Blisters on hull?

[teaklejr]

Hello. I have a 1997 GW Tigercat and saw two blisters on the port side sponson last year under the bottom paint. Just to give some more info the boat only sat in the water for less than 2 years and that was only April-October. it was barrier coated and bottom painted prior to going in water. I need to get them fixed. Does anyone have recommendations on where to go. It was painted at A&M marine and was happy with them just wanted some more input. Also how many other people with GW's have had this happen. Prior to me owning the boat it was lift kept or trailered. Any info would be great. I was quoted $2500.00 to sand blast bottom, re-barrier coat and paint. That price did not include fixing the blisters. They said have to see how bad they were once the bottom was blasted.
Thanks

 

[uncljohn]

maybe sandblasting is necessary to get the barrier coat off?

April-October is a long time to be in the water. That's more than 6 months at a time.

If the boat had previously been lift-kept or trailered, I would be dollars to donuts that A&M Marine did not apply the barrier coat properly. I mean, sure the paint job looks good, but if you only have a few coats of barrier coat on, its not going to be a "barrier". The barrier coat needs at LEAST 4-5 coats to give full protection. Its a lengthy process, and I've read where friends of marina workers say how they only put "1 coat barrier coat and 1 coat bottom paint" and that isn't going to help you at all.

Grinding blisters out isn't too difficult, need to get it dry and get all compromised epoxy/glass out, then fill w/ thickened epoxy and sand smooth.

 

[seasick]

You probably don't need the entire hull repainted. Barrier coat will help prevent blisters but it wont fix existing ones. That have to be ground out, filled and gel coated and then painted.
The barrier coat can be sanded off, you dont need to blast the entire hull. That said, it is possible that other blisters may appear but if you don't see tham now, I would fix what I see and go from there.

You need t be sure though that you are seeing blisters and not a more serious problem like delamination or structural swelling due to wet core/stringers/etc.

 

[richie rich]

If it were "supposedly" checked and OK'd initially and now you have blisters, it sounds like there was moisture still in the laminate and you trapped it in when it was barrier coated. You can do as the guys suggested and fix just the blistered area, but it may pop up elsewhere...thats a personal call....the only true way to find out would be to sand blast the hull, do a moisture check and leave it out to dry slowly for an extended period of time, or help it out a bit using heat lamps at a LOW temperature....unless the boatyard thinks it's structural, since you're in the season, I would probably wait until the Fall, have it blasted and checked and let it dry over the winter and re-read the moisture numbers in the Spring....you can sand, but it will take time for sure.....it cost me around $600 to blast my sailfish...well worth it for me.......if the readings are good, the 4-5 layers of Interprotect should be fine after the repairs are made....no real need to re-gel coat the repair areas as the epoxy repair will be better than polyester gelcoat anyway and you are painting the hull....for kicks, you can add a dab of white pigment to the epoxy so it looks invisible, under the barrirer and bottom paint.

Can you see and inspect the area from the inside??

 

[BobP]

Standard repair procedure for a fiberglass shop.