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In a message dated 10/30/2009 10:25:20 A.M. Pacific Daylight Time,
Alec.Smyth@compuware.com writes:
I highly recommend using removable SS bulkheads that seal with an o ring. Hi Alec. I agree. I've seen quite a few of the thru-hulls like that and
they are a logical choice. A sub should have at least one of those type fittings
for changes and/or upgrades.
My saucer shape requires most of the thru-hulls to be spread out close to
where the plumbing/electrical terminates at the tank or device being powered.
This reduces wire length and plumbing "low spots".
I currently have a thru-hull for air in/out at the top of each ballast
tank, hidden under the FRP fairings with the plumbing running inside the sub up
to near the hatch for ballast tank air to dump.
The electrical thru-hulls are on each side with a 4 prong set-up. Right
next to the side motors. These thru-hulls carry the power to the motor and the
electric actuator driving the dive planes.
The two thru-hulls for the back two motors are in the rear with the same 4
prong set-up.( 8 wires total.) Two wires each for the motors, one set for
the rudder actuator, and a spare set of prongs for a possible add-on of rear
dive planes actuator.
If I had made a large bulkhead fitting with all the holes in one place the
wires would be much longer and the ballast tank vents would have a lot of elbows
and fittings, making "low spots" where air gets trapped.
Having said that, I still agree that a bulkhead set-up is a great idea and
plan on putting one in up front when I add a manipulator arm. This will need
several holes, depending on how complex the arm gets.
There are a few other "holes" in my sub. The drop weight rod, the video
port in the hatch, trim tank in/out, and a few yet still to be
done. All holes get a ball valve except the windows and hatch.
When we come up with a standard thru-hull for whatever, I'll put that in
too ( with a ball valve )
I was wondering if a threaded fitting would work. Weld in a 3 or 4 inch
threaded schedule 80 female coupling, and get a thick plate like maybe 1
inch stainless, tap holes in the thick plate, and machine threads into the edge
of the plate to screw into the welded coupling. This may be more work than just
using a flat plate and "O" ring. It would need a big nut welded on the inside to
grab with a wrench for install/removal.
I think the "O" ring plate design has a "keeper" bolt on the inside doesn't
it ? Probably simpler than a threaded plate and coupling.
Anyway, a means of adding/changing is very good.
Frank D.
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