1978 Glastron Hull "Blisters"

[shirthero]

I just bought a nice old one owner Glastron, SSV 188, spent all but the last year and a half garaged when not in use, the last year + it lived in the water in a slip. Below the water line it has some small "blistering" in the gel coat, none are broke out, and they all feel firm, seems to me it is mainly cosmetic. Should I be concerned or do anything at this point? We will not be leaving it in the water, just day use and back on the trailer.

 

[redfury]

Re: 1978 Glastron Hull "Blisters"

I've got them on my boat. They won't hurt anything, but it's essentially water pockets under the gel coat that cause the blistering. I'm going to grind mine out and marine tex them because my whole boat is getting painted anyway.

 

[Mark42]

Re: 1978 Glastron Hull "Blisters"

If you trailer it, many of them may go away over time as they dry out.

 

[wire2]

Re: 1978 Glastron Hull "Blisters"

I have many small osmosis bubbles on my '84 Glastron also, a few have broken but they don't appear to be getting any worse, so I ignore it.

 

[drewpster]

Re: 1978 Glastron Hull "Blisters"

It all happens on a microscopic level. What happens is that tiny pockets of water penetrate the outer layers of the fiberglass laminate and get trapped under the gelcoat. The water reacts with the resin in the fiberglass forming glycol which attracts more water. As the water wicks in pressure builds forming a blister. You will often see, and smell, a thick liquid seeping from the blister when the boat is out of the water.
Inside the blister, the water can penetrate further into the laminate. Hull blistering rarely causes structural problems, they are mainly cosmetic. A heavy blistering problem can be evidence of poor fiberglass work. If it were a new boat I would recommend going back to the manufacturer.
Hull blistering is common in older boats like yours and mine and are not necessarily a cause for concern.
The next time you haul the boat take a little time and closely inspect the hull. Look for large areas of blistering and soft spots. If you cannot find any bad spots and the blisters are not too bad it is likely no problem to just leave them alone. As the hull dries the blisters will go away. However they will return if the boat gets left in the water long enough.
My old boat has many blisters. There are many processes and products you can use to repair the blisters if they are a problem. The best, most complete method includes removing all of them. Grinding out the wet pockets caused by them and filling them. Then a barrier coat is used to help prevent them coming back after the hull is completely dry.
In the most extreme cases the hull bottom can be completely peeled of gelcoat and a new barrier coat is applied.
How far you go to address the blisters depends on how bad the damage is and how far you want to go to fix it. A mild blistering problem is normally just cosmetic and most folks just leave them alone.