[PSUBS-MAILIST] Through hull penetrator

Sun Feb 7 21:07:26 EST 2016

Jon,There is a very easy and inexpensive way to make your penetrators.  You rotate your sub so the hole in the sub is vertical and level.  Then use casting resin, just make a rig that holds the threaded rods in place in the bore.  The bottom of the rig has to seal as good as possible.  Then just pour in high compressive casting resin.  I use a product that has a 17,000 psi compressive strength.  You can cast in a reservoir as well to encapsulate the wire connections.  Or you can do it all in one pour.Hank 

    On Saturday, February 6, 2016 7:37 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Jon,for a start you could look at something like this boat through hull with 0-ring.http://www.hotboat.com/frm/showthread.php?t=4421
Or just google through hull, o-ring or face seal. Image search is good.However it may be better to cut a thread if the diameter hole matches a standard tap.You can google hole diameters for taps.If you went for the through hull perpetrator you may find that by the time you thread a fitting in to that,that the hole isn't big enough to fit your wires through, so backward engineer.However Hank seems the best option:)Alan

      From: Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Sunday, February 7, 2016 10:44 AM
 Subject: Re: [PSUBS-MAILIST] Through hull penetrator

 Thanks Alan.  I think Doug would have had much better luck had he used threaded rod instead of wire.  His method is essentially what I am looking at doing however I would use a tapered end as you suggested as well as threaded rod for the conductors to give the epoxy something to grip onto.  Emile presented an interesting design some time ago in which he press fit conductors through nylon or some other solid plastic material.  My bigger issue from a DIY perspective is that I will require some machining no matter what method I choose.  The K-600 uses a smooth bore through-hull that must be sealed on the outside face by an o-ring.  See attached photo for type of penetrator I need.

 On 2/6/2016 3:07 PM, Alan James via Personal_Submersibles wrote:

   Jon, I sent this email out last year as an idea for using castable rubber in a electrical penetrator. Hank is already doing something similar minus the castable rubber. The idea is to buy a bronze reducer fitting of appropriate size from a marine supplier & machine an o-ring grove in it. The bronze fitting Preferably has a conical reduction shape ( not shown in diagram ). The reducer compresses the epoxy under pressure in to the narrow area & stops it extruding through. Doug was having all sorts of problems epoxying pins straight through a fitting without reduction. In this iteration I epoxy the wires & sheath in to the reducer. You could use pins which would be more in line with G. L. as if the wires are sheared water could run through the individual wire sheaths, but bend the pins. I looked closely at how my subconn penetrators were made, & they mold a thin rubber sheath over the cable about an inch back from where it enters the penetrator. So as the wiring sheath compresses under pressure this rubber sheath moves with it. The drawing isn't the greatest but I can elaborate if interested. I have a 3000 psi test cylinder to test these but haven't got round to it. 
   As this has created a lot of interest, I thought I'd follow up with a couple of drawings of my through hull idea :) (Attached at bottom.) I am using a common reducer fitting to butt or key the epoxy. There are standard reducer fittings with o-rings. I am going to silicone over the outer part of the fitting & along the cable jacket. Then mold over this with the castable rubber to  tidy it up.  The theory is the silicone will compress under pressure on to the jacket (which should itself compress), & seal the jacket better than just epoxy. I looked at a long video of Doug Jackson making through hulls for his rov by epoxying in brass pins. They were failing badly in most cases. I will never trust epoxy again. https://www.youtube.com/watch?v=UDZQIDkWs4w Regards Alan 

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