Bumps on hull
- Thread starter DLB
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Yes, I'm suspecting barnacle residue as well. If blisters, I suspect that they are cosmetic and not causing any delamination.
I have not seen a 322 with osmotic blisters. It was one of the points that gave me confidence in the pre-leveraged buyout boats.
We had what looked the same on our 272 LE...we opened them, and yes, they were blisters....then we had the hull
sandblasted then we opened each blister and filled them according to the epoxy instructions and we have never had another blister....that was maybe 5 years ago...I really believe the blisters were caused by the boat remaining in the water for 8-10 years (at least)....we used a bubbler system to keep the water from freezing in the winter; which it did.....but it of course, did not protect the boat from blisters......this could be a long story, but we no longer use our bubbler, but I am thinking about using it this coming winter ....long story short though....we have never had another blister...this was all about 4 - 5 years ago....keep in mind, we bought the bubbler maybe in late 1987 to avoid buying a trailer..the boat spent a lot of time in the water maybe 7-10 years straight, but we'll see what good ideas we have this fall...if reason prevails will probably take the boat out in a few weeks....we've never had another blister....so why press our luck..?...there is a heck of a story here, but I've bored you enough......Patrick
sandblasted then we opened each blister and filled them according to the epoxy instructions and we have never had another blister....that was maybe 5 years ago...I really believe the blisters were caused by the boat remaining in the water for 8-10 years (at least)....we used a bubbler system to keep the water from freezing in the winter; which it did.....but it of course, did not protect the boat from blisters......this could be a long story, but we no longer use our bubbler, but I am thinking about using it this coming winter ....long story short though....we have never had another blister...this was all about 4 - 5 years ago....keep in mind, we bought the bubbler maybe in late 1987 to avoid buying a trailer..the boat spent a lot of time in the water maybe 7-10 years straight, but we'll see what good ideas we have this fall...if reason prevails will probably take the boat out in a few weeks....we've never had another blister....so why press our luck..?...there is a heck of a story here, but I've bored you enough......Patrick
Thanks for the feedback so far.
The boat has always been in fresh water during relatively short seasons. One owner kept her on Lake Ontario near Toronto, the second kept her on the northern shore of Lake Erie.
Here is a better shot. Curious. As you can see many have "popped", but the ones that are still intact are hard and would require a dremel tool to open.
The other question is why so much of the vc17 washed off when power washed.
I plan to try opening them and filling, to see how they fare next season.
The boat has always been in fresh water during relatively short seasons. One owner kept her on Lake Ontario near Toronto, the second kept her on the northern shore of Lake Erie.
Here is a better shot. Curious. As you can see many have "popped", but the ones that are still intact are hard and would require a dremel tool to open.
The other question is why so much of the vc17 washed off when power washed.
I plan to try opening them and filling, to see how they fare next season.
Looks like the same thing that I dealt with after I had the bottom stripped. All the ones I opened up just went through the gel coat and not into the laminate so I simply faired them out the best that I could then applied 5 coats of Interlux 2000e barrier coat to be sure.
Definitely a case of the 'pox'. I must have had a thousand like this on my '34 this spring. Had the bottom blasted, sanded everything, used the West System for prepping & filling the blisters, sanded forever, 4-5 coats of epoxy barrier coat & the like. Took forever. biggest problem is that no matter how stiff you mix the filler, it sags & you have to sand. Worst job I ever did. My boatyard uses the 3M system to fill rather than West System, perhaps its easier to sand....
@SailingCal21 hit the nail on the head... It looks like a case of shallow blistering where it is only as deep as the gelcoat and not into the laminate. Do you HAVE to fix it? Not really, but since you are on the hard and need new bottom paint, now is the best time to address it.
- You only need to lightly grind them, not deep at all... a dremel tool is fine. Do this with all the paint still there so they are easier to see.
- After that, sand off or have sand blasted the bottom to get off all bottom paint and any barrier coat that may be present. No need to take the gel coat off completely, that is over-kill. Now let it sit for the rest of the winter to 'dry out'. Check moisture levels in the spring. Running a dehumidifier or small heater inside the boat could help speed things up, but don't bother with this in freezing temps.
- When you get a good 8 weeks of above freezing temps in the spring start checking moisture levels. Heat from the inside if necessary. Don't worry about rain, if fresh water goes on the hull it actually helps the process, the boat won't 'soak it up'.
- When its warm enough for epoxy and moisture levels are clear, Interlux Water-tite epoxy filler is great for filling these small ones. Its a 1 to 1 mix that is pre-thickened and a couple tablespoons at a time will fill many of divots.
- You can follow up with a fairing compound and torture board (long board sanding) if you like, but with those tiny blisters it shouldn't need it.
- Like LouisMK said, 4-5 coats of Interlux Interprotect 2000E and you will never have blister issues again. Photo document the whole process and it will increase the re-sale value of your boat. For your size hull you should use a full 3 gallons on the hull, keel, and rudder below the boot stripe. Use 1/4" nap rollers, don't use foam rollers (way too fine, will fall apart from the epoxy) and don't use 3/8" nap (way too much orange peel).
- You only need to lightly grind them, not deep at all... a dremel tool is fine. Do this with all the paint still there so they are easier to see.
- After that, sand off or have sand blasted the bottom to get off all bottom paint and any barrier coat that may be present. No need to take the gel coat off completely, that is over-kill. Now let it sit for the rest of the winter to 'dry out'. Check moisture levels in the spring. Running a dehumidifier or small heater inside the boat could help speed things up, but don't bother with this in freezing temps.
- When you get a good 8 weeks of above freezing temps in the spring start checking moisture levels. Heat from the inside if necessary. Don't worry about rain, if fresh water goes on the hull it actually helps the process, the boat won't 'soak it up'.
- When its warm enough for epoxy and moisture levels are clear, Interlux Water-tite epoxy filler is great for filling these small ones. Its a 1 to 1 mix that is pre-thickened and a couple tablespoons at a time will fill many of divots.
- You can follow up with a fairing compound and torture board (long board sanding) if you like, but with those tiny blisters it shouldn't need it.
- Like LouisMK said, 4-5 coats of Interlux Interprotect 2000E and you will never have blister issues again. Photo document the whole process and it will increase the re-sale value of your boat. For your size hull you should use a full 3 gallons on the hull, keel, and rudder below the boot stripe. Use 1/4" nap rollers, don't use foam rollers (way too fine, will fall apart from the epoxy) and don't use 3/8" nap (way too much orange peel).
When we did Vigah we used a special epoxy resin by Magnolia. Two part and it did not sag. Bloody awful expensive though. It is still available and used in aerospace. Was really easy to work with as it was a two part paste with a descent pot life even in the Florida heat.
Blisters. My daysailer is stored on a trailer. The hull is lexan plastic, but the rudder and centerboard are old school polyester resin and glass matt.
The centerboard was covered head to toe with blisters. Most of mine were hollow, but many were solid but almost all were gelcoat depth only with what looked like missing resin in the matt. Ground them out then filled and refaired with the west system activity kit.
Guys dont blame yourselves or previous owners for this.
Its a 99% manufacturer defect, unless you or the po used a nasty solvent on the gelcoat. Maybe the marina is polluted with solvents?
My rudder gets to rest under the trailer in the garage on a soft carpet, the centerboard stays in it housing and never sees sunshine.. seems even high humidity can be a problem. Rudder doesnot suffer same fate, given exact same life.
Interlux Watertite is much like the product you described. Easy 1 to 1 mix. One part is white the other dark blue so you know its fully mixed when you have an even baby blue. Almost peanut butter consistency, but lighter and easier to mix than that, won't sag even over-head. $60 USD here at the SBO store but you can fill hundreds of blister repairs, especially with shallow blisters. Pot life is good, you'd never mix up the whole liter at once... a few tablespoons on a plastic board with a plastic putty knife and you'll fill several square feet of ground out blisters in plenty of time before it kicks. Sands well too.
https://shop.sailboatowners.com/prod.php?3491
It is my understanding that blisters are caused by resin that did not activate in the lay up process. The ones that are on the surface are usually starting in the mat layer of the fiberglass. Minerals and other chemicals in the water that are absorbed through the gel coat and react with the under activated resin giving off a gas that eventually causes a blister. Depending on the number of blisters, the best process, in my opinion, is to have the gel coat removed, sand all of the areas of unreacted resin (they show as white) and re-coat the bottom with vinyl ester resin (several coats, I did 11), then possibly use a barrier coat, then bottom paint.
If you do not take off the gel coat, how do you know where the areas of potential blisters are? If you only treat the ones you see, then you have the potential to have more of them pop every year.
For a yard to do this job it will cost between $10,000 and $15,000. I did the job myself for about $2,500 which included gel coat peel, tool rental, resin and advisement from a fiberglass expert in the Rock Hall, MD area. We did the job more than 8 years ago and there are no new blisters since. It is a job you will only do once in a life time not because the blisters may never return which is also true but because the work is brutal. The price is right however if you are up to the job.
If you do not take off the gel coat, how do you know where the areas of potential blisters are? If you only treat the ones you see, then you have the potential to have more of them pop every year.
For a yard to do this job it will cost between $10,000 and $15,000. I did the job myself for about $2,500 which included gel coat peel, tool rental, resin and advisement from a fiberglass expert in the Rock Hall, MD area. We did the job more than 8 years ago and there are no new blisters since. It is a job you will only do once in a life time not because the blisters may never return which is also true but because the work is brutal. The price is right however if you are up to the job.
@rajhnsn , you are spot on with the majority of what you said, but I have never heard that uncured resin is part of the equation. I am not saying you are wrong by any means, I just haven't read that from any source. It is a likely explanation if PE resin wasn't fully and thoroughly mixed with catalyst. My understanding is that PE resin is not totally waterproof at a microscopic level, it allows water molecules to work into the laminate and this is more typical in 'loose' layups where chopper guns were used, higher content of air bubbles, and poor quality resins that were used during the fuel crisis in the late 70's that also persisted into the 80's. I dunno... but what you said seems to make sense, what else would cause the chemical reaction with the water when the resin (if it were properly cured) should basically be inert plastic? Food for thought.
I think your recommendation for a full gelcoat peel makes sense for larger yachts that show signs of significant osmosis in the laminate rather than between the gelcoat/laminate. At the end of the day it is probably LESS labor to do the full peel than it would be to just spot grind all the blisters. The key is the drying time and verifying a fully dry laminate with a moisture reader, a full peel makes this process more comprehensive. Using VE resin is a good choice, but the best choice would have been epoxy resin. VE is much more 'waterproof' than PE resin, but only epoxy is completely waterproof. I know all the major manufacturers are now using VE resins in the first layers of the mold and have no issues with it, so I doubt you will ever have any issues. I would lean toward epoxy whenever possible because of its superior secondary bond. for my blister job I applied a 'soak coat' of epoxy to the laminate, sanded, and then an 8.9 oz layer of cloth and floated fairing compound while it was tacky. This method wasn't to increase the strength of hull but to replace some of the mils thickness of the removed gelcoat. Labor wise I think I saved time rather than rolling multiple layers of epoxy, but my boat is also much smaller (22 feet).
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I had that on my Mark 25. I used a countersink bit to open them up. There were a lot of them. Otherwise I treated them pretty much as described above. One thing you might want to consider is that the barrier coat I used specified temperature of above 50 degrees for 24 hours after application. Check a local weather history chart to see when this is in your area. I didn't get the boat in the water until after the 4th of July that year. Otherwise you can tent it.
https://www.westsystem.com/instruction-2/epoxy-basics/clean-up-removing/
DO NOT dispose of epoxy hardener in trash containing sawdust or other fine cellulose materials-spontaneous combustion can occur. Clean epoxy resin or mixed epoxy residue with lacquer thinner, acetone or alcohol. Follow all safety warnings on solvent containers. Clean epoxy hardener residue with warm soapy water.
3m safety sheet for bondo hardener says to wash with water with contact.
If the batch isnt mixed thoroughly the hardener in the resin will be diluted with any water it comes into contact with, could be osmosis, or maybe even condensation on the inside.
So you have a hard plastic substrate with pockets of water soluble liquid mixed it. The problem could be the layup or the gelcoat.
In 2005, my 88 C30 had bumps similar to those shown by SailingCal21 but smaller in diameter (1/2 pencil eraser max). When they were popped open, the bottom surface was white and shiny. I used a stripper to remove the old bottom paint and found a factory applied gray colored paint that the strippers would not remove. Some research indicated that an option from Catalina in 88 was an osmotic barrier paint applied over the gelcoat. The bumps were this paint not sticking to the gelcoat. I used a mechanical scraper to pop the tops off the bumps and then filled them with epoxy fairing compound before applying bottom paint.
I did this in 2005 and no bumps have reappeared.
I did this in 2005 and no bumps have reappeared.
@BobbyFunn , good points but that is epoxy resin/hardener... we were talking about un-cured polyester resin in the laminate causing osmosis.