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Jim Willemin

Frogwatch wrote in news:571e39b1-f812-459a-b9e6-
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It seems that deadrise has a radical effect on the ability of a boat
to get on plane quickly and thus use less fuel. More deadrise makes a
boat punch through waves better but increases draft and reduces fuel
economy in smaller seas. I assume that variable deadrise has been
tried. Of course there are boats that try to use hull shape to
accomodate varying conditions but not too successfully.
My Tolman has about 10 degree deadrise and is very light so is very
fuel efficient but pounds a lot in chop so I have to slow down to
about 12 kts. Why not some mechanism that would consist of another
outer variable hull layer that would be hinged at the chines allowing
the keel portion to move downward to increase deadrise. It would have
a flexible stiff plastic piece at the front to keep water out of the
area between the two hulls. Is this simply too complex for too little
benefit?

Having pondered this for a couple of days, I am struck by the problem of
changing the area of the floor between the keel and the chine. This might
be tractable near the transom (overlapping leaves, perhaps, kinda like a
'sliding lapstrake' construction), but as you get near the stem you gotta
worry about major changes in geometry as well as area. I imagine a really
clever designer could do it. I suppose the question is where in the hull
would variable deadrise be most effective in the transition to planing?
That might make an interesting thesis for someone...

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