Model Maker: Volume 3, Issue 37 – December 1953

: hristmasjlumber ROYAL YACHT . H-M-S mm 7 BRITANNIA = _ ‘THE ten rater has long been the favourite class for designers allowing as it does almost > A TEN-RATER YACHT complete freedom of hull design. Because of this apparent looseness in the rating formula designs OF CLASSIC LINES vary to some extent in hull-form, dimensions and weight. A good example of this can be made by comparing the dimensions of the first three boats °* Barracuda’ in the 1952 Championships: Water Witch—Length O.A. = 75.4 in.; Beam — 11.75 in.; Length L.W.L. = 50.43 in.; Weight = 26.5 Ib. Restive—L.O.A. 55.3in.; L.W.L. 53.25 in.; B. = 9.3 in.; WT. = 23.5 lb. Triplane—L.O.A. 63.5in.; L.W.L. 51.5 in.; B. = 16in.; WT. = 20.5 lb. It is difficult to know therefore just what form BY A DESIGNER NEW TO MODEL MAKER of hull can be considered to be typical of its class. As near as one can judge however Barracuda can be considered to be an average size of 10 rater and has nothing radical or untried in the general S. WITTY Note on the name:”The Barracuda is a particularly savage fish reputed to devour any living thing in its vicinity conception. As this hull will be constructed mainly by regardless of size—we hope it augurs well for the success builders with previous experience the following article is devoted to a description and reasons for the various points of design. of this new yacht! .. y, BARRACUDA IO RATER Ga) ca ween. cats, Seeeee eee ocag panes eae el Saag SS a Ba MODEL MAKER PLANS sens -_ Sah 698 | 699 exmenntn ecmateiasetaa windward. It must be realized that although most hulls will plane providing they can be pushed hard enough without baulking or becoming unstable, the fin itself must always be driven directly through the water. According to certain tank tests a thick fin is no disadvantage but these results apply to full sized keel yachts and not to fin keel models which have a much smaller fin chord and therefore for a given thickness a more acute chord-thickness ratio. Also when a blunt nosed section is carried right up to the canoe body strange things happen to the displacement curve proper and often causes the wave hollow to form well ahead of the centre-section. The skeg and rudder is placed well inboard to obtain energy from the uprushing garboard stream and thereby counteract the tendency of the vee bow to turn to windward. Incidently it should be pointed out that while these forces are counteracting from a balance point of view, the energy obtained in the bow does not cancel out the energy obtained in the stern but is in fact additive. i.e. pressure on the vee side of the bow exerts a force acting to windward while the aerofoil effect of the skeg and rudder also gives a force acting to windward. The idea seems to be becoming quite popular in new designs and is in fact a feature of many past successful craft. The sail plan is conventional in layout with a mainsail aspect ratio of 3.6 which I feel is as high as it is advisable to go unless one is preferred to use two top suits of different ratios. Kicking straps are used on the jib as well as the the mainsail because otherwise the sail plan becomes too unbalanced in a squall and will often cause an otherwise perfectly balanced boat to spin around like a top into the wind with the subsequent loss of several precious yards, before filling away again. It is hoped that the speed and sailing qualities of Barracuda will give much satisfaction to those who build her for the fast approaching season of 1954, A: A WIDE SELECTION OF MODEL YACHT ay DRAWINGS Readers wishing to build a new yacht for 1954 in any of the Racing Classes, or simply to make a boat for pleasure sailing, are invited to send for our illustrated list of Model Plans, including all types of model boats, cars, workshop accessories, aircraft, etc., etc., which is available by return of post, price 6d., from: \ MAKER PLANS SERVICE nw MODEL | Se mos 3 38 CLARENDON ROAD, WATFORD J alata The hull form in general bears some resemblance to that of a 30 sq. metre yacht and as in this type the canoe body is reasonably though not perfectly balanced, as I regard a fine bow section as a “must” for any real performance in rough weather. Often in the case of many fully balanced 10 raters the angle of the bow section becomes parallel with the surface of the water when heeled over at the optimum sailing angle of 20°. It does not require any complicated theory to realise that this will result in the worst sort of pounding in a seaway. Much has been said on the subject of hull balance but little on the importance of the relative positions of the skeg and fin-root. It should be realised that any excessive tendency to turn into the wind can be cancelled out by the correct positioning of the appendages. This is actually no less tricky in the case of a 100°/, metacentre where the fin root has often to be cut away in order to make the boat point up at all. While any information given in tank test reports is always of interest it is doubtful whether they are fully applicable to model work except at moderate speeds as although these tests are conducted with scale models the speed is adjusted so that the results approximate to full size practice. For instance full scale yachts do not usually sail at a speed in excess of an S/L ratio of 1.5 (i.e. For a 25 foot yacht = 1.5 /25 = 7.5 knots, so that an equivalent speed for a 4 foot model would be 1.5/4 = 3 knots). But whereas most full sized yachts do not exceed S/L 1.5 model yachts frequently do mainly because the speed of the wind remains the same for both and is therefore greater in proportion to the smaller model. The type of midsection used in the design is rather more sharply ve’ed than is usual in a 10 rater as most designers tend to reduce the nominal hull draught as much as possible in order to obtain a flat run aft and a sleeker profile regardless of the fact that this causes a convergence of the hull lines at this point. In Barracuda the midsection permits smoothly flowing lines and is of a form which can pass easily through broken water. The displacement curve of the hull follows full sized practice in having its peak well aft of the midsection (3%) approx. and allows full use to be made of the aft overhang. It will be noted that the water-line is divided into 12 equal parts of 43 in., as I believe that the distance between ribs on a planked hull should not exceed five inches. The profile of the fin is of conventional shape and has its leading edge at an angle in excess of 45° while the after edge makes a right angle with the run. The sections of the fin itself have been Kept as sharp and fine as is practicable. This is particularly important at high speeds and seems to give a better grip on the water when going to 1953 Lee —— DECEMBER RIGGING — FITTINGS BY H. E. ANDREWS (Concluded from the September issue) } E must now return to the remaining sket- ches in Fig. 1. Fig. 1 (6), (c), (d) show three alternative methods of keeping the mast from bending in its own length athwartships. Either one or two 1 i= – pairs a of spreaders are affixed to the mast in the position indicated in the drawings and ‘“‘diamond” stays are rigged over them as shown. The spreaders should be of such a length that the stays make an angle of 15 degrees with the mast. Fifteen degrees is considered the minimum efficient angle for any stay to make to its spar. The plan shown in 1(6) is the one usually adopted in small full-size racing craft, but plan l(c) is preferable, because it is just as effective and it saves the weight and windage of 4 or 5 feet of wire and two strainers. Plan 1(d) is efficient but involves the use of inordinately long spreaders. The spreaders can be made of wood or metal as preferred, if of wood, resin bonded ply is an effective medium. If metal is used the hounds fitting, jumper struts and top spreaders are usually combined in the one fitting. Fig. 4(a) indicates a suitable design for this. Fig. 4(6) shows a suitable type using resin-bonded ply. The last of the three problems in rigging a mast is that of eliminating excessive twist in the mainsail when on the wind. High aspect ratio sails are particularly prone to this vice. Into the picture comes our old friend the kicking strap but in an entirely new guise. In the old days it was just a piece of cord with a: bowsie adjustment and sometimes with an elastic insertion. A glance at Fig. 3 will reveal how it has developed. In this problem, full size practice does not help us because whena full size boat goes to windward, the main sheet is so hardened down that it serves to eliminate the mainsail twist. The kicking strap, if carried is normally slacked off. On the run it is hardened down and serves to hold down the mainboom when the mainsheet is slacked off. In models, the reverse obtains, the kicking strap being hardened down on the wind and the mainsheet being used solely to control the angle of the boom in relation to the centre line of the boat. Running, the kicking strap is eased off so that the weight of the boom and the curve of the sail can act as a shock absorber against the heavier puffs of wind. If the boom were held hard down the extra weight of wind in the squalls would overpower the helm, and cause the boat to luff off the course. The gear shown in Fig. 3 was designed to secure, by a screw adjustment, an optimum setting for beating to windward, an elastic shock absorber device for use on the run, and a means of repeating either setting quickly and accurately. When beating the gear is set as shown and the tail of the bellcrank is securely held by the slide. The gear is then rigid and the boom is held in its predetermined position. When running the slide is pushed down towards the mast and the tail of the bellcrank is then free to lift between the bars, its lift (and consequently the lift of the boom) being controlled by the elastic insertion in the cord affixed between the boom and the bellcrank via the sheares on the hinge bar of the gooseneck. The knurled wheel controls the optimum setting in the windward position and once set, needs no further adjustment, except to secure extra “flow” in the sail in light weather conditions. The bowsie on the cord determines the stretch of the elastic available to act as a shock absorber to counteract the heavy puffs. The construction of the gear is apparent from the drawing, but actual dimensions cannot be quoted. As a guide, however, the point of attachment of the gear to the mainboom should be about 2/5 of the mainboom length, measured from the gooseneck. This, too, should be the point of attachment of the running sheets. In conclusion, a problem which has not been mentioned, is that of finding a method of sheeting a self-tacking “genoa” jib. The man who can solve this one will be doing his fellow yachtsmen a good service, for it is only this difficulty which prevents the use of these superlative sails on models. HOUNDS FITTING © SPREADERS (METAL) SPREADERS © JUMPER STRUTS (woop) ee — Ses aa MODEL MAKER) After treating the planking with water and rubbing it down until the grain no longer “lifts,” try a coat of weak White Polish and you will find that the grain will “lift” yet again. If you rub this down with very fine paper on a felt pad, a finish ideal for any varnish or paint will then result. The depredations of war exposed much timber now available as salvage. Though its use in the past may have been in the form of beams, girders, purlins, and every type of building joinery and its Laminated Hull Construction CONCLUSION BY F. C. BOARDMAN ee finishing the hull with enamels or paints, | I much prefer rubbing the enamel on by hand. Although this is a “messy” job it does give the satisfaction of ‘“‘bodying up” the hull and each coat of paint is very fine compared with brushwork. age may vary, after being reclaimed and machined the nature of the grain and texture has been in most cases first class. When the last coat is applied I use a bag Recently a 12 in. x12 in. beam which had been in a building for some 200 years was cut down the centre and was found to be perfect, without a knot in its whole length of 16 feet. No nails or ironwork of any description had been fastened to it. It was of great value to those who needed it, yet its market value was extremely low and within easy reach of pumice powder or some rubbing paste similar to those used in spray painting. The hull should be slightly wet when rubbing down with the powder bag. For further rubbing down, thoroughly dry the paintwork and using the pumice powder together with Linseed oil as a lubricant instead of water, you will find that skin friction is reduced of the artisan’s pocket. By using reclaimed timber one can save a con- even more. I have found by experience, that when using cement by the double application method described, it is wise and economical to let the hardener cover the greater surface, i.e.: In planking up cover the inside face and one edge with the hardener and cement that portion of the ribs which will be covered by the planking. It will be noticed also that in shaping the planks as described, pressure is applied automatically by the fitting of one plank to another, and that no other pressure is required. Using the Bootmakers’ “tingles,” the shape of these is sufficient to hold the plank to the rib and you can be quite satisfied that when you withdraw them, the cement has far greater power than any metal pin. The hole that remains is filled from the inside by the varnish applications and on the outside, the fibres of the planking are “‘lifted” by the water application. If you prefer, you can use a pointed match as a plug but I have never found this necessary as the various subsequent applications have always proved sufficient. siderable amount of money and yet obtain some of the finest yellow pine. For instance, a panelled door size 7 ft.x3ft.x2}in., cut down to the required sizes, will provide sufficient timber for an “A” class boat or a ten-rater, even including mast and spars, leaving only the deck to buy elsewhere. I have actually built boats from similar materials. Obeche is another suitable timber for model yacht work and from South America a wood which has not been extensively used in this country is Quaraba. This latter timber has proved perfect for hull construction with a weight in the region of 32 Ib. per cubic foot. Its working qualities are similar to “cigar box” cedar, its grain and colour being the same. Western Red Cedar is another timber which is plentiful in second-hand quality, usually in the form of “clap” boards, or as we know it, weather boards. This also is a perfect wood for hull construction. ee eielll AIRSCREW DRIVEN HYDROPLANES (Continued from page 689) The accompanying designs cover the whole the engine used develops its peak b.h.p. output sphere of air-driven hydroplanes; “Skimmer’’ is at 12,000 r.p.m. and the model is expected to a novice’s two-float design, safe and easy to reach 45 m.p.h., an airscrew pitch of 3.96 in. is operate. “Skipper” is a free-running single-hull required (allowing 33°, slip) and the blade diameter and area must be so arranged that the motor is able to achieve its 12,000 r.p.m. Diameter requires to be fairly small, to allow a low thrust line, but must be consistent with easy starting, etc. Normally a somewhat coarser pitch can be used, model for small motors, “Skater” a three-float fast free-runner. For tethered operation at high speed there is ‘“Skidder,’ while R/C fans will find “Scudder” an extremely uncomplicated means of enjoying an afternoon’s button-bashing. Motorsizes are shown on each plan, and all plans are and experimentation is the only sure way of getting top performance. In general, a fine pitch means quicker acceleration and a coarse pitch a available post free from the Model Maker Plans Service, 38 Clarendon Road, Watford, Herts., at the prices shown on page 724. higher ultimate speed. 720 MOEN mARER (MODEL YACHT > CLUB UPN NOTES “COMMODORE” | PRESSURE of space has limited the inclusion of these notes for several issues, but we are sure that model yachtsmen will appreciate the dilemma in which the Editor frequently finds himself. With too much to go in a particular issue, an item of more general interest must occasionally elbow out those pages with more limited appeal. Some of the interesting meetings during the latter half of 1953 are detailed below. Sandylands Open M Class Trophy Held on Sunday, July 5, at the Morecambe M.Y.C. water, this event saw twelve entries, including last year’s winner and the ex-Northern Champions Black Hawk and Gazelle. With a freshening wind, most competitors changed down to No. 2 and then No. 3 suits, and of particular interest was the presence for the first time of a “Sunkiss”—W. H. Jones’ Margot, fitted with sliding rig, synchronised sheeting, a tall narrow jib, and a mainsail high off the deck. This boat proved the eventual winner. Noteworthy performances were also put up by J. Woodhouse’s 1946 Sapper and T. Bradburn’s Nimbus, both of which are from the drawing board of M. A. Shaw of Birkenhead. Glenham Cup Staged by the Y.M. 6m O.A. at the Rick Pond, Hampton Court, this event also took place on July 5, attracting a number of entries which was reduced to twelve by drawing lots among the home club skippers. A light wind at the commencement strengthened to a comfortable No. 1 breeze, and some very close boards were seen, especially on the run. For the second year in succession, N. D. Hatfield’s Fantasy won the Cup, with a score of 46 points, followed by Lynx (D. A. MacDonald) 43, Moonraker (P. West) 38, and Glenmoriston (A. E. Richardson) 31. Metropolitan and Southern District The 10-Rater and Marblehead District Championships were sailed at Hove on July 12, and Ryde on June 28 respectively. Of the ten 10Rater entries, A. Mullett’s Fantastique produced 28 points to win; the boat is a long V-sectioned 38 lb. heavyweight designed by Daniels. Second was J. Fry’s Crusader, which is a drawn-out Heading picture shows a mixed group of Birkenhead boats tuning up on their home water. Second from top shows Poole club’s Commodore congratulating Ted Croxford (right) winner of the S.W.D. 10R Championship and second placer George Cobb.Third picture is of skipper E.L. Dawson and mate E. Greenwood with the 1953 6-metre champion, Red Rose. Bottom is a view of activities at the Altrincham Regatta, with a contestant about to hook up. DECEMBER version of W. E. Brooks’ Divine Lady design, 50 in. on the waterline. Third, after a sail-off, was A. Levison’s Suroni. The Marblehead Championships drew eleven was drawn up for the main 1954 meetings at the last Council meeting. The programme will be as follows: Class competitors, and featured in addition an Open Cup presented for annual compettiion by Uffa Fox. Winner was Buttons (J. Kicks) with 42 points, Date 2-14 August. Mid-September (Sat. and Sun. only). M Poole Whitsun: Sat., Sun., Mon. 36in. Dovercourt Easter: Sat., Sun., Mon. No decision was reached in the case of the 6-metre class. South Western District The South Western 10-Rater Championship, also on July 12, saw nine boats competing, due to Altrincham M.P.B.C.C. a mechanical breakdown. preventing the arrival The club’s annual regatta was held on Sunday, Sept. 6, and was favoured with excellent conditions. Five clubs took part and some excellent times of the Paignton entries. Held at Poole Model Yacht Pond, early rain stopped in time for the Start, and an indication of the standard of sailing were recorded. Results were as follows: is the fact that not one disqualification was flagged. Calypso (E. Croxford) led the fleet with 36 points, with Quo Vadis (G. Cobb) second and Master Mick (M. Binding) third. An interesting point is that the second boat’s weight of-17 Ib., 10 oz. was just half that of the winner. Nomination: J. Hinton (Wallasey) Submarine Felix 2.86% error. 5-10 c.c. Hydropianes: D. Innes (Altrincham) Jo Mac 47.8 m.p.h. 15 c.c. Hydroplanes: A. Dalziel (Bournville) Niada 46.0 m.p.h. Steering: K. W. S. Turner (Altrincham) Lifeboat Elizabeth Rippon 10 points. 30 c.c. Hydroplanes: F. Westmorland (Altrincham) — 39.8 m.p.h. Northern District Sept. 12 and 13 again saw a congregation of “A” class boats at Fleetwood, when twenty-three skippers contested the Northern “A” Championships. The race was sailed in two divisions, three Sail Area Models An interesting point is raised by a correspondent, Mr. J. A. Stewart of Clynder, Dumbartonshire, who asks “When will our racing model yachtsmen adopt an experimental sail area class similar to the X-1000 class so popular in the U.S.A. ?” There is no doubt that designs published in America indicate that attractive models are possible in this class, with tremendous scope for experiment in hulls and sail plans, and it is surely from each moving into the final. Saturday’s wind was reasonable, but a light variable breeze on Sunday gave crews a trying time. W. H. Jones and Shalimar won the J. H. Jones Cup and Ist prize; Pandora, sailed by G. Kirkley of Newcastle, and Rapture, sailed by W. Wright of Bury, tied for second place, and by agreement took 2nd and 3rd prizes. A. Dawson’s Embassy placed fourth. recognised that relatively unrestricted experiment- M.Y.A. 6-Metre British Open Championship Of the thirteen entries in this event, ten made the journey from Scotland, the other three being one each from Birmingham, Nottingham, and the home club, Fleetwood. The race was sailed in two rounds over Saturday and Sunday, Sept. 26 and 27, with light winds obtaining for most of the time except on Saturday afternoon, when most skippers changed down to second suits and some to third. At the close of the first round, Red Rose skippered by E. L. Dawson of Fleetwood, led with 55 points out-of a possible 60, with Zeta (D. S. Sloan, Paisley) lying second. After a delay caused by drizzle, the completion of the second round at 5.15 on Sunday saw Red Rose comfortably ahead with 104 points, followed by Zeta with 80, with Shuna (W. K. Roderick, Victoria, W.S.), 76, in third place. ation leads to innovations and developments that raise ultimate performances and prove of benefit to more conventional classes in any sphere. As Mr. Stewart says, what about it Messrs. Tucker, Daniels, etc..—why not get busy and show if we can improve on the American standard ? Skippers may find it easier to carry 27 lb. than 56 lb.! New Model Boat Club Marine modellers within reach of Gravesend, Kent, or Grays, Essex will be interested to hear of a new Club, the “Thames Group Marine Modelling Society.” Meetings are held at threeweek intervals, alternating between Gravesend and Grays, with “floating events’ at week-ends. The club already number some _ exhibition successes 1954 Programme Although, at the time of going to press, the M.Y.A. A.G.M. is still a few days off, a schedule among their achievements and any interested ship modeller is asked to contact the secretary, L. Pollard, The Mission House, Royal Pier Road, Gravesend, Kent. 723 ill Venue A Gosport 1OR Hove followed by Wait for Me (W. Turner) 38 and Kukri (A. Turner) 33. sil 1953