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lf THAMES SHIPLOVERS ANI Sth SAILING JULY 6th AT THE ROUND P GSU AL visitors to the Round Pond were completely shattered to see surface of the Pond apparently covered elegant sailing ship models. So great was on July 6 the entire with most the interest that as the afternoon wore on crowds congregated and it was virtually impossible to get near the water at any point of the bank of this enormous lake. In fact only 38 models were pre-entered, and on the day one or two of these failed to turn up. How- ever, a considerable number of models not previously entered were brought along, and as fine a display of scale sailing ships as anyone could wish to see was the result. One of the most impressive things was the tremendous variation in size; the smallest we saw was an Ilin. Santa Maria which sailed beautifully, but one model which we did not track down was an 8in. Turkish carrack. At the other extreme were the four masted barques and schooners ranging up to 5 ft. in length, and the massive-looking barges, all of which were in the 42in. region. The hours work put into the total models afloat is beyond ALAS oes from top left, anticlockwise: 1. Four- ted sch ae Flying Cloud, about 60 in. o.a., was a fine sailer. 2. J. Hardy’s Chusan fisherman, 24in., deservedly topped its class. 3. Diploma winner Sesame, 30in. gaff yawl by D. C. Eyles. 4. Quo Vadis, 32in. three-masted bisquine (lugger) by R. M. Knutsen. 5. Delightful catamaran with hollowed log hull, apparently hors concours. 6. One of the best sailers among the square riggers was J. H. Fisher’s 23 in. ship Aphrodite. 7. Another good fore-and-aft performer, L’ Alain Gerbault, 44in., by P. Blanchot. 8. Lily May, J. J. Starkey’s 42in. spritsail barge, awarded a diploma. 9. Unnamed in. 12-gun brig by M. Garnett. 10. Start of the barge race; only four contenders this year though two other models sailed in the event SEPTEMBER, SHIP MODEL 1958 SOCIETY SHIP RALLY IND, KENSINGTON GARDENS imagination, since all of these models are suitable for show-cases as well as being functional. In the past this rally has been dogged by high winds and bad weather, though last year saw an improvement. This year the weather swung to the other extreme and many models lay becalmed for seemingly endless periods. to the shore. Nevertheless the photographs here should whet the appetites of anyone considering a scale sailing model, and in this connection we hope to be publishing something of interest in the not-toodistant future. RESULTS THAMES TROPHY (Best overall model) May Queen 355 … Full-rigger F. Pearson SQUARE RIG CLASS Medal—William Ashburner 3 m. topsail R. C. MacCormac schooner Diploma—Cutty Sark … Full-rigger P. Gould FORE AND AFT CLASS Medal—Ibex “ae Brixham trawler M. T. Davey Diploma—Valerian Diploma—Sesame NATIVE CRAFT .. .. Medal—Chusan fishing junk THAMES BARGES Medal—Alice Brixham trawler Gaffyawl – D.S. Paterson D. C. Eyles J. Hardy H. D. Aldredige Diploma—Lily May J. J. Starkey THAMES BARGE SAILING CLUB’S CHALLENGE TROPHY Mirosa P. Ford = | This made photography of any particular model something of a problem, since one could wait half-an-hour for one to come ashore before departing in pursuit of something else, and no sooner did one take one’s leave when the capricious breeze brought the previous subject ———— MODEL MAHER! in Model and Full-size Yachts Part Two By Lt. Col. C.E. Bowden A MODEL designer says in a recent article, expressing the well-known model conception of the “symmetrical” hull form “One of the worst outrages ever perpetrated in the world of sailing was the insistence in certain classes that the greatest body cross section should be placed at 55 per cent. of the l.w.l This must produce an unbalanced hull in that the afterbody lines must be fuller than the forebody and the rate of delivery of the water cannot be matched to the rate of entry.” This is rather a harsh criticism of the full scale people, for experience has shown that such hulls are very well balanced, and tank tests have agreed, Certainly this large nine-foot long model absolutely vindicates the full scale theory, and the Rhodes designs like Carina have shaken their competitors complaisance in racing results. The proof of the pudding is in the eating. There are reasons for this full scale concept which are enumerated below as I see it :-— The full scale case discussed (1) Water does not flow evenly around a purely symmetrical sectioned form when upright or heeled as the speed rises. In the higher sailing speed range, the water pressure builds up forward, becoming less aft, and forming outward quarter waves. One watches this flow as one races, and it is also apparent around an opponent’s hull. This build-up forward, causes the well-known shift of centre of pressure as speed rises in a fast hull. The slightly bolder aft sections of full scale design fit into this flow pattern, and the wider sections aft gain support on the widening quarter wave to add to “stiffness” for sail carrying. See Figs. 2 and 3. If the hull were to always travel slowly, the entirely symmetrical form would fit reasonably well into the flow of water. There is a reason why the full scale entirely “symmetrical” hull is not the fastest or the closest to windward, for as the speed becomes around its maximum attainable for length, the forward pressure can actually create a slight rise forward, with a drop at the stern. This can create a slight lee helm, which reduces speed through added resistance, and of course has been proved in the tank to create a slide away to leeward, when close hauled beating to windward. There is no eagerness to eat up to windward with any tendency, however light, to lee helm. This eagerness is helped by a slight tendency to lift to the windgusts. (2) Smoothly flowing, fairly flat buttock lines, built in the after body of the hull, akin to (but of course are not today exactly usually the same) known as as the a dinghy fastest, stern, for when heeled reasonably they get rid of the water without picking it up, or creating that great deterrent to speed, suction aft, This can easily happen with the sharply rising stern angle, which is inseparable with the “symmetrical” hull to match the bow angle of drop. Keel action and “balance”. it Since keel action materially affects the hull design, is also worth examination. Voicing model Fic. 2 The author’s radio controlled “A” Class model yacht approximates to full-scale design with bolder sections aft, as can be seen by the boot-top line. Note the build up of pressure forward as the yacht travels fast in a heavy gust, gaining support on the quarter wave aft, with clean clearance of water aft thought, a model boat to designer wrote: “The weatherly yacht is NOT one that is trying to luff into the wind.” I would be the last to say that a violently luffing yacht is weatherly, but full scale racing experience by the leading helmsman of the world, finds that a slight eagerness to luff and eat up to the wind gusts, enabling good “feathering”, to the gusts by the helmsman, creates the fastest and closest windward, as well as the most weatherly and safest craft. The tank has also confirmed this to be so. It is possible that the more “grooved” course of the vane- steered hull of a model yacht may be. the best with a “symmetrical” hull, but it is certainly not so with a man at the helm, or in tank test. The radio-controlled model is similar to a man at the helm for eating up to the gusts. We sail our yachts more upright nowadays to assist the “hydrofoil” keel action, and we design our yachts to have this slight luffing tendency, instead of a tendency to bolt or slide off to leeward. The Stevens Institute of America found in respect of yachts generally during tank tests: (a) A yacht sailing close hauled to windward has the least resistance to forward motion (when reasonably heeled) when the helm angle has 1 to 3 degrees from the centreline. See Fig 4(c). Resistance increases with a change of helm from this position either way. (b) The angle of leeway decreases with this angle of slight weatherhelm, which assists windward sailing. My sketch Fig. 4 explains the modern theory of “airfoil” keel action in windward sailing, which affects designer and helmsman’s sailing technique, The slightly bolder sections aft also fit in with this action. At any rate, they do not fight it with slight lee helm. I also have experienced with a full scale six-ton sailing cruiser that develops a disturbing habit of slight leehelm when just off close hauled in a strong breeze, The lines of this hull are nearer to the “symmetrical” than most full scale craft. I also 450 — —— —_————— i i —— SEPTEMBER, have a long narrow model hull, entirely symmetrically balanced. It steers a true grooved course, but has always proved disappointing to windward, when sailed against other models of the full scale shape. A summary of the “balanced” hull in full scale practice A full scale balanced boat is, therefore, one with the forebody sections reasonably approaching the same as the aft sections; but appreciably diverging in different designs for different purposes. It is not, as in model practice today, very nearly or truly symmetrical. The forward sections are usually slightly finer at the entry for cutting the short seas and to allow for increased ferward pressure as the speed rises. The after sections are bolder, to fit into the waterflow at speed, and to give support on the quarter wave flow. Maximum beam is a little aft ot centre. A slight tendency to luff is desirable, but never any tendency to lee helm can be accepted. Helm to 1 or 3 degrees from the centreline (i.e. weatherhelm) will provide lower resistance, and lower ‘falling away to leeward, when close hauled, together Aslight weatherhelm of 1 degree to 3 degrees is advantageous when sailing to boat sailed reasonably upright with ‘Hydrofoil’ keel running efficiently more or less vertically downward A.—The action ofasymmetrical airfoil is similar effect hydrofoil ANGLE OF ATTACK LOW PRESSURE LIFT ON TOP OF ‘FOIL KEE! if windward, in 1958 to Uys Cs Sie poner, PRESSURE ——_— = LIFT BELOW SEE ‘A’ ABOVE- HIGH PRESSURE AND TO WINDWARD OF KEEL \ keel appendage, when operating at an angle of attack to the medium B.—The keel appendage acts as an ‘airfoil’, or *hydrofoil’,when close hauled to windward C.—A rudder WIND LOW PRESSURE LIFT a —_ 2ra — COURSE — _ ae ANGLE OF ATTACK 5* APPROX. STEERED —_ B LEEWAY DRIVE ‘OF SAILS PULL TO WINDWARD INCREASED TARGET ARRIVED AT QUE TOLEEWAY CRABBING Bp WIND net ot -Ft ANGLE OF with quicker manoeuverability and better weatherli- slight with ‘weatherhelm’ One interesting, and maybe rather surprising, fact, has emerged from my model test sailing. In really rough seas, on open seawater, I have found that the conventional heavy displacement “A” Class model goes through the seas like a half-submerged I have, therefore, been forced, when submarine. degrees is similar in action to ‘flaps’ slightly larger light displacement, rather wide transom hull of 6ft. 8in. long, for this model sails more over the seas than through them. In this way I have had some exciting sailing in very bad weather and I will shortly be designing a modified model on these When sailing to windward a yacht sails a crabbing course aimed above the target reached—this leeway slide is approx. 5 degrees angle of attack on a good yacht with efficient ‘*hydro- ness in tough going, Rough water and the model testing a new rig in really rough water, to use my lines for radio racing. According to the supporters of the model “symmetrical” hull creed, hulls of the “Flying” series, light cruisers like Atalanta, and many American light displacement wide beamed, bold aft, cruiser racers should be unbalanced and In actual sailing practice and, “unweatherly”. indeed, in model test practice too, this is pure nonsense. It only holds true if the individuals operating such hulls do not understand keel action and what is known as reasonable “upright sailing” Even when overheeled, such hulls, if carefully designed, are far from imperfect in balance. They have a habit of forcing themselves up to windward by luffing hard for a short spell in a heavy gust, getting rid of excess air, and then carrying on They should never be course as the gust dies. compared with the old grossly unbalanced cutters with straight narrow stem and wide counter of years ago. It is an interesting fact that Mr. Farnham Butler tested two hulls of the same overall length of 37ft. in America. One was a heavy displacement and the other very light displacement, lighter than our normal light displacement boats. He reported that the light displacement boat was faster in rough weather conditions, having less sail area, heeling less, and being much drier, albeit a bit lively, for she sailed more over than through the water. This confounds the ancient belief, generally accepted here, that the “power” of heavy displacement makes for the best heavy weather craft, It suggests something for the all rounder model radio-controlled One Design boat hull. \ of 1 degree to 3 let down on an = in- Cc to Whe airfoil, in. mrease same effect hap- pens on a kee or ‘hydrofoil’ = 5 = “COURSE STEERED ATTACK se approx REACHED CAMBER INCREASED taRGeT DUE TO LEEWAY CRABBING if RUDDER Fig + increasing lift to windward, resisting leeway drive of sails foil’ keel sailed approx. vertic-ally downwards. Fic. 3 (below, Here the “A” Class model is sailing slower and more upright on the slightly flatter wider sections aft. Note the transparent Terylene sails on trial. These can be cemented up and made in one evening Fic. 5.—The author’s light displacement fibreglass hull sails well to windward with good balance, even with wide transom running along the hull’s heeled side like an American scow, the fastest single hulls in the world. Note the clean wake at speed, and the author’s delta folding rotating rig American designer’ has to say in his article that appeared in the American journal “Yachtin g” of January, 1957, entitled “It’s Beam that Makes the Boat Go”. to needle Mr. Henry Scheel wrote: “I should like the architects to investigate means for improvement in what aviation engineers call the lift drag characteristics of the hull form, which heaven knows needs improvement, so that we can look forward to improvement in performance of the beamy forms beyond their present ultimate . We won’t get it by acquiescing to the present style pattern. We can get improvement if we realise that the beam is the reason for the built-in go-fast of the newly recognised forms, Some final thoughts designing. No one man has yet the for that either reasons is wrong and for purposes. this Who particular great room for complete pre-occupation with narrow symmetr ical hulls sailing overheeled on their ear, and overbal anced to leeward The model instead of to windward. A little more “symmetrical” rut balance obtained in a rather different way differing is I should also like to needle the model designers to think more about beamy hulls sailing more upright, with bolder sections aft, forgett ing their designer of the moment pins his faith for Vane steering on the “symmetrical” conception of a balanced hull, whilst the full scale designer adheres to good that there improvement below the waterline”. It is certain that there is much to learn in model and full scale design, of hull and rig. In this lies the interest, allure and stimulus of yacht racing and answer, for all weathers, and all waters. and ; can say experiment, and less of might produce better boats. any case, it would create renewed interest purpose? Radio-control racing hulls will probably follow full scale ideas because their requirements are fundamentally the same. Let us read what a well-known — the In in model design, which would be all to the good for we are rather tired of reading the “symmet rical” lines of practically every new model publish ed. It can become decidedly tedious for recipie nt and designer. —— YEOMAN SPRITE This neat 154 in. all-balsa model completely die-cut throughout and fits together easily and quickly. The kit includes everything except is motor, glue and paint, from finished shaft/ propeller unit and rudder unit down to flexible tube for drive con- nector, leads seat wire and and smart upholstery. clips for battery flock-paper Even the for windshields are die-cut! A step by step plan leaves the beginner in no doubt as to procedure and we would recommend this as being one of the 452 best kits yet for introducing a newcomer to model boating. Good value at 14s. 11d. Sole Trade Distributors are A. A. Hales, Ltd., 60 Station Road, New Southgate, London, N.11. SEPTEMBER, ( “I UCKER’S TOPICAL TALKS IMPRESSIONS OF ‘SCEPTRE’ 1958 of the vessel, the wind blows the same for both, and model yachts are often over-driven to an extent that would be suicidal in manned- =) up craft. One peculiarity of the yacht is the main standing rigging, which is solid bar of streamlined section, very strong and stretchless. Of this, the Daily Telegraph’s Yachting Correspondent wrote:— Although the streamlined section seemed admirable in theory, its good aero-dynamic shape would, at first sight, appear only to be advantageous when she is almost head to wind. When she is sailing, it seems possible that it might even be a disadvantage. There may, however, be more in this than meets the eye, because the most important air-stream to consider in relation to this rigging is that diverted and accelerated by the jib on the lee side of the mainsail. At one time, particularly in the 10-R. Class, model yachtsmen had a craze for pear-shaped and streamlined masts, but abandoned them because they only remained streamlined when the yacht was close hauled. Mr. Ian Proctor, the correspondent referred to above, finished his article on Sceptre as follows:— The next phase is perhaps most important of 4 O all yachtsmen, including model yachts- men, the big event of 1958 will be the races for the “America’s” Cup in September. Naturally the plans of the R.Y.S, Challenger Sceptre have not been published, nor have her dimensions been released. At the same time, quite a few photographs have appeared in the Press, and some have been quite informative, especially those taken just before her launch. From her photographs, Sceptre appears to have a comparatively short forward overhang, and a long counter, but otherwise normal profile. Her sections from forward to aft of midships look to have a slack bilge turn which hardens in the counter. I should expect her to have a quick first heel, and come easily to her sailing lines. She is decidedly thick through the garboards and the keel is likewise thick. This is doubtless in order to absorb as much displacement as possible, thus enabling her body lines to be fined. This type of section has the additional advantage of packing a maximum of displacement into a minimum of wetted surface area. Now the resistances to a yacht’s forward motion through the water can be divided into two categories—water disturbance and friction from wetted surface. Obviously, the latter is affected by the wetted area, and smoothness of the surface. When the yacht is travelling at her best speed in a strong wind, wetted surface friction only represents about 25 per cent. of the total resistances, the balance being due to water disturbances. But when the wind lightens and speeds drop, the proportion of total resistance arising from wetted surface friction increases until at ghosting speeds it has become no less than 75 per cent. of the total. Wetted surface area is, however, far less important in a model than in a large yacht, since whatever the size all—the_tuning-up of “Sceptre”, and the train- ing of her helmsman and crew. I venture to think that the outcome of the race in September does not so much depend on the yachts, which are likely to be evenly matched, but on the skill and efficiency of their helmsman and crew. How exactly do Mr. Proctor’s words echo my expressed opinion that the victory of any given yacht must be ascribed to handling rather than to the inherent virtues of the yacht herself. A few years ago I watched American crews participating in an international regatta in Bermuda, and was particularly struck with their neat, slick handling of spinnakers and balloon canvas. The result of the Cup races may well depend on how “Sceptre’s” crew compare in this respect with the crew of the American defender. ii —_— WARSHIP DETAILS = (continued from opposite page) over with clear dope laid on with a camel-hair } in. or jin. flat or “one-stroke” brush. The result looks messy for about a minute, after which the dope disappears, at the same time combining with the ink and the filling paint. The result is a matt waterproof surface identical with the real deck scaled down. The method can easily be proved by an experiment with a waste piece of plywood. The spurnwater can be fixed to the surface of a wood deck by clear dope. To do this successfully requires a large number 461 of clips to be made for holding it in place while the adhesive is setting. These are formed from circular rings as shown in (13) made of fairly strong galvanised wire bent round a rod which acts as a former. When about 20 turns have been put on, the spiral of wire can be sawn into rings by cutting it lengthwise with a hacksaw or file. The ends need to be finished truly square. Their use is shown in (13), but they are also of the greatest value for holding together small parts for sweating or soldering.
