How dry?

[bhartley]

I just got off the telephone with Interlux and am very frustrated. The instructions for their 2000E Barrier Coat says apply when "As Dry as possible." Unsure of what this meant, I called for clarification. The tech said it MUST be less than 3-5% and I MUST use a moisture meter. Don't have one. Don't have access to one. We live in rural Georgia.

The bottom is totally stripped down to the gelcoat. I really don't want to do this exercise again. There are a few old blister repairs (holding just fine) and some really crappy repairs for gelcoat damage which will be redone.

Do I just paint the bottom and hope for the best? The gelcoat is pretty marginal in places. The boat has been out of the water since October, but it has not been inside and has been rained on reasonably regularly. The boat is going in fresh water for the forseeable future.

Any recommendations?

Bly

[Ceasar Choppy]

What boat do you have and how old is it?

A few people I know with late 60's vintage boats let them dry for more than a year but apparently were unsuccessful. It of course made matters worse when they used the barrier coat because it trapped the water in the laminate. They ended up with more blisters than before.

[Tim]

As I've frequently opined here before, I oppose the generally-accepted notion today that barrier coats are "good insurance" and should be applied simply because one has stripped off the bottom paint to gelcoat. This is an opinion that is counter to most of what you will read, and most of what you will hear from others. I might be wrong, but I have what I feel are solid reasons for this particular belief, backed up by legitimate anecodotal evidence.

I feel there need to be additional circumstances in existence to justify the barrier coat application, and that barrier coats are actually intended to be part of a repair system, not simply a preventative system. When applied over boats that still contain moisture in the laminate (hence the "dry as possible/3-5%" admonition from Interlux), there's a very real possibility, as Ceasar alluded to, that you might actually trap this moisture within the laminate and create issues where none existed before.

All laminates absorb some moisture during normal use. This does not always lead to blisters by any means; it's a complex process that requires a number of factors to coincide at once. In many cases, the laminate will dry out relatively quickly when hauled. A barrier coat may prevent this natural movement; after all, they work the same in both directions. It can take a really long time to truly dry out a laminate.

Many boats do blister, and then require repair; I certainly don't deny that the problem exists--and seriously, in some cases. I admit to living in a part of the country where blistering is extremely rare; most boats around here that have blistered came from down south. Epoxy barrier coats are a sound part of the repair practice on these boats.

Sporadic "blisters", which you seem to have, may be caused by entirely different circumstances and do not point to a need, in my opinion, to slather heavy, expensive, and potentially damaging products on to the bottom.

It's going to take a lot more for me than general, uninformed paranoia spurred by the marine press and our Chicken Little mentality to start supporting the use of barrier coats as a general rule. As a repair, yes.

Do barrier coats prevent blisters in boats that have not had blister problems to begin with? Some would say that they do; after all, they don't blister after the product is applied.

Along these lines, I've found that my elephant-prevention device is working extremely well here in Maine. I haven't yet seen an elephant, so it must be working, right?

But there's real evidence that barrier coats can actually cause blisters in some cases. I've seen it firsthand; so have others. That's enough for me to suggest that they not be used unless there are truly reasons for the use. "Insurance" against an issue that doesn't yet even exist, and shows no real signs of ever existing, isn't a good enough reason to me.

That's my unpopular opinion. You don't have to agree, and if I am proven wrong someday I will be the first to say so. I'm still waiting. And I haven't put any of this stuff on my boats, and don't plan to either.

BTW, I will be happy to send you, temporarily of course, my moisture meter. All I ask is that you return it when done. Email or PM me if you're interested.

[Ceasar Choppy]

As I've frequently opined here before, I oppose the generally-accepted notion today that barrier coats are "good insurance" and should be applied simply because one has stripped off the bottom paint to gelcoat. This is an opinion that is counter to most of what you will read, and most of what you will hear from others. I might be wrong, but I have what I feel are solid reasons for this particular belief, backed up by legitimate anecodotal evidence.

...

It's going to take a lot more for me than general, uninformed paranoia spurred by the marine press and our Chicken Little mentality to start supporting the use of barrier coats as a general rule. As a repair, yes.

...

Along these lines, I've found that my elephant-prevention device is working extremely well here in Maine. I haven't yet seen an elephant, so it must be working, right?

...

That's my unpopular opinion. You don't have to agree, and if I am proven wrong someday I will be the first to say so. I'm still waiting. And I haven't put any of this stuff on my boats, and don't plan to either.

Nice rant there Tim... But I have to say that I agree with you.

[Mark.Wilme]

I can but tell you what I am doing. We are stripping the bottom of the Elite 32 that I jus sold (included in price). It has always been a dry boat, I have found no blisters so far and we are almost done stripping. There is no barrier coat on today. I will not be applying one - we will apply 3 coats of ACT (first black, then 2 blue).

That's what I am doing.

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[bhartley]

Just when I had decided to scrap the barrier coat idea, I decided to call the marina where Pyxis will live for the next several years. I was able to talk to the yard guy I consider most competent and he said ABSOLUTELY barrier coat the boat. They have LOTS of problems with blistering on all ages & types. She has had some blistering in the past.

I asked them about a moisture meter. Nope, they don't have one. He said if the boat had been out of the water since October, they would consider it dry. So... I'm back to barrier coating. Hopefully we'll get her in the water by... August!

Bly

Pyxis - Cape Dory 25D (1985)

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[Tim]

This is the sort of decision each boatowner must make on their own, hopefully using the best and most realistic information at their disposal. I only feel it's important to ensure that people know that there might be a dark side to all this that isn't frequently discussed.

Armed with information from both sides of the debate, one can make an informed choice that suits their--and hopefully their boat's--needs.

[David VanDenburgh]

Bly,

Our '79 Cape Dory 36 was barrier coated by a previous owner who kept her on Cayuga Lake in upstate New York. After her first season in the water on Lake Michigan, she had scores of little blisters that, upon closer inspection, turned out to be water trapped between the barrier coat and the gel coat. After conversations with Tim and dealing with the issue for a few years, I'm convinced that the previous owner included barrier coating as part of his ongoing and preventative maintenance but, in fact, created a problem by either: 1) Not applying the product carefully, or 2) not allowing the hull to adequately dry. It is clear, though, that the barrier coat is not solving anything. Water is either passing through the barrier coat and stopping at the gel coat, or passing from the laminate and through the gel coat where it's being trapped by the barrier coat.

Whatever the case may be, I aborted my plan to reapply barrier coat after removing the old stuff and have watched the hull closely. So far, there hasn't been a problem. We'll see what happens over the long haul.

David

[bcooke]

I was able to talk to the yard guy I consider most competent and he said ABSOLUTELY barrier coat the boat.

As someone in the "added value" industry, aka maintenance field, I thought I should add that however competent the yard hand is, there is a constant pressure in the industry to 'up-sell' work. When in doubt always suggest more maintenance. A significant amount of annual sales comes from 'suggestions' from the techs. That isn't to say the advice isn't good just be aware that the pressure to make money gets tangled up in the process a lot of the time.

...the danger date on the resin timeline...

Just to add my two cents here. It is my understanding that the 'date' in question is a period in the early 70's when petroleum prices were sky-rocketing and resin manufacturer's were tweaking their recipes to reduce costs. I am not sure how conclusive the evidence is but it appears that the changes to the resins made them more susceptible to blistering. With different recipes being introduced at different times by different manufacturer's using different construction techniques there seems to be a very loosely defined period where blistering cases become more likely.

Personally, if you haven't experienced much blistering before, and especially since you plan to be in freshwater, I wouldn't be too concerned about it.

The boat has been out of the water since October, but it has not been inside and has been rained on reasonably regularly

Another thing to keep in mind here is that I don't believe surface water is going to have much effect. If anything it might even aid in drawing out the water hydroscopically. The water pressure even a few feet below the surface is quite a bit more than at the surface which aids in driving the moisture through the laminate. Surface water, aka rain, is not going to penetrate a fiberglass hull very far. In my limited experience, several months out of the water is sufficient to dry out a hull and indoor storage is not going to improve the situation all that much. Yes, you could move the boat into an indoor heated storage facility. And yes, it will be better than leaving the boat outside. But then I come back to my first point which is how much is the yard going to charge for such a service? I bet the ratio of profit to effort is pretty favorable for them.

As has already been said, it is a pretty heavily charged issue with lots of strong opinions on all sides. The best bet, IMHO, is to spend a bit of time educating yourself and then just do what seems best to you.

And take what you hear on an online forum with a huge grain of salt. There are plenty of wacky people out there in cyberspace anxious to give their opinions :-)

-Britton

[bcooke]

Oh, and Mark you have aroused my curiosity.

Why the two colors on the bottom? Do you see the black through the two coats of blue?

I must be the only one around here that can't see these subtle shifts in color hues.

-Britton

[dasein668]

That's so's he'll know when to reapply bottom paint. When he starts to see black bottom, he knows that it's getting thin! (Ablative paint types, of course!)

[bhartley]

Britton,

My yard guy definately knew there was nothing in it for him or the yard. He knew the boat was in my yard and I had the barrier coat on-hand. My question to him was "How many boats do you haul out and find blisters?" The initial answer was LOTS. This is also a yard that charges $40 to step our mast.

The jury is still out on the barrier coat. The bottom is so crapped up with filler from the shovel damage that it looks dreadful right now. The blister repairs all look very solid. The surveyor found one active blister when she was hauled in 2006. We had none a year later.

It's been one of those days...

Bly

[Hirilondë]

If anything it might even aid in drawing out the water hydroscopically.

We have used spraying the bottom with a hose in the morning on sunny days as part of the drying process for some bottom problem projects. And for salt water boats it aids in drawing out the salt as well.

[kabauze]

Around here it is common practice to use Interprotect 2000e barrier coat as a sort of primer for bottom paint. The normal sequence goes like this: haul boat, strip old bottom paint with DA sander, sand gelcoat with some 80 grit, and roll on some 2000e followed by the bottom paint. This all happens in a matter of days and there is no real drying period. Of course most folks doing this don't apply the 5 or more coats required to reach the 10 mil thickness. I followed this procedure on Nevermind, a Sausalito Triton, in spring 2006 (strip, apply 3 coats 2000e followed by 1.5 coats Pettit Trinidad SR followed by launch).

This is all anecdotal, of course, but boats using this procedure don't seem to have gone through a blister epidemic. The diver who periodically scrubs Nevermind reports the bottom as excellent and the finest of all the boats he works on - and this a year after relaunch. If you've been on the hard a while drying out, even in the Georgia humidity, I'd still say it's about as good as it gets - for sure, a lot better than drying out for a couple of days like we do.

[Mark.Wilme]

That's so's he'll know when to reapply bottom paint. When he starts to see black bottom, he knows that it's getting thin! (Ablative paint types, of course!)

Nathan is correct, using a black base only besause that's what I have on my new boat.

Having spent time litterally chipping ablative paint off that was 1/8"+ thick in places I am anxious that the new paint is not just slapped on every year, but that I (we - not my boat anymore, except for the maintenance) can really tell how it does in fact ablate.

[Tim]

Note that blisters aren't necessarily going to crop up just from using a barrier coat. I have never said that, and I'd prefer that no one misunderstand, nor make that inference from any of the comments above.

The point is that the possibility does exist...and this has happened some cases where no previous problem existed. Therefore, this possible issue bears consideration when the only reason for using barrier coat is "it seems like a good idea". It's not, unless it is.

Blisters might appear suddenly if no barrier coat is applied too. But if blistering hasn't reared its ugly head in a 20+ year-old hull, it's pretty unlikely that an epidemic will suddenly show up. The industry would like everyone to believe that every boat is a time bomb just waiting to disintegrate beneath your feet thanks to hydraulic or osmotic blisters. Frankly, I think that in a boat that hasn't suffered from the sort of damaging blisters that everyone's worried about, it's more likely to cause water retention from barrier coating with good intentions than it is to not barrier coat and let things be.

I don't discount the tragic damage caused to a relatively small number of boats that suffer from truly significant chemically-induced blistering, but there's a huge difference between this issue and the type of sporadic water-filled "blisters" that occur randomly on many boats, usually simply because of a latent air pocket between the gelcoat/skin coat and the structural laminate beneath. This is a completely different animal, caused by completely different circumstances, and therefore requires a completely different outlook in terms of the problem's severity and resulting treatment.

Boats take months to totally dry. No boat dries completely in a few days, though the initially high levels of moisture found in typical laminates immediately after hauling decrease drastically after a relatively short time--days and even within hours. But it's true that a boat that's been on the hard, and with the bottom stripped and partially opened by previous repairs and grinding, for some time is likely to be about as dry as it will get without additional steps being taken.

3% to 5% relative moisture is very, very low. Getting to that point can take an extraordinarily long period and usually requires outside heat sources. It certainly requires that all exterior coatings be removed, including gelcoat that tends to withhold more moisture than plain laminate.

I think this level of dryness is nearly an impractical ideal for the typical boatowner looking to apply a barrier coat, and that the lack of proper dryness is actually to blame for the potential water retention that can create problems where none previously existed. For a boat undergoing major repair for blister removal, including peeling of skin coats, acheiving this level of dryness is absolutely critical before continuing the repair, and therefore typically requires heat, tenting, and other means to assist the process.

[bcooke]

You know, as often as this subject comes up, maybe someone (other than I) should gather up some good technical articles on the subject and then post them here.

I bet there is someone around here with access to this kind of stuff...


Black as an indicator coat. I knew there was a reason my first coat after stripping almost four years ago was black. I was exhibiting genius and I didn't even know it. Now that is TRUE genius :-)

-Britton