The additional trebuchet is for a physics project. It will be substantially bigger.
I was deputized to make the sling to hold the projectile (a 4-5" diameter pumpkin). Oh, just use my old jeans said Handy, and sew through here and here. I broke two sewing machine needles trying to sew through the jeans seams. Aaaargh! I cried! I'm going to do this the proper way.
It was a piece of cake after I cut the jeans apart and squared up the piece on the grain with a rotary cutter (yay, quilting gadgets). Good sewing techniques rule!
This is demonstrated with a 5" rubber band ball. Imagine the bounce if he flung that! We'd never find it! But there are too many years of work in that ball to lose it like that.
What are your plans this weekend?