Nick writes: > There is some good data about the relative efficiency. The wing paddle > is apparently about 89% efficient and the "conventional" paddle blade > is about 74% efficient. What is still an open question is why the wind > paddle is more efficient. I wonder how efficiency is defined here. Is it lift to drag ratio? In that case I would venture that the answer is the same as for an airfoil versus a flat wing- less turbulence and more laminar flow over the paddle. Of course, like an airfoil, an asymmetric wing paddle operates efficiently only in a relatively narrow range of angles of attack. Outside of that it will stall. There's always a tradeoff. -- mike ----------------------------------- Michael Edelman medelman_at_ameritech.net http://www.foldingkayaks.org http://www.findascope.com *************************************************************************** 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/ ***************************************************************************
On Tuesday, June 10, 2003, at 08:20 AM, Michael Edelman wrote: > Nick writes: > >> There is some good data about the relative efficiency. The wing >> paddle is apparently about 89% efficient and the "conventional" >> paddle blade is about 74% efficient. What is still an open question >> is why the wind paddle is more efficient. > > I wonder how efficiency is defined here. Is it lift to drag ratio? In > that case I would venture that the answer is the same as for an > airfoil versus a flat wing- less turbulence and more laminar flow over > the paddle. > > Of course, like an airfoil, an asymmetric wing paddle operates > efficiently only in a relatively narrow range of angles of attack. > Outside of that it will stall. There's always a tradeoff. Since the article calls into question whether the wing paddle even uses lift to improve efficiency I doubt that they define efficiency in terms of lift-to-drag ratio. I suspect they looked at some aspect of how much power goes to boat speed relative to how much power the paddler applies. I don't know how they determined this. Nick Schade Guillemot Kayaks 824 Thompson St Glastonbury, CT 06033 USA Ph/Fx: (860) 659-8847 http://www.guillemot-kayaks.com/ *************************************************************************** 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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