Nick, If the paddle were to be drawn straight back with the blade normal to the velocity, then the force applied by the hand depends on CD, paddle area and velocity. The work done by the hand then also depends on CD, area and velocity. Now if you had two different paddles stroked identically, working at the same velocity, with the same product of CD and area, would they necessarily be equally efficient? Even though the flow pattern around each would be different. Jerry > > Nick Shade wrote: - > Yes, absolutely. Any water motion is energy that in a 100% efficient > system would have been kayak motion. In real life water motion is > inevitable consequence of applying propulsive force against a fluid, > but that does not mean it is not lost energy. Vortex shedding may add > to lift, but the vortex is still lost energy. This not to say that a > paddle that creates a vortex is not more efficient than one that > somehow avoids making the vortex, but lost energy is lost energy > regardless of the form it takes. 100% efficiency is only possible when > pushing against an absolutely stiff object of infinite mass, for our > purposes the solid ground of the earth is a reasonable approximation. > Poling your kayak would be as close to 100% efficient as is possible. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Sun Jun 08 2003 - 19:05:58 PDT
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