RE: [PSUBS-MAILIST] Through Hulls

["Gary R. Boucher" <engineer@sport.rr.com>]

Very good point!

G. Boucher


At 10:51 PM 11/21/2002, you wrote:
>Dan,
>
>I know far less about electrical through-hulls than some folks here. 
>However one thing I can say I've discovered is that the commercially 
>available ones are not uniformly expensive. I've bought commercial 
>connectors off Subconn and Sea Con. In both cases I found helpful people 
>who pointed me to their less expensive product lines when I explained I 
>was a home builder.  You'd be amazed at the price differences between 
>their first estimates and what I ended up getting. Try SeaCon's rubber 
>molded series, for example. They've been around for decades and are in the 
>sub-hundred-bucks price range. To me the peace of mind is certainly worth 
>that much.
>
>Subconn have one connector which is not one of the cheap ones, but which 
>might be of interest to anyone using trolling motors. It's got 4 
>conductors rated for 50 amps each, which happens to be just about right 
>for a pair of trolling motors. Of course it does violate ABS rules to have 
>both polarities go through the same penetration. But if you can live with 
>that (e.g. by protecting your circuit so as not to exceed the 50 amp 
>limit), you get the 4 cables you need to the outside with a single failure 
>point and for less than $400.
>
>I think if I was making an unmanned vehicle, I'd shoot for making my own 
>penetrators. But if its my skin, and the boat is being designed for 
>significant depth, I'd consider commercial ones.
>
>cheers,
>
>Alec
>
>-----Original Message-----
>From:   Dan h [mailto:machine@epix.net]
>Sent:   Thu 11/21/2002 10:03 PM
>To:     personal_submersibles@psubs.org
>Cc:
>Subject:        Re: [PSUBS-MAILIST] Through Hulls
>
>Thanks a lot Walter
>
>I didn't think capturing the jacket of a cable like that would be enough to
>keep it secure at that kind of depth.  I was planning to epoxy each
>conductor of my cable separately to ensure it wouldn't slide through and/or
>leak.  My way is far more complicated and doesn't really keep water from
>getting into the cable jacket.  I'll make a test piece with your method in a
>few days.
>
>Thanks again!
>Dan H.
>
>Walter Starck wrote:
>
> > Dan h wrote:
> > " A description of how you design your through hull electrical
> >  connectors, what type of cable is better and for what reasons would be
> >  vary helpful to many of us in here.  This would be of far more use to
> > us
> >  amateurs.   Please describe how you recommend building an electrical
> >  through hull."
> >
> > The following is for a continous (i.e. non-disconnectable) thru hull
> > fitting.
> >
> > Start with a male NPT to metal tube flare fitting for tubing of the same
> > size as the cable to be used. Remove the flare nut, face off the nipple
> > in a lathe and bevel the resulting face at 45° sloping inward.  The i.d.
> > of the fitting can be bored out slightly if required to accept the
> > cable.
> >
> > Use cable in which the insulated conductors are embedded in a solid
> > outer casing.  The common type that uses a fiber filler inside a tubular
> > outer cover should be avoided.  To effect a seal, pass the cable through
> > the original flare nut, followed by two O-rings, then the modified
> > fitting.  When the nut is tightned the O-rings are compressed inward by
> > the beveled inner face of the nut and by the inward sloping face on the
> > modified fitting.  This compression squeezes the O-rings into the outer
> > cable covering creating an annular depression and locking the cable in
> > place with a very effective watertight seal.  For use in depths of a
> > thousand feet or less this type of fitting is cheap, robust, easy to
> > make and highly reliable.  The fitting is of course used by drilling and
> > tapping to install it where required.  Depending upon thickness and
> > curvature of the hull a flat boss may be required for attachment.
> >
> > Disconnectable through hull fittings are somewhat more complicated but
> > can also be made using the same cable sealing method but more complex
> > machine work is required as both plug and receptacle fittings must be
> > fabricated from bar stock.  They are joined with a pipe coupling nut
> > with O-ring seal  and employ an internal electrical connector for that
> > connectivity.
> >
> > Walter Starck
> > Golden Dolphin Video CD Magazine
> > The premiere publication of diving and the ocean world.
> > www.goldendolphin.com
>
>
>
>
>