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 Qwunununu 09-17-2013 05:46 PM

Keel weight

Hello
I am thinking about building a new keel for my 20 ft long sailboat, but I cannot figure out, how to decide the weight of the keel, are there any kind of mathematic formulas?

Rasmus

 knuterikt 09-17-2013 06:13 PM

Re: Keel weight

Quote:
 Originally Posted by Qwunununu (Post 1089880) Hello I am thinking about building a new keel for my 20 ft long sailboat, but I cannot figure out, how to decide the weight of the keel, are there any kind of mathematic formulas? Rasmus
Why do you want to build a new keel?
What is wrong with the old?

The keel have more than one function so there is not one simple formula.

 Qwunununu 09-17-2013 06:24 PM

Re: Keel weight

Hello Knuterikt
I want to build a new keel because I am about to make my boat more like a race boat, and the person that builded the boat, did not made it really good. He made the keel in lead from top to bottom, and then I was thinking that it would be better with a torpedo keel, were all the weight was so low as possible.

Rasmus

 Faster 09-17-2013 06:26 PM

Re: Keel weight

This is designer and engineering territory.. the hull and reinforcements would have been designed for a certain weight/righting moments of the original keel.. attaching a heavier keel could cause issues. I think you need to tread cautiously here....

 Qwunununu 09-17-2013 06:35 PM

Re: Keel weight

Hello Faster
I would not make it heavier, but lighter and deeper, to make the boat lighter also.

 Faster 09-17-2013 06:49 PM

Re: Keel weight

Lighter and deeper could still put more stress on the structure, 'depending'.... Do you have the skills to know what shape/foil to use? to maintain (or improve) the center of lateral resistance? This is all pretty technical stuff, - if you're confident you could have some fun trying something new. But don't be surprised if there's no dramatic improvement (or worse) without some input from the professionals.

 jimgo 09-17-2013 08:04 PM

Re: Keel weight

You might start with carefully matched scale models before working on the big boat.

 Jeff_H 09-17-2013 08:39 PM

Re: Keel weight

Quote:
 Originally Posted by Qwunununu (Post 1089921) Hello Faster I would not make it heavier, but lighter and deeper, to make the boat lighter also.
With all due respect, designing the shape, weight distribution, and supporting structure for the keel is one of the more complex design and engineering aspects of designing a boat. The quote a above suggests you probably do not have an adequate understanding of the way the loads work to safely design a keel and its attachments.

Jeff

 Qwunununu 09-18-2013 03:55 AM

Re: Keel weight

I am not going to build it all alone, i will try finding some professionals, that could help designing and build the the keel so it stay in place and do not brake something.

 Qwunununu 09-18-2013 10:21 AM

Re: Keel weight

Quote:
 Originally Posted by kallis2222 (Post 1090194) Dude its totally work of the engineer whose tell to you that how much feet keel is suitable for your boot..Now i discuss with my friend who is the owner of the boot and tell to you after that...
Sorry but I do not understand what you are saying Kallis2222, could you try explain it in another way?

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