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Starting in R/C Boats? Here’s of all you need to know SPECIFICATION : Length: 35. 5” (9 11” (280 mm.) Height O.A.: 62” (1580 mm.) Designed for two. function R/C. Out Price £1.25 Aug. 20 * Sail successfully into a may fascinating hobby with asts tak the aid of this Special asts take up the hobby of sais ansipearen ; from the World’s the basic practical inforNo. 1 Model model boats and see mation and guidance needed during those first hesitant steps. This ‘Special’ issue of the regular Boat magaé monthly Model Boats provides within its larger A4 pages (over 64 editorial), the major basics, i.e. radio and its installation, propellers, electric and i.c. power, scale sailing models, adhesives, transmissions, kit bashing and an exhaustive article zine detailing the many pitfalls and problems facing the absolute beginner — together with invaluable tips on starting and tuning i.c. craft and yachts. A simple 2 channel radio control yacht which makes an ideal introduction to this fascinating aspect of R/C modelling. The model has a single sail rig for simplicity of operation and features pre-formed ABS parts for ease of construction. The very complete kit includes the mast, sail, keel and R/C link_ ages, colourful decals and comprehensive building instructions. Send S.A.E. for brochure showing the full range of Krick Boat Kits MICRO-MOLD Station Road – East Preston West Sussex – BN16 3AG 526 ALL THIS PLUS GREAT An easy-to-build FREE cabin cruiser and a PLANS modern tug. Order your copy – NOW- it’s SUPER! – from your local newsagent or model shop. In case of difficulty, direct from M.A.P. (add 25p postage). Model & Allied Publications P.O. Box 35, Bridge Street, Hemel Hempstead Herts HP11EE. Tel: Hemel Hempstead (0442) 41221 Model Boats © THOSE in model yachting who have not dabbled into its secrets, the International ‘A’ Class is veiled in mystery. The class rules are not frequently published, and most skippers, and even some designers, are not at all familiar with even the basics of the class, except that ‘A’ Class are ‘big boats.’ In this article, | hope to shed some light on how the rules work, using graphs wherever possible so that the cases in point can be shown at a glance. When any designer looks at a new class (and | must add that although | have designed many model yachts, among them the 1980 World Marblehead Champion, Kisutch, | have never designed an ‘A’ boat) he first seeks all available information on the class rules, and previous successful designs, and any articles written about designs within the class, plus information that pertains to yachts of this type from other sources, i.e. full size. He then seeks to improve, select, and perfect these into his own design, as he sees it. While each designer has his own ideas about the actual shape of the yacht, he also has to work within a framework of certain dimensions, or parameters, dictated both by the class rules, and the factors which affect the yacht’s performance. Each designer has his own ideas, based on experience, observation, and theory, and also locality. It is extremely difficult to design a yacht which will perform well under all conditions, within most class rules, and it is possible to design a yacht specifically to certain conditions, in which it is a superb boat, and to have it completely uncompetitive in other conditions. The ‘best’ boat is therefore completely open to a matter of interpretation, and will almost certainly vary with the conditions. In most cases, the designer’s aim is to produce a boat which is the best compromise for the area in which itis going to be sailed. ‘A’ CLASS DESIGN PARAMETERS The Rules First off, let’s look at the rules. When Malden Heckstall-Smith devised the rule in 1922, he produced a rating formula which on the one hand encourages long light boats, while on the other encourages heavy displacement. The formula for the rating rule is as follows: Lees ‘ LxvV/S 4 12x 3/ D 1980 World RM boat designer, R. B. Sterne, discusses ‘A’ class design area. result The of the displacement penalty is shown clearly in Graph 3, for three LWL’s. The dotted lines represent what would happen without the penalty. Incidentally, for all graphs, ‘Min.’ means minimum, ‘Max.’ means maximum, and ‘Mid.’ means a point halfway between. 2000 Graph2 Sail Area v. L.W.L. 1 metre (i.e. 39.37in.) whereL is the LWL in inches, S is the Sail Area in sq. in., and D is the displacement in cu. in. Incidentally, 1lb equals 27.7cu. in. The formula was, of course, designed to be used when measuring boats, not when designing them, so if we solve for the sail These values are plotted on Graph 1, for all waterline lengths from 50in. to 60in. which covers the range in which we find 50 51 52 56 57 58 59 60 in virtually all published designs. Graph1 53 54 55 Graph 3 Displacement v. L.W.L. Sail Area v. Displacement area, S, the formula then becomes: + 4 3937- Ss . 123/D There are several restrictions on the hull, in addition to the basic formula, governing draught, freeboard, displacement, and overhangs (through a quarter beam measurement). The result of these restrictions have been a wide variety of boats which compete on remarkably equal terms. Let’s take a look at these restrictions, one at a time. The displacement must fall within a rather narrow range if the boat is not to carry a sail area penalty. The ‘Maximum’ and ‘Minimum’ displacements allowed without penalty are given by the following formulas: Max pe: sie 5 Min ee 2M. +04 5 546 Mins 26 «oh 1400 72% of MIE 30 20 so 5B! S253 54 in 55 56 57 58 59 60 The shaded area between the curves represents the range of displacements which carry no ‘penalty’ under the rules. The penalty works as follows. When the actual 3\/D exceeds the ‘Maximum,’ then the value given by the formula for ‘Maximum’ is used. This means that no extra sail area is allowed beyond that displacement, which is penalty enough. If the actual 3\/ D is less than that allowed by the formula for the ‘Minimum,’ an amount equal to the difference is subtracted from the actual 3\/ D, and the result is then used in the rating formula. The further the displacement is below that allowed, the more severe the penalty in sail area. Graph 2 shows the range of Sail Areas vs. LWL, and again the shaded area is the ‘no penalty’ ee 400 ee MAX MID MIN 90% 80% 70% 60% 50% 40% % of MIN The quarter beam measurement is usually the one that scares off the potential ‘A’ Class types, because they don’t understand it. It is an attempt to limit overhangs, or at least to penalise very long and low ones. The quarter beam length is measured parallel to the centreline of the yacht, a distance equal to one quarter of the LWL. Beam from the centreline, and one tenth of the LWL Beam above the LWL. It is expressed as a percentage of the LWL, and the maximum value allowed without Model Boats penalty is found from the _ following formula. 1/10 Beam Water Line mi Sse ja Max OBL= 100%- vy LWL 2 If the | “—~ Quorter Beam | eo Buttock exceeds that allowed by the above formula, the excess is divided by two and added to beam | lengths for Quorter Beam Length see Pe | 1/10 BWL LWL Height of sail plan , = ———o» Max.216.7 cm | = ee (85.3 in.) } FE = aaater boom butted laa Height I Mox. 162.5 cm Fig.) QUARTER BEAM MEASUREMENT the length L in the rating formula. The quarter Load Water Line P, Zz Sia length 7 ‘ . | measured quarter beam allowable ——$———<— Aa all *\. 45°70 HORIZONTAL \ XN LWL’s considered are shown in the shaded (64 in.) Total side profile area of rotting mast measured. aT area of Graph 4. For the purpose of this length is within that allowed TON TTI TTT article, it is assumed that the quarter beam without penalty, which is in line with most current designs. Z Graph4 Q.B.L. v. L.W.L. 577 557 2 ® 517 + 49 Fig.2 47 50 Sl 52 53 54 55 56 57 58 59 FREEBOARD 60 in ‘A’ Class rule specifications ds P t (Courtesy MYA Rule Book) Base O y board, given by the formula: rs Lee There is a penalty for insufficient free- Min. avg. freeboard = 28% 3\/ D + 0.9in. The freeboard is the Fig. 4 CURVED EDGES average of three measurements at the forward and after It is my opinion that the power to weight Graph 6 Draught v. L.W.L. ends of the LWL, and at a point midway be- ratio, i.e. SA/Ib, is important in all types of tween. Any deficit in freeboard shall be sailing. It is important for acceleration, for the ability to overcome wavemaking resistance, and to provide enough power for planing. | have therefore assigned it a value added to the rating, asevere penalty. Graph 5 shows, in the shaded area, allowable freeboard vs. displacement in Ibs. For the purpose of this article, it is assumed that no freeboard penalty should be incurred. Graph5 Freeboard v. Displacement 50 51 52 53 56 57 54 55 58 59 60 of 3rd in all conditions. in In light air, literally all of the yachts resistance is due to skin friction, and therefore The ‘A’ Class yacht is basically a displacement boat, and only boats considered the ratio of the driving force to the wetted to be ‘lightweights,’ i.e. well into the displacement penalty area can really have much of a chance of planing offwind. Con- surface is the best indication of yacht potential. Off the wind, this is represented by the ratio of SA/WS, but to windward, the effect of the aspect ratio on sail efficiency must be taken into account. Because of the sidering this, | have undertaken to assign a degree of importance to the various speed producing factors, which is summarised in 1. Please remember this is a maximum Table 3 T T c 20 30 40 50 60 70 80 T T T pm! lb. The penalty for excess draught is perhaps the most severe. The maximum allowable draught is given by the formula: Max. draught = 16% (LWL) + 3.5in. simplification. penalty. Again, for this article, it is assumed that no draught penalty should be incurred. Design criteria By now you should have a rough idea of how the rules work. Now let's take a look at some of the design criteria for any yacht, and try to assign some values to them in relation to the ‘A’ Class. October 1982 aspect SA/Ib is the ratio of Sail Area to Dis- is the height sail restriction areas tend to ratios, and of 85.3in., have therefore higher develop a higher force per sq. in. In this case, the ratio of DF/WS is the important factor. The re- placement, in sq. in./lb. SA/WS is the ratio of Sail Area to Wetted Surface, and DF/WS lationship of driving force to sail area is a ratio of Driving Force to Wetted Surface. Stab is the yacht'’s ability to carry sail, \/ Lis the Hull Speed factor, and D/Lis based on a graph drawn by noted ‘A’ Class designer John Lewis, and published in his the Displacement/Length Ratio. article ‘‘John Lewis Analyses International complex one, and the values | have used are ‘Table 1 The penalty for deeper draught is for the excess to be multiplied by three and added to the rating. Graph 6 depicts, in the shaded area, the allowable draught without smaller Windward Light air Off wind Windward Mod. air Off wind Windward Heavy air Off wind SA/Ib Vard Yard we yd we Stab. : 3 \/L_ D/L — Ard — Vard : . SA/WS DF/WS Ard Yard ed Yard — 2A Yard ‘Yard Yard =—e Yard 547 ‘A’ Designs” from the September 1977 issue of Model Boats magazine. | have the rule, is quite a find. The displacement of 1.5, would suggest that the longest LWL and sail area of these ‘72 per cent Boats,’ as for good windward performance in light air assigned to these values an importance of | shall call them from now on, are shown on is about 57%in. Graph 12 is for the 72 per ¥3rd in light airs, and 3rd in moderate airs. Graphs 1 and 2, for reference. | then plotted cent boats, and suggests that for these, a The other 3rd in moderate air | have these ‘72 per cent Boats’ on Graph 8, for Maximum assigned to Stability, in the case of windward work, and to Hull Length, in the case SA/Ib vs. LWL. The horizontal dashed lines on both this graph, and 7, represent the recommended. of wind work, for obvious reasons. These values are also used for heavy air, and because the wetted surface becomes rela- (lower) and Lewis (upper). Note that 400sq. about 55% in. is ft. per ton becomes 25.7sq. in. per Ib., and 5ib per sq.ft. becomes 28.8sq.in. per Ib. DF/WS has been replaced by Hull Length for windward work, and SA/WS by the displacement/length ratio D/L, which This suggests that ‘A’ Class yachts with a represents the yacht’s ability to plane, for Lewis’ suggestion, the LWL becomes even agree with the proportions | have allotted, I'm sure that they will agree with the of Graph 9 Sail Area/Wetted Surface v. Displacement minimum values recommended by Marchaj tively unimportant at higher boat speeds, off wind. While other designers may dis- LWL LWL of over 57in. should not have enough power less to at plane about well, and 55'%in. (| applying can hear Mr. the screams already!). general distribution. It is interesting at this time to look at some specific values for these criteria 44 4 Graph 7 Sail Area/ Ib.v_ Displacement 0.8- eo? 0.6 MAX MID MIN 90% 80% 70% 60% 50% 40% suggested by some of my research. In Mr. Lewis’ aforementioned article, he suggests %_of MIN the following values for an ‘ideal’ design based on his considerable knowledge of the ‘A’ Class. Graph 10 LWL 1.74 Greater than 55in. SA/WS SA/Ib Sail Area/Wetted Surface v. L.W.L Above 1.3 Better than 5lb/saq. ft. DF/WS Above 1.5 In addition, there is an excellent work by C. A. Marchaj, entitled “Sailing Theory and l 16 MAX MID MIN 90% 80% 70% 60% 50% 40% Practice’’ which gives the criteria for a ratio in excess of 400sq_ft. per ton (2240Ib), ° s NOTE - NO BOATS % 36 ABOVE THIS LINE of SS 39 _ Mr. Lewis also wrote an article, which appeared in the March 1976 issue of Mode/ Boats magazine, entitled ‘The InterFrom 5 40 4 2 (L (ft.)/100)8 national 8 Sail Area/Ib, v. L,W,L Graph 4d and a displacement/length ratio of under 150. This is found from the formula: D/L= by Lewis = 1.3 % of MIN planing boat as having a power to weight Disp. (tons) Minimum recommended MAX L.W.L. = 55hin > 5lb./sq. ft = 28.8 2g fre Soest LEWIS ee _ —MARCHAS ‘A’ Class — A Stability Study.” this, and an analysis of several current designs, | arrived at a figure for stability which | feel represents a good criteria for this parameter. Now that we have some guidelines, let’s have a look at these factors in turn, and see what conclusions can be drawn. If we plot the SA/lb vs. Displacement for various LWL’s, we get Graph 7. You may If we now look at Graph 9, we see the values of SA/WS plotted vs. Displacement for various LWL’s. There is nothing surprising about this graph, as it resembles closely Graph 3. When you check out Mr. Lewis’ suggested value of 1.3, however, it would appear that there is a maximum LWL for note with some surprise, as | did, that the curves have a peak at 72% of the downwind ‘Minimum’ displacement, independent of LWL, indicating that the power to weight is, the better it should fare in these con- ratio is at a maximum for any LWL at this value of displacement. From these curves it is seen, however, just how excellent the rating rule is, keep- ing the SA/Ib within about a 12% envelope over a range of displacement down to about in light airs of about 59in. 0.8 MAX MID MIN 90% 80% 70% 60% 50% 40% % of MIN Basically, the shorter and heavier the boat ditions, which is borne out in practice. Graph 10 isa plot of SA/WS vs. LWL for the ‘72 per cent boats,’ and is included for reference. ments, Note that the a | 0.6 Graph 12 1.9 7 Driving Force/Wetted Surface v. L.W.L, at these displace- maximum LWL_ suggested becomes about 55’in. Turning our attention to Graph 11, we a third of the ‘Maximum.’ No wonder the notice that the DF/WS ratio, which takes rule has been able to stand the test of time into account the aspect ratio, when plotted MAX so well!! Designers, however, are always vs. Displacement, yields curves having a looking for an advantage, however small, L.W.L. = 553in. maximum favouring and to be able to state that the best displacement for any LWL of ‘A’ Class boat ‘penalty’ area for shorter waterlines, and from a SA/\b point of view occurs at 72 per cent of the ‘Minimum’ Displacement under 548 boats well Minimum recommended is=. 5 by Lewis into the right at the ‘Minimum’ displacement for a boat of 60in. LWL. The horizontal dashed 1,2 50 ————or 4] 52 53 54 55 56 57 58 —- 59 60 in line at Mr. Lewis’ recommended minimum Model Boats Incidentally, the Wetted Surface data used for all the above is from an average of all the ‘A’ Class designs | had information of the ‘Minimum’ if the boat is to plane well. – Displacement/Lenth Ratio v. Displacement for* loin co M surface would vary several per cent from values | used in Boy, did | just say a mouthful! Am | trying to tell you that all the other ‘A’ Boats are no good? A most emphatic NO! As | said before, it has been proven over the years Graph 15 on, extrapolated to cover the LWL Range and Displacements required. It is certainly possible to design a yacht whose wetted the 71 per cent to 80 per cent of the ‘Minimum’ Disp. cae by that a wide variety of yachts have remarkably equal performance. Boat design, however, iS a compromise, and | feel that the my calculations, particularly in the upwards direction. | feel, however, that the values chosen really Displacement = 80% represent the ‘norm.’ 0 —— —MAX MID MIN 90% 80% 70% 60% 50% 40% If we now look at Graph 13, which is Stability values vs. Displacement, for various LWL’s, we will quickly see the effect of decreasing displacement and decreasing LWL on sail carrying power. The dashed horizontal line represents my recommended minimum for ‘average’ con- ditions, i.e. a wide range of wind speeds. Graph 13 Stability v. Displacement boats in this area may just be a little more ‘equal’ than the rest! They are light enough L=L.W.L. + 10% to plane, have enough power to plane without a spinnaker, are long enough to go fast, % of MIN Graph 16 is simply to show the have enough sail area to overcome their wetted surface in light air, and are stiff enough to carry their sail to weather. For relation- ship of hull speed to LWL, and for both this value and that of the Displacement/Length Ratio, | used a length equal to the each condition, it is certainly possible to design a better boat, but | feel that this area simply represents the best compromise, LW plus ten per cent, because of the overhangs of most successful ‘A’ Class boats. In simple and I’ve tried to show the numbers to prove : terms, longer is faster, the difference from It. a 50in. LWL to a 60in. LWL being nearly 9 Specifically, what are these boats like? Well, first of all, their shape is entirely in the hands of the designer, as so far | have had per cent in actual boatspeed. I’m sure this is where Mr. Lewis applies his suggestion of a 55in. Min. LWL. nothing to say in this regard. Their dimensions, however, are as follows: At a LWL of 55in. from 38.0lb and 1128sq.in., to 42.8Ib Graph 16 Hull Speed v L.W.L. 5.3 and 1273sq.in., and at a LWL of 551, in. 1147sq.in. to 43.9lb and 5.2 from 40lb and 1257sq.in. – 5.1 3 Minimum L.W.L. re LEWIS = 55in > 5.0 4.97 0 T MAX q i u q q T ok MID MIN 90% 80% 70% 60% 50% 40% 4.8 L=L.W.L. + 10% 50 T «(5| T T «652 «(88 It assumes a fin and bulb keel is used in order to keep the Centre of Gravity as lowas possible. If you only sail in light airs, this value would be too high, and if only in heavy a higher value might produce a winds, better boat. In any case, using it, one finds that even a ‘heavyweight’ design with a 50in. LWL has insufficient stability, as does a real ‘lightweight’ design of about 55in. LWL. Graph 14 shows the Stab values plotted vs. LWL for the ‘72 per cent Boats,’ and indicates a minimum LWL of about 53%,in. for these boats. Graph 14 T 54 T 55 T u 3 56578 59 60 in — > % of MIN 6>- Interestingly enough, Mr. Lewis had a couple of other suggestions for an ‘ideal’ design. He suggests a maximum displace- recommended by Now, is it possible to design an ‘A’ Class yacht that will meet all of these criteria? Yes, | believe that it is, as | have shown on Graph 17. The basic plot is SA/Ib vs. Disp., as in Graph 7, but it is overlaid by a series of curves taken from all the other criteria. Note that only in the small shaded portion do the yachts meet all of the criteria. This area is from 55in. to 55),in. LWL, and from ment of 45lb, a minimum sail area of 1100sq.in., and a maximum wetted surface of 1000sq.in. Any design in the shaded area on Graph 17, also meets these criteria. For the purpose of this article, | have inten- tionally refrained from offering a new design within these guidelines, as | want the article to concern itself only with the parameters involved in designing a top ‘A’ Class yacht, without dealing in specifics. | will, however, be offering a design for a yacht within this range in the very near future. Graph 17 Sail Area/Ib. 44—-4 42 | I = — 5 Minin, 5 xe 54 Minimum recommerided stability 5 A Yo x SS Wak <2 cat £ 3044 | {Minin 3/8 uu Minimum by. 2/5 Y Minimum for Ss. A Ib. c L.W.L. = 53kin Displ | 40 Stability v. L.W.L. v. 28 © = 28.8" (LEWIS) ay < 27 505i T Li T 2 45a) 364, Graph 15 Length T in is a ratio vs. T 95556. T 57 58 59 60 plot of Displacement/ Displacement. You will notice that once below the ‘Minim um’ disthe D/L ratio values for all placement, LWL'’s follow the’same curve, and that the Displacement should be below 80 per cent October 1982 u- — ee ee Le Minimum forplaning “225, = 74 (MARCHAS) mea 22] | 204 18 16 | T MAX T MID i MIN 90% I 80% : | 70% T 60% | —* % of MIN 549 was happening, and there was subsequently Model Yachting Association News gate at the Starting pontoon and distant starting pretty fresh for Dunkerque Championships. Wind was Cleave's John is nd foregrou in Yacht week. the of most . oto: Vic Smeed quite a demand for silicone bath caulk to replace cut-off bumpers! The only major problem arose when sailing started. The French use a system of bank judges who see an incident, size it up and apportion the and then hand out a penalty on the spot, a blame, well, system which they apparently find works circum- although there must be occasions when stances are not completely cut and dried. How- ever, the important point is not whether it works or not, but the fact that itis notin accordance with the standard IMYRU rules, which lay down that bankside officials observe incidents in order to report to the jury in the event of any protest. Skippers who recognise errors such as touching a mark and carry out penalty turns are not affected, to but the rules do not allow the OOD’s assistants award on the spot penalties. Obviously an IMYRU meeting must be run to existing IMYRU rules, at least unless any pro- sted ‘Fleetwood conditions’ F anyone had sugge inland in northern lice a lake four or five miles ed some very odd looks France he’d have receiv he'd but, for much of the period August 16-25, fairly have been absolutely right. A very large, yside, and shallow lake set in relatively flat countr so a north-westerly breeze, gusting to 15 knots or at times, persisting for all but the last two days was created a wind and water mixture which beyond the experience of many of the nearhundred competitors. Although 700 sails were ely in the initial processing, comparativ IMYRU WORLD RM AND R10R CHAMPIONSHIPS measured resulting in few of them belonged to third suits,sails rolled up much wielding of scissors and even at the foot and taped to the boom. The lake is excellent, and a jetty for launching to dash up and a new concrete apron for skippers as any. good as ies facilit g sailin made down and d the jury, Three Portakabin-type buildings houseteams the secretariat and the race controhljetty wasand an only 40 or 50 yards from the launc ft aircra an like ure struct ltural agricu ous enorm ed the hangar which comfortably accommodatFurthe r 100 boats in less than half its floor area. a and meals als’ offici for uee marq a was away block, toilet stall, beer s/ /chip offee ich/c sandw like the same extent in full-size racing. Protest hearings were complicated to some degree by language differences. Most com- petitors had at least some English, and the sterling services of Mme. Michele Lahure in interpreting helped enormously, but there were some who were only fluent in their own languages and and thankless task undertaken by a cheerf also a video record of each race to assist in resolv ing protests, again a gruelling job for the video of the camera operator but an indication and the thoroughness with which Alain Barthier hard and attractive sextet of young ladies. There was- other organisers had approached the event. ‘Policing’ of the competition area was undertaken by French Scouts, who were very quick to spot anyone without an official pass. sThere were two unusual problems in procesate separ ing, the first of which being that three sails and 550 race and the relatively short duration of our races raise difficulties which do not occur to anything taking notes of his descriptions of incidents —ula participants. angling the verticals inward; it doesn’ n. above bow fo make a 3-4mm difference 15-18i s had their table height. Quite a few yachttwigg ed what bumpers sawn off before someone The problems of combining the existing protest system with fleet sailing have been touched on in this column previously; this is an area whereinthea necessity of limiting the number of yachts and the French/English proceedings of the jury.ofIt is also fair to say that the standard of sailing possibly half the competitors was perhaps not quite up to world championship standards, a factor which led to more protests than might otherwise have been expected. bank On the officials’ side, each of the six ry, who judges was accompanied by a secreta and judge spent the week walking behind the The facilities and, in general, the organisation to be were magnificent and the French . are one now If efforts their on ed iment compl y warml is this oned, menti are ps hiccu minor two or and guard their on sers organi future put to y simpl should not be taken as criticism of endeabyvours all which were unanimously praised the table, was placed in position its weight bowed t take much week went on protests became fewer and were, usually, dealt with more quickly. there was no easy bridge between those tongues and caravan/camping site. measuring tapes were used to check ze when they all differed. A suit which was oversi nal on the checked with one tape was margisecon d snag, second and legal on the third. The vertical two rned conce ed, realis y iatel immed not mum maxi legal at table light a to ed secur struts belength for the RMs, each boat being stood yacht a when er, Howev check. a as them tween by posed departure has been agreed beforehand all the executive board and then notified to the participants, and the EB members present at beginning of the racing had no option but to point this out. The difficulty then lay in the necessity of resolving protests after each race, since fleet four sailing was being used with four up andthere down after each heat. Initially, at least, were quite a number of protests, which had the effect of slowing racing down, although as the with yachts and awards A happy Barry Jackson poses of his South African results after a repeat performance Ken Shaw. four years ago. Photo: Barry Jackson wins RM and is second in R10R. Of the yachts, there was nothing really revolutionary, if one excepts the superb workmanshibyp and high technology of an impressive pair Helmut Lupart of Switzerland. A feature of these the 10 was the use of wolfram for the bulbs — oner, yet the bulb was about Qin. * 1\,in. diamet weighed 13lb., we were told. There were also n. some yachts with enormous draughts, 21-22i for RM and 24-25 for R1OR, but hulls were wa total assortment from wide and flat to narro and deep. There were several chine boats, performing as well as any, and one una-rig, by none other than ace vane A skipper Kai Ipsen from Denmark. Model Boats Left: the English sailors, left to right: Tony Owens, Barry Jackson, Charles Yabsley, Tim Fuller, Mark Dicks, Jack Lee, Robert Owens, John Cleave, Russell Potts and Chris Dicks (Nigel Wilder was not present). Photo: Ken Shaw. Above: the incredibly deep keel on Spaniard Claudio Ruiz’s R10R. Photo: Vic Smeed. in extremely tough competition. The Italian RMs stood out as having masts much further forward than most, with resulting small jibs and raked fins reminiscent of early bulb- The trend towards ultra-light boats is well demonstrated by American Byron Samson‘s RM with its fabric sails and film covered deck. keelers. They held their own on the wind, but perhaps were less effective when running. The course for the first few days remained the same, and to this observer it seemed that the start The other English skippers, or some of them, had some amazing experiences. Chris Dicks had three radios go on the blink, and also had a puzzling incident when his RM rounded the lee mark and then seemed to have lost its windward performance. When he picked it out of the water he discovered that the entire fin had disappeared, all that was left being the ¥ = %in. dural strip holding the bulb on! He shot into Dunkirk to a line was a long way away from the skippers and, shift which allowed a change of hand of the model shop and bought a sheet of ply, returned and fashioned a new fin and had the boat sailing again, though he’d lost too much ground to make it back up. Radio failure also caused Neil Bennell, the sole Australian entry, to retire, Russel Potts had a servo blow, and Mark Dicks suffered battery course and most of the sailing parallel with the problems. indeed, the whole course was a long way out. Perhaps the difficulty of taking useful photo- graphs without a telephoto lens had something to do with it, as apparently none of the skippers objected! For the last two days there was a wind John Cleaves and Jack Lee had other problems. John shut his only keys in his expensive new bank, by which time, it need hardly be said, we were on our way back home! burglar-proof Porsche but, being John, selected a It seemed (again, to this observer) strange to use a course in which four legs were sailed along the other boat. Even then, if he‘d done a penalty the same ‘corridor’ of water, especially as the turn he could have won, but under the intense third leg was in the opposite direction to, but pressure decided to let it go to protest, which he immediately the second and fourth. lost. This one tiny misjudgement and quickly- 12-boat races this inevitably meant the made decision cost him the championship, the With leaders between, meeting several of the other yachts coming the other way and, with three long beat- results of which were: 1. P. Jahan (France); 2. B. Jackson (England); 3. ing legs, put an even more marked premium on Simons windward performance. (Switzerland). From early on, (South P. Lucas (France); 4. P. Africa) and 5. H. Lupart it seemed likely that Pierre In the RM Barry made no such slip and the Jahan and Paul Lucas of France would be the English boats took the team prize by a handsome skippers to beat, but there were other contenders margin. Results were 1. B. Jackson (England); 2. and whoever was in the lead, or well-placed, P. Jahan (France); 3. Torvald Klem (Norway); 4. could not afford to relax for a moment. Towards Tony Owens (England); John Cleave (England). So the end of the R1OR, Barry Jackson had a narrow with John Cleave having again won the EC12 lead but became involved in a port/starboard World Championship a month earlier in America, incident. He thought he'd just clear, but touched England still has two world champions with wins IMYRU World Championships, Dunkerque July 18-25, 1982 RM Country Points 1. 2. 3. 4. 5. 6. 7. Barry Jackson Pierre Jahan Torwald Klem Anthony Owens John Cleave Paul Lucas Tim Fuller England France Norway England England France England 127.2 158.1 203.7 204.8 246.1 254.2 PW EY i 16. 23. 28. 30. 39. Robert Owens Charles Yabsley Chris Dicks Jack Lee Nigel Wilder England England England England England 430.4 484.7 551 575.7 689 41. Mark Dicks England 43. Russell Potts England 16 countries — 55 competitors. October 1982 721 725.1 R10R RM 1. Pierre Jahan Country France 5. Helmut Lupart Switzerland 2. Barry Jackson 3. Paul Lucas 4. Peter Simons 6. 9. 10. 18. 20. 21. Tim Fuller Chris Dicks John Cleave Russell Potts David Hackwood Jack Lee 10 countries — England France South Africa England England England England England England 34 competitors. Points 771 136.7 185.6 191.4 192.8 213.1 241.8 274.2 BT tt 383.4 405.4 the side suitable piece of local stone and smashed window. Unfortunately, though parked in a private car-park overnight, someone reached in Norwegian Torwald Klem was third with this fast but most conventional of the Scandinavian yachts. Photo: Vic Smeed. a intention. In addition explanatory diagrams opposite the relevant rule are inserted to add to the clarity. It has been pointed out that unless the final rule proposal is absolutely clear in overall length 50 + 0,25" =o describing fair measurement rules this subject will be with us continually until it is resolved. This amendment is based on three fundamental PRINCIPLES as follows: COMPETITORS AREA | oe World Champs Course and removed five carbon fibre masts which John had brought over for Graham Bantock ... Jack Lee’s car was broken into outside his hotel and the glove box jemmied open. He lost car documents, passport, return tickets and a lot of cash, though we hear that he’s back in this country, so must have found a way round the ensuing problems. Great enterprise was shown by Ken and Joyce Roberts who (like us) didn't realise how far out- side Dunkirk the new ferryport is sited. They'd left the car at Dover and brought their bikes over to on attend the IMYRU General Meeting, the report which will appear next month. Where will it end? Alan Chidley of the Woodspring club won the S.W. District R10R Championship on June 20 with his Cipher using Triffid sails. Well done, Alan. So? Well, the Cipher is one of Tony Abel’s RM hulls but, with 7riffid R1OR sails, Alan had quite legally registered the boat as an R10R. A few years ago, most boats of the American Xclass had dual registration as both X and 10-rater; are we likely to see RMs with dual registration? They'd be allowed up to 1,500sq. in. as R1 ORs, so one hull would only need a change of rig to compete in either class. Such a boat would win as an R1OR only in its best conditions (almost certainly at the lighter end of the wind) but it would boost entries in R10R races and probably lead to more true R10Rs being built in the end. The present Rating Regulations (25j) do not allow one yacht to be registered in two classes (except one can be vane or radio, €.g., sailedasan M or RM, subject to strict conditions) but the new ones do (1.11), so if they are accepted by the A.G.M. such dual registration will be allowed. (Note that few R10Rs could be registered as RMs, because of hull length limits, of course). Clubs may like to talk this through, as, like model yachting generally, there is certainly more in it than meets the eye. The MYA Amendment to the Marblehead Rule In order for model yachtsmen to study the MYA ‘amendment’ to the proposal by the IMYRU the full MYA text, with reasons and comments, is set out here. The reasons for the MYA amendment to’M’ rules proposals by IMYRU. At the May Council meeting of the MYA there was widespread dissatisfaction with the IMYRU proposals and the performance for racing. 2. Any change should be made on the basis that all existing boats which comply with the present rules should remain in rating. 3. Any design or construction is permissible unless either specifically prohibited or limited by restrictions. The most controversial addition to the current rules is the mainsail half width measurement which is necessary only because of the argument a movable trim tab is prohibited that goes with other measurement methods. The freedom to adopt other shapes is not limited by this addition because the reasoning of the original rule is retained. The amount of tolerance of ‘luff curve’ in front of the measured triangle rudder may not overhang that is allowed without measurement will allow most existing mainsails to comply. With regard to registered numbers, our proposal is to increase the size so that they are more legible. The habit of using secondary numbers for racing is unnecessary if the regis- tered numbers are larger. The size chosen will allow the use of car registration numbers. Not only would the numbers be more readable from a distance, but they would be more easily available to purchase, (available locally at 7p per number). Our proposal is to show the number on its own with the national letter on a different level for increased clarity, and no dividing bar for the same reason. A ‘grandfather’ clause must be considered so that the rule would apply only to new sails (to comply with our principle 2). The other changes occurring from the rewording are emphasised as follows: Present rule No. 4(a) Rule proposal No. 4(a) Change: The MYA was not in favour of the use of trim tabs as it does not conform to the spirit of the rule prohibiting movable keels: however this does depart from PRINCIPLE 2 and the question of a ‘grandfather’ clause will need to be considered. Present rule No. no rule Rule proposal number 4(g) Change: To prevent excessive cost potential. Present rule No. no rule Rule proposal No. 4(h) Change: To prevent the use of ‘solid’ sails. Present rule No. 5 Present rule No. no rule Rule proposal No. 7(i) Change: To rate both double luff and luff groove sails fairly with other sails. Our proposal deals with a subject that we understand set off the request for fairer sail measurement rules in the first place. At present double luff sails have been unfairly rated since the rule change of about 1970 and measurement of luff groove sails is not clear. We consider these to fall into the same category where sail area is outside the measured triangle but within an area (the mast) that is unmeasured. It is unfair to measure it because it is not creating any more profile area of sail than if the sail stopped at the back of the mast. Present rule No. no rule Rule proposal No. 11(c) Change: To allow any shape to be measured as PRINCIPLE 1. Present rule No. 13(b) Rule proposal No. no rule Change: This is omitted because it is meaningless. The area control is the important thing. Present rule No.16 Rule proposal No. 15 Change: Owners racing flag and dividing bar are no longer necessary and to define spacing is quite wrong as it should vary for different number combinations. Rule proposal No. no rule 1.M.Y.R.U. no possibility of listing all the things that you can Class). Change: (a) to comply with PRINCIPLE 3: There is do so it is best not to list any. (b) as displacement is not measured this is superfluous. Present rule No. no rule Rule proposal No. 5(e) Change: to define mainsail simply. Present rule No. no rule Rule proposal No. 5if) Change: to define jib simply. Present rule No. 7 Rule proposal No. 6(a) (b) the rule rather than clause by clause revision. In this améndment the working of the existing rule has been improved without losing any of the sense of the present or original rule maker's Present rule No. no rule Rule proposal No. 7 552 bumper 1. The MARBLEHEAD js a development class and that the basic parameters of length and the sail area restrictions control the equality of boats’ MYA decided to submit ‘an amendment’ to IMYRU which was a comprehensive rewording of 0.5" maximum SS) a i Change: The omissions are as PRINCIPLE 3. Change: These definitions do add to the number of words here but they save words elsewhere! Rating Rules for ‘M’ Class (Marblehead 50-800 The yacht must comply with the IMYRU GENERAL RATING REGULATIONS in addition to these specific rules. 1. OVERALL LENGTH (a) Overall length of hull shall be fifty inches plus or minus one quarter of an inch (127 + 0.6cm). This is to be measured approximately parallel to the waterline. (b) Bumpers may extend a maximum of one half inch (1.3cm) beyond the hull measurement at the bow only. 2. SAIL AREA (a) The measured sail area shall not exceed eight hundred square inches (5161sq. cm). Model Boats 3. UNITS OF MEASUREMENT 7. All measurements shall be taken and recorded as follows. A. IMPERIAL (a) Linear: Inches and decimal fractions of an inch. (b) Areas: Square inches and decimal fractions of a square inch. B. METRIC (a) Linear: Centimetres and decimal fractions of a centimetre. (b) Areas: Square centimetres and small suits of decimal } (b) TACK — the point at the bottom of the front leech. peatvidoe is Rig 'B' oe a ore are not thanin 'A' so certificate as an alternative rig recorded on the longer than in 'B’ is recorded 'A' so 'C' is —_ recorded as another altemative rig Lee-boards, Bilge boards. measurement, (d) LUFF — the straight line between the front of the head and the tack. A mainsail mainsail (e) LEECH — the straight line between the aft end of the head and the clew. _ (f) FOOT — the straight line between tack and seh clew. (b) Bowsprits, Overhanging rudders. (c) Movable or shifting ballast. 0.75" mast (d) Outriggers, Pontoons, Twin Hulls, ‘Tunnel’ Hulls. 85" maximum cross hoist section (e) To change rudders during a race or series of Of» races, except in bona fide cases of damage to the original rudder. (f) The keel, or ballast SHALL NOT be changed during a race or series of races. (g) Ballast material having a greater than 11.5. Head q 7 part of soil within mast front edge of sail roach ' {1 round i Wr one rig. tack (c) Arig is defined as any number of suits of sails, the largest of which shall not exceed a measured area of eight hundred square inches (5161sq. taking i | | sail is clearly marked as belonging to more than the mast diagonal double luff or luff groove sails cm). The dimensions of this suit shall be recorded triangular sail on the Measurement Certificate. If any dimension of any remaining suits is greater than that of the measurement except for a headboard. head when extended intersects the front of the mast. 6. MAST AND SPARS (a) The greatest dimension of the cross section of the mast or spars shall not exceed three quarters of aninch(1.9cm). Fittings shall not be included in any measurement. (b) Masts and spars shall not be included in sail area measurement. for lift to coincide with CG position since lift roughly in this case ¥,990z for every 1Ib of full size weight). weight as well as geometry. (Scale weight equals full size October 1982 weight multiplied by half width sufficient tension to render it flat along the line of measurement. For double luff or luff groove sails this tension must be sufficient to ensure that the front edge of the sail is tight against either the front of the mast or the inside of the groove. 8. TRIANGULAR MAINSAIL MEASUREMENT (a) LUFF A is measured from head to tack. (b) DIAGONAL B is measured from clew to the Stop Press The A Class Championships have just finished at Gosport after a week of trying weather conditions. Clear winner was Dave Latham (Fleet- (scale)’, e.g. for a 1/12 scale model weight Fig. 9. In other words, model trim may be mainsail (Amendments 10-16 next month). Powerboat Hull Design (from page 532) necessarily different, even if it is scaled in and (a) LUFF QO is measured from head to tack. (b) DIAGONAL R is measured from clew to the front edge of the sail. (e) The sail fitted furthest aft shall be considered to be the mainsail. is generated within the wetted length — diagonal 9. JIB MEASUREMENT (d) The maximum height of rig, measured from the deck to the head shall be eighty-five inches (215.9cm). There shall be no sail above this point between the luff at the tack and the luff at the the measurements the sail must be pulled out with front edge of the sail. largest suit, then these suits shall be recorded as alternative rigs. height above deck of the head of the largest mainsail of that rig. The jib height measurement is defined as the point where the straight line mast. (l) SETTING UP FOR MEASUREMENT — The yacht is to be set up with the maximum tensionon the sails that would be applied for racing. When (b) Not more than 3 rigs are allowed, provided the (g) The jib height measurement of any suit of each rig shall not exceed eighty per cent (80%) of the edge of the sail considered to be the aft side of the (k) HEAD BOARD — the area of sail or other material above the head. 5. RIGS (a) Any type of rig may be used provided it conforms in every way to these rules. forward sail of the two shall be considered to be the jib. nearest point on the front edge of the sail. (i) ROACH — the area between leech and aft edge within the mast, this part of the sail shall be ignored for measurement purposes and the front front edge of sail of sail (f) Assuming that a spinnaker is not set, a suit of sails shall consist of either one or two sails: the sail. (h) HALF HEIGHT WIDTH — the straight line between the mid point of the leech and the of the sail. (h) Sails (other than spinnakers) made of material which is not of woven construction. one rig may not be used with any other unless the (g) DIAGONAL — the straight line between the clew and the nearest point on the front edge of the (j) FRONT EDGE OF SAIL — Where the sail wraps round the mast or where part of the sail is fitted specific gravity measured sail area of each does not exceed eight hundred square inches (5161sq. cm). The sails of each rig must be clearly marked A, B or C. Sails of (c) CLEW — the point at the bottomofthe aft edge of the sail furthest from the mid point of the luff. Where the shape of the sail at head, tack or clew does not define the measurement points 7(a), (b) or (c) above then they shall be clearly marked on the edges of the sail. jib height x Movable keels are defined as those which are adjusted during a race or series of races in any direction or by rotation. Fixed keels having a movable trim tab are prohibited. MEASUREMENT edge of the sail furthest from the mid point of the 4. PROHIBITED Centre-boards, SAIL (a) HEAD — the line at the top of the sail where the width measured at right angles to the front edge of sail at that point is three quarters of an inch (1.9cm). luff is longer Rig 'A' fractions of a square centimetre. (a) Movable keels, TRIANGULAR DEFINITIONS multiplied by 42 x Yo x Yo or 78; oF On this basis you can afford to build scale raceboats heavier than true scale weights. It will help in getting the trim right. On the other hand, since ultimate speedis directly wood) followed by 2. G. Wyeth (Gosport), 3. M. Harris (Bourneville), 4. J. Rose (Fleetwood), 5. A. Austin (Guildford), 6. K. Butler (Bourneville), 7. M. Roberts (Birkenhead) and 8. R. Gardner (Gosport). The France, international (England, Holland, Scotland) was won by Hans Hoogewerff. Pictures next time. related to power/weight ratio, maximum speed performance with freelance model designers will not be realised with monohulls. Hydros or cats are a better proposition as these layouts can naturally accommodate more forward CG positions. Build them light enough and power-for-power they must be faster than monohulls. 553
