Da Vinci's Catapult

Simple 3D catapult model, it should work fine, but I haven't tested it yet, you will need to print only one of each file except for the tension arm, of which you will need 2.
String is also required and glue is recommended.

Update: I uploaded new, thicker, tension arms because the previous ones weren't able to supply sufficient tension. They are the files labeled with "thick" and the mtaching base file.