Gelcoat question

[Water Bill]

We've owned our 37C since 2009 and have made nunerous upgrades or repairs using information from this site.Our latest project involves removing years of thick and cracking bottom paint. We chose to have the hull sand blasted. The operator used a reduced PSI to remove just the bottom paint leaving a bluish tint to the gelcoat. However, we noticed several small areas where the gelcoat has flaked off and previous areas that have been repaired.( see photos)
Has anyone else experienced this before?

 

[Jim Legere]

I haven't seen anything like that on my hull, but I do have a few spots like that on my deck. I think you could clean the spots with acetone or methyl alcohol, fill them with epoxy putty and then seal the bottom with Interprotect 2000 or similar...should be good for another 30 years!

 

[sandpiper10471]

Looks like a bit of osmosis to me. I have sanded bottoms in the past readying for bottom paint. Several times I have seen this and the moisture meter confirms higher than normal humidity levels. Only real cure is a peel and dry followed by a barrier coat. Takes a lot of time to dry out unless you are in Venezuela. However, I don't believe it is a serious issue as the 37C hulls are quite thick and well laminated.

 

[Johnb]

Blisters are usually slightly raised and if you pop them the liqiud that comes out smells like uncured resin. I had numerous ones on my previous boat which I just popped then sandpapered out, heated with a hair dryer, left for a week, and then filled with resin. That was a crude repair but I never had any repeat problems after 7+ years.

 

[Mathurin]

Our hull was exactly the same near the bow. On our boat, these "blisters" where only superficial, no liquid inside and the hull was very dry. We scraped the hull to open all of them, throughtly cleaned the area, filled the voids with below waterline epoxy filler, then painted with 6 coats of Interprotect. After 5 years, we have yet to see one of them reapear (and we use CSC which does not hide imperfections very well).

 

[Pilotocopilot]

A great article on Blisters "Blisters don't matter"

http://www.yachtworld.com/mustangyts/mustangyts_5.html

 

[Jim Legere]

A great article on Blisters "Blisters don't matter"

http://www.yachtworld.com/mustangyts/mustangyts_5.html

An excellent article! (I have read it before). The moral of the story - just clean up the blisters, fill them with epoxy, and forget about them. Never have a 'boat peel' done!

 

[Db421]

Those are nothing to worry about. Seal them with epoxy, fill & fair with thickened epoxy, apply barrier coat and paint the bottom.

 

[Water Bill]

Thanks for the responce, The gelcoat appears to have loss its adhesion to the hull in these areas with no damage to the laminate. Apparently the previous owner had the same problem. The dark areas in the photos are epoxy repairs. I would fill and fair if a small area was effected but the flaking covers the hull below the water line. With great consideration and with the price of bottom paint being what it is, we decided to remove the gelcoat (sand) and apply a barrier coat (several) then the bottom paint. Hopfuly this will cure the problem. By the way we are renaming our boat to SNOWBALL.