"Roy Smith" wrote

One of the fundamental truths of boat design is that the center of gravity
has to be lower than the center of bouyancy. If it's not, then eventually
the boat (helicopter, whatever) will figure out how to turn itself over so
that it is.

Not completely true, but right to a degree.

In the case of a heli or plane on floats, the center
of gravity is way higher than the center of buoyancy,
and everything continues to work out OK.

In that case the center of gravity is between the
outer points of buoyancy. Like this:


GGG

BB BB

Then if it gets a little sideways, and the gravity
is on the outside of buoyancy, things will re-adjust.

GGG BB

BB

Ker-splash! Soon it is stable again, but
in a bad (g) way:

BB BB

GGG
--
Jim in NC