Doug wrote; (SNIP) >Has anyone experimented with > painting on some kind of roughened-up traction type surface on the power > face of their regular euro paddle? Perhaps a bit of antislip deck paint, > or some such thing. Any thoughts? About ten years ago I did some tank testing of paddles and created a paddle I called the "Gravel Paddle" because it had a perimeter coated with driveway de-icer glued on and covered with epoxy. I theorized that, by coating the surface with something rough it would slow the flow and possibly reduce the size of the edge vortices. I hoped this would give the paddle a higher drag coefficient and also - just maybe - reduce flutter. It actually seemed to work. Harry Roberts, editor of the old "Canoesport Journal" wrote and article about it after trying it and concluding that I had not completely lost my mind. I found that grits of even very coarse sandpaper (I tried up to 16 grit) grit) did not have any noticeable effect in my tank or in subjective trials. Coarse rock salt glued around the perimeter 1 inch wide seemed to work best and produced a repeatable difference in the tank (about 7% on average if I remember correctly) and, according to the test paddlers, a noticeable difference in the paddle "feel" . The reason I had to use bumps with a high profile stems from the low Reynolds number of the flow across the paddle. One really has work at getting turbulent flow at low velocities. You can find the critical roughness for turbulent flow in mils (thousandths of an inch) using the formula k = 14/v where v = the velocity in feet per second. In my tests I used an 8" wide canoe paddle since I wanted to exaggerate the flutter. A smaller kayak paddle might operate at higher velocities and smaller grits sizes could produce results. I also tried some "smooth" bump configurations using beads from a local craft store but with no luck. The paddle had no redeeming aesthetic attributes. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Tue May 16 2000 - 07:25:09 PDT
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