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 confused
use safety glasses when drilling cutting wire and when firing
this 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 glasses
build 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 it
it 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
Step 1: Get your stuff
wood, midwest 3/18 X 3 X 36100% polyester string 500ydsyou will need other balsa wood i have a huge box of scrap so i didnt need to get any thing else
you could use cotton, or any sting thats not hemp or nylon thats around the same diameter as kite string or you could just use kite string.
you will also need:
wood glue 19 gauge steel wiresawexacto kniferuler square (a right angle thing)sand paper bamboo skewers Ca glue and accelerator (with out accelerator its pointless)5min epoxy the kind that you mix two elements togetheryou only need epoxy one time the when your gluing the arm, you could use wood glue or hot glue as a substitute but i dont recommend it.