RE: [PSUBS-MAILIST] Which Through-Hull?

[Phil Nuytten <72020.572@compuserve.com>]

Hi, Harry:
        Re: your 'penetrating' questions: If the metal surface is well
prepared ( cleaned) the epoxy bond is sufficient for some pretty impressive
pressures - presuming a good quality epoxy or rigid urethane - If you are
concerned, then an undersize tap run through will really give the plastic
some grip (be sure to reclean the substrate after tapping) - best is a
vapor de-greaser, but 'Simple Green' and hot water is OK. For a good,
solid, plastic plug try not to go with a plug length less than 2 X the plug
diameter - 2.5  or 3 is better.
        I like the idea of siting all the penetrations in one plate and
then have the plate itself removeable/replaceable.  On 'DeepWorker 2000' we
run virtually all the hull penetrations thru a 1" thick by 8" round
stainless disc/plate that seals by radial 'o' ring into a stepped flange
ring that is welded into the hull. The plate is secured by 4 small clamp
blocks that are bolted to the inside of the disk and catch the edge of the
stepped flange. Unscrew 4  X 1/4"-20 tpi bolts and push on the inside of
the disk and it's out! We run all our plumbing, wiring, etc. thru 2 of
these plates. Can be aluminum plate, pressure-wise, but we have had some
slight corrosion problems and so switched to 316 SS - way overkill for the
depth, though. Obviously the drop weight releases, hull release ( if you're
 the nervous type, like me) hatch latches etc., are more easily installed
where they will be used, but if you go with hydraulic, pneumatic, or
electrical  actuation, even these functions can be handled thru a single
plate. One of the design features of DW2000 that makes this approach
feasible is the use of a seperate pressure housing ( 'J' Can) that acts as
a battery junction box, so that only control wires go thru' hull. For
example, the thruster power goes battery pod -  to J can - to thruster, all
outside the hull. the 'tell it what to do' wires go from the cabin
foot-controllers to the J can and control speed ( more or less juice) and
forward/reverse (polarity). No power wires the size of your thumb coming
into the cabin! ( 'Course we run at 250 VDC)
Phil Nuytten