ghcoe wrote:So I have thought about a roof rack on my #2 trailer. I have though about all that has already been mentioned and agree that some are impractical or just add too much weight.
In my thinking the foam has plenty of load bearing potential at a compressive strength of 25psi per sq. inch. The problem is how to attach to the foam and spread the weight across the load bearing walls?
So my solution? Well some people want roof spars anyway so why not incorporate them into the top portion of the roof. Imbed the spars so that they are flush with the top of the roof foam. Then you can glue and screw a piece of OSB/Plywood to the roof. In my build I envisioned incorporating the OSB/Spars into the roof canvasing process. This should give good attachment points in itself or also allow a point to attach roof rack side panels.
Just food for though....
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I appreciate the constructive thinking! It is true that thick sidewalls have a lot of compression strength on edge.
But I think a heavy chunk of ply is overkill just as basis for an attachment point.
I know many racks are clamped out at the rain gutter, but on SUVs and minivans the rails are integral to the roof design, and in fact I've mounted a few to bare sheet metal with plusnuts very securely.
Where I'm having more doubt is that we're not talking about static loading here, and there will be *very* large lateral and also lifting forces at play.
I think having metal posts or some sort of "cage", well tied into the trailer frame, is required for stability in that context.
Perhaps simply four angle posts on the outside corners would be enough, strong support for the vertical dimension, and tightly tied into the foam walls and roof for bracing.
The addition of a flat piece spreading the load across the top of the sides would be fine as a mount point, and the rack itself is designed to not even touch the horizontal top surface.