Plywood Instead of Deadwood for Keels

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  • Pub No.: 7063
Robert M. Steward/The hollow fin keel construction described here was designed for ease of building, lightness and strength.

by Robert M. Steward

The hollow fin keel construction illustrated in the accompanying drawing was designed for the prevention of aching backs and blistered hands usually accumulated by amateur boat builders when working solid deadwood into shape. There is another, easier way out, and that is to make the deadwood slab-sided, but why muss up the water with such disregard of naval architects' experience and tank testing? The essentials of the hollow fin keel, which is especially adapted to hull construction of the bent keel type, can be explained briefly. It is made possible by the manufacture of the waterproof plywood. These sheets are made of Douglas fir, or Oregon pine, call it what you will. The outline of the fin is laid down on the mold loft, or living room floor, together with the waterlines through the fin and the outline of the ballast keel. After the ballast keel bolts and other deadwood bolts are drawn in the locations of the webs can be decided upon, the number of webs being more or less guessed at. After going through the operation of laying down the hull lines and sections it can be readily seen that a section through the boat can be drawn any place by simply drawing in a station line, picking up the half breadths, transferring them to the body plan, and drawing in the section. So don't skimp on the number of webs, because all one has to do to get one out is to draw a section where a web comes, deduct the thickness of the plywood planking, move the net shape onto a 3/4 or 7/8 inch board and slide it through a band saw. The plywood skin should be screwed to the webs and to pieces of oak forming the leading edge, the bottom of the fin abaft the keel, and the stern post, also to plain fillers on top of the keel and one bolted to the under side of the bent keel. The stern post will have the same cross-section from top to bottom and therefore can be gotten out on a circular saw. The other rabbeted pieces can probably be roughed out pretty well on a saw, too. It goes without saying that all joints and interior surfaces should be painted during assembly. Anyone with enough ingenuity to try this construction can very well work out the missing details himself. And how about filling up the spaces with cement? I am not advocating that all fin keels be built this way from now on, but do think that it might be tried on a small boat.

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