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An Uilemeve Orcs A simple model for fathers or uncles with an eye on Christmas SE a I as By A. GOODALL wood remain to give good vice-gripping surfaces while the hollowing out progresses. Next shape the hull in plan, taking care to get the sides square with the gunwale capping, or deck. The keel line can now be marked out on each side along the bilge line, by means of templates. Saw along hull just clear of keel line with a coping saw, mark the centreline on and shape the hull bottom paring from keel line at the centre down to the bilge lines. Finish off with medium and fine glass papers. A similar attack on the wood for the out-rigger hull should produce the desired result. Note that the side elevation of the out-rigger hull is the same as the main hull, but that the beam of the former is only half that of the main hull. To give a classy appearance, fit a mahogany coaming around the forward end of the cockpit. Use marine glue to secure it, and pins HE need for a small shallow draught model sailing boat- became very apparent when one day the boys and the writer arrived at the local park pond to sail a deep-keeled gaff-rigged yacht, and found the depth of water lower than normal, and for our yacht, shoals abounded, making sailing a hazardous business. It was thereupon decided to embark on a construction programme with a_ shallowdraught craft in mind. To provide more interest and as a change from the more normal boat type, and because native canoes had been a recent school subject, the out-rigger sailing canoe was chosen as a likely type. In its favour there were firstly the shallow draught, and the additional stiffness provided by an outrigger hull. The lines chosen were. modern, featuring hard chine hulls, single Bermuda mainsail (the only sail in fact), while a lee-board was fitted in preference to a centreboard which would, on a narrow-beam full-size canoe, clutter up the cockpit to such an extent as to practically exclude seats on thwarts or whatever canoeists sit on! As the cartage problem of craft to and from the local pond was acute, the canoe had to be small and easily handled by an eight-year-boy. A quick look through the woodpile found hardwood suitable for the two hulls, dowelling for boom and spars and a straight piece suitable for shaping into a nicely tapered mast. The main hull measures 15 in. x 3 in. x 2} in. after squaring up and facing, and the out-rigger hull 15in.x 14in.x2}in. Hollowing out the main hull should be done first before shaping the outside, so that the parallel sides of the if necessary. The mast is made by planing first a tapering square section }in. at the top and 2in. at the bottom, the length being 16in. The corners are taken off by further planing and the finishing off by glass paper. Spars and boom, not being tapered, are best made from }in. dia. hard dowelling. Lee-board and rudder fittings are best made of some non-ferrous metal, the former of 18 gauge or 20 gauge aluminium, the. latter of brass sheet 18 gauge, hardsoldered to 16 gauge brass wire. The rudder rod should pass through brass tubing set in the hull, and the movement of the tiller should be stiff enough to prevent movement by waterpressure when sailing. The Bermuda style sail has a long foot and gives a fair area for a low centre of pressure, although it can hardly be given the name of a true Bermuda. However, it will be found adequate for this craft. The cleats used on the writer’s canoe were small brass screw-eyes; six are required for the stays. A correct style gooseneck fitting is best used for the boom; this holds the sail at the mast foot where it should be held down, and allows the boom to lift properly towards the sheet end as the sail bellies in the wind. Rings should be fitted to secure the sail to the mast. To dispense with 560 NOVEMBER, 1956 the complication of a block and halyard, the sail peak may be furnished with a cord loop which slips over the mast head. Waterproof cordage of light gauge should be used. The lee-board, shaped and carefully filed to avoid scratching the surfaces, is secured by a lin. No. 6 brass round-head screw passing through a hole in the forward end, and through a tubular distance piece into the hull wood. It is essential that the lee-board runs true fore and ———— aft and at the same time is perpendicular. When lowered the model will have a draught of about 34 in. Good sailing can be had, though some slight adjustment may be necessary to the lee-board position, and possibly to the size of the rudder. The writer’s boat sailed well in quite a stiff breeze, but the out-rigger hull being smaller than that shown here had a tendency to drive under in | very stiff winds. On the other tack the amount of lift was very small. The beams of both hulls are somewhat larger in the illustrated model than in the writer’s canoe, so stability should have been improved somewhat. Given a good beam wind and close-hauled sail, this model will prove quite fast for its size, and makes. an interesting change to | -_ normal sailing types. 1″ SQUARES Pa NOTE: LINES OF OUT-RIGGER IDENTICAL ead WITH MALN HULL EXCEPT FOR WIDTH OF BEAM H f ! Fs : : EE ERE | NOVEMBER, STARTING ON 1956 Before the racing starts, practically all skippers elect to sail a few trial boards to check the performance of the yacht and its gear, and to establish as good a trim as possible for the course and the pre- _vailing wind conditions. Some skippers arrive at the sailing water as day is just breaking and sail up and down the course without pause until the race is to commence. This can, I think, be fairly desdue G RACIN — FIVE PART cribed as overdoing it—it generaily means that the BY D. A. MACDONALD crew is tired before the event starts—and, as often as not, conditions have changed sufficiently during ts the tuning up period to make the results valueless iE is usually claimed by horse-racing enthusiasthe when racing begins. If the skipper is sufficiently that the purpose of racing horses is to improve of his boat, he should breed. How much truth there is in that statement I familiar with the trimming points before the race: am in no position to judge, but the improvement of need to establish only twogear is working correctly (1) That the yacht’s the species has always been one of the major objects _ THE RIGHT TACK of yacht racing in all its forms. The M.Y.A., which has watched over our interests in the racing world for so many years, has always been mindful of the need to encourage the design of better yachts, and the rules it has laid down for rating and for racing have been planned so as to safeguard and ensure healthy development in design, and discourage monsters and freaks. Tribute 1s due to the wisdom and caution of the governing body for the success of their policies, which is evident in the sound design of all the successful yachts of to-day. The rules as they now stand leave no loopholes through which an easy road to success can be found, and, in the long run, racing results are the truest assessment of the merit of a yacht and of those who sail it. The first advice to the novice skipper should therefore be not to try to be too clever, or too ready to adopt unorthodox techniques until he has a certainty, backed by experience, that the game is worth the candle. In the long run, success is attained by doing the same thing as the other fellows, but doing it a bit better. This does not mean, of course, that we should always slavishly copy our opponent (especially if he is doing better). There are strategies and tactics open to the skipper who can use them effectively, as we shall see later. The racing team consists of the skipper, the yacht and the mate. In my opinion this is the correct order of importance. Both skipper and mate should have confidence both in each other, and in the yacht. (The yacht’s feelings in the matter are not normally considered), Both skipper and mate should have one object in view—to sail the yacht as efficiently as they can. Note that I did not say win the race if they can. This outlook is not in the long run the most success- tul one, and an obsession for winning detracts from the pleasure of racing and often defeats its own object. The score card is an indicator of performance, nothing more—the concentration should be on the task in hand rather than on the result. Many success- ful skippers have a regular mate and the two have learned by experience how to operate as a team. Others rely on a friend or relative, not particularly Others rely on interested, but willing to oblige. “casual labour’—someone recruited on the spot on the day of the race, who may do no more than just turn off or retrim when necessary. Obviously the experienced regular team will have an appreciable advantage from the outset, but many events are, none-the-less, still won by the other, more casual, associations. Many skippers, in fact, prefer to have a mate do no more than the essential functions of turning or retrimming on a weather shore. In any case, the functions of both skipper and mate should be decided, and clearly understood by both before the racing starts, so that confusion and omissions can be avoided from the outset. and that she trims and handles normally; (2) That he has found out enough about the prevailing sailing conditions to be able to trim for any desired course when the time comes. On a completely strange sailing water this second problem may justify a little more than usual atten- tion. If conditions are reaily bad, results will obviously depend ‘on decisions made on the spot before and during each board, in which case only the first point can really be established in advance. By the time the race starts, the skipper may reason- ably hope to know, at least roughly, how to contend with (a) his yacht, (b) the wind, and (c) local conditions. He has still to decide how to contend with his opponents. I have previously made reference to strategy and tactics. Strategy is concerned with the overall planning of the operation—the general approach to the racing contest as a whole and the techniques to be employed under conditions which might arise from time to time. It also covers the method of dealing with a particular opponent on a particular heat, as decided in principle beforehand. Once a board is in progress, and the relative behaviour of the two competing yachts becomes apparent, then strategy has played its part, and the game is one of tactics—methods of manouevring, retrimming, etc., during the board, carried out with the object of beating the opponent to the line. Let us assume that we have arrived for an open contest. We first study the list of competitors and note from our score card the order in which we are to meet them. I have often found it helpful as part of this exercise to attempt an esiirnate, knowing who the other competitors are, the prevailing conditions, and the boat I am sailing at the event, of what my position at the end of the event would be. Despite the large element of chance in many events, I have found it possible, with experience, to make a reasonably accurate forecast, and the forecast itself is a help in strategic planning of the race. Perhaps I can illustrate this by a very simple and very hypothetical example. Let us assume that we are entering a race with four opponents—W, X, Y and Z. The sailing water “is rather small, wind light to moderate, variable, giving a close-reach out and a 3 run home. We have sailed once or twice on the water before with reasonable success. W_ is an experienced skipper with an old, but sound boat, capable of a fairly good, but not outstanding performance under most conditions. X_ is also experienced, has had the same boat for five years, has been in the first four in three national championshivs, and has sailed on this water twice before. Y is a local man, who does well in local racing (so he tells us) but has sailed little away from home, and has no record of wins in open events. His boat is to 577 MODEL MAKER ee a local design, of moderate proportions. Z is a novice To provide information for planning our strategy and assessing our chances, the mate can be of great like ourselves, with a very good boat to a modern successful design—he has the assistance of a local man of some experience as mate. Our own boat has been conscientiously tuned up, is built to a successful modern design, of a rather high displacement type, but believed to be good in light winds. Having sailed assistance. He will have less to attend to during the race than will the skipper, and he should, in addition to watching his craft, keep an eye on the operations of the other competitors, watch for changes in strength and direction of wind, and gain as much local knowledge as he can from the many knowledgable locals who are sure to be present at an open event. In this way he can keep his skipper posted a few trial boards, and watched the others doing the same, let us assess our chances. Against W we have a possibly faster boat, but if conditions are variable, his skill in handling his craft may beat us. We should therefore attempt to trim our craft in the same way as his, and depend on our superior speed to sail faster on the same course. On this assumption we might presume to acquire three points out of the five against him. Against X, we assume we shall lose both with the information needed to decide a course of action for each heat of the contest. Looking over our forecasted score, it does not seem likely that we are going to win this match. Such a score would put us no higher than third or fourth. If we do no better than this we have no reason to be at all disappointed—if we do appreciably better or ways, but we do not just let this happen. When we come to sail X, we must avoid doing the same as he worse, we shoud endeavour to assess (as impartiall y does. If we know he is most likely to beat us, we as possible) the reasons. This “post-mortem” will teach us a lot, and guide our future estimations and can assume that he knows it also, and will therefore play safe and sail a simple and straight course, without taking any chances. It is we who must take the chances, and hope our luck is in. We must therefore strategy. A crucial point occurs in every event when the yacht comes under the starter’s orders to sail a board. At the start of the board, strategy gives way to tactics, and it is at this point that very many races are won or lost. Our planning has decided what course we shall sail and what trim we shall adopt against a particular opponent. Right up to the instant of search for some strategy to adopt, making use of some feature in either (1) the wind conditions, (2) our own yacht, or (3) the nature of the sailing water. If for example, the wind conditions are as described above, but apt to head from time to time on the windward board, we might play for a change of wind in that direction, and trim to sail higher in the wind, hoping that we make the course and our opponent is headed on to the lee shore. putting derived from the freer trim. Downwind, we can either course-holding and trust to the and viewed from close quarters, from what we judged it to be when we watched it sailing. The safe rule to apvly is—Don’t change the strategy at the moment without very good reason. On the other hand, if the wind is extremely variable, action: at the last moment is often essential, but our strategic planning should have taken this into account, and we should know within what limits last minute retrims can be made. The manner in which a yacht is put off very often determines the result of ‘a race, especially if the course is a short one. The beginner will do well to of success farther afield. His boat and trim obviousl y suit local conditions—our boat would probably not behave in anything like the same way as his, with the same trim, so that in this case it would not pay to copy him. We must back our own boat, trimmed our own way against his, and stand by the outcome. Let us estimate our chances of beating him as representing two points. The last competitor, Z, appears to be a known quantity. At a guess our chances are pretty equal. There are two significant differences, one is the fact that his boat is lighter than ours, and secondly his mate has valuable local knowledge. Both factors are likely to help him more downwind than to windward . On a windward board performarice counts more, and weight, even in light winds is less of a disadvan tage than it is before the wind, and. in fact, is often an advantage. We therefore decide to concentrate on the fastest possible trim to windward and estimate that we shall score the three points. Downwind we must aim to get as much drive from mainsail and spinnake r as possible and ensure we get off to a good start. with all sail full and drawing nicely. If the choice of berth to windward is not significant, we might consider (if we are allotted choice). exercising our choice for the run rather than the beat. the trim at the last moment. The trim of our opponent ‘s boat may look quite different, when it is stationar y watched while he is tuning up and sailing against other competitors. Very likely he is doing well, with what appears to be an unorthodox trim. This would tie up with his success in home racing and his lack attempt change—wind must avoid hasty and haphazard tinkering with wind we come to sail him we need to assess his performance as well as possible, and therefore he should be to may impressions of wind direction and strength may be formed at ground level in the lee of the shore, both at windward and leeward ends of the course, and we remaining steady throughout the board. Competitor Y is to be regarded as a possible dark horse—before us conditions and we may have to make a hasty re-appraisal of the situation at the very last moment. Under these conditions, one can be very easily misled. Wrong play for a change of wind, or (if we know one) adopt a trim which gives us the fastest possible sailing at the of however, may at the last moment have changed his trim also. Or if we think the wind tends to free, we could play for such a change, and hope to benefit by the extra speed expense off may change in strength or direction, or our opponent carry out extensive practice at putting-off and study the technique adopted by the experts. Yachts equipped with vane steering gear will not start awav correctlv unless they are put off at the correct sailing speed for the prevailing wind. It is a great pity that many race officials still order a standing start. The inevitable results are (1) the introduction of a large element of luck, (2) the unnecessary penalisin g of heavier and generally better vachts, and (3) the inevitable accumulation of resails due to fouls near the start. If a yacht is put off with excessive way, it will also fail to start correctly on course. Judgement of the right amount of way to impart is essential. A fair method is to watch one’s opponent and act in synchronism with him, so that both vachts start away level. at the same speed, and on parallel courses. It may seem superfluous to point out the necessity for starting the yacht on the correct course. but it is a surprising fact that yachts are very often put off in racing either too low or too high in the wind, and thereby lose valuable ground at the start. 578 Tucker’s Topical Talk H.B.T. HAS MORE ON THE MOONRAKERS : STABILITY CALCULATIONS & A USEFUL TABLE COMPARISON AND c 3 c’ OF RIGHTING MOMENTS (Not to Scale) A=Angle of Heel. Centre of B1=Heeled Buoyancy Gravity. Arm. two boats, and the only thing that could produce difference in performance is the additional weight of the keel of the new boat. In building M. IJ approximately 3 1b. was saved in hull, rig and fittings, which was embodied in the lead keel. The actual increase was 4 lb., and the extra 1 lb. presumably accounts for the slightly longer L.W.L. HEELING B= Buoyancy. Centre of *« G=Centre of a=>Righting C= Centre * * Now, when I watched M. IJ at Gosport I formed the opinion that she was not as good in light weather as her predecessor, but not having seen the two boats sail together, I was chary of expressing an opinion. Mr. West told me that M. JJ is rather better than M. J to weather in heavy winds, but apart from this, M. J is decidedly livelier. Actually, this is what could be expected. M. J has ample stability. Both boats have the same powerful, beamy, wine-glass section, but the new boat has 4 lb. more lead. M. J heels the first few degrees quite easily, and recovers gently. Her performance in light weather is phenomenal. The extra lead in M. JI makes her initially stiffer and the righting movement is more abrupt. Hence, I still retain my opinion that Moonraker I of Effort. C!=Heeled Centre of Effort. e—Heeling Movement of Centre of Effort is the best all-round heavyweight in the Class. * M* attention has been drawn to discrepancies between the Score Sheet given in my account of the Gosport Regatta last month and those embodiedin the Daily Reports sent out by the Regatta Committee. In the case of the Daily Reports, owing to the necessity of getting these off to the firm who did the duplicating, one afford to gamble on a one-weather boat. Hence I feel that the most likely dimensions are: L.W.L. 54-55 in., L.W.L. Beam 14.5-15.0in., Displacement 55-58 lb., S.A. 1,530-1,570 sq. in. the official who compiled them could not always wait until the conclusion of the day’s sailing, or for the result of resails, etc. My figures were taken from the Official Score Board after all adjustments had been made, so should be correct. If, however, there were any errors, I offer my apologies to the skippers concerned. Since the Gosport eee I have again seen Moonraker II in action, and had the opportunity of a further chat with Mr. Peter West, her builder-owner, who was able to clear up several puzzling points about the difference between his present boat and Moonraker I. The new boat appears to have her greatest beam further aft than M. J, whereas in fact it is actually the same distance abaft the midship section. On M. IJ the deckline was clubbed in aft, shortening the after overhang, and pulled out a little forward, thus lengthening the forward overhang. At the same time a slight change was made in the sheerline. The combined effect is deceptive, but in both boats the greatest Beam is unusually far aft, falling approximately 3}in. abaft the midsection. The slight difference in Beam between the two boats is accidental. When M. JJ was taken off the moulds, the sides sprang outward before ties were put on. In pulling her back, the operation was slightly overdone and the beam narrowed by j in. each side, making her } in. less beam on deck than her older sister. Thus there are no real differences in form between the x Once again the A-Class Championship has done little to resolve the question of what is the best type under the rule. The only conclusion that I, personally, have been able to arrive at is that one cannot safely go to extremes in any direction, nor for a race that lasts several days, can Of course, I may be wrong! * I have recently had some correspondence on the subject of stability calculations, S.A. required to heel a yacht to a given angle in various weights of wind, etc., and this has led me to investigate the subject rather closely. Now, as a general rule, designers of yachts and model yachts do not use these rather intricate calculations, but rely on experience with similar craft. Moreover, under all Rating Rules, except the 36-inch Restricted Class, yachts have ample stability to carry all the sail they can get under their Class Rating Rule, so these calculations become academic rather than practical. However, the problem is rather interesting so let us examine it briefly, starting with the obvious axioms. When there is no wind, or the boat is head to wind, there is no pressure on the canvas and the boat remains on an even keel. When the breeze strikes the sails the yacht heels until the heeling power exercised by the wind on the sails is equalled by the righting power of the hull. In other words, she heels to the angle at which the stability equation (Righting Moment = Heeling Moment) is satisfied. We also know that as the angle of heel increases the Righting Moment increases and the Heeling Moment decreases. It is when we try to apply this equation to a particular case our troubles begin. The orthodox method of ascertaining the Righting Moment of the Hull is to multiply the Displacement 582 NOVEMBER, (or Weight) by the Righting Arm. The formula for . finding the Righting Arm is: BEAUFORT’S -SCALE OF WIND PRESSURES GM sin 6, where GM =Distance of M/C above C.G. and 6= Angle of Heel. The orthodox method of ascertaining the Heeling Moment of the Sails is to multiply the Wind Pressure on the effective S.A. at the given Angle of Heel by the Height of the C.E. Some authorities take this as being the height of the C.E. above the C.L.R., others above the L.W.L. or C.B. I suggest none of these is strictly logical. Since two pressures are being balanced against each other, it appears to me that they must balance about a common fulcrum, and that this must lie on the centreline of the vessel. Now the Righting Arm is based on the M/C Height (or Height of M/C above C.G.), so it Calm I 2 3 4 5 6 7 8 | Ib. per Sq. Ft. | oz. per Sq. In. 0- 3 4-8 0.027 0.127 14-18 0.972 9-13 0.003 0.019 0.507 19-23 0.056 0.108 1.587 9 24-28 29-34 35-40 41-48 49-56 2.352 3.462 4.800 6.912 10 i 57-65 66-75 12.675 16.875 12 0.176 0.261 0.385 0.533 0.768 9.408 76-90 24.300 1.045 | | 1.408 1.655 2.700 From the diagram it will be seen that we are now using the base of our triangle of inclination instead of its hypotenuse, in the same way as we have used the base of our triangle of stability. In fact we have something like a parallelogram of forces. Our Heeling Moment is accordingly calculated: (S.A. cos 0=)xPX(A sin 86). As an illustration of how this works out, let us take the figures of one of the early 36-in. Class yachts, and ascertain the Force of Wind at which she would heel to an angle of 20 degrees. Here are the relevant figures: Weight 10.3 lb., C.G. 1.91 in. below L.W.L., M/C above L.W.L. 1.36in., M/C Height (GM) 3.27 in., S.A. 644 sq. in., Height of C.E. aobve M/C 17.44 in. Now, Righting Arm=GM sin 0 =3.27 x 0.342 =1.118 in. Hence Righting Moment =10.3 x 1.118=11.519 in.-lb. = 184.32 in.-oz. To ascertain the wind pressure, we have to solve the following equation: (644 x .94) x P x (17.44 x .342 =184.32 in.-oz. 3610 P=184.32 Hence Pressure per sq. in. =0,051 in.-oz. As will be seen from the attached Wind Pressure Scale this is equal to a wind of approximately 12 m.p.h. In parenthesis, it should be noted that the Admiralty formula for ascertaining pressure per sq. ft. for a wind of any given velocity is: P=.003V?. The above observations are offered for the particular entertainment of X-Chasers, and it will be of great interest to have their views on this thorny subject. appears to me that the late Admiral Turner was correct in taking the height of C.E. above the M/C to use in determination of the Heeling Moment. To ascertain the effective S.A. at any angle of heel, the formula is S.A. cos 6, 6 being the Angle of Heel. Hence the full formula for equating Righting and Heeling Moments can be stated: Weight x GM sin 0=S.A. cos 0x PH, when GM=M/C Height (height of M/C above C.G.), @=Angle of Heel, P—Wind Pressure per sq. in., and H=Height of C.E. above M/C. That great authority, the late Norman L. Skene, in “The Elements of Yacht Design”, shows a successfully worked out example of this for a 30-footer yacht, but he used the C.L.R. as his measurement point for the Height of sailplan. Personally, I have tried a number of times to work this calculation out, but with little success. In fact the only time I got a plausible result I subsequently found an agregious error in my figures! I ultimately came to the conclusion that while the orthodox method of finding the Righting Moment of a hull answers admirably for comparing the stability of different hulls, and the orthodox method of ascertaining the Heeling Moment of a sailplan serves for comparison of the respective efficacy of different sailplans, they do not work in combination when one tries to equate Heeling Moments and Righting Moments. If we consider the attached diagram, it will be seen where the difficulty arises. This diagram, which is not to scale, is merely the usual figure used to illustrate the method of finding the M/C, but the upright and heeled centrelines are produced to the height of the sailplan and the Centres of Effort marked thereon. By the orthodox method the Righting Moment is ascertained by multiplying the Weight by the horizontal distance the C.G. moves away from the original upright centreline when heeled to the given angle. On the other hand, in finding the Heeling Moment we have multiplied the Wind Pressure on the sails by the vertical height the C.E. is above the M/C. This is obviously inconsistent, and both arms should be measured in the same way. The orthodox method of finding the Righting Moment is correct because it allows for the fact that when there is no wind and the vessel on an even keel, then there is no Righting Arm and consequently no Righting Moment. Further, this takes into account the distance the C.G. is from the M/C and the angle of heel. To correspond with this, we must amend our method of finding the Heeling Moment, and multiply the wind pressure on our sails by the horizontal distance the C.E. has moved to leeward at the given angle of heel. This takes into account the distance of the C.E. is from the M/C and the angle of heel. | AND Pressure up to Speed in Knots Force VELOCITIES 1956 i * * When I was discussing ‘‘Moonraker II” in my Regatta report two misprints unfortunately crept into a single sentence which should have read: ‘ “Her displacement is above the maximum 7/D for use in the Rating formula, and would be sufficient for a L.W.L. of 54°65 in., but spacing the sections out to this L.W.L. would in turn put the displacement up to 64°377 lb., which would warrant a further increase of L.W.L.” In the report of the International Race on the first day it reads: ‘*Time and time again she gained a lead particularly down-wind, only to broach off or run off the course in the last quarter of the lake . . .” The word “‘off”’ in italics is wrong. A nautical person would never speak of broaching off, or broaching off the course. The word broach is sufficient in itself, and means when a vessel running gets out of control, runs upwind coming broadside to the wind. If she runs off, she turns the opposite way to broaching, and if she goes far enough, will gybe because she has got too far by the lee. * 583
