Now I need to fetch my planes when the wind takes them and they stuck in trees and up on roof tops. I got one of my planes stuck on the roof today. My first idea was to shoot something up toward it with a string tied to the end. But without a specialized gun though, it was nearly impossible so I resorted to using poles and other contraptions.
But, with my knowledge of spudguns, I'm setting out to build a pneumatic cannon that will help me retrieve my planes with ease.
My first design is similar to the Antenna Launcher. I plane to start with a basic over/under using either a sprinkler valve or a QEV and a "spool" consisting of a 45* with plenty string wrapped around it. If that doesn't work, I'll rig a fishing reel to it. The barrel will be 2" to fire a Micro Nerf Vortex with a string attached.

Ideally though, I want to build a compact coaxial. 4" chamber with 2" Barrel. Does anyone know of a way to make a coaxial that size without having to use a 3" cap? A piston that size would make the launcher bulky.
Ideas? Suggestions?