True catapult that uses a extremely tightly wound string to power it, it fits in the palm of your hand, it cost under $20. all supplies can be purchased at Michaels. fires small foam
objects 40 feet aprox 1053 feet to scale, about 7.5FPS when firing a 14g weight (twice the weight of the catapult its self) (i know cause i did a school project on it. This is my design and i didn't copy it) it can fire other objects farther and faster such as rocks but you can not easily recover them cause they go to far and fast to visually track.
this is for the competition so please comment and rate (this is the 4th catapult i have made they all worked good yours should to)
This is technically an [http://en.wikipedia.org/wiki/Onager_(siege_weapon) onager] but it is still in the catapult family.
this is a rather complicated instructable and is an example on how to build one yours dosent have to be exactly the same i use cm for most measurements but some are in inches ask if you get confuseduse safety glasses when drilling cutting wire and when firingthis is safe when fire foam objects when firing rocks never aim at a person animal car personal property it fires hard enough to break a paint ball if used for office war only use foam light weight objects and make sure every one is wearing safety glassesbuild this in a room with good ventilation the Ca glue and accelerator smoke when they dry
Ca glue bonds to skin on contact use un-cure do not pull apart. the glue will not separate but the skin on your fingers will.
The accelerator causes chemical heat and you can get a chemical burn from it which hearts so dont touch itit has a range between 15-50 feet depending on ammunition and angle of trajectory
Other videos on step 4 and 9
I have pics of my 6th grade Sci fair project back when i was 11