Ive build a large trebuchet (or large compared to the ones i know of). 160 cms tall, 180 cms long, and the arm is 240 cms long. Ive got everything built, but i have 2 bigs problems. 1. The bag i used to hold 120lbs broke, and i cant think of anything strong enough to hold it that i can tie up to notches in the arm. 2. I can't think of a material to make the sling out of that wouldnt release the ball before it reaches verticle. I have a job, and no bills, so there is no budget. Anyone have any ideas?