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post #482 of Old 09-19-2012
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Re: Full or fin keel?

Originally Posted by Daily Alice View Post

I got as far as finding VMG, metacenter and CB for a boat, but how do you arrive at " the ratio of mass righting moment to hull righting moment"? I mean what do you need first, for data, and what formulas are you using? I ask because your approach seems useful. Isn't hull righting moment graphed over various heel angles (like from 0-30 deg.)? Anyway, I'm curious, thanks.
Sorry it took so long to answer. The boat is now out of the water for winter storeage. I hope to create a new thread discussing this subject this winter. I have simulations to support my assertions.

For me, it is the defining distinction between a rough water boat and a non-rough water boat. Light weight racers are the worst, heavy weight cruisers like the big Island Packets are the best. For me, it is part of the answer to the age old question of "blue water" capable and it is consistent with what the experienced sailors know already.

The reasons I developed my simulations and mathematics was to understand the significance of different weight boats of similar size.

The problem with righting moment diagrams is that they become useless once you put a boat on waves (in rough water). So you cannot predict from righting diagrams what boat is best in rough water. You cannot even predict what a boat will do in rough water from its righting diagram.

Two boats of similar size can have very close righting diagrams. However, one will be very comfortable in heavy seas and the other can be quite dangerous.

Last edited by BryceGTX; 09-19-2012 at 10:22 PM.
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