Most of the blisters I've seen in pictures or on other boats have been fairly extensive and irregular. My 1984 Catalina 27 has a few small blisters along the keel on one side and none on the hull. The peculiar feature is that they are all in a line and regularly spaced. Do these look like osmotic blisters to you? It almost looks like bolt heads protruding through to me, though I can't imagine what in the interior of the keel would have such bolts. A few small ones seem to argue against that theory too. Any ideas? I'm tempted to wait until next year and see what develops.
Blister origin
- Thread starter T37 Phil
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Look Like Blisters to Me
Phil, Consider yourself lucky if those are the only blisters you have found. I doubt that they are bolts or some type of protruding connector. From my experience (I fixed over 700 a few years ago), they look like blisters. Luckily, they should be easy to fix in no time. To confirm, pop one open with a sharp knife and you will immediately know! Whats fortunate about having a blister on the keel, which is not uncommon is that you can grind these down without the fear of going too far into the glass roving as with a blister on the hull above the keel. DO NOT WAIT to see what develops, because they can just get worse over time. What benefit is their to wait if the boat is already out of the water and you can get to these well before launch time. Good luck Bob
Phil, Consider yourself lucky if those are the only blisters you have found. I doubt that they are bolts or some type of protruding connector. From my experience (I fixed over 700 a few years ago), they look like blisters. Luckily, they should be easy to fix in no time. To confirm, pop one open with a sharp knife and you will immediately know! Whats fortunate about having a blister on the keel, which is not uncommon is that you can grind these down without the fear of going too far into the glass roving as with a blister on the hull above the keel. DO NOT WAIT to see what develops, because they can just get worse over time. What benefit is their to wait if the boat is already out of the water and you can get to these well before launch time. Good luck Bob
Blister
Phil, Only fibre glass can get osmotic blisters due to chemicals in the resin reacting with water to form acid. Your keel is either iron or lead. Unless it is covered with fibre glass you should never get blisters. It may be just a paint bubble which is easy to repair. West Systems publish a book on how to repair blisters. It's not that hard, just time consuming.
Phil, Only fibre glass can get osmotic blisters due to chemicals in the resin reacting with water to form acid. Your keel is either iron or lead. Unless it is covered with fibre glass you should never get blisters. It may be just a paint bubble which is easy to repair. West Systems publish a book on how to repair blisters. It's not that hard, just time consuming.
The reason for the blisters was polyester resin
that was not completely mixed. The blisters are caused by the reaction the uncured material has with water. Many people spend the money to have the outside of the hull barrier coated but don't do anything inside. Then they have a small ammount of water in the bilge that soaks ( polyester resin fiberglass is not 100% waterproof.)through the fiberglass finding uncured material which then creates an acid the pops the gelcoat. The blisters need to be opened and then cleaned, then dried out for a period of time. The the residue needs to be cleaned out prior to the repair of the blister. When repairing blisters, make sure you use a product that is made for being submerged! Many of the Polyester products say do not use under the waterline. Phil, it could be along a piece of roving that did not get filled well during layup. They are on the keel, I wouldn't worry until they break through. I would also recommend the West System information on blisters. r.w.landau
that was not completely mixed. The blisters are caused by the reaction the uncured material has with water. Many people spend the money to have the outside of the hull barrier coated but don't do anything inside. Then they have a small ammount of water in the bilge that soaks ( polyester resin fiberglass is not 100% waterproof.)through the fiberglass finding uncured material which then creates an acid the pops the gelcoat. The blisters need to be opened and then cleaned, then dried out for a period of time. The the residue needs to be cleaned out prior to the repair of the blister. When repairing blisters, make sure you use a product that is made for being submerged! Many of the Polyester products say do not use under the waterline. Phil, it could be along a piece of roving that did not get filled well during layup. They are on the keel, I wouldn't worry until they break through. I would also recommend the West System information on blisters. r.w.landau
fiberglassed keel?
Phil: Does your keel have fiberglass over the keel or is that just paint? Regardless, this is so minor that you should not worry about it. This is a very easy repair if it is fiberglass. Just open them up with a dremmel tool. Rinse them out with distilled water and let them dry. Then fill with marine bondo. Repaint the spots and you will be good to go. If you are dealing with paint over the keel then you have nothing to do until your next bottom job.
Phil: Does your keel have fiberglass over the keel or is that just paint? Regardless, this is so minor that you should not worry about it. This is a very easy repair if it is fiberglass. Just open them up with a dremmel tool. Rinse them out with distilled water and let them dry. Then fill with marine bondo. Repaint the spots and you will be good to go. If you are dealing with paint over the keel then you have nothing to do until your next bottom job.
Need to clarify
Thanks for the responses. Catalina 27 has a lead keel and fortunately I haven't mashed it into anything. It is glass covered as far as I can tell. I had planned to just clean and apply a few more coats of VC17 this Spring, no sanding (continuing same procedure as PO). At first, up close, I did think they were paint blisters. But they don't peel or give any, they're hard. It seems like I need to open one up to be sure. I'll take some eye protection and a sharp implement tommorrow and see what I can find out. It makes sense that the line is along the edge of a piece of roving and that the water came perhaps through the bilge (meaning keep a bone dry bilge or expect more of the same next year). I know that VC17 is made to apply over old VC17 without fuss. If I open up and repair these blisters, how would you suggest I go about prepping for this year's VC17 coats?
Thanks for the responses. Catalina 27 has a lead keel and fortunately I haven't mashed it into anything. It is glass covered as far as I can tell. I had planned to just clean and apply a few more coats of VC17 this Spring, no sanding (continuing same procedure as PO). At first, up close, I did think they were paint blisters. But they don't peel or give any, they're hard. It seems like I need to open one up to be sure. I'll take some eye protection and a sharp implement tommorrow and see what I can find out. It makes sense that the line is along the edge of a piece of roving and that the water came perhaps through the bilge (meaning keep a bone dry bilge or expect more of the same next year). I know that VC17 is made to apply over old VC17 without fuss. If I open up and repair these blisters, how would you suggest I go about prepping for this year's VC17 coats?
Phil, don't touch it just do your painting.
Itis a lead keel. Don't mess with it. It is tight now, I would leave it. Those bumps are tooo symetrical to be blisters. r.w.landau
Itis a lead keel. Don't mess with it. It is tight now, I would leave it. Those bumps are tooo symetrical to be blisters. r.w.landau
Phil, as you can see from the responses,
there are many opinions on what causes osmotic blisters. You can tell if you have osmotic blisters if they have a liquid that smells like vinegar. You can leave the blisters alone, grind them out and putty with epoxy, pop them and smell the liquid, if there is liquid. Sensible folks have done all of the above with sucess. I have dealt with numerous small blisters on a dozen or so different boats. I grind them out with whatever tool is handy, wash with alcohol or acetone, dry with a heat gun or hair dryer, and fill with epoxy resin thickened with microballoons. I have never had a blister recur, with 10 years of observation on some boats. So first of all, DON'T WORRY! Do not let this keep you from sailing. It really doesn't matter very much what you do about these blisters. Are you sailing on Lake Geneva? If so the cold, fresh water (I was there last July and it was COLD) will not make your blisters grow (if they would ever grow) like tropical salt water. Florida and Southern California is where you see blisters the size of small starfish, and they still don't cause any boats to sink.
there are many opinions on what causes osmotic blisters. You can tell if you have osmotic blisters if they have a liquid that smells like vinegar. You can leave the blisters alone, grind them out and putty with epoxy, pop them and smell the liquid, if there is liquid. Sensible folks have done all of the above with sucess. I have dealt with numerous small blisters on a dozen or so different boats. I grind them out with whatever tool is handy, wash with alcohol or acetone, dry with a heat gun or hair dryer, and fill with epoxy resin thickened with microballoons. I have never had a blister recur, with 10 years of observation on some boats. So first of all, DON'T WORRY! Do not let this keep you from sailing. It really doesn't matter very much what you do about these blisters. Are you sailing on Lake Geneva? If so the cold, fresh water (I was there last July and it was COLD) will not make your blisters grow (if they would ever grow) like tropical salt water. Florida and Southern California is where you see blisters the size of small starfish, and they still don't cause any boats to sink.
Grind Them
I agree with Phil, grind them out and fix them. It really isn't any big deal and it is simple to do. You will feel better knowing what is going on under the layers of paint and glass.
I agree with Phil, grind them out and fix them. It really isn't any big deal and it is simple to do. You will feel better knowing what is going on under the layers of paint and glass.
Bilge water
I didn't make it down to the boat yesterday so I don't have more info. I did have another question. I had always thought that small amounts of water in the bilge were not a big problem. My keel bolts appear shiny and in good condition. I've never seen the interior construction of a glass covered lead keel bolt. Is it possible for water to seep from the bilge through interior spaces in the keel and blister out through the gelcoat? Has anyone seen how Catalina constructs the lead ballast and what if anything in the interior of the keel might cause the protrusions seen in the photo? The source of the water of course is a topic for another thread. r.w. - I'd be interested on your comments in the river sailing thread I am posting today.
I didn't make it down to the boat yesterday so I don't have more info. I did have another question. I had always thought that small amounts of water in the bilge were not a big problem. My keel bolts appear shiny and in good condition. I've never seen the interior construction of a glass covered lead keel bolt. Is it possible for water to seep from the bilge through interior spaces in the keel and blister out through the gelcoat? Has anyone seen how Catalina constructs the lead ballast and what if anything in the interior of the keel might cause the protrusions seen in the photo? The source of the water of course is a topic for another thread. r.w. - I'd be interested on your comments in the river sailing thread I am posting today.
The verdict is
... blisters. The bad news (not so bad really) is confirmed. I pressed the edge of a key into one of the small bubbles and a vinegary smelling fluid oozed out. The good news is that the larger bubbles seems to have receded somewhat in the past few weeks of increasingly warmer weather and dry bilge. Higgs, what did you mean by "redid" the joint? Did you grind and patch blisters or something more extensive?
... blisters. The bad news (not so bad really) is confirmed. I pressed the edge of a key into one of the small bubbles and a vinegary smelling fluid oozed out. The good news is that the larger bubbles seems to have receded somewhat in the past few weeks of increasingly warmer weather and dry bilge. Higgs, what did you mean by "redid" the joint? Did you grind and patch blisters or something more extensive?
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