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AN arn olS “TARANAKI? MODEL NEW CARGO ELECTRIC RAIL l0-RATER : RAIL : ATOMIC CABIN TACK : ARTICLE IN : ON USUAL : THE OUTFIT THE JETEX POWERED CARS : MOTOR TEST : ON SUB- OLD YACHT PHOTOFLASH RACING BENTLEY LIGHTWEIGHT CRUISER NORTH : “SPACE” MODEL: FEATURES POWERED : POWERED : RE-RIGGING AN MINIATURE RIGHT RACER PROTOTYPE “NAUTILUS” MARINE STEAM BOAT p “7 RE-RIGGING AN OLD YACHT By In circle a contemporary shot is given of the cutter inits 1922 heyday — ladies’ fashions that day of can perhaps be glimpsed. Larger picture shows the yacht restored to a place of honour in the household, and doing extra duty as an ornament in between $a fol. ale occasions i linn following description of the re-rigging of an old model yacht hull may tempt others to do likewise ! Such old hulls are to be found in many an attic. The resulting boat, besides making a very attractive orna- with an expensive “bought” boat. It was decided to alter this 1922 “Hamley’s” gaff topsail cutter, whose mast and sails had long been missing, to modern Bermudan rig with Braine steering. The work was tackled in the following order: The old paint was first stripped off with “Nitromors”, the waterline being retained with pencilled dots. The hull and deck were glasspapered smooth. It was decided to shift the mast position 24 in. aft, ASTON Braine steering, the original inclined tiller and rack rudder had, of course, to be scrapped entirely. The after edge of the keel was cut to a pleasing curve. A vertical brass rudder tube was fitted just forward of the old rudder tube. The latter was knocked out; and replaced by a suitable length of dowel rod, cut off flush with deck and hull after being carefully fitted and glued into position. The mast was stepped on deck, the latter being thick and strong. The mast socket (made from an old camera tripod tube) and the adjustable step, were made as shown in Fig. 1. The combined gooseneck and kicking strap attachment were easily bent up from stainless steel sheet; and can be sprung on and off the brass wire pivots soldered to the mast socket (see Fig. 1). The aluminium mast was made 32 in.—slightly less than one-and-a-half times the 22in. waterline length of the boat. The 14in. x 5/16in. O.D. topmast fits inside the 20in. x 3in. O.D. lower mast, and rests on the jin. solid aluminium spreader, which passes through the mast. The spreader is notched at the ends and bent slightly upwards and forwards. An aluminium crane carries Fig ! THE MAST STEP BRASS T’ to give the boat a better appearance when sloop rigged. A rectangular hatchway 34 in. x 24 in. was carefully cut lin. aft of the chosen mast position. A Zin. wide hatch coaming was cut, in one piece, from resin bonded SECTION mahogany ply and screwed to the deck with well countersunk brass screws. Next, jin. half round birch beading bulwarks, merging into shaped, 3/16 in. thick mahogany pieces at bow and stern, were copper pinned into position. BRASS PLATED SPLIT PIN For to = ee oe ment, has made several adventurous open sea voyages which would never have been risked A. KICKING STRAP JUNE, 1956 CUT FROM ALUMINIUM SHEET HOLLOW RUDDER FIXING THE Boar RUDDER. BACK FORESTAY STAY | fig? -MAST JIB Geist HEAD CRANE HALLIARD HERE MAIN HALLIARD the preventer backstay clear of the mainsail roach, and also carries the main halliard block (see Fig. 2). The main boom is }+in. aluminium tube, wood plugged at the ends. All and the remaining deck backstay fittings, fittings, shroud stemhead plates, sheet horses, and the jib rack were made from brass curtain rail, sawn, filed and drilled to shape. This was a most entertaining job! A small hacksaw, needle files and drills were all that was needed. The Braine steering quadrant was cut from brass sheet and soldered to a 3 in. length of brass tube, slotted to grip the hollow, 5/16in. O.D. rudder tube to which it is bolted. The mahogany rudder was attached to the rudder tube as shown in Fig, 3. It was made thick and un-tapered so that the smallest rudder angle would have steering effect. When completed, all fittings, together with a number washers, of small assorted brass woodscrews, screw nuts eyes, and _ bolts and two brass split pins for the mast step were sent to be chromium plated. The plated eyes, screwed through the plated washers, make smart gunwale eyes and leads for the steering lines. Next, a block of 4in. balsa was carefully cut to a good push fit in the hatchway. It was then glued to a block of Chilean Laurel—an excellent light-weight wood—and the latter planed to a rounded coach-house roof shape. A small mahogany companion hatch was let into this roof; also two perspex skylights, mounted over black-painted cavities. A “samson post” of wood, with a stainless steel wire bar, plugged the original mast hole. The bulwarks were stained mahogany. The whole boat was then given several coats of varnish. The hull was finished in primrose and green Valspar, and the deck and bulwarks left varnished. Each coat was well rubbed down with No. 400 “wet and dry” paper. The 295 small rigging screws, being beyond the writer’s capacity, were the only “bought” fittings; lanyards would serve equally well. The standing rigging is all of .017 stainless steel wire, attached to strong stainless steel wire eyes passing through the mast. The running rigging and jacklines are all of braided fishing line. Experimental suits of sails were home-made and tried out. Jibs of various sizes were tried with the one mainsail. When a good balance had been achieved, which, incidentally, involved a large jib, three suits of sails were made up by a model yacht sail-maker, and a genoa as well. The three jib made from the same }in. tube boom. Finally, all spars were with banana oil, which has effective in resisting the effects of booms were as the main well treated proved very salt water. Now a few words as to sailing: On the beach pools, a spinnaker is an unnecessary encumbrance. On the open sea, always sail close hauled if at all possible; the boat will not then sail too fast to be easily overtaken. The boat described, with her large jib, is a very steady sailer, and has often made very long cruises parallel to the beach; and a very pretty picture she looks with genoa set! The genoa is cut with the same dimensions as the No. | jib, except that it has a large overlap over the mainsail. Very great fun has been enjoyed with a carefully adjusted beating guy, the boat sailing out to sea and then returning. The guy, an adjustable cord with a light elastic section, gradually pulls the main boom to windward, causing the boat to tack. BUT—a final word —DON’T swim after your boat if she fails to guy; it isn’t just worth the risk! As the writer has found, she will eventually guy and return! Besides —a neat nameplate, with the owner’s address, is screwed to the deck ! MODEL MAKER A LIGHTWEIGHT 10-RATER eee BY $2 FTER more than six decades of model tenraters one might think that designs would be more standardised at the present time than they are, but with beam varying from 16 in. to 94in., and displacement from 20 to 35 lb., this can hardly be said to be the case. In the design shown however, all dimensions are average, with the possible exception of the hull draft which has been reduced to the minimum. Dynamic and static balance have been combined in a manner which makes for both speed and ease of handling. Much has been said on the subject of static hull balance, but little on the real problem SORCERESS * ‘ LIGHTWEIGHT 10 RATER = ot SWitty” a nyheter MAKER2 PLANS Shp che – of dynamic balance which becomes increasingly umportant as the speed rises. It has been apparent for some time that even a perfectly designed metacentroid can become totally unbalanced while under way, if the disposition of the appendages is incorrect. The key to dynamic balance in a fin keel yacht is in designing the fin root, skeg and rudder to approach as near as possible that position normally occupied by a full keel. To demonstrate this, it is a definite fact that if the skeg and rudder on a normal fin keel yacht are moved forward, the sail plan has to be moved aft to compensate. In fact, a good method of estimating the dynamic balance of a . ail SS Cric @ ay Oo ‘ 7 NE ~~ wine WVHELY al” nae) ———— WN in al =S wus rad yy, Za u c[B Pee =a “TRS MLONSS 0 _—————_}—. TTT » 9 oe eta ? – ——— 9 © ” aoa —_ poe nee aoc WL.7 WLé nal woa ( wWi.3 mia ~ ve / a‘ es SS Ss 6 vs \ os wa / a Hh \/ wos pe“ i sty Ye ae ia. Roe oe enh r= x ae =) as a EAM. es ee te _i:6 = 2s 300 er ee we fee ie JUNE, model is by checking the distance of the mast position from the C of B. The nearer the mast position to the C of B, the better the balance. This is not to say dynamic balance is a criterion for fast sailing, but it gives a hull which can be sailed to the maximum under varying wind conditions without having to adjust the mast position or resort to pinching. Neither is metacentric balance, or the perfect balancing of the in hull wedges, a necessity; such extreme hulls as “Triplane’ and “Revenge” disprove this. The thing to aim at is a reasonable combination of the two types of balance. In this design the fin root is placed in a neutral position while the skeg and rudder is mounted inboard to balance the slight tendency of the bow to turn windward. It should be noted that while these forces balance each other around the C of B, they are in fact both of positive pressure acting on the LEEWARD side of the hull. The fin is of normal type, but is unusual in having the root perfectly centralised, a point which is not practicable on a symmetrical hull 1956 due to difficulty in placing the positi on of the lead. Flipper fins do save a certai n amount of root interference drag but are difficult to balance out dynamically. Also due to the centre of area being much lower than is normal, considerable stability is lost, and as the fin has to be made rather deepe r to com- pensate for this, wetted area. there is no real Saving in The fin sections are kept as fine and sharp as possible, since it is definite that the bluntnosed aerofoil sections some times used have no part in hydrodynamics, and create much Tesistance, particularly at the higher speeds. It seems actually that these secti ons are used because designers of more or less symmetrical hulls find difficulty in accommod ating the ballast in a reasonable position rather than for any merit of their own. Sixteen pounds of lead are carri ed, which should leave ample room for the weight of the hull. If, however, an extra pound of ballast can be incorporated, the leadl ine should be increased by 3 in. The peak of the displacement curve lies approximately 14 in. aft of the mid-section, giving a forward length to the bow water-line of 284 in., making the water line length equivalent to that of a symme trical hull of 564 in. While this particular hull has a fairly long sailing length, I have never regar ded this as essential fact to short heavy sharp weather bows and performance, cut-away in sterns seem to fare much better in these conditions. In this respect it is interesting to exami ne photographs of racing yachts taken during actual competition: they seldom appea r to be sailing on a full wave length. Apart from having a reasonably shallow hull section the most important thing, to ensure a good planin g performance, seems to be ease of reverse turn in the profile of the undersurface. The sailplan has an aspect ratio of 3.5, which is about the highest practicable. Apart from the usual considerations it must be remembered that the mast becomes thicker in proportion as the sail width decreases. I don’t think the normal sail arrangements can be much improved, and we’ve tried most things, including revolving streamlined masts and a ten-tenths rig, with a double luff sail. Full-sizeTMcopies of the accompanying drawing, which gives full size body plan and fin lines with half size sheer and waterline plans, are available price 8/6d. post free from MODEL; MAKER Plans Service, 38 Clarendon Road, Watford, Herts. 301 rT FUNE, We can now begin to build up the bar or body of the vane gear, with its self-tacking mechanism. A simple arrangement for the bar is shown in Fig. 1. The block A is fashioned from square sectton The most commonly used material is material. aluminium alloy, which has the advantage of lightness, but suffers from three disadvantages, viz:— STARTING ON THE RIGHT TACK (i) it cannot be soldered except by the use of special AN INTRODUCTION TO MODEL YACHT RACING PART FOUR—THE STEERING GEAR (Continued) techniques; (ii) it is soft, and drillings are apt to wear; and (iii) it corrodes easily especially when in contact with brass or other copper alloys. Perspex is used occasionally; this overcomes the corrosion difficulty but is even softer than aluminium, and rather difficult to work. The author prefers brass, the weight being maintained by drilling out as much surplus metal as possible. The block A is drilled at B to fit over the top portion of the rotor. This and all other drillings of the bar should be done with a bench drill or lathe to ensure accurate alignment of all parts. When the hole B has been drilled, it is temporarily plugged with a tight fitting rod, and hole C (for the friction clamp) is drilled, at right angles to B, and overlapped the hole B by about ird of its diameter. A suitable diameter for hole E (and for the clamp), would be 1 in. Two brass rods D and E, 1in. diameter, are fixed into the bar as shown. They can be silversoldered (if the bar is of brass), but it would in any case be preferable to thread them (5 B.A.) and screw them into tapped holes in the bar, so that they could be removed and replaced at any time if bent or broken. The tops of these rods are also threaded 5 B.A. to receive a nut. These rods form f – tacking bearings for the two arms of the sel mechanism. A simple form of friction clamp is shown in It consists of a piece of }in. diameter Fig Il. rod B. rod A, into which is silver-soldered a threadedinsertin The “bite” taken out at C is achieved by throughg the rod into place in the bar, and drilling of A is the rotor hole (B in Fig. I). The lengththat when slightly less than the width of the bar so and the the large washer D is placed in position rotor is knurled nut E is screwed up tight, the firmly gripped in the bar. which Fig. Il shows an improved form of clampmaking d in is well worth the extra effort involve halves, it. The clamping rod A is now split into two d rod B. and drilled to move freely on the threade C (same The latter is silver-soldered into the capsoldere d to material as A) which has a large disc fits into it to act as a flange. A locating pin D does nota rod pinhole in the bar so that the screwed the bar. The turn when the clamp is inserted into are slightly total lengths of A and C (less flange)washer less than the width of the bar. Thethe rotor Ein and the nut F are used as before to clamp bar. The self-tacking system comprises two arms, one 1956 BY D. A. MACDONALD carrying the vane feather and the other carrying These arms are made of the balance weight. extruded brass strip 4in. wide by 16s.w.g. Fig. IV shows the counter-weight arm and details of the The strip A is slotted at B to carry the weight. 6 B.A. fixing screw of the weight. At C, three holes are tapped 5 B.A. to receive the machine screw D The choice of three positions provides a coarse control of vane angle when the self-tacking gear is in use. A tube E (fin. internal diameter) 1s silver-soldered into the brass strip as shown. Care should be taken in this operation to ensure that the strip is not unduly annealed by the use of excessive heat for soldering. If a low temperature silver-solder (such as “Easy flo”) is used, this trouble should This tube should fit nicely over the not arise. appropriate rod (D in Fig. 1). The tube for this arm could be #in. long, with 3/16in. of this length below the arm. The weight F is made of brass rod (4 in. diameter) with a screwed rod silver- soldered into the centre. It is secured in the desired position in the slot B by the washer and nut G. The vane-carrying arm is shown in Fig. V. The strip A carries a tube B of the same length and diameter as that in Fig. IV but this time, gin. of the tube is below the strip A. This ensures that the vane arm when in position will ride above the weight arm. The inner end of the arm has a block C silver-soldered in position. This block is drilled and tapped to house the adjusting screw D, which acts as a fine control on the vane angle. The inner part of the strip is slotted at E to accommodate the pin (D in Fig. IV). It is important that this slot is carefully made, so that the pin moves freely The along its length, but without excess play. outer or feather end of this arm is fitted with two discs (F) silvered-soldered in position and drilled through the centre to receive the fixing screws G. If desired only one disc need be soldered to the arm, the other being free to allow for the use of To complete the self-tacking apparatus, a latch is required. This can be in the form of a slider (see Fig. VI). The slider is made of thin sheet brass, varying thickness of feather. 307 pressure on the feather. This must be perfectly upright, otherwise the yacht will not sail the same on both tacks. One essential accessory to the gear is a slow-acting gye. It is advisable for this to be designed so that it can be brought into action quickly on either tack when required, and also set for the desired speed of action. Many commonly ae rN to fit on the weight arm (Fig. IV), where it is placed between the rod E and the pinholes C. The hole A in the latch (Fig. VI) is dimensioned and positioned to engage with the end of the fine control used arrangements fail on either or both of the above counts. The arrangement to be described is one of the few that really work well. Fig. VIII shows the bar of the gear and part of the weight arm, viewed from above. A light cross-bar A mounted on a slider B is attached to the weight arm. The slider is similar to that of Fig. VI, the cross-bar and nut being silver-soldered to the top of the slider. A screw D with a large head is used to clamp screw on the vane carrying arm (see Fig. VI). The assembly of the self-tacking mechanism on the bar is shown in Fig. VII. The simplicity of this gear will now be apparent. The vane angle is set as near as possible by selection of the fixing hole for the pin, with the fine control at mid-position. The exact setting is then done by the fine control which will be found during racing. Fig @ SOLDER SOLDER invaluable for quick adjustments The sliding hatch is positive and accurate, and can be so used that the self-tacker is held to one side only, as a form of gye-ing device. I have avoided laying down set dimensions for the main parts, since the design can obviously be made to suit craft of all normal racing classes. It is recommended that the constructor makes up his own dimensioned working drawings from the foregoing illustrations, and arranges his dimensions to » Suit his own requirements. As a rough guide, the bar length overall should be from lin. to 24 in. and the cross section from } in. square to 4 in. square. By reducing the diameter of the top of the rotor and of the clamp (Figs. II and III) to 3/16in., a still smaller cross section could be adopted for the smaller craft. It is advisable, however, not to make the outer ends of the self-tacking arms too short, for two reasons. One is that a small feather, and correspondingly small balance weight on a long arm can be as effective as a large feather and corresponding weight on a short arm. Therefore, lengthening the arms will reduce the overall weight of the gear. Secondly if the weight of the inner portions of the arms (with the added weight of the latch and angle adjustments) is not appreciably less than the weight of feather and balance-weight, it will reduce the “toggle” action of the gear so that the arms will tend to return to a centre position when the yacht is upright. This trouble is very common with selftacking gears, and causes very erratic performance when sailing. It is essential that the self-tacking gear should maintain the full vane angle for which it is adjusted at very small angles of heel, and this feature should be checked carefully when the gear is made up. It is also inadvisable to try making the arms too long, as they are liable to distortion caused by wind the slider and cross-bar in any desired position along the weight arm. A rocker arm E is secured to the bar which is tapped to receive the 6 B.A. screw F. A locknut G and spring washer H provide a friction grip which enables the rocker arm to be set at any desired angle. Two light springs or rubber bands are hooked between the cross-bar and rocker arm as shown. Now if the cross-bar A is locked in such ROTOR Fig 10 a position that both springs are just inoperative with the self-tacking arms open to their sailing angle and the rocker arm in mid positio n, the yacht will sail full-and-bye on both tacks. Turnin g the rocker arm will slacken one spring and tighten the other to any desired extent. It is thus possible to apply a gye of the required speed on either tack by one simple movement. This device will be found most effective in racing particularly in variable winds when the “sailing” tack is liable to change at any moment. The cross-bar A can be of. brass + in. x 22 s.w.g. the rocker arm being 3/16 in. wide at the centre and 4 in. wide at the ends, and 20s.w.g. thick. It is a great convenience to be able amidships (i.e. in line with the rotor salf-tacker is in use. To do this, shaped as at Fig. IX is attached to to latch the bar arm) when the a small block, the rotor by a countersunk 8 B.A. screw as shown in Fig. X. The 308 JUNE, Fig 14 < width (W) of the block is the same as the width of the vane bar (Fig. I). It is shaped as shown to fit snugly against the main column of the rotor and protrudes beyond the circular plate. The protruding end is drilled through horizontally to take a long rivet for securing the latch (Fig. XI). This latch is made of two side plates (A) of 3/16in. x 18 s.w.g. brass with a spacer bar B silver-soldered in position. The fixing holes C enable it to be riveted to the block (Fig. IX). 1956 effective portion is at the base, and in sheltered water the lack of area at the top can be a disadvantage. In such conditions the inverted triangle C is often used; this needs an adequate strut to mount it rigidly. If this is done it gives a good driving force for a given area, but the strut loses marks on the score of weight. The crescent form D is the most widely used. It is rigid, the area is concentrated beyond the end of the arm giving maximum drive for the area, and it is quite rigid, requiring only a light strut. It answers all the requirements for lightness, rigidity and power, and is therefore recommended for all normal purposes. A light strut in the form of Fig. XV made of 24 s.w.g. brass can be used, this replaces The complete latch assembly is shown in Fig. XII, fixed to the rotor. It is customary to provide some means of limiting the range of movement of the tiller. There are two reasons for this. One is that the linkage pin can stick at the end of the slot in the tiller arm, and it is therefore advisable to stop the movement of the tiller before this occurs. The other reason is that rudder deflection beyond a certain angie does not materially increase the turning power of the rudder, and merely increases drag. The maximum useful rudder deflection varies between 22 and 27 degrees according to the characteristics of the rudder. Some steering gears are fitted with stops in the form of a pinrack or similar device which enables the limit of movement of the tiller to be varied. In the author’s experience, a pair of fixed stops will prove adequate, and these should be positioned to allow one of the discs at the end of the feather arm of the self-tacking gear, and is fixed to the feather by 10 B.A. screws, nuts and washers, or by eyelets. The optimum size of feather can be determined only by trial and error as it depends on so many circumstances. However, it is necessary to start somewhere, so the beginner is recommended to make three feathers for preliminary trials with the yacht. The dimensions can be based on those of the rudder. Assuming this to be of approximately rectangular shape, of height H and width W, mark out three rectangular sheets of batsa to the following dimensions:— a maximum deflection of 25 degrees for a yacht with a deep rudder well inboard, to 30 degrees for one (1) 23H x 23W (2) with a small rudder very far aft. These stops may 3H x 3W (3,°34H x 34W be made in a number of ways. One neat solution is to cut the barrel portion of a turnbuckle in two halves (see Fig. XIII) and screw these to the deck These should be shaped approximately as Fig. XVI(A). The thickness should be 3/32 in. or +in. according to the overall dimensions, and the cross section should be made streamlined as shown in Fig XVI(B). This selection of feathers (preferably into a deckbeam). Feathers for vane gears vary widely in size and shape. The requirements for a feather should be adequate but not excessive turning force (this subject will be dealt with later) light weight, and sufficient rigidity to avoid distortion under wind pressure. The shapes commonly used fall into the following categories (see Fig. XIV):—(1) Rectangle or parallelogram (A), (2) Triangle (B), (3) Inverted Triangle (C) will be found useful for initial tuning up purposes, and will enable the skipper to decide on his final requirements for size and shape. and (4) Crescent (D). The rectangular shape (A) obviously gives the largest area for given overall dimensions, and for this reason is commonly used when there are limitations of space. It does not, however, give the best le driving force for a given weight. It has reasonab and rigidity. The triangular shape (B) is very rigid, most normally requires no strut to support it. The in exception of dec k and engine mount. “SUNGA MARUTHAM” Powered by an old type E.D. Mk.2 with home built water cooling The attractive model boat featured on our cover is a scale model of a Singalese customs launch built by John I. Thornycroft Ltd., the model being the work of M. Purday of Herne Bay. Overall length is 36 in. and construction is entirely of balsa, with the 309 head, etc., the model is equipped with an entirely home built radio installation with optional progressive rudder obtained on the pulse system. A smart this maroon and royal blue colour scheme make seen one of the nicest launch type models we have for some time. JUNE, at the appropriate spacing. Alternatively, a bar fine abrasive cloth if the surface ‘is at all uneven, then with liquid polish. The circuit is made as shown in Fig. 5 The strip on the top of the battery is drilled for one can be made by turning 16- or 18-gauge sheet metal over a piece of suitable rectangular stock. The camera should then fit in the channel, and the lamp be attached at the other end through bolts and distance pieces. It is advantageous to drill and tap the solid bar for the camera and flash outfit to balance nicely on a tripod, if one is used; with a channel bar, this could be arranged by brazing or Whit. nut. Clips for securing the Perspex from springy brass, or from mild The inside of the reflector is fig 4 soldering on a 4 in. wire to be guard can be made steel, casehardened. attached ° FT 1956 5 by a screw and nut; the other wire is secured in the same way to the lid of the lamp; for neatness, both wires can _ pass polished, first with : Be es through a hole in the lid. With a_ 6-volt car bulb in the adaptor, the outfit can be tested with the switch on the CIRCUIT lamp, before a Stellaflash bulb is fitted, and the fitting plugged into the camera. The switch must not, of course, be operated with the Stellaflash bulb in place—except in the case of photographing on the open-fiash principle. MOUNTING BAR CAMERA a(Gemma -\- — —+* Exposure Procedure In general, an aperture of F.8 should be used, and an exposure of 1/25 sec., with the lens set at the appropriate distance for the subject. Too short an exposure—1/50 or 1/100 sec., for example —despite text-book data—is likely to result in failure. In a poor light, excellent results can be obtained Cis : bis with the camera on a ALTERNATIVE SECTION exposure. tripod, using 1/10, 1/5, 4-sec. For cameras without a flash-synchronised shutter, the procedure is—set up on a tripod, open the shutter, provide the flash, close the shutter, Thus, it is practicable to take photographs in total darkness. WING SCREW INTO CAMERA aes TUCKER’S TOPICAL TALKS (Continued from page 322) In the course of more than fifty years’ experience of yachts and models, I have never seen a yacht that could be sailed a good full and by pointing much higher than 4 points (45°) off the true wind. If pinched much closer, her speed was materially decreased, and excessive leeway usually resulted through lack of speed through the water. In the April number of this magazine, there was an article by Mr. Guy Blogg, giving an ingenious explanation Now most of “Rhythmic Rolling” when running. yachts roll when running by the lee in a heavy wind, but by no means every yacht rolls when not by the lee. In fact, it is only comparatively few yachts that do so, and when they suffer from this fault, the cause can usually be ascribed to the design lacking sufficient natural stability, or, in other words, a weak section which encourages a pendulum motion of the heavy ballast keel. In a full-sized cruiser, which has part of her ballast inside, the usual cure is to “wing out” part of the inside ballast to damp down this pendulum rolling. This, of course, is impossible in a model yacht, and I have in mind a well-known A-Class boat, which is a notable offender in this respect, although she is very fast and has frequently figured in the prize lists. The craft in question is fitted with a vane gear which carries the balance weight on an unusually long arm, and no elastic centreing line is fitted. In consequence, as the boat rolls down wind, the balance weight swings wildly from side to side, sawing the helm from port to starboard and back again. This, in turn, causes the boat to yaw frantically, and if the yacht’s opponent is on the course, a foul naturally occurs. The result is a succession of re-sails, no matter whether this yacht starts from weather or lee berth. Usually by about the fourth or fifth re-sail, the opponent, in his endeavours to keep clear of her, puts his boat so far up to windward, or down to leeward that the offending boat is left to make her serpentine way down the lake alone, while her opponent is on the shore re-trimming. MOE MAHER At this time of the year, many new yachts are being launched, or in course of tuning up. Most new yachts, like new cars, suffer from “teething troubles,” and rarely does a new boat reveal her true form right away. Last season (1955) I was consulted by an owner, whose new A-Class had been built from one of my designs. I gathered she was not on her correct fore-and-aft trim, and as she was nowhere near London, asked the owner to send me her Rating Certificate for inspection. From this, I found that not only was the boat badly by the stern, but bore no resemblance to the design. The was about | in. wrong, the displacement pounds too heavy, differed from the freeboard to the hull from gunwale * in. more than and every possible lines. If one adds the draught, one gets the to bottom of keel. She the design. Moreover, L.O.A. several dimension midships depth of measured the port and starboard Q.B. Lengths differed by almost 3 in. I did my best to help the owner to make something of her, but obviously the case was hopeless and I ought to have told him to scrap her right away. As a result, she raced all season as a “Tucker” design, and was no credit. I am glad to say that she has now been done away with. As a result of his experiences with this boat, the owner decided against having another “Tucker” boat, and produced lines by another designer, but strangely enough though he changed his designer (who was in no way responsible for his 1955 yacht), he has not changed his builder. So, whether the 1956 boat will be an improvement on the 1955 one, remains to be seen. From the above, it might be inferred that I suggest bad and unsuccessful boats are invariably due to poor building. This is far from being the case. What I am trying to impress is that yachts must have both sides alike, or they will perform differently on the two tacks. Also one must be sure the yacht is true to design before blaming the designer. On the other hand, even the best designers do not always turn out winning designs. can ensure balance, and take The designer pains to eliminate all features liable to cause steering vices. He can also make the boat easy to drive. However, in addition, he has to select the dimensions and type that give the best results in the class. It is here, and in the distribution of displacement, that the difference lies between an ordinary reliable boat and an outstanding performer. To reach top flight, a yacht has to be built perfectly to a first-class design, and in this con- nection, please do not forget that sister craft from the same lines and moulds often differ in perform- ance for no apparent reason. Undoubtedly, the -best heavyweight A-Class to date is “Moonraker,” but she has eight or nine sisters, some of them excellent yachts, yet none is quite her equal, even if we allow for Mr. Peter West’s excellent handling. Some boats handle more easily than others, but the last word always lies with the skipper. Ultimate success comes from a good design, equipped, well tuned, and well sailed. well built and Many models do not attain their best form for several seasons. There may be many reasons for this. Possibly some slight alteration is required, such as a minor variation in the sail plan, an amendment to fin, skeg or rudder, etc. These things can only be discovered by experiment. Likewise, the skipper has to know his craft before he gets the utmost out of her. The old hands know this, but the novice often expects too much at first from a new boat. Far ec Tucker’s Topical > Talks TUNING UP & TRUE COURSES ~ e too often, brand new yachts are entered for National Championships and other important races. Very occasionally, a really expert skipper manages to do well with a new, untried boat, but generally speaking, the practice of entering an untuned yacht in a major event is greatly to be deprecated. However, let us assume our new craft is well built and true to design. The owner ‘is naturally anxious to get her into the water for a trial spin, and the less experienced often leave measurement until they have got the yacht sailing reasonably well. I venture to suggest that this is the wrong way to go about things, and the first step should be to get the Club Measurer to check the salient measurements, such as L.W.L., fore-and-aft trim, displacement, etc., since if these require correction, it is pure waste of time to sail the boat and try to tune her up, until matters have been adjusted and he craft is on her correct line of flotation. When it comes to actual tuning-up, it is often astonishing how small an alteration entirely alters performance. Many initial troubles of new models are due to steering difficulties, and though experience is a guide in the selection of linkage ratios, feather sizes, etc., only actual experiment can decide these points finally. In this connection, I was interested in the article in the April MODEL MAKER by Mr. A. Wilcock on “Vane Feather Angles and Apparent Wind.” He gives a very clear explanation of the phenomenon usually known as “Apparent Wind at Ship.” This is a point which I have often intended to refer to in these “Talks,” since it misleads so many model yachtsmen and causes them to think their boats are pointing far higher to windward than they actually are. I notice, however, that there is an apparent discrepancy between Mr. Wilcock’s remarks on pointing to windward and leeway, and my own mention of the same subject in my “Talk” in the same number of the magazine. Mr. Wilcock stated: “The course taken for a close beat is 45°, the axis of the boat, however, is probably about 30°, the reason for making a 45° course being the leeway made.” My own remarks were: “Even the most weatherly craft makes at least } point of leeway. Hence, if the boat is pointing 4 points off the wind, the course made good will be 44 points off.” Now the angle of leeway made depends not only on the amount of lateral plane and L.W.L. length, but also on speed through the water and the angle of heel at which the boat is sailed. The more expert skipper sails his boat in such a way that she does not heel to excessive angles, since excessive heel decreases the effective lateral plane as well as reducing its efficacy per square inch. (Continued on page 321)
