I'll be building a carport in the near future. I would like to make my own
frame to support the roofing panels. The span between the posts will be 20
feet. I'm thinking that some 2x4x.120 rectangle tube should be strong enough
for the horizontal, but what I need to know is will the tube sag under it's
own weight . Has anybody had any experience with this kind of framework
before, or is there some place you could direct me to find some answers?

Many Thanks,

Chuck in Phoenix