For a physics project, I have to build either a catapult or a trebuchet (treb-yoo-shay). The dimensions are 5'x5' for the base, and the arm standing up cannot be taller than 10'. I was thinking of asking if we could build a Roman Onager, which is like a simple easy ballista. The goal is not only to build it, but we have to fire a water balloon 50feet to the "castle wall," a trifold board. You get three tries to hit the wall. You get points for how far it goes, but MAJOR deductions for passing the board. My question is, does anyone know of any instructions on building on, free on the internet. Or, if anyone has a simple catapult or trebuchet design it would be very helpful. I have no idea how this is going to work out. Please offer any help on ideas you can!