[PSUBS-MAILIST] Through hull penetrator

[Jon Wallace via Personal_Submersibles]

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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