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Location: British Columbia
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Re: Pros and cons of steel sailboats
Yes bigger boats do need bulkheads, but not in the sizes I design, where they are structurally irrelevant. You can tell how much a boat is flexing by what it does to brittle fillers used on the interior. I have used oil based paint mixed with talc. Definitely not soft and flexible, yet after nearly 30 years of mostly full time cruising, including several Pacific crossings, it hasn't even cracked, which means almost zero movement.
The longitudinal girders on a hard chine boat are the chines ,hull deck joint, centreline, and in the case of my boats, the tank top -hull seam, all far stronger than any other form of girders. Curves make them many times stronger that flat ,straight ones.
Structural calculations which don't take the curve into account are meaningless.
Plywoo0d is anything but homogenous. Each veneer only has significant strength in one direction. With three piles you can only have one running in any one direction. Thus only 1/3rd the thickness has any relevant strength. Any loads on it in any direction can only run along the grain of one veneer, running unavoidably ACROSS the grain of the other two.
Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"
Last edited by Brent Swain; 02-18-2014 at 07:47 PM.