Several months ago, we used a cheat to remove Bertha's shell without using an "Airstream Gantry." Eventually, however, it became painfully clear that insulating the trailer floor and installing a new bellypan would be much easier if we could flip Bertha's frame over at will. So, we bought two new chain hoists to go with the one we already owned, purchased a bunch of lumber, and built a 13 foot tall x 12 foot wide "Airstream Gantry." And so the Gantry Madness begins.
For video go here - https://youtu.be/o0rryDTFvKA
Once we had the flipping part down, we started insulating the subfloor. We decided on three layers of 1-inch foam board. For layer one, we used three 2-inch strips per section to maintain air flow below the flooring and give moisture a place to evaporate. For layers 2 and 3, we went with solid pieces.
We cut the panels to fit with a utility knife, glued them in place, and then (for extra security) attached them to the subfloor with 3.5-inch wood screws countersunk into the foam with 1/4 inch washers.
Before screwing the panels down, we glued all the pieces together (and to the subfloor) with 3M Super 77 Spray Adhesive. We tried contact cement and 3M High Strength 90 Spray Adhesive first, but both were too agressive and dissolved the foam board. Super 77 worked great and alone might have held the boards in place for a long time, but we opted to screw them down to make sure they stayed put.
Bertha's front area is a recess for the spare tire, so no insulation there (just a shiny piece of aluminum). No insulation at the steps either or under the fridge (far right), and no insulation where the fresh water tank will eventually rest (big area in the center). We insulated everywhere else, as we plan to install a composting head in the rear and a gray water tank above the floor near the kitchen sink.
Bertha's frame upside down on saw horses thanks to our homemade "gantry" system.
We learned a critical "gantry" lesson this weekend, as our first attempt to flip the trailer failed. Make sure you put your rear hoists right next to each other in the center of the beam (not spread out) or the trailer won't rotate. The picture below shows where the rear hoists need to be positioned for a sucessful flip every time.
Next time we flip Bertha on the gantry, we'll tackle under-the-frame wiring and start the belly pan.
Until then, she'll be an excellent spot for a cattle dog to nap under. Bertha's gett'in there, slowly but surely.