place, when heeled. This promotes good balance and with short ended craft, is a great help in cleaning up the after wave formation. If desired, the hull could be finished off flush with section 10 and a cavitation plate fitted in lieu. It should be noted that the rudder projects aft of the end section and if any modification of the design is contemplated, the shape of the rudder must be considered, as the rule does not permit overhanging rudders. on the body This is to at the bow in a straight The rudder post has been given a rake forward, as this gives the maximum blade area for a given skeg and rudder combination. A few square inches of wetted surface are therefore saved. I have tried an almost identical shape of rudder and skeg on a 10-rater and-it proved. remarkably efficient. The cross section through the skeg, shows a thickening 150 ot: s] Saree MARCH, A boat with a large mainsail is more likely to suffer than one with a large jib. This is really fairly obvious, but provides us with another excuse for a large jib to assist in windward work. One must not forget, however, that the 800 sq. inches allowed a “Marblehead” is rather paltry in light airs and too small a mainsail may be a disadvantage. Here is a case for alternative sail plans. The builder of the boat can be of great assistance by making the ends as light as possible. Excessive weight at either end will ruin a “Marblehead” and it is important to go to the limit where lightness is concerned. Keep the weight midships and as much of it in the lead as possible. Thirdly the skipper can help himself and his boat by skilful use of the spinnaker and kicking : strap. It may often pay to stick to a large spin- naker and reduce the mainsail when going downwind. Fourthly, we have the design itself. The absence of overhangs does not leave much scope for the designer. The obvious way to help is by ll % finishing the forward end of the deck plan with as large a radius as possible instead of the usual sharpness. There is a limit to this and it is reached when the deck edge becomes too often immersed, sailing to windward in a choppy sea. The amount of windage when heeled can also become excessive. If, however, a false deck line is drawn beneath the true deck, which we will call a chine line, it is fairly obvious that less radius is required to obtain the same amount of flare. Also the flare is immersed more readily and can therefore take effect more quickly. The straight tumblehome from the chine line to the deck helps to reduce windage. Should the flare not prove effective enough under some conditions, then the water will either be thrown clear of the sharp angle of the chine, if sailing upright downwind, or sluice over the deck when well heeled on the reach or boat. However, we reckoned on a wet boat at the outset and a watertight boat is always a big advantage! It would be difficult to plank build this hull, so ei re : — meat Socal | — es pal cannes i noes — _——- | reece oe Se, — ese mae = LEAD LINE Ay : = xsw he DECK LINE. = LINE 8. -—_\ \\ 1954 /\ / || 2 moo I have indicated on the body plan the alternative section leaving out the chine, if this method of construction is considered. There are only two other features that are worth mentioning, these being the hollow waterlines forward and the relatively thick keel. The hollow waterlines are brought about by the fairly deep body right up to the bow, and this enables greater buoyancy in the forward half of the boat to be obtained. The centre of buoyancy will be seen to be almost midships, as are the greatest beam and greatest body depth. The rather thick keel helps to fine the hull lines for a given displacement. It has been argued that a thick keel must offer more drag than a thin one, but if the matter is carefully considered, it is difficult to condemn the idea off-hand. Firstly, several very successful full scale yachts have incorporated this feature, with no detriment. Secondly, if one considered the beam length ratio of the waterlines, which are accepted without criticism, is it logical to condemn a similar ratio in the hull sections? Thirdly, if the keel and hull have the same ratios in beam and length, then the differences in speed between the water flowing round the keel and round the hull, will be less and the resulting turbulence set up ITAL – CORSA in the garboards will be reduced. This turbulence is a well-known source of drag. Fourthly, I built two boats of identical sail plan and almost identical hull form, i.e., the 10-raters Halceyon and Moonshine. Moonshine was fitted with a shorter, deeper, and considerably fatter keel than Halceyon and her performance downwind, where drag is the predominant feature, proved to be the superior. The windward performance too, was improved, but there are many other factors which bear on that. The fact remains, however, that I am convinced that a fat keel need be no disadvantage. Fifthly, there is no need for a blunt leading edge to enable the lead to be well positioned. The sail plan of a “Marblehead” offers many possibilities and the design shows a rather tall aspect ratio, which I think is to be preferred. However, the design of a suitable plan for particular location or fancies is very simple and I do not propose to discuss sail plans in this article. I will be interested to hear from anyone who builds to this design. Their opinions and criticisms will be invaluable since progress may only be achieved through direct co-operation between skipper and designer. A SCALE MODEL PROJECT BY A. W. HOLESWORTH FILLER OF MOTOR es eos o- 1 a . eS ee i Cc ee > GENERAL ARRANGEMENT MODEL MAKER and 13th June. Events will include Open Two Lap Race for powered craft; Novelty Competition which puts the onus on the entrant to “Put on a MODEL YACHT Show”; Three Lap Handicap Sailing Race for Sailing Yachts round a triangular course; Open Steering Contest for power craft; three lap race for r/c yachts capable of being sailed together in heats of two boats fitted with tuned reed receivers. Regatta entries and enquiries should be made to: Mr. W. L. Perrett, 46 Cranbrook Road, Parkstone, CLUB NOTES Dorset. Y.M. 6-m. Owner’s Association Seven boats braved the weather to enjoy brilliant sunshine in the club’s winter fixture the Sirius Cup. Alas, progress was slow, the wind fitful, and the event had to be cancelled with only three heats BY COMMODORE completed by 2.30 p.m. That fine oldtimer Naiad (357) designed and built by the club president Major General W. C. Holden, who won the National Championship with her in 1935, has been refitted and made an appearance with her new owner, Mr. Alan Hill, a young and enthusiastic skipper who should do well with her this year. First Open Event of the year will be the Gosnell Trophy—usually raced for in the Autumn—which is scheduled for 28th March. Club secretaries are asked to note that the new Racing Secretary is Mr. D. A. Macdonald, 11 Blakenham Road, S.W.17, to whom entries for all the club’s open events should be sent and NOT to the club secretary Mr. Hatfield as in the past. ONE more there is a stirring amongst model yachting enthusiasts as they shiver down to the clubhouse to dust off their potential champions of the new season, or, in frenzied haste rush on with building programmes that had better been started in the autumn. The M.Y.A. Council, however, continue throughout the year with their regular meetings. A notable absentee was Mark Fairbrother, whom we learn has had several months of ill health, recovered in time for the Council Meeting, and then fell downstairs! Just to complete his misery he has since had flu! A proposal is being circulated that the garboard restrictions in the Marblehead class be abolished. This comes from the Metropolitan and Southern D.C. Promising portent appears in the end of the report in a suggestion that the M.Y.A. formulate sailing and rating rules for radio controlled yachts. This is only a beginning, but it is really something to get r/c matters “‘on the table.” Poole M.Y. & P.B.A. That happy fellowship of Club and Town enjoyed at Poole takes practical form this year when they will be staging their first National Event on their vastly improved water—on which the local authority spent a lot of money last year—with the Marbleheads at Whitsun on June 5, 6 and 7th. O.O.D. will be Mr. A. R. Litton of Exeter, assisted by Mark Fairbrother, M.Y.A. Racing Secretary. The following week-end the club’s annual Radio Regatta takes place on 12th Model Maker Trophy 1954 Through the good offices of Mark Fairbrother, we are happy to announce that the MODEL MAKER Novices Trophy will be raced for on the Birkenhead M.Y.C’s water on Sunday, May 2nd. This year the event will be for Marbleheads. The definition of a novice is a crew of which neither skipper nor mate has ever skippered a Marblehead which has taken any of the first three places in a National Marblehead Race. This does not bar winners of National races in other classes. There is, as usual, no entry fee. Winner holds the Mopet Maker Trophy for one year, and prizes to the value of Five Guineas are awarded to winner and runners-up. Further particulars can be obtained from the Birkenhead M.Y.C. Secretary, Mr. J. S. A. Bruce, 17 Claremont Avenue, Maghull, Nr. Liverpool. News from America Our friend Mr. A. R. “Gus” Lassel sent us the heading picture of himself with his latest yacht as a Christmas Card. Model is of the proposed new U.S. class, permitting unrestricted keel design. This one has a Sail Area of 600 sq. in., L.O.A. 653 in., Draft 13in., L.W.L. 53in., Displacement 15 lb. 168