The widow of Donald Crowhurst may hold the patent on that. His ill-fated trip
around the world was to publicize such devices.
http://www.amazon.com/exec/obidos/tg...32660?v=glance

Normally, cruising cats don't have a problem flipping, there's only been a
handful of cases. Trimarans, however, have a somewhat more checkered history,
and homemade multis also have had problems. Even so, if you're not planning on
crossing oceans or challenging hurricanes, you shouldn't have a problem.


"Parallax" wrote in message
om...
I am considering building a 32' trailerable tri so have been
considering various aspects of multis. Although I am not really
worried about ending up upside down, some people are so...........

Another useless idea. Have an airbag-like device near the masthead
that senses when the mast becomes horizontal. BOOM, airbag goes off
and suddenly you have a big floatation ball at the masthead with lots
of righting torque. This would have very low mass because it does not
rely on compressed air but on the same chemical gas generator thazt
air bags in cars use. If you arranged the angular sensor so that it
went off when the mast was more than horizontal, the angular velocity
due to the righting torque might be sufficient to fully right the
boat. Otherwise, it would just cause the boat to float with the mast
horizontal.