Buying boat with epoxy blister repair--advice? - SailNet Community
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post #1 of 11 Old 02-18-2006 Thread Starter
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Buying boat with epoxy blister repair--advice?

I am interested in a mid-1980s aloha sailboat which had blisters. It was apparently hauled for six months to dry, and then the gelcoat was peeled (assume this was done with a peeling machine, professionally), and the bottom was then coated with epoxy and bottom paint. The work was done in 2003, and there has been no indications of problems since. The boat is moored year round in the pacific northwest.
I would appreciate any comments on whether you think a boat with a "new" bottom like this is better than the original, whether you would trust this to have repaired the problem (assuming quality professional work), or whether you would consider a boat that required this work to be "suspect" for life, and to be avoided as a boat purchase.
I am also looking at another boat a 1983 ericson 30, which had been trouble free but showed about 20 "thumbnail size" blisters when hauled in 2005. The blisters were ground out and faired at that time. This boat is priced better than the first one, is better equipped, but a few years older and I am concerned that although the 20 blisters were fixed, there is no assurance that other blisters won't appear on an ongoing basis--ie. this boat may be prone to blisters, even though ericsons have a good reputation.
I have done alot of reading on blisters/osmosis. Increasingly, the studies seem to show that all boats absorb water through the gelcoat over time, and for various reasons, some end up with blisters. It seems that small blisters between the gelcoat and laminate are simply a cosmetic issue, and not really of concern; if they are large, accompanied by delamination of the underlying laminate, it becomes more serious and a potential structural problem. The recommended repair seems to be peeling the gelcoat, re-coating with expoxy, but I have not been able to discern if that repair then makes the bottom stronger and less permeable than a regular boat with gelcoat, or if the repaired boat is still more vulnerable.
I would appreciate any comments on this, and thoughts on whether you would consider either boat as a potential purchase--pros and cons.
Thanks for any replies.
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post #2 of 11 Old 02-20-2006
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I would think that a properly repaired boat would not be prone to blisters in the future. I have no experience here. It seems to me the problem has been around long enough for effective soutions to be reliable. If the Aloha was barrier coated after the repair, and it was a professional job, I would think it a pretty safe bet - is there a warranty on the job? Check out the reputation of the yard that did the job.
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post #3 of 11 Old 03-25-2006
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In my research one article discussed this issue in-depth. It stated that if there are less than ~100 blisters on the hull (on a 30-40' boat) then they should just be faired out and the hull re-painted with anti-fouling. The author even went on to say that if there are only a handfull of blisters that it should just be left alone. If the repair work is not properly done it is recipe for more substantial/costly problems down the road.

Stripping the entire hull of gelcoat and barrier coating should only be a last resort; as indicated in this article. The author states that the epoxy systems are not to be considered any more moisture resistant than the original gelcoat; and if not properly prepped/applied it introduces more problems. The opinion was that unless you also strip the chopped strand mat off of the hull you have not adequately addressed the problem (this is not normally done when barrier coat is applied). Based on this article I would not buy a boat that has been stripped/barrier coated over another boat that only has had fairing/repainting. Of course unless you could see what was done beneath the paint; you won't know for sure but in -most- cases it should be evident to a competent surveyor if repair work was extensive or poorly executed. (IMHO)

Here are the articles I'm ref'ing to. A real eye-opener in terms of exterior hull problems!
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post #4 of 11 Old 03-25-2006
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Blister Repair

I strongly disagree with Keel-Haulin on the effectiveness of barrier coats. Proper barrier coats contain tiny aluminum platelets in epoxy. It's the platelets that provide the barrier. However, I do agree on carefully assessing the need for repair. Blisters about the size of a dime can be ignored. Blister about the size of a quarter need to be looked at carefully by grinding and opening the largest. If it bleeds an orange-brown viscous liquid they will likely need to be ground out with a router bit or Dremel tool, dried with a hair dryer and filled with epoxy putty. The effectiveness of barrier coating needs to be looked at at each haulout.
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post #5 of 11 Old 03-26-2006
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I understand where you are coming from; and there are differing opinions on this of course. I am only re-posting/concurring with what David Pascoe had written in the very detailed articles on his website. From the standpoint of hull integrity; I would tend to think that a gelcoat that is left intact would be better for the most part than trying to re-bond/seal with an epoxy paint. The original gelcoat is heat/presure cured and bonded to the wet layup at the factory and should provide the best bond/seal to the outer chopped strand mat layer. From what I understand, the exposed end-grains of the glass are where the moisture gets into the CSM; and that is where the failure point begins. It's possible that a barrier coat over the top of the faired gelcoat would be a better approach; but I would not do this unless the Mfr of the barrier coat has tested and approved this as a suitable application. From what Pascoe has written; even sandblasting or heavily scouring the gelcoat with an abrading powerwasher can set up the conditions for increased moisture penetration; due to increased surface area (the scouring makes the hull surface more sponge-like).

In looking at or deciding on a boat I would consider a hull that has light repair work to the original gelcoat a step further away from a major strip-down of the hull (to the structural laminate) than a boat that has had the gelcoat stripped and a barrier coat put in it's place. I would think that the longer you can wait/prolong the integrity of the gelcoat the better off you are in terms of preserving the mat layer of the hull; that is if the blister repairs are properly executed.
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post #6 of 11 Old 04-29-2006
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Without going into technicalities, we purchased a used glass boat many years back. It was 12 years old and two years after we purchased it we saw the first blisters.
Over 12 months they slowly grew to nearly dinner plate size.
After doing somw research we hauled her out and dried her for a few days. We ground out the effected areas and left it to dry for several weeks, sometimes hurrying the process with a fan heater blowing on the areas concerned.
We then did some final cleaning and prep work before sealing the cleaned areas with epoxy and then building up the ground out areas with matting and epoxy, allowing each layer to dry properly.
We then faired the hull and repainted the effected areas before anti fouling.
We used the boat for another 3 years and then sold her to a friend who still uses her every week.
The whole operation took us a little over seven weeks and in the 17 years since we did the work there has never been any further problem with the exception of a few smaller blisters just after we did the work which we think were part of the original problem. They were dealt with during the anual haulout with normal epoxy filler.
This may not sound like a high tech fix but it certainley worked.
Regards, Rick
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post #7 of 11 Old 04-29-2006
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My boat was peeled THEN DRIED and barrier coated back in '92. According to the owner, the blisters were just starting to show, and he wanted to address the problem immediately and completely. The work was done at a yard that had expertise (as a matter of fact, the yard manager owned her at the time) and she has been blister free ever since. She was built in '76 and has a solid glass hull. She is in the water in the NE from May through Dec. and is hauled and pressure washed. I have been sanding her old paint smooth and re-applying a new season's of bottom paint every spring. This season, I am having the bottom walnut shelled. Then I will re-fair her and add a couple of coats of Interprotect. Then put on fresh bottom paint. I would have to say that from personal experience, an epoxy protected bottom is just what they advertise, protected. The problems come from boats that were left to have their blister problem get out of hand, and allow the water to intrude deeply into the mat. Then you will have a more serious problem.

C&C and Tartan now have 15 year no-blister warranties on all of their new boats, which come barrier coated from the factory. Other manufacturers offer similar warranties as well.
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post #8 of 11 Old 04-30-2006
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I have been doing more research on this; here is what I have learned about blister repairs in addition to my previous posts...

While attending the StrictlySail boat show and conference I was listening to the owner of MAS epoxies discuss various hull and deck repair techniques and here are some things I got out of his discussion:

The hull must be dried out to a moisture reading of 0.05% before applying barrier coats over either the existing gelcoat or stripped gelcoat. You can do this by letting dry for several months and checking periodically with a probe type moisture meter (the RF type can be incorrect by up to 50%). You can speed this process by tenting the lower hull and using space heaters (like the oil-radiator type) to get the temp up and promote evaporation.

The old blisters should be opened up ground/feathered out to good fiberglass and the hull should be stripped down to the gelcoat before allowing it to sit and dry out. If the blistering is severe (where it would be time prohibitave to grind out each blister); you should have a prof. company come and strip the gelcoat completely off. If you go this route dont bother stripping paint let the prof. company do everythig to remove the paint/gelcoat.

Fair out the bottom; using epoxy mixed with colloidal silica and strand silica to peanut butter conscistency; and/or a commercial epoxy base fairing compound. Sand flat, wash clean and after the hull has dried to .05% apply your barrier coats.

Here is where it gets interesting. You can either use an epoxy base paint or use 100% epoxy resin If you use the resin be sure and use slow-set hardener. Have a friend rolling it on and then lay it off smooth with a bristle brush. MAS recommends a min of 5 coats of epoxy (follow mfr's directions regarding re-coat times). If you stripped the gelcoat, a layer of fiberglass matting should be applied to build the surface back to even with the hull above the waterline. Be sure there is no resin blushing (an oily residue) on the surface after each coat; if there is you will need to scuff sand and wash between coats. Since epoxy resin is not a paint; it will be more impervious to moisture than a paint based barrier coat and the gelcoat. Once this is complete you can scuff sand and apply your anti-fouling paint.

So in the case of Frank Langer I'd say that if the boat was barrier coated with epoxy; it was probably done properly (ask who did the work and ask what the procedure was). If it was stripped not allowed to dry out and barrier coated with epoxy paint and it's possible that you would be doing this job again sometime soon.


Last edited by KeelHaulin; 04-30-2006 at 12:40 AM.
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post #9 of 11 Old 05-02-2006 Thread Starter
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Thanks for all your detailed information--clearly not a simple topic, but the various information sources do come to similar conclusions that a few simple blisters are best left alone, and more serious work should be done by very knowledgeable professionals using good quality materials, and then keeping one's fingers crossed and monitoring carefully. My earlier hope that a boat that had had it's hull/gelcoat planed and "redone" professionally would be a fairly safe purchase, is no longer a valid conclusion, given your information. Thanks for the help!

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post #10 of 11 Old 05-02-2006
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Ahoy Frank

First of all don't go into panic mode over blisters. There has never been a boat to sink because of them. Removing the gelcaot is no biggie as far a structure or strength is concerned. Until the 90's gelcoat wat the first coat laid on a mold, it remains tacky on any surface that is exposed to air. After the gelcoat cures, fiberglass and polyester resin is laid over top of the stickey gelcoat. Now both sides of the gelcoat are sealed from the air and it completely cures. No heat or vaccum bagging was done.
Gelcoat is not a sealant it is pourus.
To take care of a real bad case of blisters it is common to remove the gelcoat and then barrier coat. the barrier coat is good for 10 to 15 years before it has to be redone.
We do blister and barrier coating in our yard all the time, not me mind you, but the guys that do bottom jobs. It is a do it yourself job if you are handy with tools.
Again don't fret sooner or later they will probably show up.

Fair Winds
Cap'n Dave
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