> I wrote: Off the cuff, it seems to me that there IS potential energy stored by lifting the arms but I don't see any advantage to doing that since the paddle is no where near 100% efficient in transferring that energy into forward motion. Niels Blaauw wrote: > I'm not so sure about that. The mechanics are complicated, but let's > simply ask: If the energy doesn't transfer to the force and movement > of the paddle-blade, then where does it go? The movement of the arms > is nearly frictionless. Nothing heats up, so no energy is lost. > I think almost 100% of the energy transfers to the paddleblade - but > from there, I have no idea of the efficiency of a blade pushing > against the water. Darryl Johnson wrote: I would disagree that "nothing heats up, so no energy is lost". Exercise does create heat in the muscles, else there would be no need for profuse sweating to cool the body down during strenuous exercise. But I suspect the amount of energy referred to is small. I doubt you could get a kayak to move forward by just using the potential energy stored by the effort of lifting the paddle up. Even on a completely calm day. Niels showed in the video of the model that dropping the arms with a paddle connected will power the kayak and I agree that simply dropping the arms and paddle in a paddling position will move the kayak some. But not move it very fast, and it will take a lot more energy to lift the paddle and the arms before dropping it than you will ever get back in forward propulsion. The efficiency losses are several. One is that the angles of the paddle won't be entirely in the opposite direction of kayak motion. Another is all the turbulence (heat) shed off the paddle blade moving through the water. Nothing is 100% efficient, so there is always some loss in any energy transfer mechanism and a paddle blade is a lot less efficient than say a screw propeller for moving a boat through the water. Lifting the arms and paddle against the major force of gravity in order to get a little bit of the energy transferred is an unnecessary waste of energy. A low Eskimo type stroke is more efficient but the mechanics of a low stroke are such that it can't put quite as much energy in the water as fast (at an additional cost to the paddler I might add) to be as good a stroke for a sprint racer in accelerating a kayak and keeping up to a slightly higher (but unsustainable) speed in a sprint race. *************************************************************************** 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/ ***************************************************************************
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