its been a while since i last hit this site, but i can use some help from you experts out there.

I am working a large scale, res. project. There are power lines over head. Craning the lumber seems to be problematic.
I am thinking of building a chute that will work more like a slide to get lumber down for the first two floors which need framing. The third and top floor will be level with the street above. The top floor will be easier access because the driveway will backfilled.
My question is.
What degree of incline should the slide/chute be?
Any thoughts on the materials it’s constructed are welcome.
I’ll be on this site for 6 more months.