My teardrop trailer is in it’s early stages. I’ve already mostly built the trailer frame from 2″ square and some 1″x2″ tubing welded. I didn’t take any photos of that part, but it’s a pretty standard trailer frame, only built to the exact dimensions I want.
Torsion Box Floor
My floor is a sandwich of a 3/4″ plywood frame between 3/8″ marine plywood on the bottom and pre-finished 1/4″ plywood on the top. The gaps in frame are filled with 3/4 insulation. The marine plywood is glued to the frame using Original Gorilla Glue which is a water activated polyurethane glue. It creates a waterproof joint and because the glue expands 3x it fills in the porous and uneven surface of the sheeting grade plywood I used for the middle of the floor.
The inner frame is assembled using pocket hole joinery. I arrived at this design as a way to quickly build the inner frame efficiently using 4’x8′ sheets of plywood. I cut strips of the right width on the table saw and then cut them to length using the miter saw.
Because the trailer is longer than 8 feet (the floor is 10′ 6″) I had to spice the long runners. This is all bolted to a steel frame in multiple locations so the hope is that the floor’s strength is not required.
The Inner Floor
The upper cover, which is the inner floor, is simply screwed on. In theory I should be able to remove it to make changes later on so I did not glue it. Later on I realized this we mostly pointless as the outer walls, galley bulkhead and internal cabinets sit on top of this deck and it can’t be removed. Version 2.0 will probably have this floor glued down as well creating a torsion frame of glued layers. This is still a torsion frame, but is not as strong as if the top layer was glued.
Later in the process I installed 5/8″ carriage bolts to attach the floor to the trailer. Once the floor was bolted down for the last time (later on after I welded the axle onto the trailer), I installed the floor for the last time.
As with the inner frame, I’ve had to piece the upper and lower portions of the floor sandwich together. The trailer is sized for a queen size bed, which is over 4′ wide and is longer than 8′. The seams are placed so they won’t be visible in the finished trailer. The center seam in the front will be under the mattress. The cross wise seam near the rear is under the galley bulkhead.
Treating the Underside
Not pictured here is how the underside is treated. The underside of the trailer is exposed to the outside world, including water and road muck. The marine plywood should hold up well to the weather (that is what it is designed for after all), but I wanted more protection.
I coated the underside of the floor with a roof membrane. It looks a lot like a truck bed-liner when finished, but was not a 2 part process. The edges of the floor were wrapped with flexible flashing (self sealing variety) to protect the edge of the inner plywood and the edge of the top 1/4″ deck.
Eventually the outer side wall skin will hand down over this hiding it and adding more protection.