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post #104 of Old 11-01-2013
bobperry
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Re: Full Keel

Paulo has laid out the components and the variable pretty thoroughly here. And I totally agree, if in doubt, check the PHRF rating differences. They are not theory.

A couple things I should add;

I owe the success of the Islander 34 wing keel to Dave Vacanti. I hired Dave because he is an expert in foil performance and a buddy of mine. Dave did the geometry and foil choice for the 34’s wings. I’ll take the credit for the design, it’s a great one but Dave gets the credit for that wing keel. Google Dave Vacanti.

You can’t put fat, stubby wings on a fat, stubby fin and get good results. You’ll get fat, stubby results. You can’t put a fat, stubby bulb on a fat, stubby fin and get good results. As Paulo points out the ratings will verify this. For fins and wings to be effective they need aspect ratio. The problem is that Mom and Pop can’t live with long, thin, bladelike wings sticking off their keel. They are just not durable enough. So the designer or builder has to compromise. A highly compromised set of wings may help you lower the VCG of the boat and reward you with decent stability in a shoal draft situation but it will not give you the lift you need for speed to weather. There are no magic bullets in keel design.

Now, go to the blackboard and write 1,000 times, "There is no substitute for draft."

Please visit my blog. It's fun to read.


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Bob's Blog ....

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Last edited by bobperry; 11-01-2013 at 10:59 PM.
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