How many coats of CPES?

[tscarbroughdc]

I have done TWO coats of CPES on the Luan front and top exteriors.

And I've done ONE coat on the 3/4" marine grade plywood exterior.

1. Is that enough CPES?
2. How will I know it's coated well enough?
3. When is it ready to paint?
4. Can I take it out and try it out WITHOUT paint on it and just the CPES?

Please try to answer each number question for me. I get so much good info from this board! Thank y'all!

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[aggie79]

1. On my teardrop floor, I applied 3 coats of CPES. On the third coat I noticed the epoxy "building up" and filling in the grain/pores of the plywood. If you have enough CPES I would apply 3 coats.
2. You should notice the CPES not being absorbed - sitting more on the surface - and the grain being filled.
3. Don't paint before all of the solvents "gas off". If you can smell any solvents it is too early. Also, I don't know if it is from the solvents or the epoxy diluted in the solvents but there is an oily finish that stays on top for a week or so. I waited until most of that dissipated before I did anything. You may want to try to remove it using acetone on a rag. Before you paint I would very lightly sand the surface to give the paint some "tooth" to bond to the CPES coated plywood.
4. It's okay to take it out - I let my teardrop "bake" in the sun, but you wouldn't want to camp in it until the solvents dissipated.

[S. Heisley]

What Aggie79 (Tom) said, except I didn't "bake" mine. Get the ends and cuts of the plywood well covered with the stuff.
If you have enough on, it will start to build and you'll see a shine.
Save some to use for screw holes, etc. Mix small amounts in a washed and dried margarine tub.
With the margarine tub lid tightly on and the weather cool, it will keep for a couple days or sometimes up to a week in the winter.
Use a cotton swab to get a coat on in small holes and crevices.

Best Wishes!

[tscarbroughdc]

Thanks. These two posts helped a lot!

[tscarbroughdc]

Am I supposed to sand between applying coats of epoxy?

Do I just sand lightly to rough the surface? Or sand heavily? I'm assuming lightly but is it even necessary?

Thanks

[aggie79]

I did not sand between coats of CPES but I applied the additional coats while the epoxy in the CPES had not fully set/cured.

For true epoxy, applying the additional coats this way allows the subsequent coats to have a chemical bond and not a physical bond. You also don't have to worry about the amine blush - the waxy, oily film that happens as (most) epoxy cures - preventing the layers from bonding. If amine blush has occurred you have to remove the blush by washing it off and then sand the epoxy to give the subsequent coat a mechanical grip. A light sanding is fine. You are just trying to slightly roughen the surface and not remove any epoxy buildup.

CPES is epoxy with a lot of solvents that thin the epoxy and allow it to penetrate. I don't know if CPES has amine blush or not. I would call the manufacturer - try googling "Rot Doctor" - and tell them your circumstances and see what they say. My guess is that they will say that the solvents in CPES will cut through any amine blush.

[S. Heisley]

I did mine about the same as Tom did. I sanded before applying the marine epoxy and polyurethane, though; but, the CPES had been on for a while by then.

Yes, you have to wait a while before applying anything other that CPES but I don't remember how long. Please check with the Rot Doctor. They have a website and you can probably find out there, at their "Ask the Rot Doc" site.

[Kody]

I am using a polyester resin to fill and seal the grain and ends of the wood. I am using this as it's so much cheaper than epoxy. I can't remember the specific name of the resin but its similar to the usual resin used for laying up glass for boats. Has anyone used this stuff before? The glass on the roof will be laid down with this same resin and it will all be painted. The resin is not UV proof hence the need to paint it with a high quality paint.

Kody

[S. Heisley]

I am using a polyester resin to fill and seal the grain and ends of the wood. ... The resin is not UV proof hence the need to paint it with a high quality paint.
Kody

That's true of many epoxies, too, including CPES. They have to be protected from UV rays with another product.

[Larry C]

I am using a polyester resin to fill and seal the grain and ends of the wood. I am using this as it's so much cheaper than epoxy. I can't remember the specific name of the resin but its similar to the usual resin used for laying up glass for boats. Has anyone used this stuff before? The glass on the roof will be laid down with this same resin and it will all be painted. The resin is not UV proof hence the need to paint it with a high quality paint.

Kody

Polyester resin on wood is no where near as good as epoxy. It doesn't bite into the wood as well as epoxy, and is not as water proof. If I was going to all the effort to glass a tear, epoxy would be my first choice. I helped a friend remove fiberglass from a wood strip canoe that was glassed with Polyester resin. We removed the glass in less than a half hour by just pulling on a lifted corner. It came off easily without pulling any wood with it!! If epoxy was used that would not have been so easy.
We sanded it and re-glassed using epoxy. Go ahead and use it... It's just not the same as epoxy.

[doug hodder]

The thing with CPES is that it doesn't build. Put it on, it seals, once it's cured, that's it! It's designed for porous materials, like more porous than just new plywood. Why do you think it's manufactured by a company called Rot Doctor? It's designed for weathered material (read dry rotted). Yes, I know...they will tell you it works great on new ply, but then they are selling the product, however, I've got no dog in the fight. Do what you want. I don't think you'll find a new mainstream wooden boat manufacturer that is using CPES as opposed to a regular epoxy, probably for a good reason.

Wanna build up some thickness to smooth out, it won't do it without a ton of coats. It's not as viscous as a regular epoxy. Epoxy will build much faster for a smooth coat if that's what your goal is. I'm always surprised at people that think they can just mop on more coats of something thin, then have questions why their paint doesn't lay down really smooth when it is all said and done.

There is no quick trip to making a great looking paint job and a well sealed durable tear. It takes time to level it all out and get rid of the grain and dimples in the ply. When someone asks, "Is 3 coats enough?"...well, you are the person there doing it...so how does it look? If it's going to be a painted tear, spray some primer on with a rattle can and look at the finish. Is it what you want, are you happy with it? If not, put on some more and sand and flatten it out. The quality of your paint job is only as good as the time and effort you put into the base coats. Paint won't hide poor prep work. Just spend the time and do it correctly, it's worth it in the end. All epoxies/ or polyesters need to be top coated and don't put them over an oil based stain. If you drag it around before you shoot paint on it, you run the chance that the surface can be contaminated and will not accept paint well. It will need to be cleaned with a solvent and scuffed, and more than likely, another coat prior to painting. I'm sure others may disagree with me on this. To each their own. Doug

[Weirdnerd]

I have worked on composite aircraft, the parts out of the mold are not glossy, they require prep to finish, usually is done with bondo, sounds silly, a several million dollar plane with bondo?, yes sir...bondo, they sand it to contour, and then use PPG paint, epoxy, it looks like a million dollar, and the price to paint a plane is not cheap. epoxy paint lasts decades exposed to any kind of weather. It would last longer than the camper.

What I mean is that you can cover your camper with fiberglass cloth and your resin of choice, sand excess, and use bondo to make it flush, does not have to be thick, just a thin coat to cover irregularities and then finish with paint, prep work will show on the final coat, take your time.

[nhstt]

The thing with CPES is that it doesn't build. Put it on, it seals, once it's cured, that's it! It's designed for porous materials, like more porous than just new plywood. Why do you think it's manufactured by a company called Rot Doctor? It's designed for weathered material (read dry rotted). Yes, I know...they will tell you it works great on new ply, but then they are selling the product, however, I've got no dog in the fight. Do what you want. I don't think you'll find a new mainstream wooden boat manufacturer that is using CPES as opposed to a regular epoxy, probably for a good reason.

Wanna build up some thickness to smooth out, it won't do it without a ton of coats. It's not as viscous as a regular epoxy. Epoxy will build much faster for a smooth coat if that's what your goal is. I'm always surprised at people that think they can just mop on more coats of something thin, then have questions why their paint doesn't lay down really smooth when it is all said and done.

There is no quick trip to making a great looking paint job and a well sealed durable tear. It takes time to level it all out and get rid of the grain and dimples in the ply. When someone asks, "Is 3 coats enough?"...well, you are the person there doing it...so how does it look? If it's going to be a painted tear, spray some primer on with a rattle can and look at the finish. Is it what you want, are you happy with it? If not, put on some more and sand and flatten it out. The quality of your paint job is only as good as the time and effort you put into the base coats. Paint won't hide poor prep work. Just spend the time and do it correctly, it's worth it in the end. All epoxies/ or polyesters need to be top coated and don't put them over an oil based stain. If you drag it around before you shoot paint on it, you run the chance that the surface can be contaminated and will not accept paint well. It will need to be cleaned with a solvent and scuffed, and more than likely, another coat prior to painting. I'm sure others may disagree with me on this. To each their own. Doug

Doug,
What brand do you recommend. I'll be painting with an exterior latex from Lowe's. the edges of the ply are all sealed with titebondIII, and I want to seal everything then, fill and sand then sand and paint
Advice please
Karen at the Ladybug-out build journal viewtopic.php?f=50&t=55602