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post #100 of Old 03-17-2012
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Re: Full or fin keel?

Originally Posted by pvajko View Post
Can you recommend a newer one, at least as good as his, backed with solid physics and math?

Originally Posted by skygazer View Post
Paulo, I'm interested in this subject, only having had experience with full keels. Here is what I see, please go into a bit more detail if you see something else.

The drawing of the "tripping" on the keel looks like they are located where waves hit shallow water and break. An area we all try mightily to avoid. Seems that with a small keel or no keel the boat would be "flipping" instead of tripping. Not sure being tossed from the boat is better than filling the cockpit. Plus, trying to get some rest if the boat is rolling with the steepness of the wave fronts, that seems like it would be difficult.

No I cannot recommend another one. Taking into consideration what Jeff has said, there are 30 years of sailboat design between that book and today and 30 years where mathematical computing models of boats and hydrodynamics and tank testing have assumed a main role to understand dynamic stability and the way a boat reacts with the sea.

But more than what those studies have shown I would say that more was learned with the pragmatical work of many Naval Architects and many thousands of designs and the assessment that was made of those designs mostly by racers, that in some cases were also the designers.

Skygazer, regarding waves, breaking waves are the only real danger for a monohull and you don't find them only near shore. With a formed sea with big waves and over 35K winds the top of the waves break and if the wave is big, the top of the wave are many tons of water. On that drawing is that what is happening: it is not all the wave that is breaking (like in a beach) but just the top.

By any mean I want to say that full keels are dangerous, just showing that they have also some disadvantages in what regards seaworthiness and dynamic stability.

Those are pages of a book written by one of the biggest sailors of all time, Eric Tabarly. He was not a theorist but you can be sure he knows what he was talking about. He raced what was then modern boats (transats, circumnavigations) and him and the guys that were behind the designs he sailed had an important role in the development of today's modern hull shapes, rudders and keels. And I am saying that he knows about what he is talking about because he did not only sailed extensively racing boats but also its family boat (that he loved) the Pen Duick, an old and beautiful old full keeler.



Last edited by PCP; 03-17-2012 at 03:06 PM.
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