Leak at mast wiring deck penetration

[Rusty123]

Yesterday, it rained really hard here. Really, really hard. When I visited my boat, I noticed a damp spot on the settee, and after removing some of the headliner, traced the leak to the hole where the mast wiring comes through the deck (it's a deck stepped mast). Unfortunately, I can't tell from the underside how the penetration is sealed (the wires run up through a small hole in the deck (about 1 inch diameter), and I can't see any obvious sealant), and the topside is obscured by the mast.

I've not noticed a leak here before, and there isn't any sign of water damage inside the headliner. So my guess is that the heavy rainstorm caused an unusual amount of pooling in the mast step, enough for the water to leak through the wire penetration.

Any ideas how I can prevent this, short of removing the mast?

[asdf38]

Does the hole properly seal the deck core? Water getting into the cabin is an annoyance but water getting into your deck core, especially around the mast step is serious. I'd look into it further and make sure the deck core is protected. If it's not, you'd need to do something about it. Over-drilling and epoxy potting is the best way. I don't have any ideas for doing this while the mast is up.

One thing not to do: Add sealant from below. This just hides the problem and forces even more moisture into the deck core if that's where it's going.

[Alex W]

What kind of boat do you have?

There should be a drain near the base of the mast (or as part of the mast step) that helps the water get out from inside the mast without going into your boat. On my Pearson 28-2 these drains are easily clogged and then water will follow the cables into the boat.

[Rusty123]

Originally Posted by Alex W

What kind of boat do you have?

There should be a drain near the base of the mast (or as part of the mast step) that helps the water get out from inside the mast without going into your boat. On my Pearson 28-2 these drains are easily clogged and then water will follow the cables into the boat.

It's a Spirit 28. I came across a mention of drain holes like you describe on the internet , so I'm going to check to see if my boat has them, and make sure they're clear. If not, that would explain why it only leaks when it rains super hard.

[Rusty123]

Problem solved. PO had sealed mast drain hole with caulk. I removed caulk, and water drained out. Nice.

[Rusty123]

I spoke too soon -- cleaning out the mast drain hole didn't really solve the problem (although I'm sure it helped). Essentially, it appears that rain gets inside the mast, collects on the radar cable, and then the drips migrate along the cable into the cabin.

In looking at photos of mast steps on line, it appears pretty common for cables to enter the cabin through a hole in the step (as mine does), so what is the usual way to keep water from dripping down the cable into the cabin? Applying sealant around the cable is impossible once the mast is in place, so I'm guessing that's not the usual method. Perhaps a drip loop inside the mast? (I might be able to put a loop in place without removing the mast).

Other suggestions?

Russ

[chef2sail]

Scanstrut Cable Clam / Deck Seal

I use this for our Raystar 125 GPS antannae to go through the deck. Not sure this will fit in the sapce you have as by mast cables exit the mast inside the boat

Dave

[Rusty123]

Those deck seals look sweet -- unlike my radar cable, my VHF cable exits the mast above deck, and then goes through a similar device.

But as I sit here thinking about it, it occurs to me that when I first removed the cabin headliner to investigate the leak, I pulled the slack in the radar cable into the cabin. I'm thinking that "slack" might have actually been a drip loop. so while I solved one problem (by removing the caulk in the mast drain hole), I might have caused another (by removing the drip loop). Hopefully, I can put the drip loop back in (I can certainly push the slack back in the mast, but it may take some work to form a loop).

This also makes sense in light of the fact that there is absolutely no evidence that this leak is long standing -- no stains, no deterioration, nothing, even though this boat has been weathering Pacific Northwest winters for at least 15 years.

One good thing about all this -- I was able to identify that the plywood coring forming the deck penetration is rough and raw, and needs to be smoothed and epoxy sealed.

[Alex W]

There should be a little tube that protects the plywood there. On my mast step (Isomat-brand on a Pearson boat) this tube is part of the step and you can see it from below. The mast is coming down off of my boat today (mostly to remove caulk and clear the drain in ways that couldn't be done from the outside) and I'll take a photo if you like.

The top of the tube sticks up about an inch from the mast step base to keep pooled water from finding this way out of the mast and to have it go through the drain hole instead. Since my drain hole has been clogged I made a wick that I hooked through the tube that pulled the water down to a pot sitting on the cabin table. This is a hacky fix, but is better than having water on the table and floor. This may be a temporary solution that works for you. I made this wick by taking 3 or 4 feet of 1/8" line, decoring it, and running thin wire (piano wire) up where the core was. The top of this was bent like a paper clip and hooked on the top of that mast step tube.

I think that drip loops on the electrical cables can't hurt, but my guess is that most of the water is wicked in via the halyards, not the electrical wires. Rope just makes a much better wick than rubber/plastic insulation.

De-stepping the mast to fix this is a major pain in the butt, but it'll be nice to have a boat that stays dry in the rain. I'm also in the PNW.

[Rusty123]

A few more thoughts for consideration: I wonder if I could use a zip tie to put a 180 degree bend in the cable before I push it back up into the mast. This would then form the top side of the drip loop (or "S" shape). Downside might be that the cable wouldn't like having a semi-permanent sharp bend. Or maybe some sort of removeable wire "hook" to encourage the loop into place?

Too bad there isn't a way to make the cable seek a looped shape by itself (like a self-coiling air compressor hose).