[PSUBS-MAILIST] Castable Rubber

Sat Nov 14 14:04:58 EST 2015

Hank,
thanks for the advice.
Hmmm maybe putting pins through would be better than the insulated wires.
However with the blue globe cable gland it is the whole cable that goes through.
Re the casting; I want to use straight silicone on the cable jacket to give adherence
& for it to be able to compress with any compression of the jacket. Then to tidy
it up & add a bit more support I will cover it with the "castable rubber". The
intention is to make a 2 part mold to form the castable rubber around the cable
& threaded adapter ( as per previous dwg ). I need 16 of these for my light fittings
& light through hulls & 5 for motors alone. So it will be worth getting it right.
The castable rubber can be either sticky or not sticky depending on how much
talcum powder you mix. It may be that I cast a semi sticky castable rubber or
put a thin layer of silicon over the initial layer, then cast the non sticky castable
rubber over that to give some adhesion.
Was an artist in a past life, & made moulds & cast resins. So won't be too taxing
playing around with this.
Cheers Alan

Sent from my iPad

> On 15/11/2015, at 6:53 am, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Hi Alan,
> Can you tell I have been thinking about your idea :-)   I have been thinking about the wire you want to run through the fitting.  I always use a threaded rod of some sort.  If you use smooth wire, then consider epoxy because casting resin has no adhesive qualities.  As a matter of fact, you could pull the wire out with a pair of pliers.  Epoxy is fine to use if the cavity is larger.  I always try to keep the cavity small and the viscosity of epoxy is to thick.  Casting resin is better for this and I use a syringe.  I have had success with epoxy and a tight cavity when I heat the epoxy in the microwave when my wife is not looking.  The warm epoxy will flow when heated.  The trick is to have a large enough cavity for epoxy to flow in without trapping an air bubble.  Now that is just my two cents on the matter.
> Hank
> 
> 
> 
> On Saturday, November 14, 2015 6:44 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 
> Alan,
> Are you talking about making a mould with casting rubber that fits over the cable with a void that you will fill with silicone.  Then remove the mould.
> That  would sure look nice.
> Hank
> 
> 
> 
> On Saturday, November 14, 2015 4:38 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 
> Alan,
> If you go with casting resin, buy small quantities.  Once you open the containers, they don't last long after. 
> Hank
> 
> 
> 
> On Friday, November 13, 2015 8:47 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 
> Thanks Hank.
> I will try the polyeurathane.
> I have some subconn wet matable connectors, & looking
> at them closely I can see that they mate the head of the connector
> to the cable with a thin layer of rubber for at least an inch back.
> I am not sure whether the rubber head is molded over the cable
> or whether a layer of rubber is applied some how over the cable
> head & cable to seal over the entry point of the cable into the connector head.
> However it seems to lend weight to my idea of applying silicone an
> inch up the cable. Now all I need to do is track down or make a pressure 
> Chamber.
> Cheers Alan
> 
> From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
> Sent: Saturday, November 14, 2015 3:12 PM
> Subject: Re: [PSUBS-MAILIST] Castable Rubber
> 
> Alan,
> I made two through hulls with pipe thread bushings almost the way you are.  I use poly urethane casting resin, I hate epoxy.  I tested my through hulls in my test chamber to 1,500 feet with zero issues.  I just silicone the threaded rod at the bottom to keep the resin in till it cures.   I made a plug connector for my Perry thrusters with casting resin also, that suff rules!
> Hank
> 
> 
> 
> 
> 
> On Friday, November 13, 2015 5:58 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 
> 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
> 
> 
> From: Alan James via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
> Sent: Friday, November 13, 2015 10:52 PM
> Subject: [PSUBS-MAILIST] Castable Rubber
> 
> Was thinking about home made electrical through hulls & came
> across this castable silicone rubber.
> How to make a moldable castable rubber (homemade Sugru, Oogroo)
>  
>  
> 
>  
>  
>  
>  
>  
> How to make a moldable castable rubber (homemade Sugr...
> View on www.youtube.com
> Preview by Yahoo
>  
> Basically it's builders silicone mixed with corn flour about 50/50.
> There are other recipes with builders silicone & baby powder.
> My thought was to pot wires inside a suitable bronze or SS threaded fitting 
> & encase the electrical sheathing where it enters the fitting with straight silicone.
> Then when hardened, cast the silicone / corn flour mix over the top to tidy it up.
> The simple recipe may have a lot of other applications.
> Cheers Alan
> 
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