In this tutorial i will be showing how to build a fairly simple catapult powered by an elastic band. It fires fairly far and is made out of nothing more then paper, glue, tape, a bottle cap and an elastic band. To see the finished project along with the tests and video tutorial, check out my youtube video
Start by using a dowel to roll up a paper cylinders. you will need two sizes of paper cylinders. Many cylinders will need to be the size of the dowel, say 5 or so. Then one cylinder should be larger, made by wrapping paper around one of the normal sized cylinders.
Cut the normal sized cylinders shorter and glue them into a square which will be the base. Cut a piece off the larger tube and put it around the smaller cylinder in the base. Now the larger piece will rotate about the base cylinder. Attack another paper roll onto the rotating part. this will be used as the catapult arm. it may be easiest to understand this step by watching the video
build two uprights using the paper cylinders and put a tube in between. this will be used to stop the catapult arm from over extending. Also be sure to add an elastic band around the connecting tube before you glue it into place.
Now take the elastic and glue it behind the catapult arm. Then to finish the build off glue a bottle cap onto the catapult arm. also make sure to reinforce all paper joints with more glue to your catapult stays rigid