Steven Dubnoff wrote in message
...

Can anybody explain what rate stabilizers, how they do it and
whether
they are worth the money for slow moving displacement boats?

Earlier autpilots sensed 'heading error' through a fluxgate
compass, and applied rudder proportional to heading error to
bring the vessel back onto course. To allow for change of trim
calling for a new neutral rudder angle, they also integrated any
persistent heading error and applied rudder to cancel that out.

A rate stabiliser measures the rate at which heading is changing
from a rate of yaw sensor and applies rudder to cancel that rate
of yaw. This makes for a more active rudder (bigger power
consumption) but theoretically a steadier course.

I haven't tried it on boats (only on airplanes, where it works a
treat) so can't comment on value, tho' theoretically I'd expect
better downwind steering.

JimB, Yacht RAPAZ, sadly for sale to buy that Greek house . . .
http://homepage.ntlworld.com/jim.bae...cification.htm