MainlySteam
New member
Weight aloft does increase the mass moment of inertia of the vessel so requiring more force to accelerate it into rotating about it's longitudinal axis but this is only important for forces applied for a very short period.
Wind force, assuming it is constant, will eventually heel the boat regardless of the moment of inertia because time allows the acceleration to be slow (so a small long acting force will overcome the inertia from the high mass moment and the boat will still heel) - like rotating a car wheel, a small force will not accelerate it very fast but will still rotate it.
However, in the case of short term forces, such as those from waves, a high moment of inertia resists heeling (the force only exists for a short time so if it is going to heel the boat, the accelerations have to be high, so the force has to be high).
Putting those together I think the correct wisdom is that if you want a high mass moment of inertia about the vessel's longitudinal axis you do so by putting weight in the keel, you do not put it up the mast.
John
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Wind force, assuming it is constant, will eventually heel the boat regardless of the moment of inertia because time allows the acceleration to be slow (so a small long acting force will overcome the inertia from the high mass moment and the boat will still heel) - like rotating a car wheel, a small force will not accelerate it very fast but will still rotate it.
However, in the case of short term forces, such as those from waves, a high moment of inertia resists heeling (the force only exists for a short time so if it is going to heel the boat, the accelerations have to be high, so the force has to be high).
Putting those together I think the correct wisdom is that if you want a high mass moment of inertia about the vessel's longitudinal axis you do so by putting weight in the keel, you do not put it up the mast.
John
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