How to seal around cable clam?

[cdhickey]

I'm installing a cable clam as a pass-through for my mast light and VHF wires on deck. To do this I will be drilling a 1 1/4 hole, with the cable clam sitting on top. I plan to seal the cable clam with butyl tape, but I'm thinking that it may be wise to pot the hole with epoxy as well. The hole will be in the vicinity of the base of my deck-stepped mast, so if there's one area I don't want water penetration, it's there!

Does potting with epoxy make sense in this case, or am I just making an easy job more complicated?

[mike dryver]

you are exactly right! what you want to do is make sure that after you drill the hole that you completely seal the raw edges of the glass and especially the balsa? core. then when you drill the holes for the screws to hold the cable seal again put epoxy in the screw holes to seal the raw core and glass edges.

[arf145]

If there is wood core there, I'd want it protected. But I have to admit that when I drilled a maybe 3/4" hole in my cockpit floor for chartplotter cables, all I did to protect the plywood core was to paint the wood with quick epoxy, not grind back, fill hole, redrill, etc. The project had already taken so long I couldn't face another round trip while epoxy cured.

If I were potting a hole that big, I think I'd try to fashion a temporary sleeve to go in the middle and reduce the epoxy volume.

[captainrizzo]

You may want to think about taking out more of the core than the 1 1/4 inch hole that you are drilling and then fill with epoxy. I read an article in Sail magazine some time ago and they suggested using drill with a finishing nail bent at 90 degrees to take out the core. When you fill the void with epoxy, there is no chance of water penetration. If you are just sealing the raw wood without doing this, it won't be very thick. Just say'n.

[jrd22]

First, why do you need to drill such a large hole right next to your mast base for a couple of smallish wires? Second, if your deck is cored in that area you should definitely grind out a bit of the core and fill with thickened epoxy. It's not a hard or long job to do. I use a 1/8" allen wrench in a drill (I grind the short side of the wrench off so it's about 3/8" long for large holes). Only takes a minute to grind the balsa out, vacuum out the chips, then duct tape the bottom of the hole and fill with thickened epoxy. When set up drill your hole thru the epoxy.

[cdhickey]

Thanks for the input, guys. I like the idea of drilling back the core a bit to ensure I'm in solid epoxy. How long would you expect it to take for that kind of hole to dry enough to drill again?

@jrd22- I'd rather not have a hole there, but I'm not sure what the other options are! The issue isn't the size of the wires, it's the size of the connectors as I need to be able to disconnect the wires easily when the mast comes down. The previous owner had run the wires from the cabin through the deck in this area, sealed with silicone and then added connections on the exterior that could be disconnected as needed. I didn't like this setup because it was messy and the connections were constantly exposed to the elements, but I'm open to hearing if this is the "standard" way of doing it or offers advantages.

[captainrizzo]

I used to have these connectors exposed on one of my old sailboats. You can and should get waterproof connectors (rubber flanges on boths sides male and female). If you leave enough wire between the deck and the connector, you can tape the connecter off at the mast to keep it out of the way. I would go with JRD22 and drill a smaller hole, but still take out some of the core.

[jrd22]

cd- I understand about the size of some of those cable ends, wish there was a way they could make them smaller. The epoxy cures pretty quickly, I usually let it sit overnight though before drilling.