Bruce, I just pulled my boat out and have a rash of tiny blisters in a 4" stripe just below the water line from the bow to the stern on both sides. First question is how did it get there? It doesn't make sense that it would just be the makeup and construction of the boat otherwise it would be everywhere on the bottom and not just a stripe. Does water depth or temperature have something to do with it? And, now that they are there how do I get rid of them? After I get rid of them, do I need to barrier coat the entire bottom or just the stripped areas? I race this boat and I'll put in whatever work I need to make this right so I appreciate your advice. Thanks, Bob W.
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You probably hit something - or something hit you
maybe not too hard but I have gotten blisters twice in places where I had rubbed hard against a piling or a log had hit me. You could actually see the pattern where the fiberglass was hit.
maybe not too hard but I have gotten blisters twice in places where I had rubbed hard against a piling or a log had hit me. You could actually see the pattern where the fiberglass was hit.
I have owned four boats from the 70s. They have all gotten blisters. They have all been in a pattern. They have always been below the water line, but not all the way down to the keel. I don't have a clue why. With my 23 I went to a big effort several years ago to remove the blisters and protect the bottom with a barrier coat. I have mostly got rid of the problem. I recently bought a little American D-18 for trailering. It has extremely small blisters in the same pattern. This boat has not spent a lot of time in the water. I will probably just ignore them.
What year/model boat?
Sounds like "pox", lots of small bubbles/blisters in the gel coat that arose in certain year model boats. Do some research here at HOW and other sites and you will find a lot of info. There is debate on whether it's worth the repair or not. We'll see what the guest expert has to say.
Sounds like "pox", lots of small bubbles/blisters in the gel coat that arose in certain year model boats. Do some research here at HOW and other sites and you will find a lot of info. There is debate on whether it's worth the repair or not. We'll see what the guest expert has to say.
Blisters?
There are two schools of thought. Or so I've read. The first says haul the boat, dry it out, have the blisters ground out and the voids filled. Have a multi-coat barrier applied, bottom paint the boat, launch it, pay the monumental yard bill bill, begin sailing, wait for the blisters to re-appear, and do it again. The second says they're cosmetic in nature and you won't see them between haulouts, so go sailing and save your money. Who knows?
There are two schools of thought. Or so I've read. The first says haul the boat, dry it out, have the blisters ground out and the voids filled. Have a multi-coat barrier applied, bottom paint the boat, launch it, pay the monumental yard bill bill, begin sailing, wait for the blisters to re-appear, and do it again. The second says they're cosmetic in nature and you won't see them between haulouts, so go sailing and save your money. Who knows?
How big are the blisters and how deep?
first search sailnet.com (articles) for every think Don Casey has written on blisters, gelcote, polyester / epoxy resins. amazon or bluewaterbooks are another good source... blisters are really water intruding into the gelcote, and eventually the fiberglass. if left untreated, they may eventually go thru the hull. often they form in the bilge from the inside. these can be the most serious. west marine also has several pubs you can read on this. depeindin on how long you plan to keep this boat, should determine your repair. supprisingly fresh water is worse for the osmossis than salt. barrier coat is recommended solution, followed by bottom. proper repair also calls for a long dryout period.
first search sailnet.com (articles) for every think Don Casey has written on blisters, gelcote, polyester / epoxy resins. amazon or bluewaterbooks are another good source... blisters are really water intruding into the gelcote, and eventually the fiberglass. if left untreated, they may eventually go thru the hull. often they form in the bilge from the inside. these can be the most serious. west marine also has several pubs you can read on this. depeindin on how long you plan to keep this boat, should determine your repair. supprisingly fresh water is worse for the osmossis than salt. barrier coat is recommended solution, followed by bottom. proper repair also calls for a long dryout period.
Blister Repair
I was never able to get one to dry out just by letting it set. I finally ended up sanding into the blister and blowing the moisture out with an air hoze. Then I let it sit for several weeks. This doesn't agree with the prevailing wisdom. To me it makes since that the majority of the moisture is in the blister, therefore, you need to get rid of that moisture. Just letting it dry just doesn't seem effective. I have taped cellophane to the over the opened blister for a few days after it has had a chance to dry for several weeks. I have never seen moisture after using this procedure. My blisters have not come back even after being in fresh water continuously for several years.
I was never able to get one to dry out just by letting it set. I finally ended up sanding into the blister and blowing the moisture out with an air hoze. Then I let it sit for several weeks. This doesn't agree with the prevailing wisdom. To me it makes since that the majority of the moisture is in the blister, therefore, you need to get rid of that moisture. Just letting it dry just doesn't seem effective. I have taped cellophane to the over the opened blister for a few days after it has had a chance to dry for several weeks. I have never seen moisture after using this procedure. My blisters have not come back even after being in fresh water continuously for several years.
Assessing blisters
If you're lucky the blisters are just in the gelcoat, but the only way to know is to sand off the blisters removing the gelcoat to expose the laminate. To inspect the laminate wet down the sanded area with water and if the laminate has hydrolized then you will see white fibers. Fiberglass that is wet out properly will be translucent and not white. The reasons for and remedies for blisters can get fairly involved so I would suggest you get a copy of our 002-650 Gelcoat Blisters: Diagnosis, Repair, and Prevention manual. It has a detailed explanation of why blisters form and discusses various repair options. If you can't find one where you buy WEST SYSTEM call me and I'll see you get one.
If you're lucky the blisters are just in the gelcoat, but the only way to know is to sand off the blisters removing the gelcoat to expose the laminate. To inspect the laminate wet down the sanded area with water and if the laminate has hydrolized then you will see white fibers. Fiberglass that is wet out properly will be translucent and not white. The reasons for and remedies for blisters can get fairly involved so I would suggest you get a copy of our 002-650 Gelcoat Blisters: Diagnosis, Repair, and Prevention manual. It has a detailed explanation of why blisters form and discusses various repair options. If you can't find one where you buy WEST SYSTEM call me and I'll see you get one.
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