On Mon, 24 May 2004 19:27:30 -0400, "Armond Perretta"
wrote:

Jeff Morris wrote:
"Rod McInnis" wrote ...

My, my, my but the things one can learn on a usenet group. Just
recently I learned that cruising catamaran sailboats are
unconditionally stable, that is stable under any and all
conditions.

Unfortunately, the unconditionally stable position is with the
mast pointed down.

Monohulls are unconditionally stable when sitting on the bottom.

Why does it usually seem that this subject is argued on an "either/or"
basis.
There are advantages to either approach. Is this really surprising to
anyone here?

I've been reluctant to enter this thread because of the significant
contribution from the lunatic fringe.

Still, for what it's worth:
if you define "unconditionally stable" as meaning "unconditionally
self righting from any start orientation while the structure is
intact", there are several well-known examples.
Perhaps the one that comes first to mind, is a trans-Atlantic rowboat.
This had buoyant sponsons at either gunwale, but more importantly,
raised flotation structures at bows and stern, so that it could not
maintain a capsized orientation.
This illustrates that flotation sufficient to prevent sinking is not
enough for this classification. There must be a righting moment,
which can originate with a mast head float, and buoyancy compartments
and low CG keel mass but arranged so that the vessel will erect on
the sea surface from any roll angle. This can be arranged for
monohulls and multihulls. Sailors may not always like the features
needed though....

Brian Whatcott Altus OK