Hi Doug. I couldn't get through to the trim tank info, despite coming from
different angles. Anyway, I know there's a few wires associated with an actuator
and position sensor, but I should be able to run all the wires through one
through-hull for each actuator. The big pluses for not using hydraulics
are.....one through hull for each, (X3), elimination of the whole hydraulic
system including tank, pump, valves, supply and return lines, and most
importantly, hydraulic lines to a control box that I want to be able to move
around inside the sub and even take topside when the hatch is open so I can
drive/steer the sub while sitting on top. I took a ride in Dan's sub last year
and he has a small control box that can go topside and it seemed like a very
nice advantage when maneuvering near the dock. He drove the sub right up to the
shore, and was able to handle the ropes while maneuvering with the control box,
all while standing on top of his sub. That sub is very user friendly and gave me
lots of ideas on what I wanted to include in my sub.
I know I could still have electrical switches operating
the hydraulic valves, but why add another link in the chain when straight
electrics will work.
As for the 1 atm. housing, that should be a pretty
simple thing. I think I can seal the actuator housing with a coating of Vulcem,
and then put the whole thing inside a fiberglass bottle made to fit, with a
shaft seal on the driver rod, and a seal where the wires come through.
Much like my Minnkota motors, if the wires exit
the bottle at the bottom of the bottle, and are encased in clear tubing, I'll be
able to see if any moisture is getting in there before enough water gets in to
do any damage simply by checking the tubes after each dive because gravity will
keep the water in the lowest part of the tube, well below the motor or actuator
housing. As long as the fiberglass bottle is a tight fit on the aluminum
actuator housing, it will withstand a lot of external pressure without breaking,
and for deeper dives I will be air compensating the Minnkotas anyway so it will
be fairly easy to add a fitting to the actuator bottle for air compensation. The
air compensation system needs no through-hulls as the scuba tank and
regulator for that system are all outside the hull. I have a small 30 cu.
ft. tank for that system. That should be plenty of air to compensate a few
small devices.
The nice thing about electrical through-hulls is that
they're easy to seal ( epoxy is strong ) and with my design, can be closed at
the hull with a valve simply by pulling the wires out and throwing the
handle.
Here's a sketch of the through-hull design.
Of course, I'll have to build it out and test it before I'll know if it all
works, but just the power savings alone by eliminating the pump should be worth
the effort, and I think the total initial cost and further maintenance costs
versus a hydraulic system will be lower as well.
It just seems that by keeping the system down to as
few parts as possible, the chance of malfunction is reduced. With the electric
actuator approach, if one actuator fails, the others should keep on working. In
a hydraulic system where everything is tied together it would
probably be all or nothing. The electrical approach has the advantage of fuses,
and most of the wiring is inside so a repair may be possible while still
submerged even though an actuator has flooded and blown a fuse or needs to be
valved off because of a big leak in the actuator housing and
subsequent failure of the through-hull serving that one device. ( which
seems unlikely )
I think this is the KISS principle applied.
Anyway, I'll build it and test the individual parts in the test chamber I'm
building down to 1000 feet and see what happens before I commit to cutting holes
in the hull. I'll keep you all posted on how it all works. Wish me
luck.....Frank D.