Small blisters on hull

Hi there! Last week I started preparing my Prindle 18-2 for summer and I discovered some small blisters which seem to have humidity/water. It is a bit weird because I stored the boat just as I store it every year. A friend told me that the hull could have been humid inside and freezing temperatures could have formed tiny cracks...What is also weird is that they seem to be receding now that the boat is standing in the sun and all that is left is what you can see in the picture. Does anyone know what this is and what has to be done about it? Thanks in advance!

Is the boat gel coated? With fiberglass underneath?

I bet your friend is right, the boat either absorbed water through the gel coat or water is trying to get out from the inside.

Does your Prindle have port covers? If not you might want to add some, and leave them off in the winter while the boat is being stored, assuming its stored inside in a warm dry spot. That will help dry the hulls out equally from the inside and outside. If its left outside you can still leave the port covers off, just make sure you dont get critters, or rain inside.

To fix it, you might try to heat the blisters up with a hair dryer or very carefully heat that area with a heat gun. if you use a heat gun, make sure you can still touch the surface, if you get it too hot it will melt, so if you can leave you hand on it for a couple seconds its not too hot.

Or if they dont go away with heat, pop them with a small sharp object, and see if water weeps out. Then press them gently back down and see if they will go back to the core easily, if they do, let them dry out fully, then inject epoxy into the blister and press it down until the epoxy cures.

If this doesnt work, sand/cut off the blisters and re-gelcoat the small spots.

Or you can ignore them and go sailing.

Bill

Your boat is either suffering from osmotic blistering or you are very into photoshop. If the blisters are only below the gel-coat (or 2 part polyurethane yacht paint) I'd simply let them recede by themselves. (Judging from the pictures, this is what I'd do)

If OTOH they are deeper down, inside the glass, they need to be opened up, sanded out and filled with epoxy filler. If the damage is extensive you have a more serious problem possibly requiring removal of the gel-coat and long term drying of the laminate... Let's hope not.

Superficial osmosis is (in my experience) mostly caused by almost constant contact with water. If in storage, wet grass will do that, or even a moisture soaked tarp the boat may have been in (almost constant) contact with.

I would be very careful with heating up the blisters. If the fluid inside boils I would be very afraid it would cause extensive structural damage to the laminate.

Dennis

I had the same problem on a NACRA. The blisters formed where the hull was pressing against a carpet covered cradle. The winter was very wet and the carpet was probably wet for 3 months. I blocked the boat up on small blocks of styrofoam and the blisters mostly went away.

Thank you guys...always so helpful!

I've done the grinding/fill thing. ;^(
Has anyone opened blisters and washed them out with a few mls of acetone with a syringe? This would get out the nasty water & hydrolyzed polyester. Then warm and allow to dry and inject with (filled?) epoxy later.

Carl,
Thats kind of what I was thinking.....