Teardrops n Tiny Travel Trailers

I'm currently at the point in my build where it's time to start waterproofing my floor assembly. The floor is a 1x4 frame glued and screwed together with an OSB floor glued and screwed to the frame. This picture shows it under construction.


Outlining the 1x4s by jseyfert3, on Flickr

My walls will sit on the edges of the floor, like in this picture we took after cutting the walls out to see how the profile looks in real life.


Side One - Finished by jseyfert3, on Flickr

I plan to waterproof it with GPW's mix, 75% paint thinner, 25% poly, multiple coats to really let it sink in. I've got the floor removed from the trailer and sitting upside down on my sawhorses right now, but before I start, I need to know how the adhesion is between wood coated in poly and Gorilla Glue. The top of the OSB will be coated in 100% poly after the mix is applied to the top. Do I do this and then glue the foam sides on top of the OSB, or glue the walls onto bare wood and poly the inside top of the OSB after the walls are up?

Also, since I will be wrapping the canvas down the 1x4 framing on the outside and underneath the frame, will the TBII or primer (depending which I use to glue on the canvas) stick the canvas to wood that has been waterproofed with the mix fine? Or do I want to leave the wood bare where the canvas will wrap around?

Here's how I have done it/am doing it: I taped along the top front and sides of my floor with blue painter's tape a little less than the thickness of my walls (so that the finish would be about 1/4 inch under the inside edge of the wall, but most of the area under the wall would be raw), then I stained and poly'd the top of the floor. Didn't worry too much if some of the stain or poly got under the tape a little as there was still lots of raw wood for the adhesive to bite to. I sealed the underside and edges of the floor with a diluted coat of TB2, scuffed with 220 grit, then a full coat of TB2, then scuffed with 220 grit once fully cured. TB2 will stick to itself. I used PL between my walls and floor, but I have cedar sills at the bottom edges of my walls. GG is a better choice for your application w/o wooden sills, unless you want to spring for the foam rated stuff (PL300 or 375, I can't remember the exact number at the moment), but it is costly compared to the GG. With the GG you have to be careful about expansion shifting the parts and getting on your finish.

When the time comes I will wrap about 6 inches of the canvas under the floor, gluing it with TB2, then when I paint the canvas I will also paint the rest of the underside of the floor with it. No black goo for me, thank you very much.

PL300 is ok for sticking the flat side of a foam panel to a flat wall, but for what we all want it to do, it is garbage (from my own testing).

Use the mix on every wood surface, since it soaks in and doesn't just coat the surface, take some coarse sand paper and scuff up the areas you will have foam and fabric glued to. Sanding it will give the GG or TBII some tooth to grab onto, (the rougher the sanded surface the better)
I would also recommend using a Stanely sureform

or wall paper scoring tool

to perforate the surface of the foam. In my testing I found Glidden Gripper held onto perforated foam as well as TBII, (both samples caused old bed sheet material to tear rather than let go of the foam) without perforation they just peeled off with no resistance.

Consider this .... no matter what you use to glue the foam with , the foam is always the “weakest link” and will always fail before the glue does ... (as long as the glue is dried and cured)
The outer skin is the “sock” that holds it all together ... why it’s so important ... You could glue the foam to the wood with most anything , and it will still be the skin that completes the structure ... It’s a “System” ... Several materials working Together to produce something greater than the individual parts...

Hmm, so the mix everywhere there is wood, and scuff it up before gluing over it.

Since it was mentioned, is Glidden Gripper particularly better for attaching canvas to foam if a primer is used vs TBII? I was thinking of using primer so I can buy a 5 gallon bucket of it instead of 3 gallons of glue and 2 gallons of primer.

One more side board to add to my trailer frame and then it's time to start waterproofing when the glue dries. Later today I'm ordering canvas and hopefully making a hot wire cutter for the rest of my cuts and to kerf the foam easily.

gripper is more expensive, but gives you a long working time, TBII sticks almost instantly and is hard to work out wrinkles. from what I've read TBII really needs more than one person to help get it stretched and stuck. I discovered stretchy fabric is a real pain to work with with TBII (poor mans fiberglass link)
The best deal I ever got on gripper was $5 off a dented can (but I had to ask for it)