Julio wrote; (SNIP) >The most outrageous example of misconception for the sake of marketing >hype comes from Derek Hutchinson and his "Toksook" paddle. He claims >"it is symmetrical, which helps in sculling", but the edges are very >thin and the blade stalls at very low angles; it does not even have >the appropiate foil shape to create lift. He uses the leaf shape in >the blade just because "the Aleut did it that way"; the secret of >that shape is that it reduces the cavitation of the blade as it enters >the water, yet the modern asymmetrical paddle blades maximize that >cavitation for the sake of wrist comfort as the general public wants it. Little old nit picking just to keep evryone honest. What Julio is talking about is not cavitation but ventilation. Cavitation is the outgassing of vapour under low pressures and full immersion. Paddlers just can't develop the velocity to cause cavitation. Ventilation is the migration of air from the surface down the low pressure side of the paddle. Anyone can do that. By way of example - rudders ventilate and propellors cavitate. I find the topic fascinating but then..... :-) Also, it is not the intention of the modern blade design to increase ventilation as that decreases both drag and lift. For a fairly good discussion of this see "Canoeing, an Olympic Sport" by Andy Toro. The primary objective of modern blades is to increase the drag coeffcient and permit a more powerful vertical stroke with lower rotational forces on the boat. >I am surprised that someone like Mr. Hutchinson could get so close >and yet not get the clue. Derek is a delightful fellow but may have failed physics. His chapters on boat design are filled with errors. On the other hand, he designs some nice boats proving that one can still do the right thing even if it is for the wrong reason just as we clever bugger techy types can do the wrong thing for the right reasons. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Fri Mar 27 1998 - 06:19:41 PST
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