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Re: [PSUBS-MAILIST] Electrical thru-hulls



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

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.