Hi all, The hull speed formula is an interseting one to determine the maximum speed for displacement hulls. But keep in mind it is only an approximation. It is a good one for not to slender hulls with a pronounces bow and stern, like a lot of sailing yachts. It is a much less good approximation for slender hulls. Hulls with a length to beam ratio (at waterline) above 8 can go faster in displacement mode than calculated by the formula. Another point is that the for-aft distribution of displacement (prismatic coefficient) changes the hull speed of the boat. Boats with very fine ends have a lower hull speed that boats with the same water line length and fuller ends. This is becuase the fuller ends increase the distance between the bow and stern wave. So just mounting two feet of razor blade at the bow and stern of your boat increases the water line length, but not the hull speed. It does affect handling, however.... And like mentioned by others, at speeds below hull speed the skin friction is more important that just the water line length. For people that are interested in this stuff I can recomend Marchaij's "The aero and hydrodynamics of sailing". It is a kind of bible for the design of sailing craft and contains a lot of interesting information on hull design. Greetings, Merijn Wijnen ****************************** Merijn Wijnen Vinkenhofje 8 5613 CN Eindhoven The Netherlands Tel.: 040-2939991 (job: 040-2650539) Fax: same as tel., call before sending or try twice E-mail: Home: merijn_at_music.demon.nl Job: m.wijnen_at_ind.tno.nl Web-site: http://www.music.demon.nl *************************************************************************** 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 Mon May 14 2001 - 13:45:23 PDT
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