I may be way off base on this, but I'm going to try and make electric
linear screw actuators control the rudders and dive planes. I found some from
"Firgelli" in the UK that should work. They have 150 pounds of push, operate on
12 volts, and are nice and compact. The plus here is that just an electrical
thru-hull and two wires is needed for each one. No cables, linkages, block V
seals, or other possible leakers.
I'm going to use simple rocker switches to drive the actuators in and out.
They have built in limit switches and indicators, so should be able to tell
where they are. The down side is they won't "fail" in a set position like
pointing "up" for the dive planes or center for the rudders.
The idea is to encase them in a stout FRP casing molded tight to the
actuator body, and use a rubber bellows sealed with hose clamps and
poly-urethane coating for the extendable shaft.
These actuators are so compact that the aluminum body and stainless rod
don't leave much air space, so I'm hoping with a little experimentation I can
get them sealed up. Here's a pic of the actuators. They run about $100 each.
Frank D.