Originally Posted by Don C L
Resonant frequency. Hulls respond to waves at a certain frequency. Different hulls, different frequencies.
Exactly, rolling is a resonance phenomenon and usually the extent of the roll depends on how close to the transvers natural frequency of the boat the waves are.
Whether and how much rolling occurs tends to depend on how much damping is inherent in the system. I have noticed that whilst sailing down wind
I can sometimes stop the boat from taking up excessive roll by shifting my weight from foot to foot counter to the roll.
drillers originally went into deep water offshore
using ships and barges, heave and rolling was a problem because they make the work more difficult. To solve the problem they built semi submersible drill rigs which distribute the buoyance over a number of water planes in the columns spread widely apart. Since the support columns and lower hulls are generally full of water when they are ballasted down there is a large mass and distributed impetus consequently little heave or roll.
However, when the wave period, even though the wave heights are almost unnoticeable, match the resonant period of heave of the semi, as has occurred off the Western Australian coast, the heave can become massive. In one instance 28 feet on what looked like a very calm day.