After building a small model of a trebuchet, I started thinking in larger terms. During a whitewater rafting trip on a local river, I worked out a means of building a trebuchet out of my raft and oar frame. I made this first attempt while camped riverside, using available materials. 2 oars lashed together formed an A frame, with my spare oar used as the throwing arm. I used drybags full of river rock as counterweight, a towel and tubular web from my rescue kit made up the sling. Add lots of cam straps and some duct tape, and here is the final product!
