I made a thread like this a while back...it got sucked out with the Anything Else/Campfire switch...there were some good suggestions, hope some of you guys voice up again because I can't remember there.
I whipped up a couple of hungarian~ish horsebows...two fiberglass quickies and a bamboo/ipe/ash one. While showing them off I got sucked into a contest...I got to make a bow without using fiberglass, wood, horn, or metal for the limbs. Wood/horn/fiberglass/metal/etc can be used for non-working parts like the handle.
I have no idea what to use lol