Need Advice on Wet Deck Core

[Tom Keevil]

When we bought Rover 14 years ago, the nonskid had been recently painted with a nonskid additive. As the years progressed, sets of cracks developed. I assumed that these were old gel coat cracks that were working their way through the paint, and only a cosmetic issue. Rover spent the first 27 years of her life in frost-free California and Oregon, and has always been in the water year round. Eight years ago we moved her to British Columbia, which does get occasional freezing weather, and three years ago we moved her to Southeast Alaska, which is considerably colder, though not continuously freezing. She's now back in BC, and has a deck issue that needs attention.

There are a few areas on the side decks where some of the old cracks began to weep water. These areas of cracks are about one foot square, but most of the cracks do not weep. Tapping with a plastic hammer indicated that there was some small delamination near the weeps, but most of the cracked area seemed sound.

Well, it wasn't getting any better worrying about it, so I screwed up my courage and went at the deck with a saw, removing two pieces of the upper fiberglass layer about 9" x 12". What I found was that the majority of the glass was still well bonded to the balsa core. Most of the core was solid, but below the weepy regions the wood was mushy. All of the wood was soaking wet. There is no obvious nearby source for this water, and the weepy regions are several feet apart from each other.

My hypothesis is that repeated freeze-thaw cycles deepened the gel coat cracks until they finally let some water into the core. Freezing the core then rapidly created more cracks that let in more water, and so on until the core was saturated (It rains a lot in SE Alaska - Wrangell, where we kept the boat gets 80 inches a year).

So the first question is, does anyone believe this hypothesis, and if not, what is a better one?

The second question, is what do we do now? British Columbia has long periods of reliably dry weather. If we just let her sit in the sun, will the core dry out? Once it's dry we'll rebuild it, but how will we know when it's dry?

[Ron M.]

Your wet core will not dry out.Balsa is like a sponge so the moisture will likely migrate. I had issues with wet core in many areas, including the non-skid on the deck. The repair is a bit messy but not that difficult. I used a 1/4" drill bit with a depth stop and drilled test holes in suspect areas 5/16" deep. The sawdust will tell if moisture is present,(as will a moisture meter if available). Probe until you get dry sawdust,mark the bad locations and get started with the fix. The repair technique has been described many times in the archives and Casey' s books are a great resource. Good luck.

[Frenchy]

I think your hypothesis is spot on. Also, Ron's advice is good. Don't try to dry out the core - that's a wasted exercise.
You'll have to remove the top skin, the core and replace. I would suggest 1/2" corecell for a core (it doesn't
absorb water), epoxied to a clean lower skin. Then you'll have to laminate new glass (possibly bi-axial because it
is strong and builds up thickness rapidly). The fairing is the tedious part.
A good investment, in my opinion, is the electrophysics moisture meter as mentioned in Mainesail's website.
It'll give you a good idea where the problem areas are. Good luck - Jean

[jbenagh]

Your experience is exactly what happened to Christine C: she was stored indoors for thirty years. When I stored her outside in New England, cracks opened up in the cockpit sole. It took three years to get soft. Five to get bad.
I documented the sole repair this winter in the projects section. E glass and foam cell will work great. Buy lots of 60 grit for finishing!
Jeff

[Markst95]

Tom- usually water enters around fittings and migrates to different areas. If you have cracks in the middle of open deck there is probably some stress or flexing happening in the area. You might want to consider beefing up the area while doing the repair.

[mashenden]

Tom- usually water enters around fittings and migrates to different areas. ...

Agreed. While it is possible the cracks let the moisture in, it is also very likely that the water got in at the cleats or other hardware that penetrates the deck. When fixing the soft spots it would also be a good idea (or should I say an absolute necessity) to remove the hardware in the area, drill out the holes to 1/2" or so, fill with epoxy then redrill smaller holes (to the bolt size) to reinstall. Bed the fitting during installation (there are favored approaches on what to use and how to chamber the holes that are discussed in more detail in this forum - well worth a search).

Drilling out the holes and filling with epoxy makes it so that water is far less likely to reach balsa if the bedding fails in the future and starts to leak.