Ships and Ship Models: Volume 76, April 1954

al ~*~ LOonoor – i as stein ek sae ores, A PERCIVAL MARSHALL PUBLICATION angrysae ; The “A°’ Class Sharpie x and how to build her N the full-size body plan, draw lines on either side of the centre line and parallel with it. The inner line, $ in. out from the centre line, represents the rabbet line along the keel, and the second one, 2 in. out, the keel width. This, of course applies solely to the forward and after members, not to the centre member which is wider. The latter will be dealt with separately in due course as applied to BY H. B. TUCKER Sections 5, 6 and 7. Take a tracing of one of the sections forward, say No. 3, ruling in the datum line and also the L.W.L. (Fig. 8). Mark in the width of the keel and the position of the rabbet line. Our bilge strake is to be made of solid pine ¢ in. thick, so start by putting this in. In passing it will be noted that we are now working back in the reverse order to that in which the parts go on to the boat. The bilge strake is the last to go on. Bottom and topsides are being planked with 3 mm. three-ply, so rule these on to our plan. The bottom planking goes down as far as the rabbet line. Having removed the skin it might, perhaps, be better to revert to the order in which the frame members are assembled. Our keel is 14 in. wide X 1 in. thick, and we have its half width already marked in, so this can be put in. The thickness is 1 in. It will be seen that the skin lying in the rabbet overlaps the keel for a good } in. which will give sufficient hold. Next draw in the lower chine. Both chines are made of pine 2 in. X } in., and lie respectively in the planes of the bottom and topsides. Drawa line } in. from the inside of the skin at the chine parallel with the bottom. From where this meets the bilge strake, measure the # in. distance and put in the lower edge. It will be seen that the lower outer corner will have to be bevelled off for the bilge strake. Since the chine angles are constant right along the boat, you will be able to measure from your drawing and then set a marking gauge and run a line along one side of the chine beam. This will enable you, when you are ready, to plane the beam to its correct section. Incidentally, you should get the # in. x } in. pine in seven feet lengths to allow for some spare when it comes to fitting the chamfer at the forward end where it butts against the stem. If you have a few inches in hand, you can re-cut if necessary. The upper chine is put in similarly. Finally there is the inwale. This is also of pine but is #in. x @ in. (Continued from March issue page 103) Inwales are often known as “ shelves” since they support the deckbeams and deck. It was mentioned that the deck is also to be of 3 mm. plywood, and also that it’ is to be dropped inside the topsides, hence our inwales must be the thickness of the plywood below the top of the sides. A line is drawn next from the top of the inwale inwards to meet a line drawn perpendicularly upward from the end of the datum line, which must be ruled in. The centre part of the drawing (Fig. 8) now gives you the.shape for your mould, or rather for one half of it. However, the mould itself is in two parts. These are the lower part which becomes part of the framework of the boat, and the upper part which is simply a template to bend the sides round. The depth of the lower part, which is known as the “ floor,” is up to the top of the lower chine “ce beam (or “chine > stringer ’’). The purpose of the floors is to strengthen the bottom of the boat and resist the side wring of her lead keel, and generally act as a brace to the whole structure. Though the whole template is loosely spoken of as the ‘* mould,” this, therefore, comprises the floor and the mould proper (or upper part). Sections 1-3, 8-11 are dealt with in exactly the same way. The floors should be selected pine 1 in. thick, but the mould proper need not be such good quality wood as it is not a permanent part of the yacht. Section 10 is exactly similar except for the skeg, which is mortised through the backbone as exThis makes no difference to the plained later. floor and mould. The midships sections, Nos. 5, 6 and 7, are different in that the keel member is wider being the top layer of the fin. This is not joggled into the floor but the latter fits on top of it (Fig. 9). Along the part of the fin where the width of the fin is over 1 in., the rabbet line is along the garboard angle, but where the fin “is less than 1 in. the rabbet line keeps the same as along the forward and after members of the backbone 137 se! 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