Here are some observations drawn from airplane wings I have seen or flown and paddles I have built and/or used: -A paddle is used like a wing used at high angle of attack, making it susceptible to stall (cavitation in water world). Stalling a wing results in a dramatic reduction of lift. In our case that is a dramatic reduction in propulsive force -Putting camber on a wing helps it to achieve higher angles of attack without stalling. That's putting a curve into the blade. A simple symmetrical blade has some advantages, but delayed stall is not one. Thus, those who use Greenland paddles must incorporate motion into their stroke that reduces or eliminates cavitation by reducing the angle of attack. There is an article that addresses this in Sea Kayaker which I am too lazy to look up at the moment. -A "wing" paddle has a huge camber, just like the wing of an airplane used for low speed work, or like the wings of an airliner with leading and train edge flaps deployed for landing. -Higher aspect ratio wings have a higher lift-to-drag ratio. That implies greater efficiency when paddling a high aspect ratio paddle. On the other hand, Greenland paddles are symmetrical which reduces wing efficiency. Also, lift-to-drag theory applies to a wing that is designed to move parallel to the wing surface, not perpendicular to it. This is confusing to translate into paddling, but the velocity of the paddle through the water parallel to the blade surface creates drag which is not related to the velocity of the boat through the water. That may disconnect the lift-to-drag ratio from having a positive bearing on paddling efficiency. -Lower aspect ratio wings have more gentle transitions into stall (cavitation). That's why trainer airplanes have wings like a Hershey bar. Lower aspect ratio paddles should not break into cavitation as abruptly and my observation from lousy paddles I have built is that they do not. Conversely, my Greenland paddle required careful technique to prevent cavitation. My opinion (neither smart enough nor fast enough to make a conclusion): Racers use wing paddles because they are indeed faster and more efficient at propelling a boat through the water. On the other hand, it's not all about speed and efficiency. It's about fun. When I paddled with a Greenland paddle I was pain free (although slower) for more miles. Paddling with a high aspect ratio paddle is arguably better for your body, especially when paddling long distances. When I'm older and wiser I'll stop paddling in all situations with my WW paddle and start using something with a higher aspect ratio. Steve Brown AR=b^2/s AR=b/c Cdi= Ct^2/(pi)AR Cd(total drag)=Cdo+Cdi ........... Peter Chopelas *************************************************************************** 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 Tue Jun 10 2003 - 07:04:58 PDT
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