Niels Blaauw wrote: >I made a drawing: >http://www.nibla.nl/tmp/paddlewise/halfway.gif G'day Niels, Very nice drawing and it answers my question well, I can see what you are getting at and it seems to make sense provided one takes out the paddle at the hip or just before reaching the hip. I went on to check how much average power the returned potential energy might save for me. I don't have your original calculation so if you have time perhaps you could check that I'm using similar assumptioms. Arm mass 4kg (roughly 6% of my body weight) Paddle mass 800g Paddle height displacement 35cm Fraction of paddle stroke time that potential energy is being dissipated 0.5 Average crusing power 100W This gives me a power contribution of 17 watts while the paddle is falling through the water and an average power contribution of 8 watts being 8% of my paddling power. I'd suggest that even in a relaxed arm there will still be work done as muscle fibers retain some tension in balancing the arm and paddle weight, also as Matt says the energy to forward conversion efficiency would be an issue too. So as a guesstimate if a third of the energy was converted then 2% to 3% of ones paddling power might come from the potential energy. I'm not sure that this would be true for a an arm moving in a typical 'vertical' or 45 degree paddling stroke. The tension in an arm as it controls paddle position and balance might counter the downward movement of gravity. This would also dissipate energy as the muscle fibres are repetitively triggered faster than their relaxation time to maintain tension. Is it possible to paddle efficiently with relaxed arms during the downward phase of the stroke? If I've understood, then that is one of the points you are making and the principal benefit could be as much in minimising energy dissipated in a tensioned arm as in the potential energy contribution. All the best, PeterO *************************************************************************** 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 Fri Apr 29 2011 - 15:45:12 PDT
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