Dennis,
Roll rate is an important consideration for any boat, not just for bluewater boats, because of effect on crew comfort. Heavily ballasted sailboats have a low righting moment when upright or slightly heeled, and a rapidly increasing moment as heel angle increases. The resulting rapid roll oscillations can be quite uncomfortable, especially for those of us without iron stomachs! Sometimes while motoring my little Flicka 20 sloop in confused seas with the sails down, I've literally had to hang on with both hands to keep from being pitched over the side with every wave. I'm talking 45 degrees either side of center with a period of oscillation of maybe 2 seconds! Definitely not a comfortable ride. I expect that removing the mast would make it much worse. You could say there's such a thing as TOO much stability. This certainly is a complicated subject. I suppose that's why naval architects make the big bucks!
Anyhoo, this has been in interesting thread. Lots of food for thought.
And good luck with you project Red.
Jim
--- In electricboats@
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> Red,
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> You are mixing up roll stability (technically righting moment) and roll inertia (technically polar moment of inertia). Having the weight distributed away from the center of gravity slows down the RATE of response to a disturbance, say a big wave hitting the side of the boat. The boat will tip just as far but will move to the tipped position a bit more slowly. I believe this really only has sigficance to a blue water boat that might spend days on end with a beam sea.
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> Roll stability is more relevant to us. To a sailboater it means how far the rail will go down under a steady press of sail. To a power boater it means how far will the boat tip when a heavy crew steps on the gunwale or waves hit the boat from the side. It is determined by the position of the center of gravity (regardless of how far the weights are spread out) as compared to the hull's center of buoyancy which is dependent on the shape of the hull, it's displacement (weight of everything) and angle of heel.
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> The take-away is that the boat will tip the same amount whether its weight is distributed as with a deep keel and tall mast or concentrated as with no mast and higher ballast. The conventional sailboat will rock back and forth more slowly due to its greater roll inertia and hydrodynamic damping of its keel or deployed centerboard forcing aside the water.
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