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BB: o imi 4 Oh ary A SLE j 1a ie [* LT | |e “50 qo4 h 7 , —e have been interested in A class model yachts for a great many years. As long ago as 1925 | knew Major Malden Heckstall-Smith when he was Y.RA. measurer for yachts designed and built to the rules of the I.Y.R.U. It was his opinion that a better rule formula could be devised and in particular he thought that displacement should be brought into the rule formula. Consequently he worked out A 49in. w.l. 40.72I/b ‘A’ class design by G. K. Collyer yacht is less than the displacement required by the rule for her length on L.W.L., then the difference between the length on L.W.L. to which her actual displacement corresponds by the rule and the actual the formula used by the M.Y.A. and 1.M.Y.A. which | have before me. In the introduction it is pointed out that the formula is now length on L.W.L. will be doubled and added to the length measurement. This makes a metre class. For many years this worked with great success. more used in principle by the R.O.R.C. and the 5.5 In the international rule the displacement clause is as follows: Displacement in cubic feet = (0.2 L.W.L. in feet + .5)3. If a May 1983 very severe penalty. The A class formula makes things much flexible. The cube root of the Plan for Variation MM1 347 gives half size hull lines, one eighth size sail plan and is price code E, £2.50 plus 45p from Model Boats Plans Service, Wolsey House, Wolsey Road, Hemel Hempstead, Herts., HP2 4SS. displacement must not exceed one fifth of the L.W.L. in inches + .1 for measurement. Butifthe%,/ D_ islessthanone fifth of the L.W.L. in inches + .4, then the difference must be deducted from the 3 D to obtain the correct displacement figure for use in this formula, so between the two there is flexibility governing length and sail area. This was M.H.S’s idea: that, if a design did not quite reach the minimum required D, the boat lost more sail area but still had a chance to compete in the class with some success. However, | do feel, and many others may agree, that this minimum D clause could be dropped and let the D be determined by the formula only. It would give designers more chance at producing a planing hull. Sixty (Continued on page 258) 249 6. Mark out the basic frame using either plastic, metal or card; also scribe out building strips as shown to ensure balanced construction. B, scribe out if metal is used as shown, drill location and pivot holes as shown. 7. A. Fold the frame using tweezers to form basic shape. B. Add the frame stiffeners to top and bottom. C. Clean and smooth the frame before adding wire trim. D. Use a selection of files or sandpaper to clean completed framework. 8. Locate the launcher barrels as shown. As you will see they are staggered as shown on the centre line. Push in the locating pins and trim flush on the right leaving slightly proud on the left. Three stoppers can be fitted to keep an angle of 45° forward for launcher Basic positions inside the frame if required. 9. Tampion muzzle covers. Use a piece of dowel which fits the barrels then cut three plugs and make the wire rings as shown, fit and solder to the plugs leaving a slight indent to be filled with thick white glue. Then using a fine paint brush and pin shape the ship’s Squid Launcher crest if required while the glue is drying, then paint. ies month we take a look at the early type of squid depth charge mortar as fitted to Royal Naval Warships of the Castle class and Battle classes. This weapon heralded the start of accurate antisubmarine warfare; after all why drop 50 charges doing no end of damage to your own hull and shaking up every nut and bolt of your ship, when one spread of squid will quite easily straddle the submarine ahead of the ship causing quite a few problems; after all you don’t have to knock a hole in her to put her out of service. It’s the old story, anyone can take a submarine to the bottom but it is bringing her up to the surface which is the tricky bit, not to mention how much of the submarine gear will work after even a near miss from a squid 10. A piece of brass or aluminium tube cut to shape, then glued or soldered to a male dressmaker’s stud, will reward us with a rotating loading tray. The trolley can be made as shown using metal or Plasticard. The rail to the magazine for loading system shows safety wheels double locating on trolley stand; also porthole clamping band to aid in loading projectile. Platform Gear — Sheet 2 1, Wooden base cut to shape. 2. Metal or card base cover or bottom well. Mark out the positions for the end supports. 3. Cut out the frame shapes and building strips; also weight saving shapes in frame sides; also side supports and lower well walls. 4. Glue or solder the frames into position using tweezers as mortar bomb. shown. Building the launcher — Sheet 1 1. Metal or plastic tubes cut to the required length and trimmed to dowel and shape to form the control casing; A, this piece slots into the bracket which can be trimmed in length to suit; B, dowel piece cut 2. Drill holes to locate pins later, approximately /; of the length. 3. Capping ring from fuse wire to finish the muzzle end, solder or as shown over end support, solder or glue into position. 5. Bend top of support to form a bracket, then cut a slot ina length using file or emery board. glue into place. 4. Dowel length: cut breach end as shown and drill end piece; A, insert dowel breach which should be a tight fit; B, Breach end ring; C, fits as shown; D, Chamber hinges made from fuse wire. As a matter of interest mole grips can be used to crush fuse wire to forma flatend for hinges or use lengths of flat wire for scale levers, door and window type frames, clips, brackets, depending on the scale used. E, shows construction of breach lock; bend fuse wire into a ring as shown using a needle as a former or piano wire, then add L shape locking lever. The actual breach is very much smaller than the muzzle bore to take the fixed firing charge canister and primer round, F, location of completed breach assembly. 5. Locate pivot pins but don’t fix as yet. Variation (from page 249) years ago, and for many years since, displacement was the order of the day, but now times have changed; we are in an era of light displacement. The quarter beam measurement clause in the rules is a good one. It gives the designer the chance to carry out the ends of the boat gracefully, restricting length of overhang. But | feel this should be in combination with disallowing hollows in the surface of the hull between the L.W.L. and the sheer line. It is a pity this clause was dropped when the rule prohibiting projections and notches in the profile was brought in. The rule still says ‘or hollows’, but does not amplify. As the rule stands, 258 piece of and drilled to locate as shown but don’t fix at this stage. 6. Manual gearing box as shown; fold to form basic box and locate 7. Using fuse wire and a piece of dowel cut slots to take fuse wire spokes and insert pin into dowel jig, then solder to pin shaft as shown; work quickly. Trim the ends of the spokes before soldering the ring into place forming the wheel. Adressmaker’s stud was used as the casing cover for the hand wheel shaft. 8. Glue top assembly to wooden base as shown, then cut the gusset supports on the frames and glue or solder into position on the model’s deck. 9. Lower launcher into position adding locating pins and sealing into position B half of No. 5 control casing, then push in hand-wheel assembly to complete. The model can be shown as required; Loading Arrangement as Sheet 1 or Ready to Fire as Sheet 2, (remove tampion covers of course). designers can still keep the hull within the quarter beam length restriction, and gain unmeasured length by hollowing the diagonals. In my opinion the quarter beam length, in conjunction with prohibiting hollows, as in the original rules, makes an eye-sweet hull — preferable to class rules where girth measurements are taken forward and aft, which encourage the designer to pinch the ends of his design. advantage in light winds. Ina fresh breeze a dish-shaped boat, with ample sail area, could plane. It might be said that the wetted surface is unusually great, but displacement is a factor in this rule, and ample fin, skeg, and deep rudder would keep the boat on a especially off the wind. straight course, The freeboard is about in. over the minimum, so that the boat could float deeper in the water if required, which would increase the waterline length and Variation lose some Sail area. liberal beam and high bilge. The sail area combined with the high bilge could be an displacement, although some adjustment This design is something different from normal; short waterline, ample sail area, The lead keel is designed to outside skin measurements just over 70 per cent of the might be required. Model Boats
