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Hello Frank,
The double leak point on the interior nipple you would need to add
to attach a valve with female ends to, would only come to bare when you
needed to close the valve to deal with a leak. Unless your entangled with
some thing on the exterior of the sub at that time, having a slow leak on one of
those connections shouldn't be life threatening. Just surface and take care of
it. If you use a valve with male ends on it to connect to a welded in
coupler you will only have the one leak point.
Brent
From: ShellyDalg@aol.com
Sent: Saturday, August 08, 2009 9:45 AM
Subject: Re: [PSUBS-MAILIST] Electrical thru-hulls Nice CAD work Brent. The bell reducer on the outside with the potted
conductors makes the epoxy a wedge shape, so with a 1 inch thru-hull and 1-1/4
inch bell the epoxy block gets tighter as pressure is applied.
I considered using couplings instead of nipples, but I'm counting "leak
points" and I'm going with SCH 80 nipples.
A ball valve inside will thread right onto the nipple ( one leak point )
where if a coupling is welded into the hull, a short nipple and then the valve
is installed ( two leak points )
On your CAD drawing, you show a shiny end on the outside reducer and I was
going to use a "barbed" fitting so the plastic hose can be clamped onto it. I
could get all hi-tech and use compression fittings there, but why?
A clear plastic hose with clamp and VULCHEM painted over the assembly
allows me to see if any air bubbles accumulate in the hose, and with a designed
"low spot" in the hose, any little bit of water will settle there and be
visible. The motors and actuators will be filled with oil all the way to the
thru-hull with the hose containing the wires acting as the oil "bladder". Each
motor/actuator has it's own thru-hull and a completely separate circuit and
battery bank. If anything goes wrong with any part of one of the motor systems,
throw the breaker-----pull the wires out of the thru-hull------shut the ball
valve.
At that point the system is isolated from it's battery bank, with the
other three independent motor systems still going. If the problem was with the
motor or thru-hull, I can jump wire the batteries from the disabled motor to the
operating motors and still get all that power.
All this with one thru-hull and an absolute minimum of parts. The
wires from the batteries go through a fuse block, then to the control panel
where they connect to the motor controller and a "momentary" rocker switch for
the actuator. From the control panel the 4 wires go directly to the thru-hull
and from there to the motor and external actuator. The control panel will be a
small stainless box with the 4 motor dials ( forward and reverse built in ) and
the three "rocker switches for dive planes and rudder. The box will be "water
resistant" and free moving so I can set it in it's little bracket while diving
the sub, or move it to another bracket just inside the hatch for motoring around
in the harbor with the hatch open and me sticking out.
I remember Dan Brewer's blue sub had that set-up and it was really
convenient when he was standing on the deck and backing his sub up to the shore.
He's got a really nice sub with lots of room, well made, and all the toys like
his manipulator arm, scrubber system, big deck, and nice window set-up. I would
suggest anyone contemplating building a K boat to take a hard look at that one.
Very nice!
Frank D.
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