www.DiyCatapults.com has a contest with a grand prize of $400 for building your own catapult! You should really consider checking it out when you have a few minutes to think about your new invention. The site is a great resource if you are trying to learn more about trebuchets or catapults or if you are just a DIY buff. Historians can also consider the info on this site as there really aren't many better resources for figuring out how to build historical scale replicas of old catapults and old trebuchets. Much like the site you're on, this site is still being improved, but you should still check out their contest, which appears to be how they are launching their site. The have a few really cool catapult videos you might find interesting to watch.

DIY Catapults offers FREE online information and a cool contest, why not check it out?