12' high posts for sun shade over travel trailer

Question

I need to get my travel trailer covered so it isn't getting beat up by the brutal AZ sun/heat as much.

I bought a 20'x40' sun shade I will be putting up, I'm just trying to figure out the best way to build my posts to support the tension from the sun shade.

I plan on having my posts 12' out of the ground on the back side of the trailer and having the front posts 10' out of the ground.

The biggest concern obviously here is wood beams (4x6's were the original plan) bending from the tension that the sun shade will require.

I'm not sure what my options are with being able to have something that high up under that much tension?

I had an idea of using 1/8" thick angle iron, drilling holes in it to be able to deck screw it to the corners of each 4x6 post I used to try to make it more rigid support more tension. I was thinking of putting 1' pieces of angle on each corner spaced about 6" apart? Would this help at all/enough to prevent the post from pending?

Another concern is the depth that th post would have to go. I have a tractor with a post hole digger but I'm only able to get to about 3' down tops with it.

Another idea I had to try to really beefen the posts up would be to use my backhoe to dig down 5-6', sandwich 2 4x6's together with liquid nails and 3" deck screws, 1/2" rebar around the base of the post, fill the entire post hole with concrete and also brace the corners of the posts with angle iron. Would this be enough to handle the tension from the sun shade?

I've been really racking my brain on this one, I also will be building a deck off of the front of the trailer (we're turning it into a guest area for when we have people over) so buying a metal carport won't work and isn't what we want to do.

Any advice or help on this would be greatly appreciated!

Answer 1

Guy wires are the obvious, default, simple solution. Look at the vast majority of utility poles and antenna masts - tall sticks with guy wires into ground anchors to take the tension as needed to keep them upright.

Making the poles self-supporting without guy wires is a LOT more effort and expense. That is seen in a few utility and antenna installations, but it's the exception, not the rule.

Heck, consider the classic tent. Consider a sailboat or sailing ship.

Wind creates huge forces on a large anchored sail...

Answer 2

For a structure of this size, and especially because it may be rather sparse or skeletal, I think you may do well to think about steel. Angle iron "corner protectors" on the lumber will do little to stiffen the lumber, but if the posts were instead rectangle or round-section steel tube/pipe it would be a whole different game.

Regardless of the choice of post, some kind of rigid spreaders between the posts will help deal with the tension forces. Consider a frame built of round tube/pipe posts rising from the ground (or those 4x6 wood posts). Something in the neighborhood of 3" diameter might do. Then imagine more round tube, maybe 1.5" diameter, spanning between the tops of those posts. The horizontal pieces will support the tension of the shade sail.

There's still the problem of wind pushing the top of the whole structure this way or that. The spreaders at the tops of the posts won't help any against these forces. It helps that the sail will be horizontal and the wind may be blowing more-or-less parallel to the sail rather than broadside against it (but this depends on your local geography).