Sealing before skinning?

[jkidd6339]

I'm planing on skinning the trailer with aluminum and I have a question.
I start thinking about sealing with CPES walls, roof and floor. Then I started thinking about just using epoxy. Lately I have been thinking about just using 2 part epoxy paint. Which way would be the best aproach ? The walls roof and floor will be skined with aluminum.

[kennyrayandersen]

since you are skinning with aluminum, which will keep out the moisture, it seems like the wood treatment is backup in case there is a leak? In that case I'd go with the stuff that penetrates the most, which I think is the CPES, though I'll lay money out that some didn't use it at all when using the aluminum skins. The bottom gets the black goo... arg.

[madjack]

I've never used CPES so can't comment directly on it...I do seal all the wood under the AL...either with a heavy bodied urethane like a spar type or epoxy...the main thing is to get all the edges of the ply well sealed since that is where your danger point is...........
madjack

[planovet]

I used 2 coats of CPES on mine under the aluminum. But MJ is right, the edges are the most important place to seal.

[Arne]

sealing is always good... never know when a potentially expensive leak might occur... cheap insurance.

[kirkman]

Yep,seal!

[jkidd6339]

Thanks for the response. I was planing on using epoxy and fiberglass mat on all of the edges. Just not sure if I need to go to the expence of cpes or if epoxy paint would provide enough protection, seeing as it will never see the sun.

[LMarsh]

I'm glad this post was made because I have actually been thinking about this lately. I wasn't sure if sealing the wood under an aluminum skinned tear was necessary (although a good precaution). If all the joints are properly sealed shouldn't it be fine? What do plain old enclosed utility trailers do? They're all skinned in aluminum but I wouldn't think they would take the extra expenses/labor to protect the plywood.

Another thing that I was beginning to think about was how I keep reading about epoxy, and CPES, spar urethanes or others, and how they are good but not bulletproof. I also found this cool study:

http://www.mar-k.com/final_summary.html

So what I was coming to is all these sealants are transparent. If sealing under the aluminum couldn't you just use paint, like simple latex, and would it offer more protection? I feel like I'm beginning to get the impression transparent sealants aren't that great and an opaque sealant like a primer and paint might be better. You can paint a house or even T-111 and it can last a long, long time.

Lucas

[jkidd6339]

Lucas

That was kind of my idea behind the post. I have seen travel trailers that once the water gets behind the aluminum it messes things up bad. But because it's under the aluminum and out of the sun I wonder if paint would hold up just as well with less cost. Like I said in my previous post the plan is to seal all the corners with epoxy and glass mat. I'm just trying to decide what to seal all the flat surfaces with. Come on everyone we need your ideas. Tell me if I'm up in the night or what you did and why.

[ZendoDeb]

RE: the "tests" at the link you provide. It seems like these guys wanted to prove that paint is better.

No system that lets you see the grain of wood you are working with is going to stand up to UV for 3 years. (Not in the Florida sun anyway.)

Epoxy - properly protected from UV - will last longer than paint. By properly protected I mean completely covered with paint or interior.

BTW - Epoxy is water proof. Latex paint is not. So you may want to take that into account.

Epoxy left exposed to the sun will look like varnish for a little while, and then deteriorate.

Also the test in question used "Minwax Spar Urethane." in a couple of tests. I wouldn't use Minwax to varnish a dog house. It is cheap. (They sell it at Home Depot for a reason.) Urethane is NOT varnish. It was developed for roller rinks and basketball courts. It is (or can be) VERY sensitive to temperature extremes - it will turn milky white in extreme cold. I have no information on the UV inhibitors in minwax. (A true marine varnish or marine wood finish from Epiphanes or Petit costs 3 to 4 times what minwax costs. And even these will need a maintenance coat every 6 months. The cost difference is NOT just the snob factor - they work better. But they won't last 3 years.)

It isn't uncommon to put down 8 or 9 coats of varnish at the first application and 1 coat every 6 months after that. Again, depends on how much UV you get. Covers go a long way to improving that.

If you don't want to use varnish, use a 2 part linear polyurethane clear coat. Not all clear coats have extra UV protection. (metal doesn't require it like wood does.) Awlgrip does. Polyester polyurethanes are better than acrylic polyurethanes. (Awlgrip is better than Awlcraft... harder to work with.) 2-part systems are anywhere from $150 to $250 per gallon. And they are toxic if sprayed. A mask won't help. A respirator won't help, you need a full face mask with filtered air brought in from a distance, tyvex suit, etc.

Linseed oil "cured for 3 months?" Oiled wood in an exterior application needs to be oiled at least every 6 weeks - most people do it once a month. (It doesn't take very long.) It also isn't very popular anymore since it tends to attract dirt - seems to have a real hard time with diesel soot. Also straight linseed oil has no UV protection at all. Look for an external product like some of the exterior teak oils. (There are separate oils sold for interior teak. Less toxic, less UV protection.)

A product with NO UV inhibitors lets the wood below the finish deteriorate.

So yeah, if you want a surface that you don't have to touch for 3 years... paint is your friend. If you want to look at beautiful wood grain you are going to have to do some work. And you are going to have to do it on a regular basis. (If you are in the far north, that may be different.)

If you opt for paint, and you want a car-like mirror finish, you aren't going to get that with latex house paint.

[ZendoDeb]

CPES is good stuff, but it isn't the only penetrating epoxy. If was developed to be injected to sav plywood already in the beginning stages of delamination and wood with rot.

It is fairly expensive as epoxy goes. And some of what they do is not an issue for just sealing.

You can make a fairly good penetrating epoxy by thinning slow cure epoxy 10% to 65% by volume with Xylene. You will get a 80 hour pot life at 65%, but you will get maximum penetration. For about 1/2 the cost of CPES.

The more you thin epoxy the less it wants to cure hard. This may or may not be an issue, depending on what you are doing. But then CPES doesn't cure hard.
Check out this link

[bbarry]

This is timely...I will seal my skins today before applying aluminum later this week. I plan to epoxy (just regular 'ole RAKA) each of the edges and seams. I will then epoxy the faces of the sides and top as long as I have epoxy. When I run out, I plan on varnishing the rest, including back over the epoxied section. I don't see any reason why you couldn't do the same thing, but use a good quality paint.

It will all be covered in aluminum, trim and joints caulked, so there **shouldn't** be any leaks. But...it's an easy step at this point to give a little bit of insurance.

Good luck!

Brad

[Arne]

All the trailers that people are restoring were built not to leak. Most have water damage problems because of joint or window leaks.

I would use whatever works best in an enclosed environment, where water seeps in between the inner wood and the outer skin. I doubt that is latex paint.

I used cpes on everything (2 coats). It soaks in and does not just lay on the surface of the wood.

I would use it again, or the alternative of thinned out epoxy.. I would not use varnish or any similar product as I believe heat will eventually degrade it at a faster rate than soaked in epoxy, even if it is not in direct sun light.

[LMarsh]

OK so latex isn't the best thing out there, I know, but most of what people are still talking about is off the topic. If you're skinning your tear in aluminum then wood grain, color, UV resistance, and appearance is irrelevant because it will be covered up. I mean obviously no one intends to have leaks and you want some protection under the aluminum too, but I think the functions the common teardrop builder who wants to protect the wood under the aluminum is only looking for one of two things. 1) Affordable and will offer appropriate protection or 2) Will want the best protection possible but not care whatsoever about the looks since again it will be covered in aluminum.

It is nice to buy the best quality products available but it is not always possible for those on a budget. I don't have a ton of experience with these kinds of products but I don't feel like the actual question being asked has been answered. That is, regardless of looks and UV protection what is the best and/or affordable way to seal the plywood under an aluminum skin?

Maybe we should tar the whole thing!

[48Rob]

Maybe we should tar the whole thing!

_________________

Nah, tar would drip and be very smelly

The correct answer has already been given, that is; seal the wood, especially the edges and end grain.

I use inexpensive oil based paint, thinned for the first couple of coats for penetration.
I've also used varnish.
Though I'm not a big fan, latex paint will work too.
Expensive, or inexpensive, in this case, does not determine the quality.
A $5.00 can of mistint paint will seal as well as a high dollar product.

The biggest reason for failure of the "waterproofing" is that "most" people waterproof the parts they can see/are easy to get to.
If you attach two pieces together, then seal/paint, it is not "all" sealed.

Others get all of it, but don't apply enough coats.
One or two probably isn't enough.
4-6 probably is.

When someone thinks of protecting the wood under/behind an aluminum sheet, they generally think, anything is better than nothing...
And it is, but plugging three holes in your boat won't keep it from sinking if there are 50 holes...

If a person chooses to "seal" wood, then it must be 100% sealed, as in encapsulated.
A piece of wood properly sealed can be put underwater, and not absorb 1 drop of water.

When we think about "water getting behind the aluminum, we think of a few drops running down the side, but in reality, it is many, many drops that do not run, but search for any opening to soak in, and continue to soak in.
If you "see" damage, much more damage than you can see has occurred.

There is one other very important step to take in sealing and waterproofing, and that is sealing penetrations.

Lets say you've sealed the sides and roof perfectly, achieving complete encapsulation.
What is the next thing you're going to do?

You're going to install the aluminum roof and siding, then put a whole lot of holes through the carefully installed seal on the wood when you install the trim, doors, windows, roof vent, etc.

It can't be helped, you have to make holes.
It is easily corrected though, by installing all your screws, then removing them a few at a time, injecting sealer into the holes, and reinstalling the screws.

Sealing a trailer so it won't leak takes a little longer than just throwing one together and hoping, but the effort will keep you smiling year after leak free year.

Rob