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Old 22-06-2013, 19:51   #1
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Are barrier coatings bogus?

Most folks say that barrier coatings are required to keep a fiberglass hull from absorbing water and potentially becoming water-logged and blister laden. There are some knowledgeable folks that say that no barrier coating is needed and that they don't make a difference.

My boat currently has a clean, dry bottom that has been sitting, gelcoat only for a few years. Most of the gelcoat will be removed, due to gelcoat blisters, before I paint the bottom and I've been planning to fair and then apply barrier coatings before bottom paint to best ensure that the bottom job is done correctly. If I can skip the barrier coatings though it will simplify and expedite the bottom prep process so I'm wondering if those that say barrier coats are a waste are actually right or if I should stick with the plan to apply barrier coatings. If it's relevant my boat doesn't have any blisters of note in the hull beyond the gelcoat layer.

It's not that big of a difference either way since my boat isn't that large but I am interested in any real-world experience with barrier coatings and if they are needed or if they just make boat owners feel better and the vendors a bit of extra money.

Are any of you running bottom paint directly on a patchwork of gelcoat and the chop/outer layup? If so, how has that worked out long-term?

Have any of you gone without a barrier coat and then learned that your boat was water logged with extra weight or having other problems as a result?

Thanks,

Jonathan
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Old 23-06-2013, 07:28   #2
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Re: Are barrier coatings bogus?

Definitely barrier coat. It's very easy to do yourself.
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Old 23-06-2013, 07:47   #3
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Re: Are barrier coatings bogus?

I would be pretty worried to have chopper gun lay up without a barrier coat due to chop being highly porous. At the very least I would suggest sealing/coating the chop.
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Old 23-06-2013, 07:48   #4
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Re: Are barrier coatings bogus?

6 years agoo we make a preventive barrier coat bottom job in our boat, no osmossis and no blisters , but we do it anyway, not a funy job but the result is a peace of mind , we use Interprotect 2000E as a final epoxy primer before antifouling and we put 7 coats of this stuff, this days my bottom show 0 blisters after 7 years , yes barrier coat stuff work, antifouling paints are porous and water found their way to gelcoat, and we know that Gelcoat is not kinda waterproof right? INTERPROTECT mate...
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Old 23-06-2013, 07:56   #5
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Re: Are barrier coatings bogus?

I have seen gelcoat bottoms with blisters and epoxied bottoms without blisters. I would use epoxy.

I might be wrong, but it might be possible (?) to apply epoxy coatings over the gelcoat(?). This could be a fine solution in casee of any new boat.

b.
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Old 23-06-2013, 07:57   #6
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Re: Are barrier coatings bogus?

Dried, cleaned, and applied barrier coat on a blistered 35 year old hull three years ago; no further blistering.

Barrier coat, yes.
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Old 23-06-2013, 08:10   #7
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Re: Are barrier coatings bogus?

Quote:
Originally Posted by JonathanSail View Post
Most folks say that barrier coatings are required to keep a fiberglass hull from absorbing water and potentially becoming water-logged and blister laden.
First you say this which implies you have a good understanding of a primary reason for a barrier coat, the other being ablative.

Quote:
Most of the gelcoat will be removed, due to gelcoat blisters....
Then you say this.

Quote:
before I paint the bottom and I've been planning to fair and then apply barrier coatings before bottom paint to best ensure that the bottom job is done correctly.
Please explain what you mean by saying "correctly". Oh, my reading comprehension is fine, I see what you said but it appears contradictory to your previous comments.
Quote:
If I can skip the barrier coatings though it will simplify and expedite the bottom prep process so I'm wondering....
This again contradicts your previous comments. You really don't know which is "correct" and which is not. That's okay, no one is an expert on all things.
Quote:
If it's relevant my boat doesn't have any blisters of note in the hull beyond the gelcoat layer.
It is relevant however how certain are you that blisters won't appear in a short time or even if they have already (but you have failed to notice)?

Quote:
It's not that big of a difference either way since my boat isn't that large....
The size of your pea pod is not relevant. It's the environment in which it sits and how you address that which is important. If you mean monetary cost I guess you have a vaild point but even then with a smaller vessel you are still throwing money away.
Quote:
I am interested in any real-world experience with barrier coatings....
Would that include chemists involved in polymers? I hesitate to mention because I have been out of it for a while but at one time I was a QA/QC chemist involved with polymer resins. Given the harsh environment of UV and salt water, you are at greater risk without the barrier coat in the conditions which you describe. As a former building contractor I am familiar that people love to spend money in exchange for bragging rights. But that should not color the picture of how to protect your boat. Barrier coats are very necessary and not only for ablative purposes.

Quote:
Are any of you running bottom paint directly on a patchwork....
Patchwork? Are you describing the condition of your hull or other?
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Old 23-06-2013, 09:30   #8
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Re: Are barrier coatings bogus?

Thanks for the thorough response Richard5

There are some contradictions in my post, included to illustrate the contradictions that I have encountered on the topic, even though I'm sure that I could have written my questions more clearly or accurately.

When I said "correctly" I meant it both as the correct way to prep a boat bottom per most opinions and also my own. That is, in summary, to apply barrier coatings and then bottom paint to a clean, dry hull which is smooth and solid. For me this will include removing loose gelcoat, filling and fairing with thickened epoxy, surface prepping and then hot/warm-coating barrier and bottom paint layers.

I don't mind doing all of that in terms of time or costs but when a few guys that I really respect, with life-times of experience as professionals in the boat service industry, state that bottom coatings are a waste I can't help but wonder if I could skip a lot of work. The time is the biggest factor as I'd rather have a few extra days, always. Per these outlying opinions I can just bottom paint and go, then sand/paint/repair whenever i haul again as needed. I won't be doing all of this for another month or two so I figured I'd put it out here for discussion on the forums to see if I learn any more on the subject.

By patchwork I was describing the state of my boat's bottom which will result after I remove a lot of the gelcoat. Currently the bottom is coated in gelcoat but there are numerous gelcoat blisters so I will sand all down until those and the loose gelcoat is gone and only a solid base remains. This will result in a patchwork of chop/mat/resin and gelcoat.

Thanks again,

Jonathan
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Old 23-06-2013, 10:26   #9
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Re: Are barrier coatings bogus?

Ask these guys who are supposed experts how it is that water no longer penetrates gelcoat or polyester resin. If they say water never does penetrate gelcoat or resin then ask them to explain how blisters occur. If they don't believe that blisters occur then break out the pictures.
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Old 23-06-2013, 10:35   #10
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Re: Are barrier coatings bogus?

you've gone that far, this is the opportune time to barrier coat it with Epoxy resin. Use only real Epoxy resin (JMHO) Any boat that has proven to absorb water will likely continue otherwise.... dried out or not. Some boats never have a blister, some boats are loaded, many boats are in between.
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Old 23-06-2013, 10:39   #11
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Re: Are barrier coatings bogus?

It's hard to speak for others, but some of their thoughts on water penetration seem to be that it depends on the quality of the layup and that blistering is caused or results from construction issues, not water ingress. For instance, if a hull is constructed with the wrong timing so that solvents/etc. in early layers are contained vs. being able to gas-off or move to the surface then those will form pockets and/or lead to, or find their way to, voids and cause blisters. Overly dry laminates or laminates with voids in the layup probably make water ingress and blisters more likely as well.

Of course, they may say otherwise and I may misrepresent a few points. They also say that many boats don't have barrier coats, and that they don't/aren't going to sink, even after years of being in salt water. Looking around marinas, and the yard it's hard to imagine that not to be the case for many older boats.

I should probably restate that I'm more in the barrier coating camp, but with a bit of time before I do this work I thought it would be interesting to find out if there are more folks with experience that agree with the "no barrier coatings are needed" school of thought, and why. For that reason it's easier for me to argue for, not against, barrier coatings.

At the same time though I don't know the chemistry involved and assume that a chunk of quality polyester/glass laminate, if put in salt water would not become water-logged, spongy, weak or dissolve. If that is true, then perhaps just a few layers of bottom paint really are sufficient?

Jonathan
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Old 23-06-2013, 10:45   #12
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Re: Are barrier coatings bogus?

It seems no one knows the chemistry involved... oh they will give you long paragraphs of theory..... But no one seems to know why some 40 year old non barrier coated boats dont have any blisters, and others 10 years old have them. If your boat has blister history... take the safe route.
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Old 23-06-2013, 11:39   #13
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Re: Are barrier coatings bogus?

I don't see any downside to adding epoxy coating, other than the cost, which doesn't seem too much compared to what might happen without it.

Having been thinking of how to build a big cat, I'm thinking this is the best way to go.
Build the boat with less expensive polyester resin, but coat the outside hull with a layer of epoxy.
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Old 23-06-2013, 11:45   #14
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Re: Are barrier coatings bogus?

I cant believe the so called experts say that, without a good layer of epoxy primer your gelcoat is exposed to sea water , and sooner or later you got blisters ,gelcoat is not 100% waterproof, putting solid epoxy coating over a wet hull covered with the original gelcoat is bad to, you just trap all the moisture in the laminate , the best way to get a dry hull and later a solid barrier system is peeling all the gelcoat and dry the hull as much as posible , cost and time is huge , if your hull is dry , moisture meter, window test etc... i sugest you to use a good epoxy primer as a barrier coat and keep that gelcoat and hull healty for more years , almost all the profesionals use a brand or other to barrier coat a epoxy bottom job , Interlux, etc... is up to you ,, later when you need to get rid off all that old antifouling you risk to damage the gelcoat, best way to keep a healty gelcoat in good condition is barrier coat....
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Old 23-06-2013, 11:50   #15
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Re: Are barrier coatings bogus?

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Originally Posted by Cheechako View Post
It seems no one knows the chemistry involved... oh they will give you long paragraphs of theory..... But no one seems to know why some 40 year old non barrier coated boats dont have any blisters, and others 10 years old have them. If your boat has blister history... take the safe route.

Some old 40 years boats dont have any blister at all, but full of deep hydrolysis,, others not, it depend of the quality of construction and the care take it in the hull lay up, without removing antifouling and see whats going inside, hard to tell.
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