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Hi Frank,
I'm not sure what shinny end you are referring to, but I added a
light coating or Sikaflex on the outer most part of the potted
reducer to have a flexible seal and help protect the epoxy from UV and what not.
I've considered coating the bare solid copper wires where they go thru
the epoxy with Sikaflex, to allow for the different expansion
coefficients of the epoxy and copper. So far I've not heard if that's
not the best plan, so it's still on the plans.
Unless your planning on using a reducer with female ends on both
ends then you would need to add a coupling to the exterior end of your welded in
nipple. Which would mean two leak points. One can see how they could add a
couple more wires to the assembly I currently have there. For some
electrical thru hulls I currently like the design Alec worked up with all parts
removable on his pods. I was thinking I would change the O-ring gland he has in
the copper to the Delrin part instead and add a second one, giving me a double
seal and making the connection have less resistance. I also like the look of the
commercial connections he has on the stern plate thru hull on his K
boat.
B
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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