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OCTOBER 1972 15p U.S.A. & Canada Seventy-five cents HOBBY MAGAZINE meet“ilie ‘N’ Class Championships ¢ H.M.S. Iron Duke Waterline models ¢ Electric record-holder e Two yacht designs Raised quarterdeck Coasters —_ Radio controlled sailing OCTOBER 1972 R/C Sheeting Systems to the shaft. The drum is simply three discs of ply with 3/16 in. spacer discs (sawn from a dowel or INPHE radio currently fitted to the original Star-C is – shown in the photographs above. It uses the completely reliable Flight Link two-function set, the cotton reel) clamped on the bush with a nut. Two wire loops epoxied rudder servo of which is conventionally used, mounted at the rear of the Formica panel which forms the hatch top. Cork from a bathroom tile forms the plug of the hatch. The throttle servo is mounted, with the receiver and Deac, in a clear sandwich-type box, inside the hull, and astride the servo is screwed feed-on guides. Weight is around 25 oz., with the extra battery, one, of hard plastic, bolted to the arm with two IOBA bolts, to depress either microswitch. This is clearly visible at the left of the left-hand picture. Wiring from the microswitches is such that only a single 3 or 44 v. battery is necessary to drive the winch motor in either direction. The winch is a Super Milliperm motor driving a Mini-Richard gearbox (this can be bought as a single one-piece unit, but we had the bits separately) and a screwed bush is epoxied The sketch below is of a system used by (then) Bdr. Geddes, sailing by R/C a year or two ago in Germany. The method has been used by other modellers, but this is the only one we have seen where the chain is not an endless loop. The ends provide a physical limit stop, providing, presumably, they do not disengage from the sprocket. Note that both sheets are doubled and travel the same distance, so that the boom attachment points must be equidistant from the pivots, which is now the rule rather than the exception. OE f (¢ EE My a = ‘reo RING SS i= Se a BOLT BRASS T Vey | \ a, ts! the Formica provide but this is an acceptable figure. It was necessary to tension the sheets with shirring elastic to prevent tangles, and limit switches will be fitted on the next the microswitch assembly made to fit a Graupner ServoAutomatic, which can be fiddled to fit over most servos. The servo arm carries a cam filed from a scrap & through ast Ts CHAIN Xe BRASS PLATE INSIDE t PULLEY BLOC | [@ MECCANO CHAIN TTT : 10 TEETH RING BOLT A BE X I? | [motor | FORE SHEET <0 v2 SW oBeK weccano orive IL arr) oo TaD TT OO PULLEY BLOCK (0) NYLON CORD 2 ee MAST ee : ee ge Sr SSS eS 1 — Se ee OSS SSS = NYLON CORD OL 425 PORE SHEET SOS 5 Se MAIN SHEET DECK CENTRE LINE ‘ AND OUTSIDE FOR STRENGTH BOTH ENDS Z =RING BOLT MODEL BOATS CINQUE and NERANG Two interesting Marbleheads designed by R. Dunster WHEN the Quartet series was being designed a round bilge version was schemed out and after some rather uncomplimentary comments from fellow club members in Greenock were passed, it was put away but not exactly forgotten while the process of proving the Quartet was carried on, as well as various other things, like shifting to Australia. More of this later. Now, after several years’ experience of the Quartet, both in U.K. and here in Australia, it was felt that there was room for improvement in two ways — planing attitude and performance in light weather. As regards planing attitude, the originals planed rather nose up and with a tendency to ‘stall’ as the pressure eased. They planed readily, however, but not as readily as some other designs; there are certain de- signs which seem to plane at the drop of a hat, so to speak, and although I am certain that this is mainly due to the skill or feeling of the skipper for this particular boat, or even a correct matching of spinnaker to the boat and conditions, I am also of the opinion that certain characteristics inherent in the design contribute considerably to this behaviour. Observations made over a period of time lead me to the conclusion that this is brought about by — a lightweight, shallow draft canoe body, with a flat fos NERANG The Model Maker Plans Service 426 mid section fore and aft and a well-placed centre of buoyancy in conjunction with the CG of the lead ballast. The forces acting on the sails are opposed by the drag of the hull and ballast, and if these items are placed in harmony with one another it seems to me that the whole outfit will plane easily and readily and consistently. I see these properties in a boat designed and built locally which, when it planes, and it does readily and rapidly, seems to have all these items in balance. On other points of sailing it performs well but not as outstandingly as downwind. So what do we need for easy planing? Flat sections or vee? Both will do the job, but which goes better to windward? As usual we have to compromise and choose the section or form which will fit to a certain extent all conditions (but no one perfectly) in order to get a good all-round boat. For this I am sure is what we need — a boat which will perform well in most conditions with average or even below average skippers. I know of many boats that perform well in spite of their skippers! All these things were taken into account when revising the Quartet series, and in Cinque (pronounced ‘Chinkway’, i.e. Italian for five) or Fivon the basic shape was altered by flattening the mid section at stations 5, 6 and 7, and in fact making the profile straight between these sections and then fairing in the run-up to the transom. A further alteration was to ‘lose’ the upper chine around No. 10 section so as to have a single knuckle transom. This was useful to improve the balance as when the run was added to the revised mid sections it became necessary to fine the extreme end of the hull as much as possible to retain balance. When the boat was built it did FULL-SIZE COPIES HERTS. OF BOTH DRAWINGS ARE AVAILABLE REFERENCE NUMBERS ARE MM1149 FOR be FROM Fivon MOE ANE MODEL BOATS ahead of him, just when he thought victory was in his grasp. It was the German ships that now took the punishment, though they were still to inflict heavy losses on their opponents. By intricate manoeuvring, the High Seas Fleet was eventually able to turn about, but not before yet another British battle cruiser. Invincible, had blown up and the armoured cruiser Defence suffered a like fate. With his flagship heavily damaged, Scheer extricated himself by sending in his torpedo boats, which caused Jellicoe to turn temporarily away. The first stage of the battle had ended with heavy losses on the British side and the German fleet desperately trying to get back home. The flagship of the German battle cruisers, Lutzow, had been forced out of the battle and was eventually to sink, the major German loss of the engagement. Jellicoe lay between the Germans and their base and Scheer made the almost fatal blunder of returning to the attack in an attempt to break through. Again Jellico crossed the German “T’ and Scheer had to repeat his earlier manoeuvre of turning about. To cover his second withdrawal, he sent in his battle cruisers on what was to become known as the ‘death ride’. They absorbed tremendous punishment and it speaks well for their construction that they all survived, albeit with appalling casualties. It was in this phase of the battle that the greatest German loss of life occurred. The coming of night ended the major fighting, though a series of minor skirmishes between light forces continued through the night. When dawn came a frustrated Jellicoe found that the German fleet had slipped around the rear of the British fleet and had successfully eluded him. Casualties had been heavy on both sides. but the British losses far exceeded the German. The Grand Fleet had lost three battle cruisers, the armoured cruisers Warrior, Defence and Black Prince, and eight destroyers. More serious was the loss of life, over 6,000 on the British side or about three times the number lost by the Germans. The Germans lost the battle cruiser Lutzow, the pre-dreadnought battleship Pommern, the light cruisers Elbing, Frauenlob, Rostock and Wiesbaden, together with five destroyers. The casualty list caused the battle to be hailed as a German victory SAILS (continued from page 436) and this is why H.A.R. sails are primarily used in light conditions and the yacht’s ‘working suit’ is of slightly lower aspect ratio. A sail’s performance is affected by its camber and flow. Flow is basically adjustment of the camber, to a limited extent, by altering the tension in the foot. Easing the flow deepens the curve of the sail, increasing the distance the air has to travel on the fore- side and therefore adding a little to the drive at, perhaps, the expense of increasing the chances of flow breakdown, for which reason flow is eased in light winds and hardened as the wind freshens. Camber is in effect the aerofoil shape assumed by a sail, where the point of maximum curvature is usually around 30-40 p.c. of the chord from the luff. To help achieve this shape, stiffening in the form of sail battens is used, and because these are quite significant in effect, most rating rules lay down a maximum number, length. and approximate positions; another reason for limitation is that battens can support a large roach. The roach (Fig. 6) is the area on the leach of the sail outside a straight line drawn from head (top corner) to clew (bottom aft corner), and in most rules is unmeasured, i.e. free area. Some way of limiting this area is necessary, 430 in some circles, but time was to prove otherwise. The German High Seas Fleet never seriously challenged the Grand Fleet again, and finally mutinied in November, 1918, an act which was to trigger the German collapse in World War 1. The Germans relied on the submarine more and more after Jutland and, but for the timely introduction of the convoy system, might have succeeded. Jellicoe stepped down in November, 1916, as Commander-in-Chief and was replaced by Beatty. He served as First Sea Lord for a year before retiring. Tron Duke ceased to be flagship when Beatty hoisted his flag in Queen Elizabeth, from which he was to witness the surrender the German fleet in November, 1918. Iron Duke saw service in the Black Sea following World War 1, when the victorious allies tried, in vain, to bolster the anti-communist cause in Russia. She ceased to be a first line ship in 1929 and, under the terms of the Washington Treaty, was converted to a training ship. Two turrets, ‘B’ and ‘Y’, were suppressed, belt armour was removed, and boiler power reduced. She was stationed at Scapa Flow through World War 2 as a base ship. Damaged by a bomb attack early in the war, she was bottomed but con- tinued to serve. She was sold for demolition in March, 1946. Iron Duke was painted dark grey with weather decks planked as shown. Superstructure decks were brown corticene. The Dark Admiralty Grey, HN 2, found in the set of Humbrol naval colours is correct for hull and superstructure. Humbrol Brown Earth, Number 29, is a good approximation for brown corticene. The waterline was black. Particulars of /ron Duke were as follows: Built : Displacement: Machinery: Armament: Complement: Portsmouth Dockyard, January 1912 to March 1914 25,800 tons. 30,380 tons full load Parsons turbines: 29,000 SHP=21.25 knots 10 — 13.5 in.; 12 — 6 in.; 2 — 3 in.; 4 — 3 pdrs.; 4 — 21 in. TT 995 to 1,022 Next month: Japanese Cruiser Kumano and the cloth itself helps, since it curls if too much roach is cut in, thus ruining the airflow, but if it is stiffened by unlimited battens. this self-limiting aspect is lost. Battens are usually made from thin ply or cellu- loid, sewn into tape pockets, and we believe that there is scope for much more experiment with the composition of these apparently minor items to improve the camber or aerofoil shape of the sails. There is still wide variation of opinion on proportions between jib and main areas. The ‘classic’ approximation is 4:7, but some recent successful boats have had the jib of almost the same area as the main. The M class rule limits the height of hoist (i.e. the point of attachment to the mast) to 80 p.c. of the main hoist, the A class to a maximum of 64 in. above deck (mainsail 854 in.). In the Ms, a recent rule change limits the main to 85 in., but in 1OR and 36R classes there are no similar limits. Measurement of sail area varies from class to class, e.g. in the A the jib is not actually measured, but the triangle made by luff. mast. and deck, called the foretriangle, is (Fig. 7). In M and 10R the system is half luff x the shortest distance from the clew to the luff. This type of detail is to be found in the actual rating rules set out for the classes. OCTOBER CABS VARNISHED TEAK h . E ae Te Cooteerp r ete PERMANENT AWNING OVER SKYLIGHT pe) oa “~~ 4 DERRICKS STOWED uP MAST SEE NOTE —— ma" WHALEBACK a ul Sar, BOATS AS STBD. Ss DECK CRANES Ga . Ese> WHALEBACK ) oe: —— —- BLACK STEEL BLACK STEEL A WINDOWS AT SIDE ARE THOSE anes mesneeee) VARNISHED BRIDGE FRONT ‘ NOTE 1972 DEEPER THAN ACROSS BRIDGE FRONT ; = LIFEBOATS “2? 3*5″ OPEN SPACE 0 M.S. OPHIR (1928) KONINKLIJKE OPEN SPACE ALL DECKS PLANKED UNLESS 0 eo] INDICATED PAKETVAART MAATSCHAPPI (K.P.M.) PASSENGER & CARGO LINER . DUTCH EAST INDIES COASTAL .LENGTH OVERALL 385 FT. BEAM 51 FT. HULL- WHITE WITH RED BOOT TOPPING HAWSE PIPE – BLACK UPPERWORKS-WHITE FUNNEL-DEEP BUFF WITH BLACK COWL. SKYLIGHTS ON ENGINE CASING VENTS & TANKS — DEEP BUFF DECK WHE CRANES – WHITE M.S. Royal MASTS .& DERRICKS — DEEP BUFF Another 100 ft. – 1 in. simplified miniature by R. Carpenter OPHIR Packet Navigation Company was re- sponsible for almost all local shipping services in the Dutch East Indies. In addition, services were operated to Java, Australia, China, the Philippines and East and South Africa. By the late 30s the fleet amounted to about 150 ships, making the company one of the largest in the world. The activities compared closely with those of the British Indian Steam The majority of the vessels carried deck passengers, in the case of the Ophir more than a thousand. They were housed in the ‘tween decks and the large open- ings in the sides of the hull ensured maximum ven- tilation in very hot and humid climatic conditions. With white hulls and buff funnels the larger vessels were yacht-like in appearance. The Ophir was a typical unit and makes a fine subject for an unusual Navigation Co. waterline model. CINQUE AND NERANG (continued from page 427) ago gave a lot of light on this subject. Nerang, therefore, should be a fitting companion to Fivon and it doubt, reading from result sheets and reports, that at last Foxtrot has been outmoded by the Stollery/ Shepherd/ Dicks designs. A great pity, for I had a great liking for Foxtrot. It always looked to me to will be interesting to see how the pair behave. To digress a little, I was very much interested in Mr. Draper’s remarks re the Quartet in the March 1969 issue of Model Boats. Before I left Scotland in 1967 I drew up a scheme to fit a bulb keel to Foxtrot, Which I left with Brian Cowan of Inverleith Club, Edinburgh. Two were built to this scheme and sailed in the British championships and, no doubt, local championships. The early reports of these boats were very promising and as several other people have done the same thing now it seems apparent that although the conversion may have improved Foxtrot (or not, I don’t really know) there is no 431 be a design full of character and very efficient. | am currently sailing one and have used it for about three years now with considerable success. It is a very pleasant boat to sail and handle but should be left alone, as again I feel that it is at the peak of its development. My only regret, so to speak, is that the current designs do not measure up to what we older people regard as elegant when it comes to yachts. Not that Marbleheads were very elegant, anyway, but there is always the fact that a good product invariably looks good as well. So it’s really a matter of getting accustomed to the ‘new look’. MODEL BOATS 1972 British and Open ‘A’ Class Championships Report hy Howard Dodd 1 2 3 4 5 6 7 8 9 10 12 13. Peter Pim Spinaway Clockwork Orange Anita Emperor Campari The Shiralee Colleen Dawn Philippa Bobcat G138 K919 K921 K929 K877 K918 K917 K787 K789 K833 K. M. R. V. C. H. G. T. D. B. Kraken K924 K. Zerlina K875 R. & R. Pollahn Harris Cole Knapp Dicks Dovey Sheward Schollar Priestley Burton Hamburg Bournville Guildford Gosport Clapham Bournvill 2 Y.M.6m.0.A, Gosport Fleetwood Eastbourne Foggatty A. 18 19 20 B41 K879 K922 K802 K940 G139 G. R. R.. D. N. Fr. Van Hoorebeke Gardner Starkey Armitage Hatfield Jacobsen 22 Moonraker III K862 P. West 24 Mora Norwest Blue Knight K847 K915 K900 D. Francis P. Latham Nash 32 K836 H. H. K, P. J. M. E. G. 34 Rufus K923 Mrs. S. Armour 29 33 Sorceror F56 K822 K902 108%: 113 69 91 109 1103 12 37 78 95 16 Bournville Atkinson Shields Jacobsen Mustill Hoogewerff Bertoux Latham Watford Trilby K831 D. 36 37 Hot Pants Constellation K911 KS25 A. Bell T. McGinnis 38 Sovereign Harpoon K914 K880 G. P. 105 105 70 84 74 66 84 Ad 95».2=102 94 99 86 99 90 97 90 96 81 89 Gosport 18 39 61 76 83 South London 10 10 14 France Fleetwood Y.M.6m.0.A,. Leeds & Bradford Fleetwood Scottish ‘A’ Class Gosport Hove & Brighton C, 33 28 32 47 51 46 68 83 65 78 56 74 89 88 88 80 19 12 10 8 0 9 12 i 36 24 27 27 36 26 32 27 53 41 39 39 41 41 41 37 58 56 46 50 51 56 51 48 67 74 70 73 72 71 62 58 80 79 78 78 77 74 69 67 5 20 37 44 54 62 13 5 35 25 39 32 47 30 59 42 59 47 5 6 16 15 22 28 36 32 43 36 45 36 13 Leeds & Matthews Shaw 1025 48 68 61 58 57 72 Gosport Bush 1G57 37 45 45 33 42 40 Bradford 35 60 58 36 = Total 14 28 21 20 16 14 Fleetwood Greenock Hamburg Birkenhead Holland E. Carter 37 29 Belgium Gosport Gosport Birkenhead Y.M.6m.0.A, Hemburg Fieetwood K925 KS24 G130 K932 H15 30 31. Foi 48 11 Birkenhead Playtex Hielan Laddie Bumble Bee Mandy Anicea 3JM Colley Gretal 26 27 62 16 Gosport Lippett W. Jupp D. 38 O5.109 127, S437 71 OA 117 132 80:2-1002 11 429 79 9B; 112. 1! 427 74 93 114 1254 62 i Rn sm 78 63 113:120 76 90 111 118 57 85* –402— 9117 60 85 108 113 Bradford K619 K930 22 59 45 56 53 41 48 49 45 41 39 Leeds & Flamingo Genesis Stardust Confusion Aubade Westwind Alberta 15 25 17 21 18 16 14 18 21 21 10 Gosport Armour The Stranger 15 16 6 heats 23 37 52 66 66 RETIRED YACHTING MONTHLY CUP 1 2 3 4 5 6 7 8 9 10 71. Peter Pim Spinaway Clockwork Orange Flemingo Anita Westwind Hielan Laddie Bumble Bee — Bumble Bee Anicea Constellation 3JM G138 K919 K921 B41 K929 G139 KS24 G130 H15 KS25 F56 : Hamburg Bournville Guildford Belgium Gosport Hamburg Greenock Hamburg Holland Scottish ‘A’ Class C. France Johnnies Cup: Peter Pim 17 windward boards Ist day 41 38 36 28 25 26 13 15 18 19 16 2nd day 38 33 28 27 19 17 25 14 10 6 8 Wing and Wing Cup: Anita 1 432 Total 79 71 64 55 44 43 38 29 28 25 24 min, 52 sec. OCTOBER 1872 rpuls year there were 39 entries for the championships at Gosport, 31 from England, three from Germany, two from Scotland, and one each from Belgium, Holland and France. On Saturday evening the O.0.D., Mr. Ken Jones, outlined his plans for running the race, ie. sailing in one division so that everyone sailed in the same wind, Sunday dawned overcast with a moderate wind blowing from the corner away from the clubhouse. This wind usually allowed boats to sail through in one leg. There was no official start to the race because it was Civic Sunday in Gosport, so the race started prompt at 9 a.m. Right from the start there was a lot of very close racing. After just one heat the wind started to shift considerably, making life difficult for the sailors. During the day the Scottish boat Constellation was dropped and suffered a damaged skeg and rudder. With help from several other sailors they managed to repair the boat in time to continue racing. Towards the end of the afternoon the wind began to drop and sailing had to stop at 5 p.m., after six heats had been completed, due to lack of wind. At this stage Genesis was leading with 28 pts. out of 30, followed by Peter Pim with 25, Clockwork Orange, Stardust and Philippa with 21. Monday started in brilliant sunshine, which was to last most of the week, with a light wind from the clubhouse corner. The sailing continued to be very close despite the shifting winds, which gave the two scorers a hard job separating some pairs. After four heats had been sailed the wind died and went through a full circle before settling to a fresh south-westerly. With the stronger wind five heats were completed in the afternoon, making a total of 15 heats completed. Resails were also brought up-to-date, except for Blue Knight which had a broken kicking strap and missed the last heat. Sailing finished at 7.50 p.m., just before lighting-up time, as some thought. Now Peter Pim was leading with 59/75, followed by Clockwork Orange with 56/75, Anita with 53/75, The Shiralee with 49/70 and Campari 48/75. Tuesday was sunny again and an 8.30 start was made in a light, southerly wind, which stayed long enough for just a few pairs to reach the other end of the lake. After 30 minutes the wind returned from the south-east giving a beat out and a run back. Again there were many close races, notably when dropped, as it had done each day, after three heats had been completed and the O.0.D. decided to take lunch and await signs of some wind. In the afternoon the wind returned from the south-east, very light and variable. This wind made sailing very frus- trating for those who did not know the lake and its winds, and there were many who did not, because they did not know where the wind would come from show, top, the winner, Peter Pim, sailing Alberta, centre, third boat, Clockwork Orange (at rear) and tenth, Zerlina, and bottom, fifth placer Emperor and Kraken. Photographs The Shiralee sailed Westwind where The Shiralee was leading comfortably until five yards of the line and Westwind crept through to leeward to take the three points by a matter of inches. Seven heats were completed by 5.30 and a halt was called because of the I.M.Y.R.U. meeting to be held that evening. The lead had closed by now, with Peter Pim still in the lead with 85/110. Clockwork Orange had now caught up with 80/105, Anita with 79/110, The Shiralee with 78/105. Harpoon dropped out of the race on the Tuesday because the skipper had a car breakdown in Brighton and could not get to the lake before Friday, so this gave two byes. Wednesday started cloudy, but dry, with a light north-easterly wind blowing, giving a long leg out towards the creek and a spinnaker run back. The wind Note that although these pictures were all taken on the same board, some boats used spinnakers while others preferred plain sail. Opposite, 76 Ib. of winner! next. After the first board in the afternoon the wind swung through a complete circle before freshening from the north, giving reaching conditions. One boat which astonished many skippers was Clockwork Orange by the way it sailed so well in the light conditions experienced so far, most people expecting it to have a poor light wind performance because of its light weight. Sailing eventually finished at 7 p.m. with 29 heats completed. Peter Pim was still leading with 109/145, Clockwork Orange was still lying second with 100/140, followed by Anita with 98/145, Spinaway with 94/140, and Emperor with 93/140. The Shiralee had a very bad day, only picking up five points out of 35, and so dropped back quite a few places. This now left 10 heats to be sailed on Thursday and Friday, and the 0.0.D. hoped to complete seven heats on Thursday so that the race would finish early on Friday for the dinner. Thursday started cloudy with a light NNE wind blowing giving reaching con- 433 MODEL BOATS ditions, scoring three out and two back. The Shiralee made up for its bad day on Wednesday by gaining 30 points out of six heats. Roger Cole had what was probably his worst day with Clockwork Orange, scoring only 17 points out of 30, which allowed both Spinaway and Anita to catch him up. The sailing finished at 5 p.m. with a very tight situation, three boats in second place. Peter Pim still held the lead with 127/170, followed by Spinaway, Anita and Clockwork Orange with 117/170. Then came Emperor and Campari with 114/170 and The Shiralee with 113/170. The start on Friday was 9.15 so that skippers could catch up on lost sleep. Again it was sunny and the wind light from the north-west, which gave a run out and one leg back. By the end of the second heat it was possible, to say nothing of probable, that there would be five boats in second place and the O.O.D. was expecting to be sailing until well into the afternoon. As it happened, the last heat decided everything and no sail-offs were required. As many people remarked, this was the closest championships that any of them could remember, and the two scorers would back them up because of all the close finishes there had been. Not only had the sailing been close, it had been very clean, with very few blue flags being given. The final positions were: Peter Pim first with 137/ 185, Spinaway second with 132, Clockwork Orange third with 129, Anita fourth with 127, Emperor fifth with 1253, and Campari sixth with 124. This year the difference between the top boats was much more marked than in previous years. Peter Pim is a 76 lb. Lewis design, beautifully built by Ken Jones, Spinaway is a 62 lb. J. Meir design, built by Bill Sykes, and Clockwork Orange is a 35 |b. design Readers bag the the | of by Roger Stollery. It would appear that the middle displacement boat, of between 50-60 lb. displacement, is possibly better overall because the success of these three boats is more than partly due to their topline skippers. Y.M. Cup This year the top three boats from each country competed for the Y.M. cup. It was decided to sail two rounds and to finish when one boat could not be caught. As it was during the week it turned out sunny on Saturday with a light variable WNW wind blowing which settled to SE later. These conditions suited Peter Pim and the Pollahns scored 41 out of a possible SO points in the first round. The wind was still light and variable on the Sun- day and Peter Pim continued to increase its lead. It was not until CRACKERS Dear Sir, | have just read the letter by Geoff Sheward in September Mode/ Boats criticising Mr. John Lewis and his Cracker 10 Rater design. | must admit | am puzzled why a normally sensible chap like Geoff should write such a letter for publication. Having sailed against some Crackers. at Fleetwood and seen others performing at Birkenhead, | can say that they suffer from none of the faults mentioned in the letter. One in particular, Mustang, has a forward raked fin which was suggested by the designer in the Cracker article as an alternative to the drawing, and he was carrying top suit when | was down in second suit, and streaking to windward as straight as the proverbial arrow. That takes care of the ability to carry sail and the so-called ‘tendency to wander and lurch’. The only other criticism about the design was _ its ‘tenderness’ carrying a _ spinnaker. Again . . . Bosh! If you try to carry an old style 10R spinnaker on this new type of boat I’ll agree they don’t like it; just as the lightweight ‘M’s carry a By the time this letter is in print the predicting a satisfactory showing by the design. Possibly the skipper of the boat in question (who was not named) has been given some incorrect advice on how he should tune and sail it. By the way, | do not own a Cracker — | was fortunate enough to have one of Chris Dicks’ Shallahs before Cracker appeared. My reason for defending the designer and his creation is because such criticism was unfounded and unjust and can only do harm to model yachting. May | suggest that in future the help of the designer is sought before exploding into such immature drivel. | have always found John Lewis very helpful and concerned with all aspects of model yachting including his own designs. but you asked for it. Dave Knowles M.Y.C. Dear Sir, Your contributor R. Dunster raises the question of alternative keels on model yachts, and as he is clearly en- thusiastic about the idea | feel a reply necessary to redress the balance. That the I.M.Y.R.U. has considered the implications of the idea and (quite rightly in my opinion) decided against it is evidenced by the wording of our class rules which quite clearly dis- 434 the afternoon courage such a development. | am a little surprised at the Australian authorities permitting it in an internatonal class. By allowng a skipper to fit alternative keels in the manner Mr. Dunster suggests we are giving him the best of both worlds under all conditions. In a blow he will fit a keel that enables him to outpower his opponents; in lighter winds he will fit a keel that will enable him to heel readily and that will cause a minimum of drag and resist- ance. The ‘all-round’ boat equipped with just the one keel has no chance at all. If ever there was a ‘bomb-shell’ to create wholesale confusion and obsolescence overnight this is it. | see no disadvantage in carrying around smaller suits of sails, nor do | see why Mr. Dunster should consider that it ‘does not help the sport very much from the average man’s point of view’, whoever the average man may be. They change down in full-size, don’t three they? But as one who sails all classes | see a welter of dis- advantages in carting around a number of different keels, quite apart from the difficulty of obtaining place. In conclusion ALTERNATIVE KEELS is in canteen. results of the 10R National will be known and | have every confidence in Sorry Geoff, freshened two scorers, Mr. Dicks the line judge all week, Ken which has its fullness lower than medium/heavyweights, so it is with new 10’s. have no more to say about the rest the letter as it isn’t worth an Birmingham wind Jones for running the race to a successful conclusion and to all the ladies who worked so hard in the answer. Write… the that anyone began to threaten them. Also the Wing and Wing cup looked set to go to Germany along with all the other trophies, with Kay Jacobsen and Bumble Bee Bumble Bee holding a time of 2 min. 2 secs. Then, in the last run of the day, Anita returned a time of I min. 52 secs. to keep one cup in this country. After the race the officials were thanked for the work they had put into running the race; Mr. Long for the work he did behind the scenes, Mr. Brazier who was the marshall, Mr. Foggatty and Mr. 22??? the two starters, Mrs. Jones and Howard Dodd the them in the first let there be no mistake, for | do not wish to appear to be condemning Mr. Dunster’s idea out of hand. If a new free-for-all experimental class were to be adopted | would advocate alternative keels, feeling that this would stimulate interest and encourage a new line of development. But in the mature reached stage in this that our country classes it is just have not on. Hornchurch. A. G. Sheward rr OCTOBER 1972 BOATING FOR BEGINNERS Let’s Go Sailing Part Four — Sails [Tt has often been said that the sails are the ‘engine’ of a yacht, since they are obviously what drives it along, the basic source of power being, of course, the wind. It follows that the more efficient the sails are, the more power is harnessed. There is nothing we can do about the wind, so that given identical or closely comparable hulls, the only way that we can make one go faster than the others is to increase the efficiency of the sails and, having done so, to trim them to exploit their efficiency fully. Evolution has shown that the Bermudan (or Bermudian) rig is the most efficient for our models, using two sails, jib and main, for most courses, and hoisting a spinnaker for off-the-wind courses. To some extent, sails act like aerofoils and draw the boat along, which is why the boat moves forward when the sails are edge-on to the wind; it is only ‘blown along’ when travelling downwind. To understand how this drawing force arises, we can use a simplified (but sufficiently accurate) version of Bernoulli’s law, which states that the energy of pressure plus the energy of movement plus the energy of mass equal a constant, so that if one increases one aspect of the equation, one or both the others must decrease. Since mass remains constant, this means that increase in movement means decrease in pressure, and vice-versa. Air moving over a curved surface has to travel faster on the outside of the curve to reach the trailing edge at approximately the same time as the air taking the shorter route across the inside of the curve. Thus the movement is increased and the pressure decreases (Fig. 1). The pressure difference between the two sides of the sail is very slight, but an average of one thousandth of a pound per square inch on a Marblehead’s sails means a tractive force of 0.8 lb., and a constant force of this size will move the boat fast. As a comparison, a live steam model locomotive with a and hot-rolled after weaving. The heat softened the fibres and the rolling squashed them flat and cooled them, thus filling the interstices and rendering the material airproof. These cloths have been widely used for the last five or six years for models, but although easier to use than varnished Terylene, there are now beginning to be doubts as to whether the latter is drawbar pull of 7 Ib. will easily haul three adults on a free-running trolley. Experts please note that these are very round figures! One way of ensuring the maximum possible pressure difference is to be certain that the sailcloth is airproof, so that air cannot leak through the sail from high to low pressure. Years ago when Union Silk (Egyptian cotton) was standard for sails, the closeness of the weave was felt to suffice, until someone treated the sails with banana oil (a cellulose varnish) and increased their efficiency notably. At one time many skippers had their ‘secret’ mixtures for proofing sails without interfering with other sail characteristics, Round about 1951 a skipper turned up with a boat (D. A. Macdonald, with Lynx?) fitted with sails cut from varnished Terylene, made, it is understood, for submarine cable insulation, but superb for model oe sails, and virtually overnight outmoded Union Silk. In the early 1960s the full-size dinghy boys got on to the idea of better proofing, and a series of cloths appeared which were synthetic (nylon or Terylene) 435 not more efficient for longer, in that it does not go out of shape so readily. Whatever cloth is used, it is essential that the same basic material is used for tapes, threads, ete., in making the sails. Obviously, different movement of the materials— shrink or stretch — could ruin the most careful cutting and sewing. Sail cutting has always been considered a highly skilled job; usually a tiny trace of an S shape (Fig. 2) is cut in the luff (fore edge) and this is eased straight as the luff is sewn into its tape. The effect is to put a slight belly in the sail, the width of the S and its actual position determining the extent and site of the belly. Any tiny variation can mean the difference between a suit of sails which sets well and draws nicely, or one which is completely dead. One or two currently top skippers do not cut an S luff, but make the luff completely straight, which, with hot-rolled nylon, appears to give an entirely satisfactory result. Since national championships have been won with such sails, they are quite clearly com- petitive! It is likely that the belly in the sail gets more important as the aspect ratio decreases. The aspect ratio is, strictly speaking, the square of MODEL BOATS a sail’s height divided by its area, but in normal sailing usage it is normally considered as the height divided by the maximum width, i.e. luff divided by foot. Thus a luff of 80 in. with a foot of 20 in. gives an aspect ratio of 4. High aspect ratios, ie. tall, narrow sails (Fig. 3) are more efficient, for two reasons. The first is wind gradient. Wind blowing over land or water is slowed by friction with the surface; this is why if you lie down you feel less wind than if you stand. Probably, as a guess, over water in a ‘top suit breeze’, the true wind speed is not encountered until a height of some 3 ft. is reached, and below this the wind strength tapers off (Fig. 4). Thus the part of a sail below this height is not providing as much drive proportionately as the area in the true wind; making the sail taller increases the proportion in the true wind and thus increases the overall drive. The second reason is aerodynamic. Pressure ‘leaks’ from the after side to the lower pressure area of the foreside by creeping round the leach (after edge) and foot of the sail. Because of the movement round the foot, the airstream on each side of the sail receives a bias to its movement, downward on the h.p. side and upward on the lI.p. side. The two streams meeting at the leach are thus travelling at an angle to each other, with the complication that one is curling in to the other anyway. The result is the formation of a stream of vortices all along the leach (Fig. 5), with a surprising amount of drag created. This drag both slows the boat and increases its propensity to make leeway. A higher aspect ratio sail, being of narrower chord (width) has a consequent smaller difference in pressure between its sides (though, of course, since it is taller the total pressure difference amounts to the same) and a narrower foot, thus minimising the bias and reducing the angle between the airstreams at the leach. The result is a considerable increase in effi- ciency. The other side of the coin is that the centre of effort of H.A.R. sails is higher and there comes a point when the heeling force reduces the projected sail area (August issue) and possibly reduces hull efficiency. Thus a change to lower aspect ratio at this point proves desirable to maintain performance, (continued on page 430) Pre oes =~; ji M.S. CLAN MACDONALD QO’ completion of my last sailing ship miniature, the four-masted barque Bidston Hill, 1 felt that I needed a change from sail. Looking through the Model Maker Plans Service I selected several plans of miniature steamers at the scale of 50 feet to the inch. My first choice was the M/V Clan MacDonald of 1928. Building a 50 ft. – 1 in. model By R. A. Wilson the block roughly to shape and take out the correct sheer with a small spoke-shave. Glue the painted maindeck to the block and allow to set. The plans are ideal for miniature work as_ they show sufficient clear detail at a convenient scale, The length of the Clan MacDonald is nine inches, with a beam slightly less than 14 in. I began with the maindeck, tracing the shape direct from the plan to a piece of bristol board. The deck was cut out, painted with matt paint, and set aside to dry. A piece of balsa wood was used for the hull. Cut The hull can now be trimmed off to the shape of the main deck. Draw the load waterline on the bottom of the hull and then trim up with a sharp knife. The raised forecastle and boatdeck sides can then be added. I found balsa wood far too soft for this. Obeche was ideal. Smooth the hull down with fine glasspaper and apply the first coat of paint. In my opinion matt paint looks better and photographs better than gloss. It also dries in about a quarter of the time. Fixing rails on to a small model is always a problem. Fortunately, in the Clan MacDonald it is not so The too-tall effect of the funnel in early stages of construction is clear in the picture at left. That it assumes correct proportions when all the detail is added can be seen in the pictures of the finished model. Mr. Wilson’s previous undertaking was the barque shown on the opposite page. 436
