Model Maker: Volume 5, Issue 57 – August 1955

AUGUST 1955 REGULAR ra| me [a4 Lu LL. ‘ed SPACE i MAKER MODEL VISITS DOVERCOURT FOR THE 1955 NVIPARSERR IM! © ID 18 lh T HE Model Maker Trophy, for novice skippers, was this year held at Dovercourt, on June 17th/18th, for 36in. restricted yachts. Despite the attractions of the venue and the excellent organisation which had been put in by the Dovercourt M.Y.C., the event drew only seven entries, a very disappointing number after the way in which this trophy’s contestants had snowballed in previous years. Scheduled for 10.30 a.m. on the Saturday, the start of the race was delayed for a time in the anticipation of the arrival of further competitors, but when it became evident that no more could be expected, the O.O.D.., Mr. C. Seabrooke, decided to get under way and sail two complete rounds. The showed stiff sea skippers breeze that soon third or even fourth suits were desirable, and after a few runs most spinnakers were reefed well down. While beating gave little trouble, some difficulty was experienced when running; least troubled was Catania, whose nice balance of sail and duck-ish bow gave her extra speed while other boats were burying their noses. So choppy was the water that Sprite, hatch trouble, suffering from shipped enough to sink her, necessitating the borrowing of a child’s paddle boat for salvage operations! The scoreboard showed Catania opening a good lead, a position maintained through to Sunday, when similar weather conditions with, if anything, a _ stronger breeze, were experienced. Most skippers had by this time got the measure of wind and water, however, and some very close boards were sailed. The most exciting Anti-clockwise, from the top: 1. Just as the yachts need water, so do their skippers need tea. Here reinforcements arrive! 2. Gazelle and second-placer Rondo ready for a beat. . Media, herself not looking too happy, passes all that showed of Sprite after her unfortunate foundering 4. Reefed spinnakers, as on Sprite and Eriska, were the order of the day, despite the apparent calm in the lee of the bank. 5. Fair young paddle-boater comes to the rescue and restores a wet but non-the-worse Sprite to dry land! WROP Ely WAC RP run of the day was between Rondo and Sprite, who kept within inches of each other for the whole length of the water. The gap closed as they approached the line, and Sprite won by no more than a bumper; a fraction of a second later the boats touched. As Sunday wore on, the wind began to drop and_ skippers changed suits. Catania’s commanding lead narrowed slightly, but she retained her position to finish an easy first, with Rondo second and Chad II third. Councillor No. 1 2 Be 4 5 6 7 Mole, the Dover- court club’s chief protagonist in local affairs, presented the prizes at the close of what was considered to be a very pleasant and well-organised meeting which needed only a slightly larger entry to make it a four-star affair. Yachtsmen will be interested to learn that arrangements are already in hand for the 1956 race for this trophy; the water will probably be Bournville, the event will be for Marbleheads. With such a central venue, no rail strike, and what is now the most popular Catania Rondo os. —1Ghad fi. Eriska Sprite #£xMedia Gazelle yacht class, a anticipated. YACHT 836 904″ tere: 903 603 672 709 model bumper entry can be confidently SKIPPER Re T. J. D. E> G. TOTAL eritchard=-—… Harris BAe Ri vOxley 4… Tomlinson … Eadbrook.” … … Swinyard T. Chapman … pap e6 Ha nn ce A £3 95 86 13 64 60 23 19 Clockwise, from top left: 1. The camera catches Catania showing an amazing amount of fin 2. The winner ends a run in real ripsnorting fashion. 3. Two Model Maker designs, Lancer and Razorbill, in Chad II and Eriska. 4. Calmer airs attended the last hours of the race; here Catania glides in by a street on her last round. 5. After the race, Skipper Pritchard dressed his winning boat in her top suit for this picture. 6. Dovercourt’s Hon. Sec., Mr. Chapman lends a hand with Gazelle. 7. Some idea of the uninterrupted sea breezes can be gauged from this between-round picture. Third boat, Chad, in foreground. 8. Councillor Mole presents the trophy 1. Col. Taplin (head hidden at bottom!) watches his boat head for disaster and a brick wall at Hove! 2. Prettiest “commercial” at Poole—Dudley’s Nic~ Nac beautifully built from a Veron Marlin kit. 3. Most impressive engine room—C. Townsend, Victoria Park, entered this grand 30 c.c. own design powered model at Poole. 8. George Nurthen’s Jone at Poole—still in a class of its own amongst the “big boys’. 6. Dick Box, Eastbourne, with his model at Hove and the club’s communal steering gadget. 7. J.C. Hogg, pioneer yacht r.c, enthusiast, with his Marblehead at Poole. 9. Fast even at half speed Max’s” Sirius Star goes through the buoys at oole. 12. Townsend starts up his 30 c.c. engine with a single pull. Radio control regattas provide far more in pictures than they can in words, so that we trust readers will EV a E WwW accept this pictorial report of recent meetings at Hove Lagoon and Poole in lieu of a more formal account. Max Coote provided the pictures from Hove; our own photographer the Poole pictures. We have more to come for this latter event, again from Max Coote, and they will be appearing next month. A lot of new boats as well as trusted old favourites have made their appearance this year and the switch over to reed operation is now in full swing. 4. Verney Jnr. makes up another father and son team with father Bill Verney. 5. Max Coote, nautically bearded, handles his American Babcock transmitter. 11, Everready rep Firmin has a last minute adjustment to his Fibreglass r.c. yacht. 13. Eastbourne their boats Brighton at radio Club members Hove. and 15. Popular dealer Arthur Sallis with his Wavemaster at Hove. 16. Bill Verney’s boat at Poole, another Channel Islands Special powered job. 10. Cummins’ W avemaster—another expert who has succumbed to this little design. 18. Cummins with his control stand, successful as ever, and certain as income tax. MODEL MAKER to type of wood used. STARTING ON THE RIGHT TACK tected. THREE: FITTING OUT (1) PAINTING & VARNISHING BY D. A. MACDONALD (1) FrOoR the purposes of this part of our discourse, let us assume that the reader is now equipped with a hull designed and the yacht, and equip it to a satisfactory for racing. Let us first consider hull itself. This is either newly built Standard the and awaiting painting and/or varnishing, or is an existing hull. satisfactory but in need of re-decorating. Unless the owner is absolutely certain of the existing paintwork and of the condition of the hull beneath, it will be advisable to strip it down to the bare wood, a process which is reasonably simple with the aid of modern chemical paint stripp ers and suitable scraping tools. We have, then, in both cases, a bare wooden hull to be painted and/or varnished. The first thing to do is to have a really good look at it, viewing it critically from all angles, and gettin g one or two friends to do the same. If there are any flaws in the form of the hull-bumps , flats or minor irregularities, these must be removed. No attempt should be made to put a finish on the hull until it has passed a careful scrutiny, aided by checking with a suitable batten laid along the hull in as many positions as possible. When it appears perfect, it Should be put away for a few days, and then examined again. Almost certainly it will be found that one or two things have previously escaped notice and these should be dealt with. Only when the hull has passed a final inspection should the finishing proce ss begin. The inside of the hull should receive attention first. For this purpose a robust yacht varnish is best, and two thin coats (diluted with about 40 per cent pure turpentine) should be applied with thorough brushing, allowed to dry and soak in. From three to five full- strength coats will then be needed, according 456 which has already abrasions. To provide a surface suitable for easy propulsion, i. resistance. part II, in possession of a satisf actory comWe can now proceed to fit out existing hull To protect the huli against the ingress of water and against minor bump s and (2) built to conform to the requirements Iaid down in part I, and is, as a result of our findin gs in plement of sails, plus some knowledge of how An been varnished inside will no doubt benefit from a couple of coats of varnish to ensure that it is well protected. Turning now to the exterior finish , I said in my opening remarks that the purposes of the paint and varnish are:— AN INTRODUCTION TO MODEL YACHT RACING PART to use them. If, after a few days have elapsed since the last coat, there is no trace of grain structure left on the inside surface, the huli can be considered adequately pro- with a low. skin Both these results can be achieved by either paint or varnish, provided that the material is suitable for the purpose. The methods of application depend largely on the type of material used, and the gener al principles of painting and varnishing boats have been adequately described in othe r articles. I do not therefore propose to give any general advice, but I wili describe a method I have used successfully for achieving the required results quite simply, and with great economy in weight. Assuming that the hull has had its final rubbing down, (with the fines t grade of glass paper) it is given two coats of “Valspar” clear varnish, thinned down with about 40 per cent. White spirit (turps substitute ) and brushed well in. The white spirit is preferable to pure turpentine for this tub down coats is with type of varnish. No. 0 glass desirable. carborundum paper should be used, with but not wet. After a further light rub After paper the A light between second coat, (about No. 320 grade) the hull slightly damped the damp has dried off, down with glass paper should be given and all traces of dust removed, The next coat is of full-stren gth Valspar, the varnish tin being heated by stand ing in a bowl of hot water or before a fire until the varnish feels distinctly warm to the touch . The brush should be washed thoroughly in “Surf” and warm water, and preferably suds over the previous night . should to soaked be dried, and rinsed in remove remaining water. in the Before use it white spirit This coat of varnish should be applied quick ly, and allowed to flow on with a minimum of brushing—in fact, applied like cellulose lacqu er. All coats so far should have at least 24 hours to dry. Rubbing down after this coat should be AUGUST, gentle but thorough, again with No. 320 paper, and the job should be kept thoroughly wet, preferably with a little soap added to the After drying, the hull should be water. degreased, by wiping with a clean rag soaked in white spirit, and dried again with a soft cloth. This coat and its subsequent rubbing down should be repeated. The result should be the complete filling in of the grain of the wood, and the boat should now have a good protective undercoating for the later stages. If the boat is to be bright varnished, the remaining coats will again be varnish, but if it is to be coloured, we now change over to Valspar lacquer of the desired colours. The owner must, therefore, decide on his final finish, and he has a wide choice in the following : — (1) Bright varnish all over. (2) Bright varnish with a coloured boot-top. (3) (This is a very attractive finish for a mahogany or cedar hull). Bright topsides, coloured underbody. (With or without a boot-top for good measure). Painted one colour, with contrasting boot-top. (5) Two colours, dividing on the load water line. (Again, with or without a boottop). _ For the purpose of our description, let us assume that the most popular colour scheme will be used, i.e., two colours, dividing on the load water line. Before applying the colours, the last varnish coat should be given several days to soak in. It may then be found that with some porous woods, a further varnish coat will be necessary to ensure that the grain structure is fully covered. If in doubt apply the extra coat and rub down as before. The next step is to mark the load water line. To do this, stand the boat deck down on a level table or floor, with chocks under bow and stern. A scribing block is required to mark the L.W.L., but if this is not available, one can be improvised with an ordinary marking gauge, with the sliding portion moved to one end to act as a base, and a compass tied to the vertical post as in Fig. 1. The chocks should be adjusted so that the L.W.L. endings are the same height above the table, as indicated by the scribing block. Care should be taken to ensure that the boat is not tilted (4) to one side, as this will result in a wrong L.W.L. being marked. Using the scribing block, mark points on the hull every inch or so all round, at the same height from the ee 1955 table as the L.W.L. endings. Check that the midships freeboard indicated by this L.W.L. marking is the same on both sides. A masking tape has now to be put round the L.W.L., to allow for painting the underbody of the hull. The best masking tape I have found so far is “Lassovic’” (Adhesive P.V.C.). This is permanently sticky and can be pulled off quite easily after painting. It also gives a more perfect line than anything else I have tried. The next best is ordinary gummed brown paper strip, but this entails laborious washing and peeling off afterwards. The best width for the masking tape is about in. Two coats of Valspar lacquer of the chosen colour should be applied, heated as before, to the underside of the hull, with the same rubbingdown process between coats. After the second coat has been given at least 48 hours to dry, the masking tape should be removed. Remove any traces of paint which may have under-run the tape, and any of the tape adhesive left sticking to the hull, by rubbing off with a small piece of rag soaked in pure turpentine. A new masking tape should be applied to the underbody, and the topsides painted in the same way. The masking tape is again removed and any surplus matter underneath rubbed off as before. The whole hull should now be rubbed down very carefully with No. 400 carborundum paper, keeping the job thoroughly wet, until a perfect matt surface is produced, and no rough edge is left where the colours meet. A final coat should now be applied to both topsides and underbody using the masking tape as before. The paint for this coat should be thinned with about 20 per cent. spirit and strained through two thicknesses of silk stocking material. It should be applied warm, as before, with a minimum of brushing. Whereas a normal type of paint brush (I find a “Harris” Standard quite good enough) will serve for all previous operations, a soft lacquer brush is best for this purpose, thoroughly soaking and cleaning it before use. A cheap brush which does this job very well is one known as the “Macson”. obtainable at Woolworth’s. Due to the thinning of the paint, the finish provided by the final coat will be semi-matt. The final touch is given by burnishing the hull with a slightly abrasive polish, e.g., “Simoniz” Kleenoff paste. after which the hull should look like a piece of fine china. One word of warning—do not forget (as I sometimes do) to include the rudder in all painting operations. (To be continued) 457 TAKER) RAKED H. B. TUCKER EXPLAINS MIDSECTIONS THE WHYS AND WHEREFORES OF RAKED MIDSECTIONS IN YACHT DESIGN WITH THOUGHTS ON CIRCULAR ARCS N a recent article, I referred to Raked Midsections. In consequence, questions have been received about them, and it has been suggested that a short article on the subject might be welcome. In a displacement type boat, the point of Greatest Body Depth is placed either at the middle of the L.W.L. or a short distanc e ahead of it, the latter being common practice in modern designs. Locating the G.B.D. ahead of the centre of the L.W.L. gives shorter and steeper forward profile and buttocks, with longer and less steep after profile and buttocks. This is of benefit on all points of sailing, but particularly when running. On the other hand, if the G.B.D. is too far forward, it will have a deleterious effect on windward work, though possibly it will assist planing. The point of Greatest Beam, however, is a different matter, as this can, with advantage, be placed somewhat abaft the centre of the L.W.L. This enables the designer to get a balanced and sightly deckline, with a transo m instead of a pointed stern. Not only does this give valuable additional deckroom aft, but also assists us to flatten the run, which benefit s performance off the wind. It must also be recalled that on heeling, a boat lengthens more aft than forward, and our object must be to make the boat fit the hole in the water that she makes in her forward passage in such fashion that there are no cavitation areas at any point on the skin. The latter phrase may require some explan a- tion. I recently had the Opportunity of seeing several model hulls tested in a waterstream tank. Amongst these was a model with hollow bowlines. The waterstream bridge d the hollows leaving an area of the hull which was out of contact with the water. did this produce eddies,. bound Not only to affect her speed, but this cavitation area was not doing its share in supporting the hull. The lesson of this is that the designer must shape his hull as advantageously as possible to the if we course the water will take round the hull. The reason the entry should be shorter and bluffer consider than the delivery is obvious the different functions of her bow and stern. The bow meets water that is not 462 in motion, and has to push this aside. The delivery has to deal with water already in motion, and to replace that water where it came from with a minimum of fuss and dis- turbance. pressure In connection with the latter, back- has to be considered. A_ troubled wake is evidence of back-pressure, and in creating this, energy is absorbed that otherwise would be expended in forward propulsion. Having placed our G.B.D. ahead of the midship section, and our Greatest Beam abaft it, Our “Master” Section, which includes the greatest measurement of every longitudinal line in the ship, must be a raked section. The points which fall on this section are: — (a) Greatest Beam on every W.L. in the (b) canoe body. Lowest point of profile of canoe body, and of every Buttock. (c) Widest point of all Diagonals. The actual “Master” Section is taken out thwartships, and not in its own plane. Thus, though this section entirely governs the design, it does not appear on the final lines, and is not an actual thwartships section. If, however, we drew the Master Section in its own plane, made a mould from it, and erected this, raked aft, with the centreline on the position of G.B.D., and the point on its periphery that represents the Greatest Beam point at the position this falls on the plan, it could be used to shape our boat, and at the same time would locate the positions detailed under (a), (b) and (c). To do this on our design, we spot the position for the G.B.D. on the centreline in the Waterline Plan. We likewise locate the posi- tion of Greatest Beam. These two points are joined by a straight line which represents our raked midsection, raked on a vertical axis as explained. It is also possible to rake the section on a horizontal axis. To do this, spot the exact position for the G.B.D. on the sheer plan, and the position of Greatest Beam. Join these two points with a straight line, which will represent the section raked on a horizontal axis. This is not as satisfactory as raking the section on a vertical axis, and far more complicated for the designer. Nevertheless, AUGUST, 1955 Correspondents have pointed out that in the “Circular Arc” System of designing, the master section is not raked, and both G.B.D. and Greatest Beam fall at the centre of the L.W.L. In this system, the delivery is an Likewise the exact replica of the entry. in-wedges and out-wedges are identical, the height of the M/C remains constant at all I have seen several boats designed under All of these this system actually sailing. were admirably handled. Further, they had admirably chosen dimensions. The latter is a very important point in all Classes that give scope for variation in dimensions. Actually, all the M.Y.A. Rating Rules do. except the 36-inch, which limits the main hull dimensions but does not measure S.A. Naturally, everyone of the boats in question troid”. put up a good performance. there is nothing to stop him using this method if he fancies it. angles of heel, and the yacht is a “Metacen- The main advantage of this system of design Another advantage is is perfect balance. that it requires no knowledge of naval architecture, and anyone can design a boat by it. Further, it is the lazy man’s ideal method as it takes about as many minutes to design a boat this way as it does hours by normal methods. As regards balance, it is possible to design a boat by normal methods with the same academic perfection of balance as the circular arc boat, but it has been found that no ill effects ensue if a tolerance of movement in a fore-and-aft direction of the Centre of Buoyancy up to 4 per cent. of L.W.L. I, myself, work to a Length is permitted. tolerance of + per cent. On a L.W.L. of 50in., this represents a movement of 4 in. This, of course, applies to Volumetric Balance. Whether the M/C Shelf System of balance, which is additional to the Volumetric Balance, is any more accurate or gives further information is a debatable matter, which I cannot discuss here. As mentioned above, the in-wedges and out-wedges of the Circular Arc boat are equal, and the height of the M/C is constant. Hence there is no reserve buoyancy in her topsides, and since the M/C does not rise as she heels, her form gives her additional stability as the heeling angle increases, and she depends entirely on the artificial stability given by her ballast. Most experienced designers prefer to use a section that gives an easy initial heel in light breezes, but becomes increasingly stiff as the breeze freshens and the angle of heel increases. This is impossible with a circular arc section. Earlier in this article I explained the advantages of making the entry, and delivery, of different lengths and forms. This again is impossible with the Arc Form boat which makes the forward and after parts of the canoe body exactly alike. showed faultless balance, and, in consequence In writing this article I have been careful not to express any personal opinion, and confine myself entirely to proven facts. From these, the reader can form his own opinion as to whether the advantages of the Circular Arc System of designing outweigh its disadvantages, and also on the merits of using a Raked Midsection. settien LET’S MAKE A LOCO BODY (Continued from page 458) Just a word as to the use of very small taps. To avoid heedlessly breaking them, no force should be used when screwing in a clock-wise direction into a tapped hole, and after two forward cutting turns, three anti-clockwise turns should be made to remove the swarf Then advance made by the cutting turns. cutting turns extra two take and four turns in the forward direction, and follow them by four anti-clockwise turns; continuing thus until the hole is fully tapped. A No. 55 drill should always be used for a No. 10B.A. tappinz hole. and a No. 50 drill for a clearance hole. Don’t try tapping a too-small sized hole, it spells a broken tap, and taps are not too cheap. Next month, painting, lining and lettering the X-14. 1955 10-RATER CHAMPIONSHIPS, BIRKENHEAD Dick Priest, winner of this event, tells us that our report gave dimensions for the old Tornado, which was wrecked hitting the bank in a terrific plane at Bradford. The new version has the same fittings, sail number, etc. but is a new hull to an extreme design by Dick. Correct data should be 1328 Tornado, designer B. H. Priest, owner B. H. Priest, builder J. Lace, 1.0.a. 77.5, l.w.l. 58.75, disp. 271b., S.A. 1017, beam, 10.5 Apologies to Dick and all concerned. 463 e e Readers write… The’ elegant little plastic walletcontain- ing chrome vanadium double – ended are, by the nature of the medium they use, forced to increase the efficiency of their craft despite the R/C equipment. So I will look forward to seeing some wise designer using the weight of his R/C equipment to the advantage of his yacht’s performance… .. Vy Yours faithfully, D. R. McSweiw B.A. spanners in the hard-toget model sizes will which be pre- sented to our *‘*Readers Write” cor- respondents. “Husky” M.M. Class Registered Dear Sir, I have now completed the M.M. class model yacht to the design of Husky, by Mr. MacDonald, which appeared in a recent edition of MODEL MAKER. This is the first model yacht I have ever attempted but I have derived infinite pleasure from building her, and hope to have many happy hours sailing her. The method of hull construction I adopted was as follows: tin. resin bonded ply formers (cut out to +in. wide) with tin. balsa planking; keel was built bread and butter fashion from silver spruce zin. “slices”. After casting and fitting lead to keel and keel to hull, the whole was covered with a single layer of “Bondaglass”, then well rubbed down CE ___ and filled and painted with Brushing Cellulose; the result is truly magnificent and well worth the labour involved. The rigging and vane gear is as given for Water Baby znd Sea Urchin except that the mast is Zin. Birmabright tube instead of 4 in. as stated. The weight is 51lb. 5o0z., a little above Mr. MacDonald’s weight of 5 Ib. Will you please allocate a number for my sails. Incidentally, I am calling her Karo. Yours faithfully, RONALD NorGRove. Hyde, Cheshire. “The Cart” and “The Horse” of Radio Control Dear Sir, After reading Mr. J. M. Fitzgerald’s letter on the Radio Controlling of Yachts, I was left with the impression that he saw no use for it, as he himself did not get any satisfaction out of it. As this appears to be the case with several Yacht enthusiast s. a special course should be laid out. so that a reasonable degree of skill is needed to navigate it. Mr. Fitzgerald emphasis would appears move to from believe design of that “the yacht to design of radio”. I do not believe that this would be the case, for aeromodelling enthusiasts who use R/C do not spend their time designing radio equipment instead of planes, in fact they usually use commercial equipment He also states that the use of detriment of a yacht’s performance. as a spur to any yacht designer. radio is to the This should act All Ayrshire Col. Bowden has the Very Last Word! Dear Sir, In view of the unfortunate attacks by Mr. Tucker and Mr. Macdonald in the May and June MopEL MAKERS, in connection with my articles, class boats. and my model yacht book, it is only fair to accept the opportunity of correcting*some of the inaccuracies and false interpretations contained therein. I entirely disassociate myself with the Tucker (May issue) interpretations of my aspirations. his version of which is false reasoning from beginnin g to end. Any experienced sailing man will realise that I suggested :— (1) That a planing model hull is now a real pos- sibility for certain purposes, particularly is this so since Uffa Fox’s 24 ft. planing, non-sitting out, sailing cruiser with twin side-by-side hydrofoil keels has shown remarkable windward qualities—vide “Yachting Monthly,” April, 1955. (2) That fully displacement hulls like the “xX” Class, the “Y”, the Dragon, the 5-5 metres, etc., etc.., all have a slight measure of unbalance in hull lines to provide quick manceuvreability combined with good windward work for racing tactics, (3) That radio racing models of the future will also require this same certainty of quick manceuv re even in a squall, as opposed to the more grooved course of the Vane or Braine steered model which pursues its directionally stable course to the target, having, quite correctly, a symmetrically perfectly balanced hull. (4) The owners of the Flying Fifteen term their boats light “Keel Boats”, vide “Yachting Monthly ” of May, describing this class. Also the “X” One Design Class, described in “Yachts and Yachting”, 23rd July, 1954, is, of course, a full displace ment yacht with a heavy keel. Therefore, Mr. Tucker’s remarks in this direction do not make sense. (5) I deeply deplore the Tucker expressions, such as ‘““Ham-handed radio control”—“Sneaking round buoys by radio control”, etc., etc., which embellish his attacks on radio racing. This is a new branch of model yachting, going through its teething trouble, but will be a power to contend with in the future. (6) Regarding Mr. Macdonald’s attack on my book, and his expressed wish to “throw overboard the aerodynamists”, I would remind him that every modern feature in the racing yacht today, too numerous to list here, in connection with sails, sail- ing technique, hull, and the keel, is the direct result of sensible application of aerodynamics. (7) Macdonald tells us that the term “upright sailing” has been abundantly disproved in practice. Its correct application is described with sketches in my book “Model Yacht Construction and Sailing’, which brought it to notice in the model world some years ago when it was not fully appreciated. It is now aeromodellers 464 ——_” AUGUST, known by everyone to mean sailing very closely upright, even on a displacement hull when going to windward, and even in a strong wind, and as near upright as no matter when off the wind. Finally ,as Mr. Macdonald has attacked my book, I would remark its fourth revised edition is nearly complete dealing with aerodynamics and _ hydrodynamics of sail and hull in simple language as well as Sailing technique, fibreglass construction, radio control, etc. The despised aerodynamics will explain why and when a jib can be used or dispensed with. Why a genoa has developed. Hence why my special rotating cantilever stiffened rig has no jib for single- handed sailing. It is now being tested out on a 54 ton sailing cruiser, and Mr. Macdonald, it has a quickly variable camber to suit different wind speeds, although you tell readers my sail has no camber! Yours faithfully, C. E. BOWDEN, Sandbanks. This correspondence is now closed—Ed. Brickbat Department! Dear Sir, I would like to point out to readers of the MODEL MAKER the fiollowing two small errors on the plan of the remote control Aston Martin D.B.2 (page 201, April, 1955). They are both concerned with with a Dooling 61 “B” (11:1) which was very successful—but the car which at present holds the F.E.M.A. European 500 metre record at 199 + K.P.H. is, I believe, fitted with a 61 “B” with the ratio reduced to 9:1. So, ye tikes yer choice! Doolings made three types of head:— Type “A”—with the projections into the cylinder sharp. “High Compressions”—similar, but with .008 machined off facing and projections. Type “B”’—similar to “A”, .010 machined off facing and projections, and used with liner and cylinder from which .010 has been removed. After quite a long series of experiments, I settled on a ratio of 9:1 as being about the best for most conditions—and afterwards found that much the same conclusion had been reached in the U.S.A., where the common modification to a “B” engine was to replace the head with one off an “A” engine. It will be seen that this gives an intermediate ratio of about 9:1. between the “A” (7.1:1) and the “B” (11:1). As a matter of interest, according to figures quoted by Mr. H. Frank some time ago, when 9:1 c/ratio with 1.84 gears, the fuel used was Nitro Methane and the ignition advance .190. 8.2 cjratio same gearing. the fuel used was n/m and advance .195. (1) The wire from the reversing switch to the micro-switch should, in fact, go to the other contact of the switch, i.e., it should only make contact with Cable A when the micro-switch In the extreme right-hand diagram there are two cables marked D. The lower one of these should be marked B and connected to B on at least Iam in good company ….. Sr See oe In a series of articles there are many details which have to be left out, so for my sins of omission ft the other diagram. I hope this information will be of assistance to Wolverhampton. d in which I found that the engine definitely held its tune longer when the rings were pinned—and I prefer to strip as rarely as possible during the season. Pistons modified by Fox in the U.S.A. are pinned, so is depressed. your readers. using 20% With 40% Mr. Other’s tests with broken rings are interesting. Like Mr. O., I have never been bothered by rings getting into parts, but I do know of two cases where a broken ring did scrape the liners. My preference for pinning is based solely on my Own experience, the theoretical circuit in the bottom right-hand corner:— (2) 1955 must ask the readers’ indulgence. Yours faithfully, Yours faithfully, K. SHACKLETON (aged 15). R. A. BROWNSON. Weybridge. This has now been corrected on the plan—Ed. Dooling Developments Dear Sir. It is very pleasant for a contributor to see a letter correcting something he has written—it shows that at least one reader has actually read the article! It is possibly even better when one finds that the correction was undeserved. In the June issue. Mr. A. N. Other quotes some figures for converting a Dooling 6la to a 6I1B. These figures are correct. He then states that I gave a figure of .008 as the amount to machine off the “A” cylinder head to convert it to a “B”. However, if Mr. Other will read the article again, he will find that nowhere do I mention converting an “A” to a “B”. I specifically avoided doing this, as it has been my experience that the “B” compression ratio is on the high side. and that a lower ratio has much to recommend it. I suggested that the best ratio would probably be between 9:1 and 11:1, and that it should be found by experiment on each particular engine. Mr. Other complains that everyone is vague about compression ratios. Surely this is only to be expected, since no one can be dogmatic about some- thing when the optimum figure may vary from engine to engine and fuel to fuel. I know of one car fitted NorReader fine grove’s Bondaglass armoured model Karo built from the lines of D. A. Macdonald’s Husky, which was published recently in Model Maker. 465 ih AUGUST, 1955 eg Fis A. WILCOCK CONCLUDES 64 HIS TWO-PART ARTICLE FOR NOVICE & “EXPERT “OM THE SECRETS “OF f: 7S GUYING ELASTIC = = BAND WITH VANE STEERING A reminder is appropriate at this point regarding mast position, and sail plan. It is, that when using vane steering the mast is placed so that in light airs with the rudder fixed centrally and the vane inoperative the boat will come up into the wind (in irons). Thus it is seen, reverting to gying, that to remove the effect of the vane from the first tack of the gye the boat will come up into the wind. If, at this point, the feather and counterweight can be operated to the opposite side, helm will be given to complete the turn through the eye of the wind, and on to the opposite tack, so completing the gye. As mentioned in the introduction, successful methods are amongst the innermost secrets of racing skippers. The author can, therefore, expound only on the methods of which he is aware, and the action behind them. Let us consider the “Fisher” type first, since it is the more difficult, and what will work with a “Fisher” is helpful in considering the Ballantyne. Since the Fisher motion is locked by the force of gravity on the counter- weight, it is clear that this must be neutralised to unlock the motion. The simplest gye— now using gye as noun—is the light elastic band Fig. 6. It can be connected from the counterweight to a rack on the main body as in6 “a”, or between racks on both feather and counterweight arms as in 6 “b”. In either case, if the elastic is strong enough to restrain the movement from going as far as the locked position on the first tack irrespective of the heel of the boat, she will behave on the first tack as if the vane was inoperative and will come up into the wind in a distance depending on the mast position, and therefore the boat’s tendency to come into irons. At this point, the boat shivers in a vertical position, the gravitational force is off the counterweight and feather, and the elastic should snap the vane mechanism on to the other tack. At 467 ELASTIC BAND the same time, helm is given by the new position of the feather and this should turn the boat to the new tack and the gying operation is completed. This method is not wholly satisfactory, for the following reasons :— (1) Being dependent on the mast position and the vane being out of action on the first tack, the boat has little way on it when it comes into the wind, then, although the vane snaps over and gives (2) helm for the new tack there is insufficient way on the boat to complete the turn, and too much time is wasted in coming about. Because the method is dependent on mast position and the vane being out of action on the first tack, the distance sailed before gying takes place is too dependent on average wind strength at the time, i., if the wind is light it will be slow to come about, and if strong it will be quick. It is, however, found that some timing can be achieved by adjustment to the length and strength of the elastic attached to the vane mechanism, and by sail adjustment. The action of coming about is still liable to be slow, and the fitting of a “Liverpool boy” to the jib will help. The “Liverpool boy” is shown in Fig. 7. It consists of a light elastic connected to an adjustable line, and attached between the jib boom and the Ul LIVERPOOL LIVERPOOL BOY BOY deck tending to keep the jib on the first tack. 7a shows the arrangement for a normal jib, and 7b for a radial jib boom. When the boat comes up into the wind the tendency given by the “Liverpool boy” to hold the jib over on the first tack gives head pressure to push the bows on to the new tack, and once round the wind pressure on the jib is more than adequate to stretch the “boy” and make it then inoperative. More precise timing can be obtained by using the plain main boom gye of “Braine” steering days. This is illustrated in Fig. 8. It consists of an elastic band and line with bowsie adjustment terminated in hooks similar to a “Liverpool boy”, but the elastic in this case must be much stronger. It is connected between the end of the main boom gunwhale eye opposite about halfway and the vane gear should be weakened to the point where, when the boat 1s heeled, the counterweight is capable of moving over fully to the locking position by extending the elastic, but when the boat is upright or nearly so, the reduction of the effect of gravity on the weight allows the elastic to pull it right over the other way. The only elastic the author has found to’ meet this requirement is “shirring elastic” obtainable from the popular chain stores or haberdashers. Gying is now performed by adjustment to the boomgye, lengthening it or shortening it or varying its strength. It will be found that the vane gear operates on both tacks normally, and the arrangement now on the vane gives a snap action at the appropriate moment with helm which produces a quick turn without faltering. Considering finally the Ballantyne type of gear, it will be found that the last arrangement described for the Fisher using a boom gye and light elastic on the vane gives the happiest combination. The increased feather and counterweight weights for successful operation with this type of gear will call for a stronger elastic than for the Fisher type. a ELASTIC BAND along the main boom on the windward side on the first tack. (Gunwhale eyes, of course, are fitted on both sides in this position). The length of this gye in the first place should be adjusted so that with the elastic unextended the end of the boom is just on the windward side of the centreline of the boat. While fitting and using the boom gye the elastic on BOOM GYE —__ TALE OF A TALBOT (Continued from page 453) Many models fall down badly on the “scale” of the cockpit layout. Most amazing, as the size of the human chassis which will have to sit in the car can be checked right in the model maker’s own house, how easy to sit on a box, holding a plate or round tray, in order to mock-up the room required for the driver. Steering wheels seem the pet pit-fall and mostly are far too small. 16in. to 18 in. is the normal range, on a }in. shaft on cars like Bugatti and Alfa-Romeo to 14in. on types that use a tube over the shaft. Details of Lamps, Instruments and Shockers are obtainable from the study of cars in car parks, etc.; make notes and take photographs as and when possible and build up a file for future use. Note make and type of car. 468 If in doubt use black leather for racing car seats and paint rather than plate fittings. The No. 5 Talbot shown is in French racing Blue, a light shade is correct, with race numbers in black on white discs. There is no wood in the model, the body is of brass sheet over brass frame, with wire wing stays and detailed axle assemblies. The finned effort behind the bonnet is an oil cooler and the tube on top of the bonnet feeds air to the engine. Bright parts are chrome-plated, the axle parts being left matt chrome. In common with my other models for the same collection it is in 1:12th scale, and is now in New York alongside the 44 litre Bentley and S.S.K.L. Mercedes already featured in MopEL Maker.