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Despite all my efforts to construct a waterproof coil, I think water finally made its way inside one of my windings that is completely encased in potting compound. I have no idea how.. I have used this one on my Baracuda for a few years and it finally started acting erratic this week after a few days of surf hunting. Guess I need to come up with a newer idea..
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Don you have been hunting an interesting place. -
Don, the weak link might be the Heyco fitting.
I tap the coil shell hole for the Heyco, tighter fit. When placing the nut on from the underside of the fitting, I add some JB Weld to the threads of the fittings and nut. That more or less secures that will be waterproof.
Next area of concern is inside the Heyco fitting is a rubber sealing insert. They may not seal tightly around your wire when tightening the strain relief. There is actually another insert that is smaller than what you use. The hole is just a tad too small for coax. So you have to take the insert out, grab a drill bit just a bit bigger than the hole, twist the drill by hand thru the insert to enlarge it. It will then slide over the coax with just a little snugness and will sqweeze down tightly when the strain relief is tightened. To make sure there is no way of water getting past the insert, after I poured the epoxy and it has cured, loosen the strain relief, dab a bit of Marine Goop before placing and tightening the strain relief on again.
Added note, when you pour your epoxy, make sure the coax is saturated with the epoxy and an air bubble does not get trapped inside the fitting. You won't notice that happening if you do a single epoxy pour. Since I do a double pour, I have noticed where the air bubbles would could have formed, so they get popped right away. In the fitting a big one can form without popping on its own.
Another trick that could help with your inserts, is after pouring the epoxy, loosen the strain relief for about 20 seconds, the epoxy will wick down into the insert if there is any gap. Tighten back up.
I haven't had any issues with my coils to date when doing the above with the 832B epoxy. I found you have to make sure you really stir the black resin extremely well the day before using it to make sure the black pigment solids are mixed into suspension. Then flip flop the container every 6 hours or less until your ready to use it. If the pigment comes out of suspension, by the time you use up the last portion in the bottle, weeks down the road.....your resin will be more pigment than resin. Then when mixing the catalyst in the ratio will be off, too much catalyst vs. resin. It will not cure properly, even tho it may look it.
What I have also been doing lately is sanding down the bottom of the finished coil with 80 grit sand paper and spraying on three to four nice coats of Truck Bed Liner spray paint. It's tough, and will give the look of approx. the coil shell texture.
There is another option, instead of using the 832B epoxy try the 832HT.
http://www.mgchemicals.com/products/...e-epoxy-832ht/Comment
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Thanks Sven. That all makes perfect sense. The only possible way water could get in is around the cable. Also, I think my cable may be undersized.
Don.Comment
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I was hunting Virgina beach last week. It must have been an artillery range at one time.Comment
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Hello Don you can dive the complete coil into liquid latex 3 or more times thin layrsComment
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Hi Don. Maybe this could explain how the water comes into the coil, and help you to fix your problem:Originally posted by dfbowers View Post
http://www.homebuiltrovs.com/howtosealingwireexits.html
Regards,
FabiánComment
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Fabian, thanks for posting that link, that is something I hadn't thought of doing before with the wire jacket, what a great idea...Comment
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somtimes the rubber sleeve/bush has flash from the molding and they dont give total seal when you go more than a few inches.
SteveComment
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The techniques covered above are excellent for sealing the coil but nicks in the jacket can also cause trouble if the wire insulation in the cable has additional damage. Any electrical supply house will have 'self sealing tape' which is silicon based. This will cling to the sheath and rapidly creates a bond between the layers of tape. It doesn't take much time until it is actually one solid, but flexible mass, unlike ordinary vinyl tape which will usually unravel if it stays wet.Comment
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I had a commercial coil which stopped working and decided to take it apart after checking all other possibilities (connectors etc.).
I found the problem which was water ingress IN the cable. My coil was not wet inside though.
The outside cable insulation had a nick in it. This was not directly visible but hidden and caused by the spiral strain/bending relief tail which is screwed into the coil.
The outside edges of the tail are nicely rounded but on the inside they are sharp and will easily cut into the outside cable insulation when bent.
Some water seeped in through this nick and wicked its way down to the coil via two thick cotton? strings intertwined with Tx & Rx.
Tx & Rx each have their own shielding braid and insulation here. Inside the coil the Tx & Rx grounding braids are no longer insulated.
The water reached them first dribbling down and wicked back up the braiding inside the Tx & Rx wires. The braiding was extremely oxidised up
to a length of around 30cm above the coil and at some points disintegrated (crumbs). The "hot" Tx & Rx conductors were like new, no oxidation!
I was wondering why my detecting setup was getting more and more erratic over around a year, but never managed to contemplate this kind of problem
thinking my detector might be at fault as well.
I did contact the manufacturer, but my questions were not answered and was briskly told to buy a new coil.
I do know what it takes to put a product into production and that all kind of things can go wrong on the way.
But the feeling of getting stonewalled left my trust in shambles. I will not buy from major detector manufacturers any more,
but rather DIY with warts and all.
The positive side of all this is that I found this website whilst researching about defective coils back then.
I am enjoying experimenting and building my own stuff now.
Sorry for rambling on so long.
Ah yes, the link from Fabian is excellent and solves the problem I encountered.
The suggestion from bluebelly to use self-sealing tape works well for any length of the cable!
With kind regards, PolymerComment
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