How can I maximise a trebuchets efficiency with the guidelines below?

Question

I am build a trebuchet according to the rules for the Storm the Castle Science Olympiad event. The rules are it can only be 65cm high, 75cm long, and 75cm wide. Only the counterweight they give us can contribute to the launch. Basically w/out the counterweight on the arm it has to sit dead still. How can I maximise the treb's efficiency? Also where should I place the axsis on the arm (1:3,1:4)?

Answer 1

Check out the attached link - you'll need to modify it a bit to match your maximum dimensions criteria ...