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Old 31-07-2005, 16:15   #1
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Epoxy barrier coat and blisters

When we purchased our boat, we were told that the bottom had an epoxy barrier coat applied in 1998. We are now stripping the bottom paint and have found two things:
1) Numerous area where the bottom had been repaired (see first pic). These areas are NOT flush with the hull. They protrude 1/32". If the repairs had been done when the epoxy barrier coat was applied, why are they not fair?

2) There are numerous raised areas (see second pic) that are exactly the same size. I have ground into several and the underlying material is granualated. If the bottom was epoxied 6 years ago, why do I now have blisters?

I would love to hear your thoughts.









Thanks
Roger
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Old 31-07-2005, 20:32   #2
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Several possiblities, concluding in many possible answers. Any of which could be compleatly miss leading. I suggest you get an expert to take a look. It needs close up inspection, more than what a few photo's can do for us.
But my misleading answer would be, maybe it wasn't done properly.
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Old 01-08-2005, 14:21   #3
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Most 'bottom jobs' usually fail.......

Unless the *cause* of the blisters is addressed. Simply draining, grinding, filling and fairing will not usually 'fix' blisters (sometimes a DIY blister repair can 'destroy' a hull). Most blister 'repairs' seems to be expensive hype.

For a fairly compreshensive treatise on 'blisters' go the www.yachtsurvey.com and follow the links to articles/comments on 'blisters', etc.

hope this helps
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Old 01-08-2005, 18:59   #4
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One very good source of info for blister repairs

For about a decade the success of vinylester resin in resisting hydrolization and subsequent blistering of FRP has been recognized and the following paper is a good authority on the subject:
http://www.zahnisers.com/repair/blister/blister1.htm

For about a decade it also has been known that epoxy barrier coats, in general, are NOT very impermeable to water as was originally believed. In addition, once epoxy has been applied one can not successfully apply non-epoxy resins and expect them to adhere. Like silicones, once they are applied it is difficult to remove all traces of the chemicals and, therefore, should not be used on the outside of a hull.
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Old 01-08-2005, 20:05   #5
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A poor repair is worse than no repair. These repairs would appear to have been done over the top of everything else and then faired to the surrounding area including the previous anti-foul etc. therefore probably a poor repair. I wouild definitely get a meter reading on them and the surrounding area, and I think I would be grinding these out and re-doing them. Alternatively, you could consider a gelcoat peel and a complete re-finish.

A new system in UK is to blow dry ice at the anti-foul. This strips the antifoul, and also freezes the osmotic blisters and blows them open and cleans them up at the same time supposed to be an intermediate solution between individual blister re-pair and the full peel and re-coat.
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Old 01-08-2005, 21:01   #6
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Tell me more about the dry-ice

Hi Talbot,
Wow! How does the dry ice "treatment" work? What machines are required to do the job? How effective is this, in general, to remove anti-fouling paint? Cost?

rick
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Old 02-08-2005, 00:10   #7
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i agree with the advise to get her surveyed by a top surveyor. there are lots of causes and lots of options and lots of incorrect info going around about blisters. the university of rhode island / uscg study is, i think, the definitive report on blisters. i'm not bright enough to make the web address appear here, but yahoo will find it. aside from your bottom rash, very pretty brewer - i enjoyed the other photos. capt. lar
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Old 02-08-2005, 11:03   #8
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Sorry but I dont have the details available. The report was in Practical Boat Owner a couple of years ago.
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Old 02-08-2005, 18:14   #9
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They are beginning to use dry ice for kitchen cleanup
(commercial). equiptment similar to sandblasting is used. Dry ice expands going fro solid to gas, cleans well, no sand to clean up , no dust.
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Old 02-08-2005, 18:50   #10
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here's the web site

http://www.daviscoltd.com/nams/Docum...er_Report.html will take you to the URI/USCG report on blisters. enjoy. capt. lar
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Old 02-08-2005, 21:28   #11
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Thank You all for your input. After spending two days gouging & grinding I have determined that:

-the original gel coat is still present
-the old patches are approx. 1/8" deep
-the new blisters are in the gel coat and the first layer of resin, no more than 1/32" - 1/16" deep. The layer under that is clear, hard, dense and glossy.
-there are numerous cracks in the gel coat that also need attention.

It appears that I will need to have the bottom peeled and recoat with vinylester in the near future, but will seek professional opinions.

Thanks again!!!!!
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