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  #101  
Old 11-01-2013
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Re: Full Keel

Quote:
Originally Posted by jraymer View Post
Hi Paulo.
So I take it leeway would be worse with bulb/wing keels?

Jim.
Some confusion here. I was talking about deep draft bulbed keels versus wing keels.

Yes on a wing keel assuming it is a shallow draft wing keel you will have more leeway and also less pointing ability.

Some American boat builders like Hunter or Catalina only started to use bulbed deep draft keels recently but they are the standard on cruising boats for almost two decades.

Previous to that the standard was a fin not bulbed keel (iron or lead). In what regards leeway and pointing ability it is the same: Way better than in a shallow draft wing keel.

Regards

Paulo
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  #102  
Old 11-01-2013
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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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  #103  
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Re: Full Keel

Sure, there is nothing like reality and I don't know the fin keel you are talking about (or the wing keel) but that is an exception in what regards the typical deep fin keels and typical swallow wing keel, the ones that are used by most designers. Why?

Because otherwise all will be racing with low draft wing keels. I don't know of any boat with a version of low draft wing keel that has not a significantly higher rating (PHRF) so if the boats had the same performance it would be a lot easier to sail the wing keel to the higher rating, even sail easily over it and win all the races.

Boats with fin keel and big draft would not stand a chance: Their performance would be similar and the rating a lot lower, I mean the PHRF number would be lower. They would win all races on compensated time and would be as fast on the water.

That is not what happens.

Regards

Paulo
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Last edited by PCP; 11-01-2013 at 10:42 PM.
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  #104  
Old 11-01-2013
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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."
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Last edited by bobperry; 11-01-2013 at 10:59 PM.
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  #105  
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Re: Full Keel

There is no substitute for draft, there is no substitute for draft, there is...

Thanks for adding your knowledge Bob. I really appreciate it. I am shopping for a boat and the ones I like are coming with wing keels but I really prefer deep fin. Thanks for your input Paulo. You guys cleared up a big question of mine.

Jim.
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Old 11-02-2013
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Re: Full Keel

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Originally Posted by bobperry View Post
...

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.... 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.

..
Bob, It seems we are talking about a very special keel with foils as wings, not the typical mass production keel. It seems very interesting. I would like very much to have a look. Can you post a drawing?

Yes, I found out very interesting "stuff" by Dave Vacanti. Interesting read. Thanks!

Regards

Paulo
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Last edited by PCP; 11-02-2013 at 01:00 AM.
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  #107  
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Re: Full Keel

Paulo:
Those drawings are hand drawn. I will have to get them digitized but I'd be happy to do that next week and post them.

The other thing I should have added was that we were in agreement that the deep draft boat was the more pleasant boat to sail. We preferred the feel of the deep keel boat. Dave Vacanti also flew to Calfornia for the test sail. Somewhere in my archives I have a report Dave wrote on the test. I'll see if I can find it. It was fun. My friend lent me his Mercedes 6.3 litre SEL while we were there.
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  #108  
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Re: Full Keel

Compromise is a good thing in keels. A new Jen 379 at the yard I'm at has the "Catalina" smile. The dealer says yard blocked wrong. Not sure who is going to pay for the fix. I think a lot of finger pointing is going to happen. Long narrow fins are good for ultimate performance up to the point where you ground out or a little bump breaks the boat.
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Re: Full Keel

Quote:
Originally Posted by ctl411;1113695...
ong narrow fins are good for ultimate performance up to the point where you ground out or a little bump breaks the boat.

If the boat is well built, as most are, a little bump is not going to break the boat. Some way back on this thread there is a movie with a racing boat with very narrow and deep torpedo keel being dragged (after having grounding with waves) on the beach to the sea (with waves again) and being put afloat again. Lots of hard bumps and the keel remained solid and on its place.

Regards

Paulo
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Re: Full Keel

Being put afloat and being OK are not the same. Was the boat floated then pulled for repair? I'm not saying it can't be made strong just takes better design and build to do it. I've hit bottom with my Cherubini hunters moderate fin keels no damage. But the Jen 379 was just blocked a little wrong and damage occurred.
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