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post #821 of Old 05-20-2013
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Re: Full or fin keel?

Originally Posted by bobperry View Post
Paulo those are lovely photos you downloaded from the internet. I'm not sure what they have to do with the tandem keel though. I see no mention of the tandem keel in any of that downloaded material.

I have no issue with CFD at all. It's a wonderful tool when used correctly. My original question had to do with why was Paulo so certain CFD had been used to design those tandem keels?
Bob, I don't know if the several modern tandem keels designed recently by some major NAs where designed used CFD, a speed prediction program or tank testing.

Originally Posted by bobperry View Post
... I wouldn't make the automatic assumption that CFD is being used for every new keel you see from a major design office....
Not all NA are using yet CFD or based speed prediction complex programs but big NA offices are (in general terms) and some smaller ones too. Those images that I downloaded from the internet were from the sites of two Naval Design offices : Ker and Berret/Racoupeau.

But I would find hard to believe major NAs making statements like these ones without knowing about what they are talking about:

“Those looking for small draughts will be delighted to know that cast-iron tandem keels …offer almost the same sail stiffness and the same ability to go close winded as lead keels with far deeper bulbs”

"The tandem keel is an alternative to the twin keel, it increases lift while reducing drag "

Both have recently worked and used tandem keels on their sailboats designs. Do you think they don't know what they are talking about?

Both firms are well respected and credible, we are not talking about a boat manufacturer making publicity, they work with several different types of keels. I don't think they are making these statements without knowledge. Sure, there are several ways of testing to acquire that knowledge, from tank testing to testing in real size, but CFD or a based speed prediction complex program is the more inexpensive way.



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Last edited by PCP; 05-20-2013 at 09:53 PM.
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