HTERVORT_at_aol.com wrote: > I once read an explanation by an engineer who championed this > idea that it is the drag caused by the vortices that really > generates our grip on the water, and it fit in with other > explanations I'd read about sails and wings and things. He said > that if you compared two 100 square-inch blades -- one one-inch wide, the other 10 inches wide, the first would have 202 lineal > inches of edge while the second 40 inches of edge, and the first > would have a good deal more grip in the water. But it was his > contention that (for som reason I don't remember -- probably > having to do with the fluid densities), that the aspect ration > of the blade had the opposite effect in the wind -- the thinner blade would be pushed around less. Anyone have a hard scientific > explanation for this? I've heard this too, though I'm not entirely sure I'm convinced. For one thing, boat screw do tend to have pretty low aspect ratios. I believe the advantage for Greenland style paddles has to do with the different Reynolds numbers involved in moving a paddle through water and through air. It's not that the effect is opposite, but that the long, thin blade is relatively inefficient efficient at moving air at the low speeds involved in paddling while being reasonably efficient at generating thrust in the water. (As was pointed out to me, my airplane wing analogy in a previous post was less than accurate.) Is the narrow Greenland blade more efficient at turning effort into thrust? I don't know, and as Peter points out, you'd have to measure O2 uptake, strain on the blade, acceleration and probably other factors to know for sure. But there does seem to be a general agreement that moving a smaller blade more quickly is less tiring than moving a large blade more slowly. This is the bicycle gearing analogy some have invoked and other have challenged; as someone who bikes a fair amount (about 3700 miles April through September), I find that it's very appropriate. It's much easier to bicycle 50-100 miles by spinning 90 strokes per minute than 60. At high rates with low effort the load is more on the cardiovascular system than on the muscle stores. Since switching to long, narrow paddles, I find that I never have any sort of muscle ache, even after a full day of paddling. -- mike --------------------------------------------------------------- Michael Edelman mje_at_spamcop.net http://www.foldingkayaks.org (nomadics) http://www.findascope.com (choosing a telescope) *************************************************************************** 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 May 15 2001 - 10:24:22 PDT
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:30:42 PDT