This catapult is doable in about half an hour to forty-five minutes. It doesn't launch very far due to the elasticity of this bungee cord, but a motorcycle strap would much work better.
Submitted by Powell Middle School for the Instructables Sponsorship Program.
Step 1: Parts
3" hinge (I bought a door hinge from Walmart with the screws)
8' of 2x4
12 decking screws
4 eye bolts
3' 1/4 inch rope
90 degree angle support
Tuna Can or other small 3" diameter can
phillips screw driver bit
3/8 inch drill hole bit