Nick Schade <nick_at_guillemot-kayaks.com> wrote: >> Work is defined as a change in energy. If you measure the work done by your hand and you have all the parameters of your paddle matched such that they multiply together right it is absolutely possible to make the work done by your hand match with substantially different paddles. But remember that the work done by your hand is not the same thing as the work done on your boat. >> Nick, a small correction: Classically, work is defined as the force applied multiplied by the distance through which the force is applied ( W = f x d), not a change in energy. The change in energy in the paddler arm/back system is not all directed at accomplishing work. Some goes into generating turbulence in the water ("vortices") which ultimately ends up heating up the water a bit. (The water at the bottom of Niagara Falls is warmer by a tiny fraction of a degree because of the "stirring" achieved by the fall and subsequent random mixing of the water.) Consequently, if one is interested in determining efficiency in the paddler/boat/water system, he/she has to be careful to delineate what is doing work on what. The paddler does work on the paddle (pushing it rearward). The paddle does work on the water (pushing it rearward). And, in turn, the paddler's body does work on the boat, pushing it forward. How much work gets done on the boat, from all the thrashing of the paddle, is the key. I believe the original thesis was whether "wing" paddles were more efficient than traditional Euro paddles (ones with an oval-shaped blade on the end of a shaft). Whether a low pressure area is created behind the paddle as it slices through the water may be moot if other features of paddle passage through water are less efficient. I think, to advance the cause, we need __data__ to sort out what's going on in this system. It is too complex to discuss piecemeal or to solve by gedanken analysis. Albeit, it has been fun to scan what you guys have been writing. -- Dave Kruger Astoria, OR *************************************************************************** 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 Mon Jun 09 2003 - 09:10:00 PDT
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