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epoxy barrier coat sun exposure how long is too long?

4K views 18 replies 11 participants last post by  lancelot9898 
#1 ·
Hello all

My boat has an epoxy barrier coat that was applied 10-12 years ago. The boat is out of the water for the summer and I want to tackle several projects including sanding off the anti-fouling paint. I also have a minor blister problem that needs to be addressed as well as several thru hull's that have been removed and need to be glassed over. I would like to remove the anti-fouling paint this summer and not apply the new paint until several days before drop in next spring. My concern is that if I remove the anti-fouling paint now the epoxy barrier coat will be exposed to the sun and yellow over the summer. Is this a concern?

Most of my blisters are between the epoxy barrier coat and the hull, so by removing the anti-fouling paint now I hope to find other potential problems and fix them. Area's where the epoxy is not adhering to the hull.

Good, bad or other wise I thought I might sand off the anti-fouling paint now and fix the problem areas. To "protect" the epoxy barrier coat I would paint latex house paint over the hull after all repairs are done. The logic being that it would prevent the epoxy from yellowing and would be much easier to sand off in the spring. A good idea or not so much?

My problem is that I live in Canada and to wait until spring to remove the anti-fouling paint can be an issue. Doing this before April is not a possibility and April can be a tough month to get work done. Again the thought being that removing a single coat of latex paint in April will be much easier that removing 10 years worth of anti-fouling paint.

Thanks,
John
 
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#4 ·
Johnny,

If you have more than just a few hull blisters (behind the barrier coat) you may have a damp hull. If this is the case you really need to strip the barrier coat now as well so the hull can breath for a year and dry out. If it is just a few isolated spots then that isn't necessary.

If it is just a couple, I would tarp the hull once the paint is gone. Putting latex paint over epoxy may be fine, I have never done it, but a $5 blue tarp from Wal Mart will do just as good a job at keeping the epoxy in good shape, and be a whole lot easier to remove.
 
#5 ·
DO NOT paint that nice epoxy coating with latex house paint. Do like Stumble say's and buy a tarp. In 1993 I coated my hull with 5 coats of WEST SYSTEM and the alluminum additive and it's still rock solid. We don't yet know the life span of modern epoxy's because they are still holding strong. You'll greatly compromise the integrity of your epoxy coating in the process of removing the latex. Hell, buy the 40 dollar tarp from Home Dope and cover the whole boat.
 
#6 ·
Hello all, thanks for the replies.

I am of two minds right now.
1) Sand down just the blisters and remove the anti-fouling paint.
If I do this I don't want to tarp off the hull as I want the sanded blisters to be exposed to the sun and wind to help the drying process.
So perhaps I sand down the blisters, let them dry for the summer and remove the anti-fouling paint late into the fall. Then tarp the hull.

2) Remove all of the existing barrier coat and start from scratch.
I am leaning in this direction. My only concern is that it is going to be a mother of a job containing the dust I mean. I have been doing some sanding over the last several nights, both with a palm sander and a grinder with a flap disk. The palm sander isn't up to the job(full barrier coat removal) where as the grinder is. My concern with the grinder is dust collection. So I guess I tarp off the full boat and spend a few days grinding.

Any thoughts on a power tool up to a full hull sanding that also has a reasonable amount of dust collection? Regardless of the hp I don't see a orbital sander up to the task. But I am open to being corrected on this.

John
 
#8 ·
Hello all, thanks for the replies.
2) Remove all of the existing barrier coat and start from scratch.
I am leaning in this direction. My only concern is that it is going to be a mother of a job containing the dust I mean. I have been doing some sanding over the last several nights, both with a palm sander and a grinder with a flap disk. The palm sander isn't up to the job(full barrier coat removal) where as the grinder is. My concern with the grinder is dust collection. So I guess I tarp off the full boat and spend a few days grinding.

Any thoughts on a power tool up to a full hull sanding that also has a reasonable amount of dust collection? Regardless of the hp I don't see a orbital sander up to the task. But I am open to being corrected on this.

John
John,
I am doing my bottom right now. Previous owner applied barrier paint over gelcoat cracks and blisters. My boat has be covered on land for 3 years now. Kind of stupid to put it back in the water without fixing the problem. You are right about the orbital and flap disk sanders not being up to the task. I have been using a Ridgid 3" x 18" belt sander with 36 grit. I have it attached to a Ridgid 4 gallon shop vac with a paper filter bag. I also have the heavy duty hose accessory which is far better than the standard hose that comes with the vac. It fits loosely on the sander dust port. When it starts falling off the bag is filled. So far I have filled 5 bags! There is some dust, wear a respirator and googles. However it is far far less than without the vac.

This is brutally hard work. I can only do it for about 6 hours. So far I have about 5 days in it, and should finish my 26 ft boat in about 2 more 6 hour days. Buy lots of belts, I've gone through about 12 already and will use at least 8 more. Knowing what I know now, I'd have gladly paid $1000 to get it sand blasted, and in the water!

Gary H. Lucas
 
#7 ·
Take it down to the gel coat, do the glass repairs. fair it all out, and wait till you drop her in the drink. Two weeks before launch start the epoxy show.While your last coat of epoxy barrier coat is still tacky, apply the first coat of anti fouling, let harden and re apply ..l.Food for thought
 
#10 ·
The one job I refused to do when I worked in a boat yard was stripping bottoms. Couldn't pay me enough to make it worth the pain of holding a sander up above my head all day.

There are a few, very few highly skilled guys that can strip a boat with a hand planer. Unless you have a few bottoms to ruin while learning how don't try it, but it is the best way to strip a boat.


These days though I doubt there is a yard anywhere that is using sandpaper to remove the bulk of old bottom paint. It is massively labor intensive, an environmental nightmare, and well known to cause health problems to anyone who breathes in the dust (remember bottom paint was designed to kill living things). At least around here most yards wont even allow you to sand your own bottom, let alone do it themselves.

If you have to strip the boat yourself chemical strippers are the way to go. They are much easier to clean up since the residue can be scraped into a bucket, and take a fraction of the work. Soda blasting is easier, and cleaner, but the machines are rarely rented.

Figure about $40/foot for chemical or soda blasting. For sanding, well again I wouldn't consider it so I have no idea. But it should be pretty cheap since all you are buying is sand paper.

If you happen
 
#11 ·
A tarp skirt around the bottom of a boat can be a problem for an extended period. You should not attach them to the stands and, depending on whether you can stake them in the ground, they may not withstand a good storm.

I would not worry about a blister drying out properly if left exposed for a year.

My plan A would be to grind whatever you need to fix and have her soda blasted next year. They will tent her in to do that job and can probably do so earlier than you could stand getting under there for a couple of weeks. They only need a couple of days.

If this is all you have to do, I would actually sail her this season and do this all next year, including professional stripping.
 
#12 ·
Hello All

An update

I have started to sand into the hull, using a small belt sander. The ridgid mentioned in this thread. So far so good, it is small enough that I have enough control to not make a mess of things and it's dust collection is working well. At this point it is more exploratory work than a full hull strip. None of the areas are blisters, just areas that look like the epoxy has been compromised. For the most part things look dry but I am finding some pitting into the hull;



Can anyone tell me is this the result of a flawed layup at build time or a result of osmosis/hydrolysis?

After sanding I flush with water, let dry then wipe with acetone, a day later the pits are dry.

John
 
#13 ·
Without seeing it they could be anything from a bad fairing job, to slight water intrusion points, old repairs poorly done, ect...

The really question is if they are wet after cleanup then you may have some moisture in the hull. Since you are planning to keep the boat out of the water for a while anyway I wouldn't worry about it. In the spring come back and fair the hull with thickened epoxy, then reapply a barrier coat, then bottom paint and off you go.
 
#14 ·
I'm pretty sure those are just air bubbles left when the glass mat was laid up against the gelcoat. It is nearly impossible to get all the air out during layup. Note that non-woven glass mat is ussually the first layer against the gel coat so that the woven cloth pattern doesn't print through the gelcoat. When moisture gets into the glass mat it follows the glass fibers and the fiber changes color in a very obvious way.

Gary H. Lucas
 
#15 ·
Interesting about your barrier coat. When my boat was new I had the yard put a coal tar epoxy barrier coat on the hull prior to launch. That was 25 years ago with the boat spending almost it's entire life in the water with a haul out every several years for new bottom paint. I wish I could tell you that I have no blisters, but that is not true. Now I find out that the barrier coat is good for only about 10 years so my question is why apply it in the first place if it needs to be removed in 10 years. (I don't think you would just apply another barrier coat over the old coat.) Seems like removing a barrier coat would be harder than removing just the gel, but I expect to find out soon. Trying to get a good price on a peel and then letting it dry our for a year. Good Luck
 
#17 ·
"14 layers of epoxy barrier coat?" Sounds like either BS (of the let me impress you variety) or someone needs to do a little more research. The companies that make barrier coats spend a fair amount of time testing their products and they probably have a pretty good idea of how many coats are necessary. I've never seen 14 coats recommended by anybody.
 
#18 ·
Most manufacturers recommendations require a certain thickness regardless of the umber of coats. Interlux recommends 10mills, though how you get it is up to you. But it shouldn't take anywhere near 14 coats to get there, 4-5 is pretty typical.

I guess if you were doing an ultra high level racing boat, and applied very, very thin sprayed on coats it might take that many... But I have never heard of anyone doing that.
 
#19 ·
I also have never heard of so many coats needing to be applied. When the boat was previously done there was just one coat applied via sprayer. Not sure of the thickness. Still think it's interesting that only a 10 year life is projected for that original coal tar epoxy barrier coat. Maybe more thickness was needed. As I get into doing this project more will be learned.
 
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