Rotten wood around portlights?

[Lazy Jack 32]

I started replacing a portlight on the Lazy Jack schooner (vintage 1977) and found the plywood between the fiberglass outer cabin side and the plastic veneer on the inside cabin wall was mushy and wet. First thought was to remove the portlight and soak penetrating epoxy into the exposed wood (the rot is mostly below and to the sides of the portlight), but descriptions I found on-line of penetrating epoxy say the wood must be totally dry first before the epoxy will soak in. So the next plan would be to remove the portlight, and cut away a generous portion of the inside veneer to let the rotten plywood dry until next spring before treating it with penetrating epoxy. I have an oscillating Dremel saw and am ready to operate, but thought I would check with this community to see if anyone had done this before. Is there an alternative to cutting away the veneer? There are two portlights for sure that show signs of rotten core around them.

Any advice will be appreciated.

Charlie

[Cheechako]

Well, if you are cutting away the veneer anyway, just replace that plywood with new marine ply saturated with epoxy or fiberglass resin. No way you can get the veneer panels off and re use them?
Is the ply core just at the portlights or is it full length?

[Lazy Jack 32]

Originally Posted by Cheechako

Well, if you are cutting away the veneer anyway, just replace that plywood with new marine ply saturated with epoxy or fiberglass resin. No way you can get the veneer panels off and re use them?
Is the ply core just at the portlights or is it full length?

That makes sense. Yes, I'm planning on re-using the veneer panel. The panel extends several feet beyond the portlight with the rot and behind a cabinet, so I hope to cut away a piece of it carefully and using it again. Looks like there is a slight curve to the cabin wall, and if so, it will require layering up thinner sheets of marine plywood.

Thanks.

[psk125]

As Cheech says, replacing the plywood is better. If it’s rotten, letting it dry out won’t help - the plys have come unglued (delaminated) and there is no structural integrity left. The grain of the plys going in different directions will impede the absorption of epoxy and you’ll end up with a weak cabin trunk that will flex and end up leaking again.

[Tillsbury]

Yes, you need to remove everything that’s wet, until you’re back to solid dry plywood. Then epoxy in new plywood to the area before replacing port lights.

[Wotname]

Another vote for cutting out the wet plywood and unfortunately the moisture always seems to penetrate far further than first expected.

But it must be done - as others have posted, there is no strength in delaminated wet ply.

[Nicholson58]

Add my +1 to the vote. If the area turns out to be not so big you lay up a glass and epoxy repair as structural filler. If the port is sealed to solid structure it is less likely to leak. Check your other ports. Easier to re bed before they are damaged.

[Lazy Jack 32]

OK, thanks for the advice, all. Replacing the wood is what I'll do. Oscillating tool in hand, I'll start cutting away the veneer this afternoon, as big a piece as I can, assuming the rot has spread pretty far, and don't want to cut the veneer more than once.

Charlie

[tml]

Been there. Don't try to fix incrementally cut it back to absolute dry. Most importantly replace the plywood with something that will not rot. Several types of composite material are available from structural foam, Coosa board, and honey comb. Glass it in and while it may leak someday but it won't rot.
Tom

[Locquatious]

We have done a lot of these repairs on our boat.
1. Do not replace the wood with wood. Replace it with fiberglass or poured-in epoxy.
2. Normally the rotten wood does not extend past the portlight flange. Cut the rotten wood to just inside the flange and you will not see damage to the interior wood.
3. In some cases, where most of the wood under the flange was damaged, we used the portlight itself as one side of a fiberglass mold and a wooden ring as the outer mold surface. We then built up epoxy/fiberglass rings inside that mold to slightly over the thickness of the old wood. Use clear box tape as the mold release surface. Epoxy won't stick to it. Lay-up the epoxy fiberglass slowly so it doesn't overheat. The rings on our boat have lasted for 15 years and show no sign of leaking even though the portlights are below the rub rail.
4. Sometimes just portions of the wood is damaged. Chisel or cut the bad portions out. Establish a box tape "mold" spanning between the good portions of the wood. If the box tape buldges, clamp a flat stick against the box tape to hold it flat. Fill the mold w/epoxy. Also coat all the good wood surfaces w/epoxy to prevent water infiltration. This method works but sometimes it takes a second go to completly seal the portlight.
5. The seal of the portlight is not primarily via the edges normal to the hull. The main seal is the clamping of the flange and under the flange. The caulk normal to the hull will eventually give way to sunlight and flex, but the clamped flange caulk will always hold.
6. We use UV 4000 or Sikaflex caulk. Avoid using 5200. If you have any rework on the portlights, 5200 will pull off the gel coat when cleaning surfaces.
7. If your portlights are bronze, do not use stainless bolts. Use silicon bronze bolts or if you can find them marine bronze bolts. Stainless bolts will corrode quickly and introduce new leak points in as quickly as a few years. If you pull out the bolts, the center region will be corroded down to a thread.

[Cadence]

Originally Posted by Lazy Jack 32

I started replacing a portlight on the Lazy Jack schooner (vintage 1977) and found the plywood between the fiberglass outer cabin side and the plastic veneer on the inside cabin wall was mushy and wet. First thought was to remove the portlight and soak penetrating epoxy into the exposed wood (the rot is mostly below and to the sides of the portlight), but descriptions I found on-line of penetrating epoxy say the wood must be totally dry first before the epoxy will soak in. So the next plan would be to remove the portlight, and cut away a generous portion of the inside veneer to let the rotten plywood dry until next spring before treating it with penetrating epoxy. I have an oscillating Dremel saw and am ready to operate, but thought I would check with this community to see if anyone had done this before. Is there an alternative to cutting away the veneer? There are two portlights for sure that show signs of rotten core around them.

Any advice will be appreciated.

Charlie

This may be a dumb suggestion? If you are going to let it dry till spring what about drilling a couple of holes through the veneer at the lowest point. Injecting something like get-rot with a large hypodermic needle come spring.

[Lazy Jack 32]

Well, one question just got an answer.
After the inside veneer (70's vintage Formica, it tuned out) was cut away, what was left of the plywood came out by the soggy handful, the whole way down to the bottom of the panel below the portlight and an inch or so to the left and right of the bottom half of it. (The Formica, sorry to say, did not survive the operation. But this boat ain't the Four Seasons, and I'm sure I can make it look OK again as well as water tight and pretty much unrotten). The good news is that the outer wall is 3/8 inch fiberglass, so the cabin will be OK until I can get back to it in the spring.

Thanks, all, for the advice. Now I need to go find some of the non-wood alternatives for the core filler y'all recommended.

Charlie

[Lazy Jack 32]

One more question: there is a slight curve to the cabin wall and the core is about half an inch thick. Whatever the core turns out to be will need to hold screws from the inside of the portlight. Coosa board sounds like a good substitute for plywood, but is it a little flexible?

[Wotname]

Dissenting view - I prefer to replace with rotten ply with new plywood, I find it to be easier and it maintains the structural integrity.

However you do need use quality marine grade ply and it isn't cheap. You also need to epoxy saturate it during the repair and it won't rot again. By the way, it is highly unlikely that any epoxy was used in the original build.

[Corrosion-Eng]

Important: Is the soft wood darkened or black?
Corrosion-Eng