Boat Pox "Cure"?

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Bob Salter

Hello- We are Rocky Mountain sailors who own a sweet and tough Potter 19 that has never been a problem of any sort- However we are planning to become part time cruisers in the Florida Keys and beyond, and have been investigating used pocket cruisers such as Com-Pac 27s and Island Packet 26s- recently we found a Com-Pac 27 that we discovered had sat at slip for 3 yrs and when hauled was found to be infested across the entire bottom with dime size blisters- this condition was treated by sanding off the entire bottom down to original glass, and re-applying epoxy and gel coat, then re-painting. Now the "Broker" refers to this vessel as "Bristol", which it does have the outward appearance of being. We would be very interested in a range of informed opinions regarding the seaworthyness of a vessel repaired in such a way. Thanks- Bob and Sue- Ouray, Colorado
 
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Don Berger

common cure

As long as the bottom was done properly, it will be better than new. What you need to do is find out who did the bottom job and specifically how, i.e., stipped how deep and with what?, allowed to dry for how long? coats of barrier coat?, etc. If in doubt, talk to the folks who did the job and get a good surveyor who knows how to assess the quality of the job. If done correctly, you needn't worry further. Don
 
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Steve Winkle

More than skin deep

Bob, I second Don's response. The "drying out" period is critical. Insure that the surveyor knows the boat's history and ask him/her to specifically measure the amount of moisture still in the hull. See the attached link for some good info. Good luck, Steve S/V Options
 
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Debra B

gelcoat beats barrier coat

Gelcoat is waterproof - mostly. Epoxy is not. Gelcoat is better than epoxy barrier coat - and is much harder to apply. Sounds like this was done right, but it is always best to be VERY sure.
 
Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Debra, I think you have it backwards.

Debra: I think you may be confused. The common procedure is to epoxy barrier coat the Gel Coat to prevent osmostic blistering. Some of the newer gelcoats actually have some type of epoxy in the gelcoat finish.
 
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Bob

Each of those blisters

held a pocket of water/acid resulting from water that was absorbed through the original gel coat. If each of those pockets was opened up and dried out in the 'bottom job' process, the boat is probably OK now, though there could be some latent pockets that will show up later. The good news is that you don't often hear of a boat's sinking due to blisters.
 
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John Dawson

Confused

Your description suggests they sanded down to the polyester/glass hull, then added a layer of epoxy, followed by re-gelcoating, and then bottom paint. Or, that they faired the stripped hull with more resin (presumably polyester) and re-gelcoated it to its original composition (without a barrier) and then painted the bottom. And by paint, do you mean bottom paint or a polyurethane, awlgrip, or other finish? The common solution is to remove the old gelcoat and blisters, then coat the hull with required thickness of a barrier coat (Interprotect, Copperpoxy, Epoxy barrier), and then bottom paint. I suppose you could re-establish a gelcoat layer before applying a barrier coat, but the expense and necessity make it unlikely. Perhaps you could clarify the procedures and materials mentioned? As everyone says, this should be an acceptable cure for the pox if done right.
 
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Gord May

POX

As previously noted, a good blister repair job can leave the vessel in better-than-new condition (“Bristol”). All good advice so far, excepting gellcoat beats epoxy (! WRONGE!). Here's the rub. It's very difficult to determine how the job was done, after the fact. You can try to “sound” the hull, with a small mallet. Listen for “sharp” sound, indicating a good hull. A dull or flat sound indicates a wet or delaminated area. I’ve witnessed many professional bottom jobs that were improperly done; and therefor not worth doing at all! Some of the common errors: ~ Grinding the blisters, in such a fashion as to heat up the hull. Grinding must be carefully performed on smaller areas, and peeling is preferred for larger panels. Grinding/peeling to small an area around the blister, not getting the blister fully “open”, and not beveling the divot (12:1). ~ Failure to wash the hull to remove dissolved contaminates (salts, glycols, & acids). ~ Improper or insufficient drying, including the interior bilges. ~ Improper application of new barrier coats; including too quick overcoating, applying coats too thickly (>5 mil/each), too thin a final barrier (<15 mil)... Let me re-state: Most professionals don’t do a great blister job, and nearly ALL owners do it very poorly. As someone else said, blisters won’t kill you, but they sure can cost. Regards, Gord
 
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Craig Cody

The product used is important!

When I bought my boat almost 5 years ago, part of the deal was the repair of blisters. The bottom was covered in dime to quarter size blisters...THOUSANDS of 'em! The yard that did the work was totally incompetent, and what's worse, they used a product (3M) that was not suited for the application. Within just a few months of the repair, blisters were once again appearing on the bottom of my boat. I've contacted 3M, and it seems we're going to end up in court. They're blaming the yard (who were partly to blame, they did a rotten job), but it is my understanding that 3M has had to pay out millions of dollars to redo boat bottoms that were repaired with their product. Check out Gelstrip of Southern California and USA. This site shows the ins and outs of blister repair, and I'm going to have them do the fix once I settle with 3M.
 
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Frank Ladd

How long has it been since the cure?

If it has been a year or two since the cure was applied and there are no more blisters, then it was likely it was well done. If it was just done see if it will be warranteed by the yard that did the work. I know a local yard that covers any problems that come up from their paint jobs. Still customers have to aggree to let the boat sit for the required dry out period and ussually the boat owner does not want to have the boat sit in the hard for the required time. In the worst case you can figure the cost of fixing it right should not be more than a few boat units so maybe that will help you decide what you are willing to pay. In addition I have to applaud the broker for sharing this information with you in the first place
 
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John Dawson

barrier trend

I read recently that there is a trend away from barrier coats because they are rarely done right under perfect conditions. Professional jobs like the one mentioned here may be prevalent in the future.
 
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