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post #202 of Old 12-30-2012
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Re: Production boats- justified bias?

Originally Posted by Lou452 View Post
Thanks for the 20 plus pages ! I am new and trying to digest all this and learn. Can I ask for stability, do sailers have a world index for each type of boat? ISO 12217 ? Categogy A,B,C, 1,2,3 ? Do they hide this data? I was looking at the Chicargo to Mac. race. They are trying to make a (safe) boat rule. Is there a way to put a stamp or number to every boat to judge apples to apples ? You have upright and inverse stablity. You can build a huge pencil put a weight on the bottom a sail on the top. It will have a large phrf and not out run the weather. It will not capsize. Should I have some easy way to know this? THANKS, LOU
A class A boat means that conforms with a complicated set of measures some of them having to do with stability. Any modern 36ft boat should pass that conformity and a very well designed 30ft can manage that even if for that has to have a very good stability for its size. A good example is the A 31.

That kind of very narrow boat you describe with a lot of ballast deep down looks like the last AC monohull. A boat like that is great upwind but not very fast and very tricky to sail downwind. Not fast because it would be very difficult or impossible to reach planning speed, tricky because the boat will tend to balance from side to side, specially with lateral waves since it has not a substantial hull form stability to damp that movement. Besides these inconvenients a narrow boat will need always a lot of heel to sail and will offer a very small interior space.

Regarding accessing a boat stability the better instrument is a stability curve. On the interesting sailboat thread I have a post explaining how to read one regarding the meaningful data.

Some boat builders publish the stability curves, others will give them to you if you ask and others don't really like to give them but if you say that you won't buy the boat without seeing it, they will give it to you

They all have them because they are needed for the EC certification of the boat.


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