Kevin wrote; >Matt and John are discussing whether water is displaced sideways (Matt's >idea) or vertically (John's idea). I think I may not have made myself clear. I said that the flow dives under the hull and follows the buttuck lines. As the water dives under the hull it displaces water to the side. This is established by flow tests in tanks (not my idea although I wish I had thought of it first). The result (Admiral Taylor appears to be the first to show a proof) has had repeated support in other tanks and tests. >To them I ask, why one or the other, >and not a combination of both? My intuition tells me that water is >displaced normal to the local surface of the hull, and probably in a >uniformly thick layer. This sounds so logical that one likes to accept it and I once thought the same thing (as did a lot of sailsboat designers). How disappointing to discover that water didn't see things our way. :-( >Another interesting question is what happens to the displacement direction >of water at a hard chine? The chine tends to redirect the flow much as fins or keels etc do. Nick provides a good example of the effect of flow under the boat. I will ask Professor Inverbon about the Brit boats. David wrote; >I have observed bulbous bows on commercial vessels. I recall reading that >they are used to increase fuel efficiency. I have wondered what effect one >might have when used on a kayak. (Other than being an efficient kelp catcher >that is.) Bulbs have positive effects on resistance through wave cancellation. They only work when the bow is fully immersed and kayaks rarely spend much time in conditions where the bow can stay immersed. Also, their draft works against them in this respect. Followers of Baidarkas will have read Dyson's comments on this as an explanation for the bifid bows on some baidarkas. Regrettably, videos show the bow emerging from the water. I say regrettably because one would like them to work. 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 Wed May 26 1999 - 03:44:34 PDT
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