Mike >>The best example is in a sailboat with the mast removed. Although the weight hasn't changed all that much, the boat will develop a vicious fast roll because the long mast has a high moment of inertia and serves to dampen rotational acceleration.<< My experience with sailboats has been the opposite. I would venture to say the reason the boat rolls more without the mast may have been that it is also without the steadying effect of the sails. I have been at sea with the sails down and the mast up and had rolls severe enough to through things around the cockpit. I also know from experience that placing a radar antenna high on the mast added roll. You may want to check your math again, A couple of factors you have forgotten are the metacenter and that the CB moves outboard with a role. A good source on small ship stability is "Seaworthiness the forgotten factor" by C.A. Marchaj. Don Dodds

I guess I didn't make myself clear. Reducing the moment of inertia makes the rolls less comfortable because the rotational acceleration is higher. The roll has "snap" to it. I've done a couple of deliveries under power without a rig and it can be pretty uncomfortable. However, the amplitude of the roll may well be higher with the mast in place because once the roll is started the rotational inertia tends to keep it going. You have only to watch sailboats with no sails up rolling in your trawler wake to see this effect! Obviously a sailboat with the sails up and reaching or beating rolls very little. This is a naturally stable situation where if the boat rolls to leeward the force on the sails decreases, creating an increase in the restoring force, and vice-versa. Mike T.