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
How far does it launch? I want to use it in my yard for my dogs
I did this as a kid and used a bike tube. The tube would really fling it. Can also take a frozen juice can and cut it in half to use as a cup on the end of the arm. Works good for throwing fruit or rocks or whatever.
I may try this but using a triangle base for stability.and some bike tube. Please put that Bungy thing in the bin. They are dangerous, People have lost eyes and one killed a trolley boy in Oz.
Nice, simple design. I might add a pulley to the top so the bungee cord doesn't wear as quickly, and maybe a block so the arm will stop at the optimal angle to get the best distance. Also, if you have a quick release mechanism of some sort, instead of a rope that has to be pulled along through a ring behind the arm, that might improve the speed, as well. <br> <br>Good job, though. You've got me wanting to build some sort of siege weapon, now.
Nice one because it's so easy and simple <br> <br>by the way filesizes for the movies seem incorrect (for 2013-05-20 19.25.52.mov it says (516x290) 22 KB but it really is 20.7mb in size) <br>
I just started to wonder if the ball is losing quite some momentum due to the tuna can's design. <br>As the catapult's arm accelerates the ball will in addition accelerate from one end of the tuna can to the other (upper) and then bounce against it. possibly at a very bad time which will work against the momentum gained through the catapult's motion. <br>or, more likey, it will give the ball a detrimental (slice) spin. (which is what seems to happen in your video)
My local tennis ball fiend says &quot;Two Paws Up!&quot;
Great work

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