Bumpy Deck Gelcoat

[TomandKarens34]

Here's a new deck issue that I haven't seen before. I have a 29 year old foredeck which seems solid. No flexing, the rubber mallet sound check seems good, but its got to be delaminated. Its lumpy. Like 1/16 high, 2 1/2 inch dia. bubbles under the gelcoat. And to really screw things up, no gelcoat stress cracks. Stepping on it shows its hard, no deformation. Its three feet to the nearest place where water could enter the core. I've recored deck and this damage just isn't the same. Perhaps the fiberglass is just really thick here and I'm missing a core problem. Perhaps there is some delamination in the fiberglass. I'm going to get into it, but I thought I'd throw my observations on the floor here in hopes someone here has seen this before. This is new to me and a search didn't come up with any answers.

[junkmeister]

I would guess that you have voids where there was not enough resin when the initial layup was done. I'm in the middle of doing a major fix-up on my deck and I found many places with small voids where initially there was improper wet out of the area which caused voids.

[eherlihy]

But would you not have detected voids by the "hollow" sound when you try the rubber mallet test?

I'm guessing that there is something (water, acid, sumthin') in there. A simple test by drilling a small (1/4") hole would solve the mystery. Make sure that you wear goggles if you decide to drill, as it could be acid, which can spurt out under considerable pressure.

[Isaac-1]

I have a similar problem on 36 year old sailboat, except even stranger, mine is inside the cabin on one of the dinette seats. This is not cored, but solid glass, with similar sized or maybe a little smaller "blisters". In my case I think something may have once been trapped between the seat cushion and the liner as it is isolated to one side of the dinette.

Ike

[TomandKarens34]

Well, I'm commited to drilling a couple of test holes tomorrow. I'm going with bad wet out in the fiberglass and voids, not big ones, just poor wetting. My theory is that over the years moisture has found it's way in somehow and acid has developed in the laminate and is separating the fiberglass. Hope I'm wrong as it will have to be gouged out and filled. Like a hull blister on the deck, where they aren't supposed to be!