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ia 7 fe iy , | a , 3 ae , oe fh | HINS Dido-LightCruiser = *Kit Review-Oil RigSupplyVesse MARCI by Vic Smeed A LIGHTWEIGHT ELEGANT MARBLEHEAD FOR WOOD CONSTRUCTION HIS DESIGN started life as an exercise some twelve months ago, when interest began to be shown in the possibility of a one-design radio yacht. It was of features likely to attract newcomers (like the inclusion of a bit of grace in the shape rather than a stark racing machine, or the inclusion ofa suggestion of a scale cockpit, etc, on a moulded deck) might reduce performance fractionally has to be faced, but the importance of this would thought that if a potential one-design fitted an existing class, the opportunity of racing in that class would encourage builders initially, and when sufficient of the diminish as numbers grew and in any event it offers a design challenge. Sport sailers tend to operate in light and boats had been built, transition to onedesign-only racing would not prove very difficult. medium weather, so performance at this end matters perhapsa little more. The old sailing adage that the fastest boat is likely to be the longest, narrowest Part of the philosophy behind this was that it is difficult to approach a manufacturer with a new, non-class boat and invite him to take a plunge on it without some sort of official encouragement. A boat which fits a recognised class is more likely and lightest, with as much sail area as possible, was considered, as was the fact that the lighter the boat, the less material used and hence, for production purpose, to attract early sales, particularly if it is produced at an extremely the lower should be the cost. Length and sail area are limited in the M rule, so oneis competitive price. The possibility that the introduction reduced to narrowness and light weight. | was judged that 95-10 Ib displacemen was the lowest safe figure (below that ar RM would be rather experimental anc possibly call for expertise in weight saving on ancillaries and that a narrow boa would need a fairly powerful hull sectior and a deepish draught. An easy entry and exit is always desir able, with a light boat in particular, bu’ fairly full bow sections are needed fo! off-wind performance and balancing sterr sections might create a slight suctior effect tending to slow the boat. It was decided to use a reduced waterline witt the overhang for’ard easing entry, and < shallow, thick skeg or embryo bustle afi helping to break up any possible suction; water tends to flow across the hull aft o: the fin, and such a skeg or bustle would set FULL SIZE COPIES OF THE DRAWING REPRODUCED HERE ARE AVAILABLE FROM MODEL BOATS PLANS SERVICE, PO BOX 35, BRIDGE STREET, HEMEL HEMPSTEAD, HERTS HP 1EE. QUOTE PLAN MM1304 WHEN ORDERING. PRICE CODE G (£2.85 PLUS 35P POSTAGE AND PACKING). OVERSEAS READERS MAY OBTAIN COPIES FROM LOCAL AGENTS DETAILS ON PAGE 538. NOTE THAT NO MODEL BUILDING DETAILS ARE INCLUDED ON THE PLAN. MARCIE. vic SMEED —_( CODE coowrgm of G The Model Maker Plans Servic 13-35 Brage Street. Heme Henpateed. Herts. WL at i2/bs WL at 9-85ibs DOTTED LINES POSSIBLE WEIGHTS HULL & FIN Me - 225ibs RADIO. LEAD - SECTION OF FIN 1*25ibs 5:6 lor7-6ibs) 9:9.(or 1! Sits) \\ ORIGINAL INTENTION WAS \ MOULDED HOLLOW FIN WITH CE AND LEAD REQUIRED WEIGHT ORAUGHT 9-85ibs 41 2 fe os 50° 4S LWL BEAM 5 3 DISPLACEMENT LOA 16-0" 12 lbs. 50° 4475" 8-6" 8-9" 16-25" ORIGINALLY INTENDED FOR VACUUM FORMING (DOTTED LINES ON BODY PLAN SHOW VERTICAL SIDES INTENDED TO BE DRAWN IN TO SLIGHT TUMBLEHOME WHEN FITTING DECK) en ee MM 13( Model Boats up a little disturbance in the cross-flow, reducing the tendencyof the water to stick to the hull. A possible disadvantage might be that a skeg or fence would cause the hull to be over-stable directionally, but on the other hand boats with narrow, deep fins can be a bit twitchy; the rudder is positioned a little deeper than is often found and will thus possibly gain in effi- ciency (less top edge loss, for one thing) and a combination of the shallow skeg, narrow fin and powerful rudder could well produce a hull which turns precisely and, equally if not more important, stops turning when required. The hull when draughted to come in the displacement range considered has a w.|. beam of only 8.6in and a very gentle rocker with a waterline of 413in, however, the waterline increases noticeably when a fair heeled, and the fore overhang allows margin of reserve buoyancy to combat the bow-depressing effects of a high rig when running. A weight break-down based on styrene hulls (and some grp ones) indicates that at least 5$Ib should be available for lead, say 56% of total weight, and this has proved adequate on other RMs if carried reasonably low. Deep draught has its disadvantages fram an operational standpoint — some lakes just aren’t deep enough — but may in fact show a slight gain in overall efficiency in controlling leeway as well as restricting heel. A tall rig is necessary to reach clearer, stronger wind and to reduce variation in the fore and aft position of the sailplan’s centre of effort, which is what may cause twitchiness with a narrow fin. High aspect ratio sails are in any event aerodynamically more efficient. Other factors were taken into consideration; for example, a nice rounded hull can be adequately stiff with thinner material than one with flattish planes. Vacuum forming should avoid undercuts, so if the plug has vertical sides and the shell formed on it has the top edges pinched in slightly, it is easy to mould, stiffer when the pinching-in stresses are introduced, looks attractive, and reduces (fractionally) in/out wedge difference. The hull was designed to cut down on the amount of material by reducing freeboard, and a deck was drawn with raised areas providing stiffening and introducing a splashboard, cockpit outline etc. Internal structure was minimal — one formed bulkhead which positioned the wood reinforcement strip for the fin, which itself was a two-part moulding with a hollow bulb into which lead shot or trimmings could be introduced to bring the boat to a standard displacement figure. The bulkhead also took compression loads from the mast keel. All in all, it seemed a fairly satisfactory attempt at a nice-looking lightweight RM which met manufacturers’ requirements and could well prove popular with cus- tomers especially since it seemed pos- sible that it could be in a customer's hands, complete with one suit of sails but minus ballast and radio for only about £35. However, one of the criteria subse- quently adopted by the MYA fora possible one-design was that it should not fit an existing class, so exit Marcie. On the other hand, there are a good many model sailwho build for pleasure and ing enthusiasts who might think the design slightly less inelegant than many modern Ms; a sur- prising number of these seem uncon- cerned about factors such as design weight and so on. The drawing was recently dusted off, by request, and examined from the viewpoint of a wood built proposition. The main snag seemed to be the target displacement, wood hulls usually coming out a little heavier for the same impact resistance, but with the short waterline, overhangs, and the rounded section it seemed likely that sinking a bit deeper would not have serious effects. In fact, an extra two pounds sinks it around jin deeper, lengthening the waterline to 443in, without upsetting balance drastically. Since itshould be quite easy to build a wood hull and fin for 34lb instead of the 2; originally intended, there is extra available to go into the lead, enabling the boat to carry its sail longer and therefore increasing performance in, particularly, the higher end of the windspeed range. A 12Ib Marblehead is not uncommon nowa- days. It might be thought that if the boat is likely to perform better at 12lb, why not design it at that in the first place? The ans- wer here is that it is virtually impossible to design for the best performance under all conditions, and at least as many races are sailed in light winds as in hard blows. A boat which performs in very little breeze can always reduce sail for strong winds, but a heavy weather design cannot increase area when the wind falls light. Rightly or wrongly, the original design aimed for a boat which would be affected by the lightest breeze; when a group of yachts is lying becalmed and a waft of air arrives, the ones which keel first start sailing soonest. Such a boat will not carry so well when a breeze dies away, although the narrow hull helps in reducing wetted areas and thus resistance, so that a light and narrow hull will probably carry on a little further than a wide one of similar weight. It might also be necessary to change sails down earlier, at, say, 10mph instead of 12mph, but this does not mean that the boat will sail slower. A common misconception is that changing from, say, 800 to 650sq in means a loss of drive, but at an excessive angle of heel the projected area of the top suit is no more than the projected area of the second suit at a more moderate heel; excessive heel can alter the hull balance and make a boat crank, so that a boat will sail better and probably faster over a course, if sail area is reduced at the correct time. Light weight is no handicap over most of the sailing range, proved by the success of lightweight A boats which also incur a sail area penalty. A heavy boat may have an advantage to windward in strong wind, but off the wind the lighter boat is usually faster. In medium winds there is not a great deal in it, and in light breezes the lightweight can be at an advantage in beating, running and certainly reaching. This is a topic which can be debated endlessly, like so much in sailing. The truest statement is probably one made at the recent Boat Show, — ‘In the end, it all comes down to the nut on the tiller’. Run by enthusiasts stocking good range of boat kits, materials and accessories. Radio by — Futaba, Sanwa, etc. 47” “WATSON” lifeboat at 1” to 1ft scale. Hull and deck (bonded) plus superstructure as illustrated, moulded in scale colours, £49. The latest in our range of hulls with drawings. Send SAE for our fully illustrated lists. J. B. MOULDINGS Springfields, Penisarwalin, Caernarvon, Gwynedd, N. Wales “sEXPORT ENQUIRIES — MODEL EXPORTS August 1980 Kits by — Aerokits, Lesro, Graupner, Robbe, etc. All makes of engines and accessories. Kit building service - PROMPT MAIL ORDER Access and Barclaycard accepted 120 GLEDHOW VALLEY ROAD, LEEDS 17 Tel: (0532) 684309 499 other skipper twice, as a rule. All results counted, as of course the more results you get, the fairer the final positions will be. This schedule also positioned the races very evenly through the day and enthusiastic response for the day’s sailing came from all ten of the clubs that had entered. The wind was due south and gusted and swirled down on to a square course divided into two sailing triangles, givng legs of the course on all points of sailing, a very interesting course. Danson went home with the most club league points of 79, followed closely by New Forest with 78. The final individual positions are below. It was nice to see three “own designs” taking home league points. Points The Andrews’ Whirlwind winch described in text. ©.) ae c"eo 1 2 3 4 Tim Fuller Tony Owens Peter Freeman Chris Dicks New Forest 247 Danson Trapper fl Danson Trapper Il Clapham 247 5 ChrisEagle Cheltenham Jrapperi// 21.5 6 7 8 Robert Owens Ray Belding Norman Curtis Danson New Forest Woodley 9 10) 10) 12) Mike Belding Vic Cooney Dave Robinson Don Forster New Forest Woodley Chiltern New Forest Trapperli Own Design Seahorse Iii Seahorse /i/ Trapper Ill Own Design Trapper //l 24.5 27.5 30.00 32.00 33.00 33.00 36.75 Woodley Seahorse ill 36.75 12) Jeff Hoer 12) Dave Croxon From Our MYA Correspondent shop facilities), (d) an adequate performance (i.e. not too slow and unexciting, and capable of sailing in a variety of wind strengths) and (e) almost certainly most important, of scale-like appearance. It is a fact that a sizeable number of those who build a non-class kit for sports sailing develop an urge to race at at least club level and move on to an RM. To meet a newcomer’s interests, the MYA at present offers the A or RA, which meets (d), the 10r or R10R, which meets (d), the M or RM, which meets (d), begins to meet (a) and may even beconsidered by some to approach (b) and (c), and the 36R or R36R, which could meet (a), ° (b), (c) and (d). The 36s, however, have not proved very popular or perhaps have lacked promotion, at least until the recent advent of the Mickey Finn. None of these classes is less than 45 years old, although there have been occasional modifications to update them. The only post-World War 2 class to achieve a real degree of popularity and, now, international acceptance as a one-design is the American EC12m, a 5ft scale model of a full-size 12m project; this boat meets (e) and approaches (c). It would seem, therefore, that the introduction of a smallish, inexpensive, simple model of good all-weather performance and scale-like appearance could well be useful to attract newcomers, not necessarily as MYA members initially, but certainly pointing them in the right direction. If it was introduced as a class, in two or three years’ time a design may have established itself as the most successful or popular and be worth a manufacturer's consideration as a kit, in which case a gradual switchover to making it a one-design class could take place. As things stand, if such a boat appeared and at least 50 were being raced by not fewer than four clubs, the MYA would accept a proposition for its adoption as an official class. It might be thought that this is a little cart-before-horseish, and that the Association might profit by giving a lead rather than. sitting back and waiting for things to happen to it. If, of course, the argu- August 1980 = 9.75 10.75 16.25 19.75 Decoy Own Design 36.75 Mr Frank Parsons from Nylet came along to present the prizes to the first seven skippers and congratulated New Forest on having such a splendid sailing venue. ments put forward are valid; the most cogent of these is the scale-type appearance, and evidence for the modern trend to scale can easily be seen in virtually every other aspect of modelling. In a sentence, scale-type models attract people, andthe more people who are attracted to sailing models the greater the potential membership of the MYA. Dunkirk Although a full report has not been received, the Dunkirk meeting at the end of May was, we hear, very successful, with entries just topping three figures and a superb array of prizes. The one disappointment was that only four countries were represented, but one of these scored a notable first for the meeting — a Chinese team competed! )here were three skippers and a team manager, and the hulls were built of balsa, filled with inflated balloons. Nylet Trophy The Nylet Trophy was sailed at the New Forest Radio Yacht Club on the superb waters of the Kingfisher Country Club. The weather on May 11 was sunny and warm with the wind varying between 10 and 20 knots, providing a very pleasant and exciting day’s sailing for 30 com- petitors. The Nylet event has been promoted up the league scale to an important district level and it was in fact the first league event to be held on the 50 acre lake of Kingfisher Club by New For- est. A launching jetty and sailing platform had just been completed to enable skippers to take full advantage of the excellent facilities now offered for sailing, while the lawn and clubhouse provided excellent views of the racing for wives and families. Trevor Reece, commodore of Poole MYC, was the OOD, and as with all Southern events so far this year, a schedule racing system was used, the computer readout being provided by Dave Robinson of Chiltern MYC. It involved 8-yacht racing with every skipper getting 8 races during the day and meant that skippers sailed every Lighter There has been a trend over the last two or three years towards lighter boats and, particularly, lighter radio equipment. One winch which has played a part in this move, but has had little publicity, is the Whirlwind, developed originally by Dave Andrews of Leicester for his own use and now extensively used by many regular competitors. So often an individual with a good one-off product is prevailed upon by clubmates to ‘make me one’ and ends up as a manufacturer! The Whirlwind is in appearance rather like a deepened Futaba servo, the deepening holding extra gear reduction stages of robust construction, ending in a ball-raced output shaft, and the odds and ends of electronics needed. This has the effect of putting the total weight of the winch up to 2.90z; the body size is 1.7 x 0.9in with a depth of 2.3in, so that the whole thing is a quarter the size and a quarter the weight of some winches. Further, it can be supplied in separate power supply form or to run off the receiver battery pack, making a very compact and very light (100z) installation possible. Power supply is preferably 6 or 7.2v, and the size of the winch belies its power; stall current is 1-1.5a, depending on voltage, and pull is roughly 10lb on 7.2v. Travel with the drum (spool) provided is 11—15in in 2—23secs, resolution within 2 p.c. and idling current 30ma. Efficiency has been proved by many examples used in all wind strengths over at least three seasons of hard racing, and the maker's practical experience is recognisable in the care taken to waterproof the case screws, wire outlet and so on. The winch will work with the most modern three or four wire systems and will arrive with matching plug etc for specific equipment if make and model are stated exactly. Brief but useful installation instructions are included and there is a one year guarantee. The price? a modest £37.95 inc VAT and postage, and the address is D. H. Andrews, 49 Aberdale Road, Leicester. 527
