Epoxy barrier coat - pros and cons

[A30_John]

I have an Alberg 30 sitting in my back yard on stands. I bought it last Fall. The previous owner bought a new boat, and so didn't launch the A30 at all in 2004. It was last in the water in the Fall of 2003.

The condition of the bottom paint is rather poor. There is coat upon coat of paint, and it is starting to flake off, crack, etc. It's probably good for a season or two, but sooner or later it will need to be stripped and repainted.

Here are my questions:

1) I'm thinking about the pros and cons of applying an epoxy barrier coat before the new bottom paint is put on. I understand this can help prevent water absorbtion in the glass, but that's about all I know. Are there any other "pros" to doing this? Any cons? The boat is 38 years old and hasn't suffered without it yet. However, I'm planning on sailing it to tropical climes in a year or so, and it will spend long periods of time in the water (as opposed to 4 months a year in Maine).

2) If I were to put an epoxy barrier coat on the boat, should I do it now, before relaunching in 2005? Should the fact that the boat has had a year and a half drying out weigh into my decision to do it now instead of a year or two from now? My usual procedure with a new boat is to sail it "as is" for the first year, then decide whether I like the boat, come up with a list of things to do, etc. But if I did that would I be passing up a rare and valuable opportunity to do this procedure "right"?

3) How long does a hull usually need to dry out before applying a barrier coat? What is the minimum time? What is optimal?

Thanks!

John

[Tim]

This is a subject that's bound to arise over and over again. I've covered it a number of times, but am happy to offer my thoughts again.

I believe there is much misinformation, and a general state of fear, surrounding blisters, osmosis, and barrier coats. What follows is not necessarily stone-cold fact, but is my informed opinion based on available information and experience.

First of all, boats built in the early 60s rarely, if ever, form the sort of serious osmotic/hydraulic blisters that are known to form on some boats. Boats that are susceptible to terrible cases of boatpox tend to be 70s and 80s vintage, largely dependent on the formulation of the resins used in construction, as well as on the overall construction quality of the boats. No boat is entirely immune, of course. But I absolutely do not buy into the commonly-heard boatyard talk about how all boats will eventually form blisters. I just do not believe that any blister formation is inevitable; conversely, I don't believe any boat is necessarily blister-proof, either.

Secondly, I feel it's important to keep the blister problem in perspective. No boat has sunk or come to grief because of blisters or boatpox. Even the worst cases don't affect the structure of the boat in quite such a detrimental fashion. A serious case of blisters will admittedly be a major headache, and time consuming and expensive to repair.

No one wants this to happen to their boat, obviously; hence, the current state of fear, and the rampant application of heavy, expensive, and time-consuming barrier coat systems. Boatyards love this current fear because they can send their lowest-paid grunts to do the miserable work entailed, and the yard can charge the customer large sums of money for what is, in my opinion, completely unnecessary work--and it might even cause damage where none previously existed.

Allow me to expound. All fiberglass boats absorb moisture into the laminate when in the water. It happens in a short season; it continues to happen in a longer season. Does this absorbtion automatically mean that blisters will eventually form in any boat? I don't believe it does, and there's no evidence to support this theory either. While it's true that boats in the southern waters, and in year-round use, are more likely to form blisters, that's not to say that your boat will. Again: some boats, by virtue of their construction and, specifically, the formulation of the polyester resin used at that time, seem to be less likely to ever form the sort of widespread blisters, or boatpox, that keeps boaters awake with the cold sweats all night.

I believe that epoxy barrier coats, as originally designed and marketed, were intended to be used as part of an existing blister repair system. Over a short time, this morphed into the current trend of suggesting barrier coat systems as a preventative measure. I don't believe that is is automatically prudent to use these products when there is no evidence of an ongoing or pre-existing blister problem.

There have been many cases where application of barrier coats to undamaged boats actually caused blisters to form where none had ever existed. The reason for this is clear: epoxy barrier coats are very effective at blocking moisture infiltration. So effective, in fact, that they also block the natural back-and-forth movement of water, both when the boat is in and out of the water. Suddenly, moisture inside the laminate is trapped behind the barrier coat. It's this trapped moisture that, in some cases, chemically reacts with the styrene in polyester resin and causes a blister.

There is a big difference between an isolated blister located here or there on the hull, and widespread blisters that affect the entire surface. The small, isolated blisters are best dealt with one-on-one, in my opinion. They are easy to repair, and cause no lasting effects. If any blisters were to occur in a 40 year-old boat at this stage of the game, they would be of this isolated nature. I believe that more harm than good could come of applying barrier coat at this point.

There are undeniably many cases of serious blister problems, and they occur on all types of boats. Expensive boats have been affected, as have inexpensive boats. I don't think there's any way to tell from looking at a boat whether it is more susceptible or less susceptible to future blistering. I do think that older boats tend to be more resistant.

It's true that hulls need to be extremely dry before applying barrier coat. Drying is the most time-consuming portion of any blister repair; hulls retain trace amounts of moisture almost indefinitely unless heat is applied constantly, and long-term. This fact is why boats, even those that have been on the hard for some time, can still have moisture in the hull that might cause the barrier coat-induced blistering that I spoke of.

Phew. The long and the long of it is: I do not think that it is necessary, or even desirable, to barrier coat your hull, unless it is for an existing blister repair.

That's my story and I'm sticking to it! I might be completely wrong, and there are many who might say just that. The party line is that barrier coats can do only good. But I just don't believe in barrier coats as a preventative measure.

[Guest]

Thanks, Tim. Your reasoning makes a lot of sense. The hull is basically "blister free" at the moment, and from what I understand, there is no history of serious blistering problems with the Alberg 30 hulls. Who knows what will happen when the boat moved to warmer waters, but if it ever becomes a problem, I'll deal with it then.

I was under the impression that epoxy barrier coating as a preventative measure was unquestionably a good thing, but, as you point out, where will the trapped moisture go once the epoxy is on there?

I appreciate your candor, and I'm certainly happy to scratch that one off my list of considerations. Removing all that antifouling paint will be enough of a chore I'm sure. :-)

[A30_John]

Sorry, I wasn't logged in... I wrote the previous post.

John

[windrose]

Tim, thanks once again.... you just put some jingle back in my pocket as the hull is all prepped and WAS ready for barrier coat. Your rationale makes sense (or cents). The more I hang around here the more I learn about these old boats....sure am glad you are here. Cheers!

[Jason K]

This is the second older post I've responded to this morning. I'm putting off another long day of sanding and paint prep as long as I can...

Just a bit of insight from a Southern latitude. My Triton, when I purchased it in August '04, had been sitting in its slip on the Mississippi Gulf Coast for a number years without a recent bottom paint job and, to the best of my knowledge, has never been epoxy barrier coated. When I had it hauled in February of this year (for the first time) to clean her bottom and determine her condition, I was pleasantly surprised to find fairly fouled but blister free - it is definitely time for bottom paint though. The prop, however, was a well formed barnacle colony - I honestly don't know how it moved water.

[JonnyBoats]

For what it is worth, I read somewhere that the Univ. of Rhode Island did a study on blisters, and determined that standing water in the bilges can be a major cause.

If you think about a boat with epoxy on the outside and standing water for a long time on the inside does seem like a recipe for problems.