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EeZeBilts From Keil Kraft

Martin, tables of offsets are rather like a land surveyor writes down. Because a boat is generally a curved shape in every direction (even more so than some aircraft shapes) it is necessary to divide it up into regular sections and then measure those at equally regular spacings from a datum. That way you get a frame shape which is effectively the shape of the boat in cross section at every regular spacing. 1 or 2 feet from the stem head, all the way back. As long as the boat is set up level, you can take measurements from a fixed datum (say the centre line through the length of the boat or a wall that is parallel to the keel) to any major point such as the deck edge and chines. You need a vertical measurement too which would usually be the floor. Where these measurements cross is where the dot goes. Eventually, for each section, you join the dots, so to speak and you get a shape, per section. On the Thames launch, Freebody's boatbuilder, who had worked at Andrews (where s originated) lent me the original table of offsets, from which I was able to make frames. Despite the svelte look of a they are actually all straight lined sections/frames, except frame 1 because you can't twist the plywood quite that tightly so there has to be a slight curve in that frame. Also frame 2 is 1 1/4" out on the starb'd side! and every boat they build has an extra bit of oak added! As indeed I had to on the model. When I asked the Freebody kids who now run the firm since kindly peter died if I could borrow them again they abruptly refused, proving the son is so very often not what the father would have hoped. Martin

5 years ago by Westquay