So I am making a ballista for history class and I was wondering if anyone had any suggestions or ideas. This needs to be as historically accurate as possible (wood, ropes, ect.) and is about 10' wide at max. Thanks for any help.

This photo may help:

http://scientificsonline.com/product.asp?pn=3123801&bhcd2=1206762905

 

I kinda know a bit about it, but don't trust me too much. Use some strong rope to attach to two ends of a steel sheet, to create a bow. Mount a wooden stock to it and tie the topes to a dowel. Mount the dowel on some wheeled frame and attach a crank to one end. It will look like a wheel-mounted crossbow (the ballista was its predecessor). Put your projectile (historically boulders and such) on the stock, so that it is in front of the string. Crank the handle to pull the ropes and bend the steel sheet. Release and send whatever you've packed flying!

 

Hope you got all that mumbo-jumbo.