How often do epoxy barrier coats have to be put on bottoms

[videorov]

I read where people are epoxy coating barrier coats on the bottoms before bottom paint. I wonder how often the barrier coatings have to be put on. Everytime you bottom coat or when on older boats say in the 80's and 90's years fiberglass hulls.
What is the cost of these epoxy coatings?

Im thinking the Aluminum hulls might be better so a person would not have to do those epoxy barrier coats, just bottom paint.

[Cheechako]

I think they are usually done once, either to fix a previous blister problem as p art of the repair system, or when the boat is new to avoid any blister issues. Shouldnt have to be redone unles someone goes after the bottom paint too aggressively.

[jgbrown]

Originally Posted by videorov

I read where people are epoxy coating barrier coats on the bottoms before bottom paint. I wonder how often the barrier coatings have to be put on. Everytime you bottom coat or when on older boats say in the 80's and 90's years fiberglass hulls.
What is the cost of these epoxy coatings?

Im thinking the Aluminum hulls might be better so a person would not have to do those epoxy barrier coats, just bottom paint.

Once, if done right and not damaged in future, realistically I'd say once in the time you own the boat.
Aluminum is much more fussy, and requires more care with paint below the water line.

[gonesail]

doing it right is the problem. if there is any moisture in the hull you can get blisters under the epoxy.

[lancelot9898]

I had a coal tar epoxy barrier coat put on the boat when new prior to launch back in 1985. Several years ago I noticed some blisters in the paint thinking it was just due to paint build up. It turned out to be blisters and I was told by the yard that did the work some 25 plus years ago that the barrier coat will not last forever. No safety issues, but I decided to peel the gelkote and put on new barrier coats. Not sure how good that coal tar epoxy barrier is or how it compares to new products today.

[Pete the Cat]

Originally Posted by gonesail

doing it right is the problem. if there is any moisture in the hull you can get blisters under the epoxy.

As someone who paid 14K to fix thousands of blisters intiated by a barrier coat being put on when the hull was a bit damp, I would caution anyone doing it that it can more harm than good if the hull is not dry. I wonder if more harm has been done by them (I have seen similar problems in the boatyard) than they have prevented. Probably not, as--in most cases--they were not needed in the first place. They are a solution to a rare problem IMHO. The whole blister fix thing has been a boon to boatyards.

[onestepcsy37]

pete the cat -

i agree. i hauled out last year and decided to do a really serious heavy sanding job to remove decades of hard bottom paint. but i couldn't find anyone who did heavy sanding; they all wanted to do 'gelcoat peeling'. i can understand why.

sanding is hard work. a peeling machine takes off your paint AND your gelcoat in one $1000 day. then of course you have to put on a barrier coat where your gelcoat used to be - figure another $1000 - and then bottom paint. the guy insisted i had blisters, and pointed to every paint imperfection as a 'blister'. but i didn't have blisters. so i sanded it myself, and yes, it's dirty hard work. but at least i still have a dry hull (had a surveyor do a meter reading) and my original gelcoat. and i never found any blisters.

i agree that some boatyards are selling peeling/barrier coat projects to unknowing boat owners with the threat of 'blisters'....

[starfish62]

What Pete & OneStep say. If the hull isn't dry completely, the barrier coat traps moisture in and can create more problems. Plus, stripping that epoxy off is much harder than getting the gelcoat off. I'm on the hard now, and have a lot of blisters to deal with, some quite large, almost all are in areas that were previously treated for blistering (good news, there). I'm going to do a barrier coat, so I'm budgeting for 6 weeks or so on the hard with heat on the hull for at least a couple of weeks until the moisture content gets down to where it should be.

To answer your question, if done correctly you should expect 10 years+ for the barrier coat.

[Jon Hacking]

The next question, of course, is: how much barrier coat? The West Epoxy folks say 0.5mm, or 0.020" of epoxy. For our catamaran, that works out to 35 liters of epoxy (straight resin, not "coal tar" epoxy)