Hi Doug. That seems like a low tech solution and is adaptable to many tasks
on one of our little boats.
I have considered the oil compensation idea for the actuators, and will
investigate it further when I start fabricating the mechanisms.
With the bellows, there will be some drag on the rod, and I'm not sure just
yet how that will affect the operation. I think a lot depends on the geometry of
the bellows. For sure, there's empty space between the ribs of the bellows that
will compress once the bellows is submerged at depth. I'm building a high
pressure test chamber and will put these in there to see just what happens when
they operate.
As for "wear" on the bellows, they are so cheap that replacement won't be a
problem, and carrying "spares" will be easy. Frank D.