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post #218 of Old 03-30-2012
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Re: Full or fin keel?

Originally Posted by pvajko View Post
That's really odd, could you give us a link to that paper?

(I hate to mention, but Marchaj's book also references tank tests showing boats are more likely to capsize without the mast, but he is saying they'll be slower to recover with the rig because of it's dampening effect.)


Yes, I will give you the name of the paper and the University (I have to look) but you have to pay to access it or to receive the papers home.

But it is easy for you to mention what test tanking is Marchaj referring (just say the page and the chapter). To my knowledge all tank testing regarding sailboats stability was done after Marchaj book.

If I remember correctly he refers not tank testing under controlled conditions but what happened on the 1979 Fastnet . It was found that a boat after losing is rig was easier to capsize than with the rig intact.

Off course, without controlled conditions and without isolating causes saying that is due to a lesser roll moment of inertia is just a hypothesis that has to be confirmed with tank testing.

Personally I think that the reason is other and it has to be with a boat sailing or sitting on the water at the mercy of waves. With 40 or 50K winds even if you don’t carry any sail, the boat is sailing, moving on the water with directional stability and much less at the mercy of waves.

There are some great images of an Open 60 on bare poles sailing at over 10K.

Regarding Marchaj's saying that a capsized boat will be slower to recover with the rig because of it's dampening effect, it is just an hypothesis that has to be verified under controlled conditions. It was what those researchers have done: Marchaj hypothesis is wrong, it is not in accordance with reality.


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