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post #102 of Old 11-01-2013
grumpy old man
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Re: Full Keel

I have some interesting first hand experience in this area. I designed the Islander 34 about 25 years ago. We did two keels for the boat. One keel drew 5’ and had wings. The other keel ,sharing the same root fin, drew 7’ and was a clean tip fin keel. One keel was on hull number one. The other keel was on hull number two. Both boats were launched the same day. Both boats had identical new sets of sails. I flew to California with my right hand man, Paul, and we spent two days racing the two boats against each other, upwind, downwind, reaching, tight windward course, and long downwind course. For two days we did this while switching crews. Paul and I never sailed on the same boat. I wanted to be certain that the boat I was racing against had a skipper I trusted, one with far better than average sailing skills. Paul was a skilled racer.

After two days of constant sailing it was clear. Neither boat had a boat speed edge on the other. This was not what we expected but it is what we found to be true. Upwind and down either boat could beat the other depending on wind shifts and tactics but not boat speed. Much of the time we sailed very close to each other to access the speed differences. We sort of thought the wing keel might be faster accelerating out of a tack. We sort of felt the wing keel did not track downwind as well as the deep draft keel. But there was no definitive performance difference. For sure, we looked for one.

This is not theory. This is not conjecture. This I first hand experience with real boats and real sailors. It was the chance to do an experiment with two identical boats and that is a rare opportunity.

So what I would like you to take away from this report is that all wing keels are not created equal. All deep draft keels are not created equal. All bulb keels etc. You can theorize and generalize but leave room for exceptions to the generalities. You can have a very well designed wing keel or a very poorly designed wing keel. The only thing they will share in common is that they both have wings. The geometry of the wings could be totally different. The geometry of the fins could be totally different, Lots of variable availables here. Good bulb shape vs bad bulb shape. Good bulb on a bad fin? Bad bulb ona good fin? Lots of variables.
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Last edited by bobperry; 11-01-2013 at 10:27 PM.
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