We have a factory that makes those small plastic signs that you see in people's front yard at election time. We have a pyramid sized mountain of leftovers that we wanted something to use it for. What better than to build a full size airplane with leftovers, a hit glue gun, washing line, and some wheelbarrow wheels?
We designed it with 5 napkins and a 12 pack of beer.
Our only rule was that it had to be plastic. We build the entire airplane out of leftover plastic, used PVC plumbing for the controls, plastic washing line for the rigging, and covered it with clear vinyl.
We got a local racing car company to sponsor pay for the engine, and went to fly it at the local airport with me as the guinea pig.
I'm a pilot so I know basic aeronautical engineering (classy speak for what shape airplanes should be). Using that knowledge we designed the parts on some napkins over a few beers.
The hardest part to envision was the control systems to make it a full 3 axis airplane, with roll, pitch, and yaw, for which we needed aerilons, elevators and a rudder.
I came up with how to do it while I was actually in the shower not thinking about it. I built a full gimball system for the control stick out of 1 inch PVC pipe, using standard fittings from Home Depot to create a universal joint.
The joints that were solid were glued, and the joints that were meant to rotate were not glued.