I am trying to design a catapult launcher for a ~20 lb UAV and was curious if anyone has designed and built one for a similar weight range. Based on my calculations, using a 70 ft/s final velocity over 12 feet at a 11 degree angle, I will need ~ 950 lbf after building in a 20% safety factor for friction within the system.
After looking into available designs on the market, it seems that for in this weight class the best launching methods use pneumatics. I have looked into numerous designs available on the market and one of the ones that stands out is the UAV Factory's pneumatic launcher (http://www.uavfactory.com/product/21). I have been trying to design one for my unique UAV design, but am hung up on the pneumatic design. I have not been able to find a pneumatic capable of providing this force with accelerations of 245 ft/sec^2.
Does anyone have any advice or personal experiences with catapults or catapult design that may be able to help in my case?