Gelcoat Blister Repair

Joined
Nov 25, 2008
Messages
15
I am thinking of buying a 19 Cape Horn that has blisters in the gelcoat pretty heavy on the very bottom of the boat. None of them seem to have broke through yet. I was planning on sanding the entire bottom down to get the blisters out and fill any deep blisters with Marine Tex. What I was wondering is what would I use to finish the job as far as a build up coat, any fairing material, primer and paint? It will stay on the trailer for the most part. I may leave it in the water for a weekend, but that would be it.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: Gelcoat Blister Repair

Actual blister repairs are rather expensive on an complete hull. It normally involves removing all of the gel coat (that's all the gel coat on hull) and then as much of the laminate that's affected also, this may be the first few layers of glass. An epoxy or VE resin is used with glass to replace whatever glass was removed and then an epoxy fairing compound is used to get the hull true again, after that its painted.

This would come to a couple thousand bucks (+) to do on your own and a year of weekends, it also involves flipping the boat upside down. If you don't plan to do the whole thing then don't just do a spot repair.


The good news is that Blisters aren't normally a structural issue, they're more often than not, just cosmetic. So if they don't bother you and the fish don't complain about them, just go boating.
 

Yacht Dr.

Vice Admiral
Joined
Feb 26, 2005
Messages
5,581
Re: Gelcoat Blister Repair

welcome to Iboats FF..

Is it possible to post a pic or 2 ?

What is the hull bottom finish right now ? What do you want/care it to be when finished ?

Normally on a semi-blistered hull you can die grind out the blisters and fill them with epoxy/cabosil mix .. fair and top coat.

Sounds like this vessel has been stored in the water. OR It has some kind of thane paint on it ( which is NEVER good in the water )

YD.
 

ondarvr

Supreme Mariner
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Apr 6, 2005
Messages
11,527
Re: Gelcoat Blister Repair

The only problem with doing spot repairs is it's only a temporary fix. Everything in between what was repaired may blister at any time in the future and there are most likely many spots that are 90% of the way down the path to a blister, you just can't see them yet, that's why I say all or nothing is the best bet.
 
Joined
Nov 25, 2008
Messages
15
Re: Gelcoat Blister Repair

Thanks guys for the replies... I can't get a picture of the boat because it is about 6 hours away in Rockledge, FL. But it is just the bottom of the boat, the sides are fine and do not show any signs of blisters. I was planning on re-painting the boat because it also has some scratches in the side I wanted to fix. My thoughts on the project were to sand it down and flatten out the blisters, dig out any spots that were deeper than the sanding job then putting some Interlux Watertite on there, prime and paint. Would this be wrong? I want to boat to look brand new if I can keep it under 1000 or 2000. I don't think the blisters went all the way to the laminate, but you never know till you get in there.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: Gelcoat Blister Repair

I would say that close to 80% of all blister are in the laminate and when blisters are below the water line that % goes up.

You won't see blisters on the sides because that part of the hull isn't under water.

Is this boat free? If you want a new looking boat, don't buy a blistered hull, lots of money and time to get back to where you would be if you were starting with a non blistered one.

There is also no guarantee that they won't return and the less thorough (spot repair) of a job you do in repairing them, the more chance there is for them to return.
 
Joined
Nov 25, 2008
Messages
15
Re: Gelcoat Blister Repair

The boat is a 1996. Would it be wrong to sand/cut all the blisters out, smooth it out, use a build up coat then prime and paint?
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: Gelcoat Blister Repair

Blisters are a result of chemical reactions within the laminate, the current blisters were the sites affected first, the rest of the laminate is just in the process of creating blisters and new spots will show up as the reaction continues.

To have a good chance of it not blistering in the future you need to do the entire process I discussed earlier, and even then there can be problems.
Doing less just increases the chance of failure.

At a minimum you should grind out all blisters and leave the hull in a dry, warm, low humidity environment until the laminate has dried out, this can take a very long time. Then fill all blisters with an epoxy based product, the next step is to use an epoxy blister preventing barrier coat on the entire surface, then prime and paint.

This method "may" work, I say may because most reputable shops won't do this type of repair because the chances of long term success are low.
 
Joined
Nov 25, 2008
Messages
15
Re: Gelcoat Blister Repair

Thanks a bunch for all the help. I was planning on running the boat as is for the season, then doing the work over the winter. Hopefully that would be enough time for the hull to dry out. If I decide to get the boat and do all the work, I will post up the pics as soon as I get started. Thanks again!
 

Yacht Dr.

Vice Admiral
Joined
Feb 26, 2005
Messages
5,581
Re: Gelcoat Blister Repair

hey fly..

Try to find somebody with a moisture meter and check the water content of your hull.

Blisters are caused by water mixing with uncured resin..creating glycol.. then starts to blister out.

If your hull is dry then your only going to need to repair those blisters. ( I would not flatten the blisters out..grind out..then prep then Barrier coat ). I would suggest Interluxs' Interprotect 2000. then bottom paint ? or are you doing like.. paint paint ?
 
Joined
Nov 25, 2008
Messages
15
Re: Gelcoat Blister Repair

I was planning on taking care of the blisters, letting the boat set up for a while to dry out, then I was thinking of using Interlux Watertite for a barrier coat, then prime and paint. I'm thinking of using either Imron or Interlux for the paint. I will not be bottom painting the boat because it will be trailered. And I will try to find someone with a meter. There are some boat builders here where I live that should have one. I live in central GA where boat rebuilding, especially anything dealing with salt water, is very rare, so finding resources is not as easy as if I was living on the coast again. Here is the link to the guys who build boats here if anyone wants to look. Not a very detailed website, but it has a few pictures of the boat.

http://www.rambo27.com/
 
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