wrinkling skin

[Jim T]

Hello all,
After thoroughly enjoying our first season of camping in our partially finished trailer I put the tarp on for the summer about mid may. I recently uncovered it preparing to do some work and discovered many areas of the finish that looked like it had wrinkled and in some cases was peeling, much as your skin would peel after being sunburned. When I applied the finish, I first sanded the wood smooth finishing with 180 grit sandpaper, stained, lightly sanded again and wiped down with a rag moistened with paint thinner. Then I brushed on Spar Urethane and allowed to dry. For the next coats, I would sand the entire surface again with 180 grit sandpaper by hand, wipe with a rag moistened with paint thinner, and then brush on another coat. I did this for 6-8 coats.
So my question is, what went wrong? Did the finish get to hot under the tarp which caused it to do this? I did apply it during the summer, could the trailer have gotten to hot while it was drying? Did I make a mistake when applying the urethane? When I refinish, so I need to use an epoxy or other material? I chose the Urethane route because my walls were already vertical and I read that epoxy works much better when the surface you are applying it to is flat. Any help would be appreciated!
Thanks, Jim

[Larry C]

It seems like moisture is getting through the walls. I am in the process of painting my house that exhibits the same symptoms. Are your walls insulated?

When you cover a closed box (teardrop) in the summer, the air inside cools overnight, and stays cooler that the outside during the day. When the hot humid air of the day hits the cool inside of the Tear, it condenses into water.

As the day gets hotter under the tarp, the inside also gets hotter. As the moisture laden air inside expands from the heat it has to go somewhere. If there is no vent system, the moisture will be forced through the walls and ceiling. However, you have the outside sealed, thus the moisture is trying to remove outer protective surface from the inside. That's the blisters and peeling just like my house

That's just my theory, and I may be full of #$@&^!!

Larry C

[Steve_Cox]

You might want to change the title of this thread to "DON'T TARP YOUR PLYWOOD TRAILER IT WILL DELAMINATE". This has been a hot and albeit humid topic since the beginning of this forum several years ago, and it has happened from Canada to the deep South. Some people have gotten away with it....... but just a few. Really sorry you didn't pick up on this before the damage happened and hope your experience will help someone else.

[mallymal]

I wonder if a better option for storing a tear would be a carport type structure which would shade it from the sun, protect it from the rain, but most important, let the air circulate. [sorry dont know if "carport" translates across the pond...]..... [ok, just Googled it........yes it does]

So sorry to hear about your damage - hope you can get it sorted. I know some folks swear by thinning the first couple of coats of varnish with spirit to let it really impregnate the wood. Maybe you could do that on the section you sand back.

[Jim T]

Ok. Let me see if I understand this.
In a no cover situation, the sun and heat would hit the outer wall and heat it. Since the wall is insulated, most of the heat would stay in the outer section, and it would heat and cool as the day passed. What a tarp did is put the trailer in a bubble, and heat the entire structure. Not only did it heat the wall all the way through, but the temperature was higher that it would have been otherwise, probably 110-120°. When the sun went down and the whole thing started to cool, cooler moist air rushed into the inside of the wall through the window and storage compartment, and condensed inside the hot walls. So what I created was much the same condition as when the seal fails in a double paned window, and you get a fog inside. That would explain why the urethane is actually peeling at the seams of the wall, and why the wrinkling is worse toward the back of the trailer, where the cool air would have entered.
Now that I know what's up, and have removed the tarp from the trailer, can I expect any more damage? Will the plywood delaminate, or have I taken a bullet but dodged the mortar?
Jim

[Miriam C.]

What they said. When mine did it I treated it like a faux finish and epoxied over it a few times...Stuck like a charm. Any moisture will swell if you get it too hot...and tarps will do that if it can't breath. Ya got to put something under the tarp to make an airs space... Still can do it if it is hot enough out.

[Gary and Cheri]

A similar problem arises with car guys. If you are going to put a covering on your tear or car it needs to be breathable. I store my tear with a breathable car cover to protect it and have not had problems. Our tears are roughly the same size as our cars and what will work well for your car should work well for your tear.

Gary