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Old 27-04-2012, 14:38   #16
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Minaret,

I would love to see new estimates on Center of effort calculations based on the cut...

The work seems to be done professionally, but what are the performance changes? How well does the boat go upwind, vmg not pointing angle
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Old 27-04-2012, 14:47   #17
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Re: Keel cutting

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Minaret,

I would love to see new estimates on Center of effort calculations based on the cut...

The work seems to be done professionally, but what are the performance changes? How well does the boat go upwind, vmg not pointing angle


It would be an interesting comparison (though I believe you mean the CLR would change, not CE), as would some carefully taken polars. The NA stated that he believed the boat wouldn't point as high, but would make less leeway due to the flattened "wing" bulb. The owner stated that as far as he could tell that was exactly the case, he couldn't point quite as high but made less leeway, making VMG about the same. He said he noticed no difference in the boats speed, which seems unlikely at least in light airs. I spoke to him about it only a couple of months later and he probably hadn't put in enough time to notice the subtle differences. In any case it was a surprisingly easy job to do and went quickly. I would say it can be done proffesionally for 5-10k depending on size of boat and the yard, DIY for 3-5k and fairly easy to do.
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Old 27-04-2012, 14:48   #18
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Thumbs up Re: Keel cutting

GO FOR IT! Think of Thomas Edison or Henry Ford had they heeded to much advice from naysayers! Find a yard to do the work; get your cost estimates and plan worked out to a reasonably workable level and do it. Take pictures and keep us informed.
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Old 27-04-2012, 14:53   #19
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Re: Keel cutting

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I have just purchased a DB-1 sailboat the problem is it has a 6.6 " draft has anyone have any knowledge of cutting off say a foot off of the keel? my idea is to weld on some wings just up from the bottom of the keel about 1' up and then when I| am lifted up cut off the keel just below the wings any ideas?
thanks

Good lord, I JUST NOTICED that this is a steel boat, probably with a steel keel with internal ballast or just steel plate. A whole different can of worms than a lead ballast keel on a glass boat. If it's just a plate keel then it's a no-brainer, just make sure the wings weigh a good 20% more than the section you remove. If it has internal ballast things are obviously complicated by that.
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Old 27-04-2012, 15:17   #20
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Quote:
Originally Posted by minaret

It would be an interesting comparison (though I believe you mean the CLR would change, not CE), as would some carefully taken polars. The NA stated that he believed the boat wouldn't point as high, but would make less leeway due to the flattened "wing" bulb. The owner stated that as far as he could tell that was exactly the case, he couldn't point quite as high but made less leeway, making VMG about the same. He said he noticed no difference in the boats speed, which seems unlikely at least in light airs. I spoke to him about it only a couple of months later and he probably hadn't put in enough time to notice the subtle differences. In any case it was a surprisingly easy job to do and went quickly. I would say it can be done proffesionally for 5-10k depending on size of boat and the yard, DIY for 3-5k and fairly easy to do.
Your right in that the CLR, Center of lateral resistance, is the predominant change of force with the keel being cut, but the CE and CLR are like a bassist and drummer, you can't change one without directly affecting the other.

Using the anecdotal evidence of an owner who is emotionally committed to unconsciously validating his own expensive decision is not the best evidence either...but based on the tone of your post you obviously know this.

There is no way that the increase in set due to the loss in keel size combined with the increase in resistance due to the bulb and wings would be offset by anything that would result in a net gain in vmg upwind...

....however the owner probably has a net gain in vmg overall since most cruisers do not beat to windward for any substantial period of time. And the keel profile described would be a benefit downwind and allow entrance to more harbors....

But steel??? Didn't cop that myself either on first read
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Old 27-04-2012, 15:24   #21
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Re: Keel cutting

Totally do-able, but time consuming & fiddly. But then I'm slow and careful.
As long as your righting moment & keel area are kept the same you will be
fine. The nay-sayers have no penchant for challenges.
The boat attributes will alter as Minaret has said, mileage will vary & there is "X" risk
of a trait you do not like.
If your engineering skills are limited & your don't have the ming for a pro to do it, don't. Resale?
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Old 27-04-2012, 15:28   #22
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Re: Keel cutting

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any ideas? thanks
Took a while to find but:


Magic Keel
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Old 27-04-2012, 15:32   #23
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Quote:
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Took a while to find but:

Magic Keel
Nice.
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Old 27-04-2012, 16:04   #24
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Re: Keel cutting

Nice! The BS Bulb, I love it...
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Old 27-04-2012, 17:07   #25
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Re: Keel cutting

It's been done many times. Alot of work, but if you have to have that boat and are going where shallow draft makes a difference.... go for it.
I doubt if the "lead" (ie: the sail plan balance) would change much at all... Let's face it... that changes all the time depending on headsail selection and reefing the main.... no problem. Weigh what you take off, determine how much to put back on.
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Old 04-05-2012, 14:52   #26
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Re: Keel cutting

I firure the weight loss will be less than 100lb. so may not put anything on this year. I love the magic keel idea and will try to fabricate something similiar for next year. to clarify my old boat is a steel hull, the "new" db1 is fiberglass with a "lead" keel and as the boat will not be pushed too hard I don't think I will have problems will use a grinder with a cutoff wheel to make the chop and as I only paid $1000 for it Im not too worried about resale will upload pics in a month to busy to do the job now. Thanks for the suggestions and links liked them all although tryng to fly with a water cooled engine may not be too practical
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Old 04-05-2012, 16:33   #27
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Re: Keel cutting

cool..... send us a pic!
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Old 04-05-2012, 16:48   #28
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Re: Keel cutting

I prefer my stihl chainsaw, to a grinder. 'Cept dont hit any bolts! Grinder tends to grab, unless you use the coarse "chainsaw" head. CS is also good for skimming as opposed to using electric planer.
Ditto, pics,pics!
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Old 04-05-2012, 17:28   #29
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Re: Keel cutting

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I prefer my stihl chainsaw, to a grinder. 'Cept dont hit any bolts! Grinder tends to grab, unless you use the coarse "chainsaw" head. CS is also good for skimming as opposed to using electric planer.
Ditto, pics,pics!
For Steel?
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Old 04-05-2012, 17:33   #30
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Re: Keel cutting

Isnt there a boat that was designed with a cutaway keel. I remember seeing here on cruisersforum. Manufacturer designed it as such and you could just cut a predetermed piece of the keel away.
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