Gel coat blisters

superiorvoyager · #1 (**permalink**) 11-08-2009

Planning my projects for the spring with repairing the deck around the mast step first but also am developing a problem with Gel Coat Blisters. I believe the hull (under water) may already have been repaired but over the last few years I have been developing little blisters the size of a pencil eraser on the Hull above the water line. 4 years ago there were only a few but now they are probably covering about 40% of the hull (above the waterline). Some are starting to crack but most are still just little bumps, almost looks like the hull has a rash. Not noticable from a distance cause they are so small but up close looks bad. I've dug out a number and they are dry inside so not concerned about that but they are spreading, probably twice as many as there were last year. As I said there are lots, in the areas effected, 100-150 in a 1"circle. SO how do I repair this. Most advice says to dig or grind out the blisters but with the amount I now have that would take forever and I would still have the problem of new blisters. My thought is to sand the gel coat down on the whole hull, seal it and then paint with 2 part paint. Any better ideas?

sailingdog · #2 (**permalink**) 11-09-2009

It would help if you said what kind of boat this is on, and whether the boat was painted or not. If the blisters are dry inside, then it is likely that they are not OSMOTIC blisters, but most likely due to some contamination of the gelcoat during the layup process.

Unfortunately, fixing them is going to require sanding them open, filling and re-fairing the area with thickened epoxy and re-gelcoating or painting the area.

superiorvoyager · #3 (**permalink**) 11-09-2009

It is a 32' voyager Ketch. The hul is not painted just old gel coat. I understand that the usual practice is to sand them open, fill and re-fair the area with thickened epoxy and paint the area but with 40% of the hull effected I would see the need to repaint the entire hull. As well what will stop the rest of the gelcoat from developing blisters after it has been painted. Between last year and this year the affected area has at least doubled. Would it make more sence to just remove the entire gelcoat seal it and paint it. And if so what would be the best way to remove the gelcoat. I also suspect that there is a problem with the gelcoat and would think that just filling the effected area leaves the possiblity of the rest developing the same problem.

Stillraining · #4 (**permalink**) 11-09-2009

Hire a company to "Peal" the hull...you can buy the tool yourself for 800.00 or so but it is a little tricky to not go to deep.

I have heard ( Not verified ) that a 30' hull around here costs about a grand to have peeled...it only takes a day for some one who know what there doing I guess.

I have only seen the hulls after the fact I haven't had the pleasure of seeing it done yet...so take all this with a grain of salt.

But what I have seen it does a very nice job and it is amazing to see how much of the glass never got saturated on some of these boats.

Stillraining · #5 (**permalink**) 11-09-2009

I Should clarify that was for below water line so a whole hull would be considerably more.

superiorvoyager · #6 (**permalink**) 11-09-2009

The problem is that is far as I know there is no one around here who does this kind of work. In Thunder Bay there is a fellow who does blister Jobs below the water line but he grinds the hul down doesn't peel. That would still mean Transporting the boat 120km. Otherwise I wouild probably have to haul the boat 1000-2000 km to get the job done. As well, Below the water line there is no indication of blistering and I suspect it might have allready been repaired if there had been a problem. It there a do it yourself way of successfully stripping the Gell coat?

tommays · #7 (**permalink**) 11-09-2009

Being able to dry out a hull enough OUTDORS so they wont come back is the subject of a lot of heated debate

mitiempo · #8 (**permalink**) 11-09-2009

I don't think the peeling machine is that big - they could travel to the boat wherever it is.
Brian

osirissail · #9 (**permalink**) 11-10-2009

You really do not want to peel or sand off the gelcoat above the waterline. You will end up with a supremely ugly boat. The normal "fix" for gelcoat blisters above the waterline is to individually using a very small tool route out and dry the existing gel coat blisters use heat lamps to assist the drying, but keep the temperature of the hull low enough that you can place you hand on it without burning your hand. The use thickened epoxy filler to individually fill each blister and when cured sand it smooth - very carefully. Then an epoxy topside paint to paint the boat. Do not use a polyeurthane paint as it is not compatible with epoxy and that type paint will also develop blisters is repeatedly immersed in water. The epoxy paint acts like a barrier coat to help prevent new gel coat blisters from forming.

Stillraining · #10 (**permalink**) 11-10-2009

Agreed...Below water line peal..but above ....boy absolute last resort.

How bad is it really? any pictures?

I mean if your boat has Leprosy and parts of it are falling off then yes pealing would be in order..but if it is cosmetic only then weigh the effort and cost and probable poor looking out come to its current value and your current ability to enjoy the boat in its current condition to what you will gain.

OK so it has a bad case of acne...it still has a useful life...no?

I would not peal myself but sand down the affected ares to the roving and repair those using the unaffected ares to fair into. It may take several years to get them all as new areas developed but that is in my mind a doable way of getting or maintaining a nice faired hull.