Nick wrote: "I frequently here people talk about paddles working like wings and am prepared to accept that it is possible. Yet whenever I ask people to describe how the paddle is working like a wing, their explanations fall flat." I use my GP with a very vertical stroke. The angle of attack the blade is relatively low, like 45 degrees to the motion. A "euro" paddle is used at 90 degrees. I am quite certain that lift is involved, as I can see the water flowing over the paddle, just the way a fluid flows over a foil from leading edge to trailing edge. The leading edge is towards the boat, and the trailing edge is the outside edge. Only one vortex is formed, not two, by this stroke. I experiment with even lower angles of attack, but find that the direction of the force produced is not in the right direction to give good drive. More of the force produced is across the boat, less towards the direction of motion. The paddle is hard to hold, too, as the force produced is quite large and in a direction that does not suit the arms and hands. The blade area of my GP is quite low, as it is cut for my hands and height (5'-6") but I find my cadence to be the same or lower than that of my friends travelling at the same speed. I find I use quite a high paddle velocity through the water to achieve normal cruising speeds, that speed being defined as the speed I have to maintain to keep up with my friends, about 3 kts. I get a rest between strokes. Since the integral of the effort I put in must be roughly the same as produced by my friends (speed is equal, therefore total horsepower must be roughly equal), the peak loads must be higher, yet I find this paddle and stroke to be much easier on the body. Perhaps it is because of the rest between strokes? Before I found the 45 degree angle of attack, I used it like a "euro" blade at 90 degrees, and found the GP to be quite ineffective. Cadence was way higher than normal, like above 60 per minute, versus the usual 30 used when cruising. If this is isn't lift being produced, I don't know what to call it. It is really cool to experiment with the angle of attack, and watch (and feel!) the effect on the water flow as the blade stalls. It is also possible to see how minor dings and imperfections in the leading edge of the blade affect the flow. No wonder the Inuit used bone insets in their leading edges. I hope this explanation is clear enough? In any case, I would recommend you just build a Greenland stick and go try it. Using a vertical stroke, so you can watch the flow and see what happens at various angles of attack and so on, is worth a thousand e-mails trying to describe what is going on. Rob. *************************************************************************** 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 Sep 07 2004 - 12:28:12 PDT
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