I've read a couple stories by people who have used epoxy to attach stringers/mounting blocks for their cabinets, only to have then fall
off when they hit a large bump. I think this is likely due to a couple of things you should probably think about.
First, stringers/mounting blocks are usually straight, flat, and smooth, where our trailer walls are curved, irregular, and rough, making it difficult to form a full-contact connection betrween board, epoxy, and trailer wall. The result is the typical epoxy only really connects board to wall in a handfull of places where the two actually touch. If you're going to use an adhesive to connect stringers to your walls, get an epoxy that creates a thick paste and apply enough that is gushes out from the edges of the board when you put it up. An alternative to more expensive epoxy might be Bondo Glass; just be sure to clearly mark the locations and pre-fit your boards before mixing up enough Bondo Glass to liberally cover the entire mounting surface of the board in one mixing, and then work very, very, very
fast. Bondo Glass sets up in five to ten minutes from the time you mix it. Remember the board has to be held securely in-place for about 20 full minutes to give the Bondo Glass time to both set and cure before you release it.
Another thing that can lead to failure is not cleaning the mounting surface thoroughly. Little bits of wall covering and adhesive will interfere with the adhesive bond, so wire brush the area to which the board will be attached clean and wipe it down with either MEK (wear gloves and be careful, MEK is a powerful, toxic solvent that can dissolve your wall coverings) or acetone (safer, less effective).
You are better off attaching a rough-sawed board or rough-sawed side of a board to your trailer wall than a sanded or planed-smooth board. The adhesives we've mentioned here don't absorb into wood very well, like wood glues do, and the rough texture gives the adhesive more "tooth" to grab on to.
For applications requiring strength, trailer manufacturers "tab," or attach strips of fiberglass mat that wrap the stringer/mounting block on three sides and then attach to the wall. Tabbed-in stringers/mounting blocks are the gold standard for strength and durability.
One last bit of advice: clamping. Whatever adhesive you use, it won't do you any good unless it's held firmly in-place until the adhesive has not only set, but has actually cured. When installing ribs into our Surfside
, we used both Bondo Glass and tabbing to secure them, and held them in-place while the Bondo Glass set using screws with fender washers inserted and tightened through pre-drilled holes in the shell that ran every 8-10" down the center line of the boards. After the Bondo had set and the tabbing went in, we removed the screws and used Bondo body filler to fill in the screw holes.
The attached picture, courtesy of Mike Morrison who posted a picture Escape
Trailers sent him of his trailer being built in the Tabbing fiberglass cabinetry??
thread, shows a trailer that employs both techniques. You can see where the adhesive has gushed out from under the stringers and been flattened out with a putty knife, and other stringers that are held in-place by fiberglass tabbing.