Blisters


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Posted by Alex on February 14, 2005 at 03:25:01:

Posted by alex on November 29, 2002 at 09:37:17:
I have a 25 foot sailboat which is between 15 - 20 years old which I bought 3 years ago.The boat was surveyed by a professional surveyor and moisture readings taken using a Sovereign meter which produced readings of between 20 - 35% on the relative scale.
In the survey report the surveyor stated that these readings indicated that "there was little or no moisture or laminate breakdown products locked into the hull".At haul out last winter I noticed about 8 blisters within a square foot area of the hull, the blisters being about 1/4" in diameter and maybe 1/16" in height perhaps and just noticeable. I popped the blisters with the point of a knife (which took some doing as the gel coat seems to be quite thick) and some sweet smelling liquid came out.I left the blister areas open for a couple of months and washed them out with acetone regularly before filling with gel coat filler( the laminate below was tested with the point of a knife and was still very solid) I then primed the hull with primocon and antifouled the boat before launching the following spring.This haul out I had all the antifouling removed by slurry blasting and inspected the hull finding the previously repaired areas still in good condition and solid.I did find several other areas with same sort of blisters( about 60 in total) which I have broken open and washed out.I then hired a sovereign meter and took readings all over the hull showing relative readings of between 20 - 35 % or 12- 17 on scale A. The areas where the blistering has occured are where there was some fresh water lying inside the hull when I bought it due to a couple of leaky areas on deck fittings which I have now cured. Could it be that the water has seeped through from the inside to cause hydrolosis and these blisters? My intention is to fill the 60 or so blisters in the same way as previously and apply a coat of International primocon or similair underwater primer then antifoul the bottom and launch the boat in the spring.I would then inspect the hull each year at haul out to see if there is any further problems.The rest of the hull appears to be in good condition. Can you please advise if I am doing the right thing? Another boat owner suggested treating the hull with epoxy but I feel this may just cause problems in the future by trapping in any moisture.


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