Originally Posted by codprawn
Basically the self righting comes from the design of the superstructure - big volume on top means that there is more buoyency above the waterline than below. Of course this also puts more weight aloft as well which makes them more top heavy.
In a way not a problem becuase they will always come back the right way up but it does make for a rolly polly sort of ride.
I accept that increased water tight superstructure will raise the CoG - but presumably one can at least partially counteract this with extra below water line balast.
They presumably can't be top heavy or they wouldn't come back up again when they do capsize.
So - they are really nothing like a beachball - which has no right way up, and which has its CoG right at the centre.