Forward deck rot fix

Hey all, question regarding deck rot. The surveyor noted a very wet forward deck, but seems pretty solid when walking on it (no spongy feel). I removed all the hardware (chain deck pipe, samson posts, etc..) to allow whatever moisture inside the deck to dry out before rebedding. After removal, I can clearly see the wood around those areas was so rotted that it practically wasn't there...not sure how far the rot goes in any direction. The forward deck is double sandwiched...glass, ply, glass, ply, glass. Both layers of ply is approx 1/2" (metric...made in South Africa). The top and bottom layers of glass are around 1/4" thick while the sandwiched glass inside is about 3/16". Sounds confusing, attached pics.

It's hard to see the missing wood in the chain deck pipe hole pic. Also attached a pic of the ply/glass sandwich when I removed the mast collar...good wood there.

I know of only two options, remove the first two layers of glass/ply and replace. I'm looking at removing approximately 4' down and across of the forward deck (shown in 2 pics where the tape measure is out on deck). Instead of replacing with 2 layers of marine ply and epoxy/glass I'm thinking of replacing with 2 layers of foam (Divinycel, CoreCell, Coosa board, etc..) and epoxy/glass. OR I was looking at the epoxy injection method (perhaps vacuum sealing?).

I want to fix it correctly and by removing the rotten wood this sounds like the right path, though I don't really want to cut out two layers of well laid up glass.

Any thoughts?

 

replacement is the correct way to go but commonly the area is drilled like swiss cheeze and let to dry out as much as possible - then a solvent free (important!) epoxy that bonds to wet or dry surfaces is injected. Even serious boat professionals do it this way on their own boats - not telling anyone

 

Looks like a case of not sealing the ply after the holes and apertures were cut. If you are lucky the rot is local, I'd be pushing a thin chisel or bradawl in there until it hit solid. It might not be bad at all, all dependent on the quality of the original ply and species as well as how long it has been leaking along the veneers.

If you do replace with a local bit of ply, it might be worth changing to solid just to minimise any further episodes of a similar nature. Or as you suggest, splicing into a foam core.

 

...And the time to support the 'glass is before any integrity of shape is lost. In other words, before cutting away the outside skin. Use any means inside the boat such as (many) props, etc. to prevent drooping, just so long as no distortion has yet occurred.
No doubt it's due to poor sealing around drilled and cut holes.
The color of test-borings into plywood tell whether the wood needs to be dried (light color but saturated) or drilled to allow drying (rotton brown/black and saturated).
If you drill all the way through and then force air by fan into the cabin, it will dry more quickly than drilling only part way through. You will have to fill the inside holes but at least filling those with epoxy alone will finish the job off. Outside, a layer of 10 oz cloth set in epoxy is my recommendation where holes have been drilled, and a complete redo of the entire laminate schedule where the skin has been completely removed, well tapered at edges.

 

This is common to see on polyester coated wood or improperly prep'd epoxy jobs.

Drilling holes doesn't work very well and takes a very long time, with plywood substrates. It works a little better on solid wood, at least it will dry uniformly, unlike plywood. To be frank, I wouldn't even try to dry the plywood. Just cut it back until you get into known good substrate and scab on new plywood pieces, using a Payson butt joint to bond and cover the seams of these repairs.

The new pieces will likely be around deck openings and under hardware, so fairly easy to sort out, fit into place and bond down.

 

I haven't drilled any holes yet, but looks as though I will need to in order to see how far out from the deck openings/hardware the rot goes (where I can then open the deck up...if I go that route).

With the Payson butt joint, I always thought this joining must be done on both sides of the glass, which in this case can only be done on one side.

Is it not better just to lay up solid glass versus glass, ply, glass, ply, glass? The deck in that area is almost 1-3/4". The only real difference would be the added weight in the deck from the glass. Not only would it guarantee to be stronger than before, but I will never have to worry about rot in that area again.

 

I prefer a stepped butt joint on the whole, if you can't scarf. However there is no absolute so as long as some good integrity is kept, it doesn't really matter which type you use. One advantage of the step is it only needs to be one sided, and if you can get a router in from above should not be too tricky. Chisel out the corners.

If you replaced the rotten ply, as PAR suggests, you could 'glass up the edges vertically sealing the ply properly. The important bit is also the screw holes and bolt holes. The latter are best drilled over sized filled with epoxy and filler then redrilled, correct size. Any screws can be bedded in a slightly lower melting point epoxy (West/SP melt 225 deg C, Araldite 150 deg C) so thay can be removed by applying heat to the head, if removal is necessary in the future. Latter tip from Forum members, see Thread on 'Screws left in wood'.

 

There are a number of ways to approach this set of problems. I tend to just cut to the chase and get it done, without so much fuss (waiting months for the core to dry, for example).

What I'd do is simply take a grinder and cut back around the deck openings, until good wood is found. I would use some care with a diamond blade initially, to preserve the skins, but I'd hack out the wet and rotten wood with little mercy. The "scab" line can be one of several. I prefer a tapered joint on stuff like this to prevent point loading along steps or ridges, but it really not that important except in racers.

 

Thanks for everyone's input, it has been very helpful!