We've used:
Baltic Birch Plywood:
here,
here,
here, and
here.
Maple and mahogany
here.
Fibreglass sheets (we cast them ourselves on urethane foam cores),
here, all the white sides are sheet fibreglass.
And thin walled 3/4" square aluminum tubing TIG welded together
here. Oh, wait... there was baltic birch in that shot, too.
We've used the KoP frame in several years... albeit welded, chopped and otherwise hot-rodded, and I can't find any quick photos of our nerf-ball shooter which was also 3/4" thin wall tubing.
So... yeah... they all work great, so long as the structure you use matches the materials you have. In general, though, I have found the aluminum tubing to be best for "space frames" that occupy a large volume, simply because you can build them lightweight yet rigid. I like the baltic birch for anything that allows you to get sufficient joint strength and will undergo massive abuse. The upper arm in that "Triple Play" robot with the red background could sustain two judges BOUNCING on it. (We had a display with a spare arm set up in the pit... it helped win us our first FRC award.)
Actually, now that I think about it, our
overdrive robot had a lot of wood in it, too.
Thinking of the engineering and design awards that we have won, we've had our use of wood cited three times, our use of fibreglass cited once, and our use of aluminum never mentioned. Thinking outside the aluminum box has paid off for us, both in unique, functional, robots and in resultant recognition from the judges and teams in our area.
Jason
P.S. Ever thought about using Bamboo? Use some fibreglass tape and epoxy at the corners and you might have a good (mostly) biodegradable, eco-friendly replacement for thin walled aluminum tubing for use in space frames.