02rangeredge
Adventurer
I'm reinforcing my aluminum truck cap with 1/8in aluminum so I can haul my 2 kayaks (90lbs) and was just trying to lay out where on my truck cap I can safely put the feet of my rack towers
As close to the edges and as close to the front and back as possible would be my suggestion.
Depends on all sorts of dimensional criteria. You'd do better to use a tubular extrusion if you want load strength. If you are worried about tear-out / -thru, then the flat reinforcement would be ok.
I'm with Raya - flat stock will bend under a load that would not affect square or round tubing. If the structure is fiberglass, that may be a problem.
If the reinforcement must conform to a curved surface, the tubing option is out.
These needs some photos of the cap or a same-product and some sort of explanation of your plan.
My suggestions are predicated on the idea that your cap skin is corrugated aluminum and the grooves run from the forward edge to the tailgate. Thus a rack or whatever is being attached on the roof ought to be sitting on some form of runner / rail, in continuous contact wtih the skin, to spread the weight as much as possible. And in the rivnut discussion my suggestion was some reinforcing flat stock (or large 'fender' washers) on the inner surface of the cap, so the thin cap skin would be sandwiched between outer and inner rails. Maximum support and maximum resistance to tear out, without having to put a larger more complicated support structure inside the cap or outside on the sides.
I suggest you contact the cap manufacturer and ask them what they think the max weight load that could be borne on top of the cap without permanently deforming it. They'll very likely tell you zero pounds, out of liability concerns.
The rack on my work truck is 1/8 wall 1" square aluminum tube. It has had a canoe and 2 kayaks on it. I think the actual structure of your capper is what you need to worry about. Does it have support ribs at each end built into the corners? Either way attaching the rack to the vertical part of each corner may be your best bet. Or to the sides, where the ribs are