Teardrops n Tiny Travel Trailers

Sealing the exterior of a home-built plywood based camp trailer can ranging from a basic house paint finish to high-end automotive clearcoats with many options in between. Some finish methods take practice to master and specialized equipment. There are two finish methods that I normally use, a clear finish to highlight the beauty of the wood and a colored polyurethane “workhorse” finish.

After using clear finish marine varnishes like Epifanes for sometime, I started looking for a “better way”. When I say better, I was looking for faster recoat times, easy to brush on and less toxic, all while being as durable and weathering as well as a good oil-based finish.

After testing a number of products, a new oil-modified exterior varnish by Target Coatings called HybriVar stood out to me. It was a breeze to brush on and leveled out great, showing no brush marks. In 62-65 degree conditions it was ready for recoating in 2-3 hours. Lastly it cleans up with water. All this is great but water clean-up clear finishes exposed to the weather don’t have a good track record of holding up.

So I set up and started a durability test November 2007. The test panel is a piece of 9mm marine grade Okoume plywood. It was first sealed on all sides with CPES. The CPES was cured for 5 day. It was then sanded with 220 and 6 coats of HybriVar were applied. The panel was cured for 2 day then positioned horizontally in full sun outside.

** December 2008, one year results:
Over the year the panel has seen a temperate range of 22-100 degrees, it’s seen lots of rain, been cover with snow for about a week, been through many freeze-thaw cycles and baked in the sun. I’m happy to report that so far it is holding up great and shows no signs of degradation. It also shows no notable fading or change in color.

The other finish I mentioned is a colored polyurethane, this is sold as a roll-on finish for pickup beds. It is very durable, holds well against rock chips, is low maintenance and the textured finish covers up minor surface imperfections. The brand I use is Durabak. I’ve been using it over epoxy (normally CPES) sealed wood with no problems for a while now. Since I was doing the clear finish test, I decided to test Durabak over bare plywood.

As with the clear finish, the test panel is a piece of 9mm marine grade Okoume plywood and was started November 2007. The panel was light sanded with 80 grit and two light coats per manufactures instructions were applied. The back and edges of the panel were left bare. After the same 2 day curing period it was also positioned horizontally in full sun outside.

** December 2008, one year results:
I’m happy to report that so far this test reveals no signs of problems; there is no instance of checking, cracking or delamination. The finish is still shiny and hasn’t faded.


On top one is the Durabak test panel, on bottom is the HybriVar one. The HybriVar is in the middle portion of the panel. On the right side is what happens when an interior clear finish without UV additives is exposed. On the left is a “box store” exterior finish which is still intact, although started to have fogging issues when water pools on it one month into the test.

Based on these results I’m definitely going to start using more HybriVar for my exterior clear finish needs. It also looks like forgoing the CPES sealing of Okoume plywood that will be coated in Durabak will work. For Fir or Pine plywood I’m still thinking I’ll first seal with CPES because of their higher tendency to check. One last thought; if your Teardrop or Tent Top camping trailer is stored inside or under a cover when not in use like I do, this one year full exposure test is probably equal to the exposure your trailer would see in 6-9 years.

Interesting test and results. Thanks for taking the time to experiment and sharing the results. Where do you buy Durabak?

Paul Cook

Thanks for sharing your findings.

How does the price compare?

dave

schanny....I used Duraback on my tear. It has been stored out side year round for the last two years and is holding up great no problems as of yet. I am very happy with it. I did not coat my plywood with any thing before I applied the duraback. I used ordinary 1/4" Luna plywood. I did how ever do all the plywood edges with epoxy.

Paul, I get my Durabak through NewLineSafety

Dave, it retails for about $75 a gallon, so it's priced similar to quality marine varnishes like Epifanes.

As I've been researching finishes, this got my attention. However, going to the website this product appears to be geared more for interior use. Am I looking at the right product or interpreting this incorrectly?

http://www.targetcoatings.com/oxford-hybri-varnish.html

"
Available is High Gloss, Semi-Gloss, Satin and Flat, Oxford® HybriVar Waterborne Alkyd Varnish will provide the inexperienced finisher with a brush and spray friendly product that is well suited for interior trim, doors, window sills, family furniture, patio and cottage furniture and special projects that require a vintage finish.
"


Thanks,
Fred

Yes Kirkman, sealing the edges well on plywood is important.

Yes Fseider you have the correct link. I discussed my criteria when I started my search with Jeff Weiss the owner of Target Coatings. He recommend HybriVar because it's UV stable and describe it as great for exterior doors and bright work trim on boats. He said this is his best water clean-up, brush on finish.

schaney - That's what I wanted to hear.

Thanks for confirming.

Fred

Time for an update, my test panel has almost four years of weathering on them now.

Durabak Panel: It's holding up just fine with minor fading. What I'm finding is some rotting away of wood where the panel has not been coated, but just fine under it. I poked around the edge and there is no sign of lifting.



HybriVar / EM2000 Panel: This test has made it to the end of it's useful life. In the Summer of '10 it started breaking down around the edges. From what I could see, as the finishes on either side failed, the CPES failed because of UV exposure. This started lifting the edges and causing the bond to fail. Before the end of Winter it had completely failed. So it lasted a little over 2 1/2 years. Again assuming indoor / out of the weather storage when not in use, I would see a 10 year useful life.

schaney wrote:Time for an update, my test panel has almost four years of weathering on them now.

Durabak Panel: It's holding up just fine with minor fading. What I'm finding is some rotting away of wood where the panel has not been coated, but just fine under it. I poked around the edge and there is no sign of lifting.



HybriVar / EM2000 Panel: This test has made it to the end of it's useful life. In the Summer of '10 it started breaking down around the edges. From what I could see, as the finishes on either side failed, the CPES failed because of UV exposure. This started lifting the edges and causing the bond to fail. Before the end of Winter it had completely failed. So it lasted a little over 2 1/2 years. Again assuming indoor / out of the weather storage when not in use, I would see a 10 year useful life.

Thanks for the update. I wish you had included the traditional marine varnish (Epifanes) on the same bright panel as the other coatings. It would a have been a good comparison of the oil vs water based coatings.
Also, 9mm Okoume is a very stable, water resistant plywood that may have contributed to the longevity of all coatings. A side by side comparison using lesser grade plywood's in the same test would be interesting.
Again, thanks for sharing your experience. Final coatings are what make or break any build, and hearing of real world testing is always welcome.



Larry C

I'm thinking about setting up a new test that would include Epifanes and a few other plywood types.

just remember that the real world results of any comparisons of durability are geographically based.. a finish that last well in a damp cloudy coastal environment may not do so well in a bright dry desert environment..

from my experience the sun is responsible for most failures.. if you can keep UV exposure to a minimum your finish will last a lot longer no matter what it is.

afreegreek wrote:just remember that the real world results of any comparisons of durability are geographically based.. a finish that last well in a damp cloudy coastal environment may not do so well in a bright dry desert environment..

from my experience the sun is responsible for most failures.. if you can keep UV exposure to a minimum your finish will last a lot longer no matter what it is.

Good point! The sun deteriorates the finish, causing tiny cracks, and lets water in. We call it water damage when actually it's sun damage.

Larry C

I agree UV is a major factor in finish breakdown. I'm inland, not on the coast, so I get plenty of sun, although not as much as someone in the desert.