Teardrops n Tiny Travel Trailers

After using West Systems epoxy for a while to encapsulate plywood kayaks and trailer boxes, I decided to give Smith Company’s CPES / MultiWoodPrime a try. Overall I was very happy with CPES.

Here are a few observations:

The watery nature of CPES made it easier to apply than normal epoxy.

Even though the Cold Weather formula has less solvent odor than the Warm Weather formula, it still has notably more solvent odor than West Systems epoxy. In the winter I’d have no problem using West System in a closed up garage / shop, with an organic vapor mask. I will only apply CPES outdoors, also with an organic vapor mask and let it cure for 8-10 hours before bring it inside.

On Radiata Pine and Okoume plywood it only took two coats to completely seal it. On a test piece, three coats completely filled the grain, two coats 95% filled the grain. If I wanted lots of depth to a finish, I would start with two coats of CPES to seal the wood, then switch to normal epoxy to build thickness.

Different woods have different absorption rates. The Radiata Pine sucked up three times as much as Okoume did. A 24 sq ft area of Radiata Pine took 18 oz on the first coat and 6 oz on the second coat. A 49 sq ft area of Okoume took 20 oz on the first coat and 6 oz on the second coat

For others that have used CPES:

Were your experiences similar?

Have anyone used a water-based top coat over it? How has it performed?

Here is an “Explorer Box” freshly CPES’ed, sanded out and waiting to be top coated.

Scott

Good data on the CPES, I've always been a West epoxy guy, but often have need for a good waterproofer. Those absorption/usage rates with different wood was pretty interesting. I once used ROT Doctor on a rotten boat keel timber, I started out using a big syringe but ended up drilling holes for a funnel it was sucking up so much product. It turned into one big piece of plastic..... sort of

I have a question about the West System epoxy. With regular epoxy glue, working on RC airplanes, we thin the glue with alcohol, and paint it on the wood as a sealer just like the CPES, and it works great. One coat and the wood is sealed against the fuel and oil in the fuel.

Would West System epoxy work the same way if you thinned it with alcohol, or another thinner? The reason I ask is West System is cheaper and more readily available.

Fixing rot with it, I'd be worried you'd spring a leak that you don't see and it just keeps pour in

A while back I called the West Systems tech line about thinning. They don't recommend it. If you could come up with the right blend it does look cheaper to mix your penetrating epoxy.

Ok, do we have any chemists out there? Whats a good blend? I'll test it out.

Not really a chemist. I changed my major after the first year. But I work with epoxies now and don't know of any approved thinner for epoxies. I guess you have to buy a different thickness. Any type of solvent will pretty much ruin your epoxy as the epoxy is not suspended in a solution. If you are looking for penetration then you need to vacuum bag the area.

SteveH wrote:Would West System epoxy work the same way if you thinned it with alcohol, or another thinner? The reason I ask is West System is cheaper and more readily available.

Steve, This is what West says:

Thinning Epoxy

There are epoxy-based products specifically designed to penetrate and reinforce rotted wood. These products, basically an epoxy thinned with solvents, do a good job of penetrating wood. But the solvents compromise the strength and moisture barrier properties of the epoxy. WEST SYSTEM epoxy can be thinned with solvents for greater penetration, but not without the same compromises in strength and moisture resistance. Acetone, toluene or MEK have been used to thin WEST SYSTEM epoxy and duplicate these penetrating epoxies with about the same effectiveness. If you chose to thin the epoxy, keep in mind that the strength and moisture protection of the epoxy are lost in proportion to the amount of solvent added.

There is a better solution to get good penetration without losing strength or moisture resistance. We recommend moderate heating of the repair area and the epoxy with a heat gun or heat lamp. The epoxy will have a lower viscosity and penetrate more deeply when it is warmed and contacts the warmed wood cavities and pores. Although the working life of the epoxy will be considerable shortened, slower hardeners (206, 207, 209) will have a longer working life and should penetrate more than 205 Hardener before they begin to gel. When the epoxy cures it will retain all of its strength and effectiveness as a moisture barrier, which we feel more than offsets any advantages gained by adding solvents to the epoxy.

Thanks Rocky.

Well I figured it had to be a little more difficult than, a little of this and a splash of that or Smith Co wouldn't have the market cornered on this stuff for the last 20-30 years.

Here is the list of hazardous compounds from the CPES MSDS:
Aromatic Hydrocarbon
Xylene (Xylol)
Toluene (Toluol)
Isopropyl Alcohol (2-Propanol)
2-Butanone
4-Methyl 2-Pentanone
2-Heptanone
4-Methyl 2-hexanone
2-Pentanone
Dipropylene Glycol Monomethylether
Diisobutyl Ketone
Ethyl Acetate
Isobutyl Acetate
Ethyl 3-Ethoxy Propionate
Propylene Glycol Mono- methylether Acetate
Hexyl Acetate
Isobutyl Isobutyrate
Diacetone Alcohol
Cyclohexanone

Scott,

Did they leave anything out? That's some nasty stuff !

I've thinned West with acetone to waterproof and seal delaminated plywood boat decks. It will stop further rot and delamination, does nothing for adding strength and was a poor substitute for replacing the wood. I've had 50/50 epoxy/acetone travel as much as 18 inches inside plywood injecting it with a syringe. It's kinda fun to play with.

Yes that is quite a list

On various boat forums I've seen thinning epoxy with both acetone and alcohol mentioned. My worry with thinning West is reducing it's water resistance. Next time I have some leftover epoxy I'll play with thinning a bit.
SteveH, What type of alcohol did you use?
Steve_Cox, What type of acetone did you use?

I did think of another different between West and CPES. With West you need to let it fully cure before top coating. With CPES you top coat with many finish types before it's cured so you get burn-in / chemical bond. So with CPES the finishing process goes quicker and you get better finish adhesion.

SteveH, What type of alcohol did you use?

Schaney,

It was just rubbing alcohol from the grocery store, but keep in mind, I was thinning regular 2 part, 30 minute, epoxy glue. The manufacturer of the glue also does not recommend it, but lots of modelers have been doing it for years. It just takes lots longer to harden, like about a day, and that's a good thing when you are trying to get a wood seal and lots of penetration. We don't do it to keep out water, we do it to keep out the fuel and oil from the exhaust, which is much harder actually than keeping out water. If the oil get into the wood, all the glue joints come apart, and then you also cannot repair it later with any kind of glue.

asianflava wrote:

SteveH wrote:Would West System epoxy work the same way if you thinned it with alcohol, or another thinner? The reason I ask is West System is cheaper and more readily available.

Steve, This is what West says:

Thinning Epoxy

There are epoxy-based products specifically designed to penetrate and reinforce rotted wood. These products, basically an epoxy thinned with solvents, do a good job of penetrating wood. But the solvents compromise the strength and moisture barrier properties of the epoxy. WEST SYSTEM epoxy can be thinned with solvents for greater penetration, but not without the same compromises in strength and moisture resistance. Acetone, toluene or MEK have been used to thin WEST SYSTEM epoxy and duplicate these penetrating epoxies with about the same effectiveness. If you chose to thin the epoxy, keep in mind that the strength and moisture protection of the epoxy are lost in proportion to the amount of solvent added.

There is a better solution to get good penetration without losing strength or moisture resistance. We recommend moderate heating of the repair area and the epoxy with a heat gun or heat lamp. The epoxy will have a lower viscosity and penetrate more deeply when it is warmed and contacts the warmed wood cavities and pores. Although the working life of the epoxy will be considerable shortened, slower hardeners (206, 207, 209) will have a longer working life and should penetrate more than 205 Hardener before they begin to gel. When the epoxy cures it will retain all of its strength and effectiveness as a moisture barrier, which we feel more than offsets any advantages gained by adding solvents to the epoxy.

Hmm, now I see why we are not allowed to thin epoxy in aviation. I do know that MEK plays havoc with it even when cured. Thinning has never been an issue since we do our layups under vacuum and with a heat blanket or in an autoclave. Good penetration in an autoclave!

SteveH, thanks, that's good additional info.

Asianflava, Do they let you run personal parts through the autoclave? I would love it if I have access to one.

schaney wrote:SteveH, thanks, that's good additional info.

Asianflava, Do they let you run personal parts through the autoclave? I would love it if I have access to one.

I think you were refering to me instead. As far as they know I have never done my own work in the autoclave. That's my story and I'm stickin' to it. Actually, since it is a small shop we have been allowed to use out dated epoxy and throw items in the autoclave when we are cooking something else. Mostly just g-jobs.

schaney wrote:Yes that is quite a list


Steve_Cox, What type of acetone did you use?

Just the Ace hardware store variety, are there others? Just because I have thinned epoxy in the past doesn't mean I would ever do it again, the results were underwhelming to say the least.