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From: Tom MacNaughton
Date: 19 Feb 2008
Time: 11:20:07 -0500
Remote Name: 66.252.35.241
Again, with apologies to Marc Lombard, I am very dubious that anyone can design cambered toed in keels by any simple rule of thumb and actually get a vessel with all around better performance. It is possible that a very subtle optimization as a result of extensive tank testing will provide, say, a 1% advantage if you get the camber and toe in just right. But I can tell you that after somewhere over 40 years studying this sort of stuff I have not seen any actual studies that indicated that such advantages could be obtained reliably without such tank testing. To tell you the truth I haven’t even seen any studies which actually demonstrated any advantage even with tank testing though I have been told that some vessels which have been tank tested have shown some advantage to very particular keel arrangements which employ particular cambers and particular toe-in angles. However everything I have heard indicates that these are very subtle questions which cannot be eyeballed or developed by rule of thumb. Rather than try to do that I believe we are better off simply using very carefully designed twin keels without worrying about adding camber or toe in. There are enough advantages to twin keels under conventional naval architectural knowledge and methods without having to resort to unusual practices. Also we here again the theory that somehow the windward keel will give some unusual increase in stability. While I have heard these assertions repeatedly for over 40 years, I have never seen the slightest evidence that anyone has actually constructed a formal theory to this effect and tested it scientifically. So far we have not been able to construct any flow model which would actually allow this to be true. Without even a theoretical basis in flow analysis to indicate that this theory should be tested, it would be hard to regard this as other than mythology.