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AY WWOWEL IMIANKIE!R} TUNING UP AND RACING TACTICS FOR MODEL YACHTS Practical Oe articles from one of today’s top-flight the course of a number of years sailing models the writer has noticed that a large number of boats are incorrectly tuned and that a knowledge of racing tactics is almost unknown by a large percentage of skippers. This is because in the past a vast amount of tripe and secret “mumbo jumbo” has been talked and written about tune. It is admitted that in the days of Braine steering and unbalanced hulls the tuning of a boat was an art known to very few and those who did know it did so more by instinct than by precise knowledge. The advent of the vane, however, coupled with balanced hull forms has ‘made the tuning of a yacht a simple operation which can be carried out during the course of an afternoon, provided that the boat is correctly rigged and attention is paid to the type of vane used. It is hoped to take the reader step by step through these points so that all may tune their yacht Both jib and main booms must have a scale marked on in half inches and the booms controlled by a double lead of chain arranged so that half an inch movement of this is fatal to a yacht’s HIGHthe 1961 A Class Cham pionship, which he to a screwed tensioning just, but only must be tennot overtight. stainless wire device. Nothing To begin with the rudder assembly must be checked to be certain that it is 100 per cent free. The only way to ensure this is to make the rudder tube out of 2 in. dia. brass tubing and the rudder stock out of 4% in. brass tube. This gives ample clearance all round the stock. Next the rudder must sit on a needle point on the bottom pintle, the tube being plugged top and bottom and drilled to accommodate the needle. Many owners let it go at this, tune. Now to the rigging of the boat. The mast is first of all stepped on deck in exactly the position the designer put on his drawing and the foot of the mast so positioned that the mast has about 3 in. of rake at the head. This amount of rake is about right and should always be carried. The old idea of altering mast rake was only another method of adjusting the C.E. of the sail plan within very fine limits and in most of today’s designs is entirely but this by itself is not good enough as the rudder stock can flop from one side of the tube to the other and cause friction. The rudder head must also be supported by a needle point and this latter should be adjustable so that the tiller arm will move unnecessary. The right re- est. Lastly, both jib and main travellers must be checked to make certain that they do not jam or stick in any as (seen at trimming LANDER during is followed to the letter no boat will ever give her the bowsie only moves the boom a quarter of an inch. manner PRIEST, tension from board to board; and too few realise that the trim of a yacht can be varied by slacking or tightening the kicking strap. We have one thing left to do before sailing and that is to fit the vane. I have left this fitting to the last because it is by far the most important fitting on the yacht, and yet so few give it the attention it deserves. The writer believes that unless what he is about to say next be in an adjustable slide on deck All this is shown in Fig. 1. H. M. I. Mar. E. attached and the foot of the mast resting in an adjustable step. by B. else is good enough for a kicking strap, as one that is of cord, or adjusted by a bowser, can vary its it is as well to not use bottle screws on the runners until the tuning up process is complete; in their place a short length of cord attached to the end of the stainless wire will be found to be more convenient. must One should now be set up so that they are just, tight. Finally, the kicking strap sioned. This tension must be firm, but The kicking strap must be of good Attention to the standing rigging is essential. This must be of stainless steel wire and forestay, shrouds, and runners must all have bottle screws, although mast Part won.) correctly. The skippers port and starboard shrouds are now set up just hard enough to take any sag out of the wire. by the touch of a feather. Actually the only test to find if all the rudder and vane gear is free enough is to set it up on the boat in a room and blow on The shrouds should meet the shroud plate exactly half an inch aft of the after edge of the mast. Next the forestay is lightly set up and the jib put up. Only now are the port and starboard runners set up. The mast is now sighted to make certain that the the vane from a distance of three feet. If the rudder does not move hard over with this blow it requires attention. runners are not bending it aft or the forestay bend- The slot in the tiller for the vane linkage pin must be filed so that it will just take the linkage pin without it sticking, but not opened up too much to allow lost motion between the pin and the side of the slot. There is only one correct position for the linkage pin. This is found by measuring the distance from rudder head to vane pintle, which is say 6 in. in an A boat, and divide this distance ing it forward. Runners, forestay and shrouds are now tightened up until all are firm, but not bar tight. The mainsail is now fitted. From the top of the mast come the fore topmast stay and the back stay. They should be of stainless wire with a short cord tail and bowser. These 18 JANUARY by three which is 2 in. Then the position of the vane tiller pin should be 2 in. from the vane pintle. This is all shown in Fig. 2. Finally, a long very thin elastic should stretch from the vane linkage pin forward past the rudder head to an adjuster on deck. The tension on this elastic should be eased off until it will only just pull the vane back central when it Fig.1 STAINLESS FORE TOP MAST STAY STAINLESS STEEL is given a swing. BACK I must diverge slightly at this point for reasons STAY which will be seen later. When a yacht is moving on a beat she is sailing on not the true wind, but the apparent wind. This is because she is moving against the wind. For example if one is driving a car directly into a head wind of 30 mp.h. and the car is travelling at 30 m.p.h. then one is facing an TAINLESS STEEL RUNNER apparent wind of 60 m.p.h On the other hand if the car was going in the opposite direction then the resulting wind left by the car would be nil. I STAINLESS STEEL spent some time with a very good A boat, Com- mando, at Birkenhead lake. I measured out the lake with a tape and, by the aid of the wind speed given by Bidston Observatory, which is near the lake, and a stop watch, I was able to draw on a scale chart of the lake the boat’s course to windward. From my tests I proved that an A boat points from 38° to 40° to the true wind when beating and from stop Vv watch timings does between — = 1.0 and — = 1.3 VL ic where V = speed in knots and L = Waterline in feet, but the boat is sailing on the apparent wind and one can now find its speed and direction. This is done as shown in Fig. 3. This shows that the angle of the wind over the ship when beating varies from 30° to 32° according to her speed on a 40° course. If the course is 38° then these angles become 29° and 31°. Now we have what is required and that is the angle the vane should be set to, for correct windward tune, which can vary between 29° and 32° as being a fair average. This being the case all we have to do is tune the boat to a 30° vane angle. With 90 per cent of the vanes the writer has seen this is not possible because there is no method of knowing just what 30° is. Usually in any typical vane layout, the markings do not make any specific angle and one cannot sight an accurate position across the adjusting wheels. In Fig. 4 the writer shows how a vane should be. The quadrant is marked in 20°, 95° 3073-35″ 40″ 45″; and the friction adjusters are so arranged that any vane angle can be selected accurately to one degree and as a result is capable of being repeated at any future time. The writer believes a vane of this type is essential for perfect trimming of a yacht. All the hard work required for tune has now been done, the remainder is very simple. One must sit and wait for a nice eight knot wind. This is what most people call just a nice sailing breeze. This wind must also be true in direction and giving a beat. The boat, rigged as instructed, vane at 30°, is set off on the port or starboard tack and observed. It will be either in irons or off wind. The former is easy to spot, the latter not quite so easy. The best way is to remember that when a yacht is doing her best the leading edge of the jib should every couple of minutes give a faint flicker about 1 in. behind the luff. So if this flicker cannot be seen the yacht must be off wind. If she is off, move the mast on deck slide and in the step 1 in. aft. Or if she is in irons 1 in. forward. The one leg of a beat 1962 FORESTAY STAINLESS STEEL KICKING STRAP WITH SCREW ADJUSTER ADJUSTING CORD FORESTAY BOTTLE Ew ee CHAIN SHEET ADJUSTMENT BOTTLE ChAIN SHEET ADRISEMENT,. y SGrews. is repeated again and the mast moved again until she is beating correctly on that leg. Probably the first movement will straddle the target and so a 2 in. movement in the opposite direction would not be very far away. Usually the writer has found he has got his position right after three movements. Note neither sail trim, mast rake, or vane trim have been altered. Only now is the boat tried on the opposite tack and if she is not 100 per cent right the vane is opened up to take her off or closed up a degree to bring her up on that tack. It is strange but very few boats sail exactly to one degree of vane angle the same port and starboard. Of course if the vane has to be altered about 4° on the opposite tack then either hull or rudder are out and one is wasting time until this fault is put right. The yacht is now tuned. Fit bottle screws to the BACK STAY la Fig. 2 FINE ELASTIC —— es ADJUSTABLE TOP NEEDLE 2 – -}, EYE IN BACK STAY HOOK TO KEEP ELASTIC FREE OF RUDDER HEAD GEAR TILLER m.—— VANE PINTLE = Lok Ske LINKAGE PIN I” BRASS RUDDER TUBE 4—¥4 BRASS RUDDER STOCK TUBE PLUGGED ANO DRILLED TOP AND BOTTOM BOTTOM NEEDLE (WOW MIA\KIEIR 2° Fig.3 AD= WIND AT 8 KNOTS OR 9-2 MPH | ANGLE ADE= YACHTS TRUE COURSE OF 40* TO WIND XDE= ” “ 3e° « BD= BOATS SPEED IN KNOTS at & =13 OR V 21-3 XVLOR V=1 3X2-12= 2-76 KNOT | CD = BOATS SPEED IN KNOTS AT X= Lo OR V=1-OXVL OR V=1-0X 2-12 =2°12 KNOTS | water. ANGLE ABD= DIRECTION OF APPARENT WIND OVER | | ts YACHT WHEN BEATING AT 2.76 KNOTS AND IS 30° AND WHEN ANGLE XDE IS 36° XBD IS 22° ANGLE ACD = DIRECTION OF APPARENT WIND OVER | YACHT WHEN BEATING AT 2:12 KNOTS AND IS 32° AND WHEN ANGLE XDE IS 38°ANGLE XCD IS 31° | | WIND 8 KNOTS | | | | NOTE | | runners so but over the whole they move. +2° range the over the original ARM CUT BACK HALF DIAMETER END FILED TO KNIFE SO THAT TRUE ANGLE and wire them up cannot to Most people already know that the trim for OF PIN AND OUTER EDGE | 40° boats, main and jib going to windward for a normal boat is about 12° from the centre line for both, but few know that a very deep vee sectioned yacht can be trimmed into about 10° each whilst a flat floored boat will go better if both are eased off to about 14°. Incidentally, whatever angle is selected for initial tuning, the boat must be laid at her side and sighted along main and jib booms and so adjusted that each makes exactly the same angle to the centreline of the yacht. | TRUE most 30°. This is why a vane that can be adjusted to a degree is a must for consistent sailing. The writer, in fact, used to make a note of his vane angles in various wind strengths in a book! The final point to adjust in tuning is done when racing against other yachts and that is to ease both jib and main slightly the same amount until the point is reached when the yacht is still pointing as high as before and yet going faster through the DATA FOR. YACHT OF 54″LW.L. ! on tune will vary only —2° iS MEASURED FOR’D WHEN BEATING At VANE ARM ROTATIONAL CENTRE EXTENDED TO FORM PIN IN QUADRANT SLOT any future date the mast can be replaced with the same rake because it is supported by a Stainless steel tripod consisting of forestay and two runners. Sails can 4 \\ancLes 20% 30°, 40° be replaced on the same boom markings and vane angle of 30° repeated STRUCK FROM VANE ARM CENTRE and one will no longer have to go hunting for 8 a windward trim in a nice sailing PORT ANGLE ARM ON FRICTION.AT breeze. In lighter winds the apparent wind angle will cause the vane angle to be closed 2° to 3° and in a limit top suit breeze it will cause the vane angle to open up about 1 ” 34¢.c. MARINE DIESEL inu {Continued from om resistance is felt then power is switched on, and a similar twisting and sliding motion applied. When no resistance is felt the piston is wiped clean with paraffin and then a dry rag while in position. A light smear of tallow is applied to the piston an attempt piston. is made to slide detailed drawings engine are available, of this NOTE ST’B’D PORT AND ST’BD TO BE CAPABLE OF INDEPENDENT ADJUSTMENT with tallow and the cylinder tried on. If the contrapiston half enters the cylinder top it is left in the cylinder and the pair unscrewed from mandrel, then with soft punch the contra-piston is tapped home. If too tight the contra-piston is punched out of cylinder and replaced on mandrel and lapping When the lapping is finished the three lapped com- the cylinder over the ponents are washed in hot water with a detergent. If the piston slides 50 per cent to 70 per All screws and studs are best located from their respective cover, i.e. cylinder top, side water covers, and crankcase end cover. When using the first batch of castings the metal was found to be rather soft so it is an improvement to use § in. Whitworth studs for the cylinder top and side plates. The carburettor is straight forward turning using the three or four jaw chuck, but any 23 or 33 c.c. straight through spray bar carburettor will do if speed control is not required. The engine is assembled with oil, and it will be fairly stiff to turn over, so it will be best to run it cent up the cylinder and is then tight, the cylinder Fully ARMS ALSO NOTE repeated. can be turned with the hand to unscrew the piston off the mandrel, then with an aluminium punch the piston is struck light blows from its inside. The piston should then travel its full stroke, if it does not, the lapping process has to be repeated. Then with the screwed mandrel still in chuck contra-piston is screwed home and lapping technique is repeated, then wiped clean and smeared marine VANE ARM CENTRE ANGLE ARM OMITTED FOR CLARITY AND straightforward plan M.M. 657, price 5/- including post, from Model Maker Plans Service, 38 Clarendon Road, Watford, Herts. While the in by gripping the flywheel in the lathe chuck and supporting the cylinder with a wooden block; a quarter to half an hour should be sufficient. The engine can then be mounted on wooden base and started up in the usual manner for diesels. Constructors having any problems can contact me. entire engine can quite easily be machined from the solid, those who prefer can obtain crankcase castings direct from the designer, C. R. Starnes, 104 Wilberforce Road, Finsbury Park, N.4. 20
