I figured out a better way to hold it down. I'm building a cantilevered facade, at the floor line, that serves as the strength for the bottom of the sides. I don't want to draw a picture. I don't want to use a computer to draw a picture. I can build an entire custom home from a drawing on a napkin. So I'll paint a picture with words as if I were telling my lead carpenter how to do it. I hope that satisfies.
I need the standee to be low. I've figured out how to get a full sized trailer that only sticks up 36" above my Toyota Corolla.
Everybody has framed out the floor on their Harbor Freight 4 x 8 trailers with 2 x 2, 2 x 4, or 2 x 6. I'm going to just run two sheets of 3/4 inch Douglas Fir tongue and grove sub floor and let it cantilever out without a frame under it. I need it to stick out 7" on each side of the steel frame. I discovered that I will use shims on top of the uneven points of the top of the HF trailer so that the sub floor is dead on flat. This method needs to be shimmed and bolted to the cross members of the HF frame as well in order to prevent up and down flexing. Once that is properly achieved it is going to get a very strong rail type "Box Beam" configuration that is built out of 5/8" Fir plywood for the outside runner that makes up the bottom of the side panel. It will run the full length of the floor, including the cutout for the wheel, including the drop step for the standard industry RV door, and will be glued and screwed to the edge of the cantilevered 3/4" floor making the beginning of the box beam structure.
So you have a 3/4 inch floor running into a 5/8 inch perpendicular rail that sticks up 6" above the floor and 6" below the floor. On top of the floor a channel is added to the inside of that rail, made out of 5/8" plywood, both bottom and side, to receive the 2" foam panel that makes up the sides. The top of the rail / channel is beveled at 45 degrees inside and outside. The foam will be glued and doweled before the 18 oz duck canvas is applied. I found a great resource for that too,
http://www.mytarp.com/numbered-duck-natural-canvas.aspx You can get 18 ounce that is six feet wide without a seam and in almost any length.
http://www.mytarp.com/no-8-cotton-duck- ... -yard.aspx Below the floor, in the cantilever on the outside, the box beam will be framed out of more 5/8" plywood and filled with scraps of 2" foam, all glued together to prevent the frame from deforming, It will have TB II and screws all over the place.
Because this lock down technique is being used, I decided to go with the PMF with one layer of 18oz duck canvas. I will only run 1/4" stringers in the roof, not in the sides or the back. The front will have three layers of 1/4" stringers laminated together to form my rounded front stringers with 2" foam in-between. A beveled matching base board will match up with the side bottom panel to complete the effect both front and back.
Now that I've decided how to do the cantilever I can get started as soon as the snow melts. I will take plenty of pictures for this build. Then you will have your images of what I mean.