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Old 01 April 2009, 12:45   #1
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elctrical properties of resin (as a waterproofer)

folks,

I'm tidying up the wiring on the boat and want to run a common earth cable from the transom to the consolse. This means I need to join 4 earth cables (port/s'board/white lights & bilge pump) to one somewhere around the bottom of the a frame.

As this is quite an exposed spot I thought that even the waterproof boxes might not be ideal so I've been wondering about using a cheaper box, making the connections and then pouring in a small amount of resin. When it sets, the connections should be well protected. doesn't matter if the resin conducts (does it??) because it's a common earth anyway.

Maybe it's an over-engineered solution, but I do usually like to 'fit and forget' where possible, being confident of not running into future problems. I'd leave a little extra length in the cables for future connections 'just in case'.

Any thoughts or comments? Would this work?
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Old 01 April 2009, 13:10   #2
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Unfilled epoxy or polyester resins will not conduct, but I'm not sure whether your suggestion is such a hot one. It often the case that capilliary action draws resin up inside a wire. Once set, the individual strands of the wire are no longer free to move relative to one another. This leads to an increased risk of fracture (normally at the edge of where resin has reached) as the cables move around in normal use................Somewhat in contrast to you idea of "fit and forget"

If you must go down the encapsulation route why not choose something that is flexible (silicone or PU rubber)

HTH
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Old 01 April 2009, 13:27   #3
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Quote:
Originally Posted by AndrewH View Post
If you must go down the encapsulation route why not choose something that is flexible (silicone or PU rubber)
HTH
I would agree with that - but would go further... there is always the possibility you will want/need to add some other feature to the junction box on the future Or replace a cable if it fails elsewhere. If it is encapsulated this is impossible. I would go for a very good waterproof box and if wanting to go belt and braces go for the shirk sealed connectors inside the box, and then smear any exposed metal/bus bars etc in vaseline.
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Old 01 April 2009, 14:03   #4
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Fill it with silicone, worst case is you have to dig it out to add more stuff.
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Old 01 April 2009, 17:23   #5
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good stuff

thanks guys.

I hadn't thought of the capillary action thing (I figured once the box was tie wrapped to the A frame there wouldn't be much movement anyway).

A good waterproof box and some heat shrink connectors makes sense, whether filled with silicone or not.

In terms of future conections I just can't think of anything else I'd need to fit on the back of the boat? What else do folk have apart from nav lights and a bilge pump??

THe only other thing I can think of might be a work light, but in x years I've only twice had a boat out at night once when a couple of dives took a lot longer than planned, then on my advanced pb course. Even then, I'm wiring in an 'accessory socket' on the console so if I needed to I could clamp a worklight onto the A frame temporarily.
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