So, I was going to use the decayed roof truss as a template and just replace, but they are not original, plus I've decided to replace the (worse than I thought) aluminum roof with plywood deck, new trusses and a membrane. Anyone build your own truss? Any suggestions? Dimensional sizes? A true truss or 2x6 with the arch cut from it? Thanks for any wisdom.
Post by wisconsinjoe on Aug 17, 2022 15:40:31 GMT -8
I used pine lumber milled to 1-1/2 x 1-5/8 and reinforced some of the roof framing with aluminum C-channel (1/2 x 1-1/2) or aluminum tube 1-1/2 x 1-1/2 (both 1/8" wall thickness). Another way would be to make a glued sandwhich of interior plywood (I used 1/4" prefinished birch), 2x2 framing, and another layer of 1/4" on top. by gluing all surfaces, you create a "torsion box" that is amazingly stiff and strong. That's how they make big conference tables that aren't super heavy. I am supposing you want this to support a heavier load, like an AC unit?
I detailed my method in my book, Rosie: Scratch-building a Vintage Camper Trailer. There is a thread I posted about the book launch at the last topic category.
My roof is an arched roof from the factory. Although I'm eliminating the original roof system I had planned to build back with an arch. The easiest to build would be 2x6 cut with an arch. Not sure if that would strong enough though since they end up at 2" on each end, suppose I could double up arch every 16". I hadn't considered a 2x2 with plywood 3 sides. Do you rely on the glue? I assume such. I've also seen a few photos I've found online, looks like a 2.5 x 2.5 to span the camper width with 3 small posts (one middle, tallest and 2 shorter posts spaced evenly from middle). On top of the posts is a 1x2.5 laid on its side to form an arched and attached to the 3 posts and ends making an arched truss.
In the interest of saving weight, especially top heavy weight, the 1x2 or 2x2s with 1/4" plywood sandwiching them on each side, stapled and glued, would make a very light, dimensionally stable, and strong roof truss. You can make a pattern, then rough cut the arches and finish them with a flush router.
Post by wisconsinjoe on Sept 3, 2022 5:34:01 GMT -8
I'm confused about the arches because a flat sheet of aluminum roofing will not bend in two planes (if following the curves of a canned ham). However, what Chriss said above, if making a FLAT section, would be very strong. That is essentially a torsion box, with the 1/4 inch plywood on both sides glued and stapled over 2x2 framing fights bending because of opposing compression and tension forces. That is how large conference tables are built, to save weight.