RE: [Paddlewise] Skin on Frame Boats...

Steve Brown wrote:
>>>>>>Flex can also store energy as in a spring and all its practical
applications
such as the archery bow.
Is it possible for energy stored in hull flex to be returned in a useful
way? Can this be why some claim that their skin boats are faster over rough
water?<<<<<<

It can work for paddles if they are springy enough so that the flex unloads
while the paddle is still in the water at a more efficient angle than when
it was flexed. However, even if the kayak was stiff enough (which skin on
frame kayaks aren't) I can't see how flexing of the hull side to side during
stroking could return energy in any useful direction to increase a paddled
hull's efficiency. As I've already said, flexing up and down will allow a
finer bow (above the level waterline)  to lift over waves rather than plunge
into them, although that same bow would be inadequate to the task if it were
rigid. That vertical flex might possibly cut some extra drag caused by
burying the bow but compared with a stiff kayak with adequate lift at the
bow I doubt there is any significant advantage. Unless the side to side flex
(that's robbing energy from the paddle strokes) could be reduced to that of
a hard shell while the up and down flex was allowed to remain there would be
a net loss. I'm not positive of all this. I'm certainly willing to listen to
any arguments to the contrary, but I'll be very skeptical. There is a reason
racing kayaks are made as stiff as possible for a given weight.

Matt Broze
www.marinerkayaks.com
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