The material that they are using to make wings (and fuselages sometimes) at teh spadtothebone website is "CoroPlast" its similar to cardboard mad eof plastic. Typically you will see it used for camapign signs, beer signs, soda signs.... (any modern sign shop will have it but you can get some free by asking the locak "quickie mart" for un-used signs)

Lowes and Home Depot sell the correct yardsticks (for the spar) for about 50 cents each. (sometimes you can get free ones at furniture stores)

Preparation f the plastic material for gluing is the only "hard" part.... if using a sign, you have to remove the paint from where you will be glueing. If using new material you have to either lightly sand the area you will be glueing or "Flash" it with a propane torch. (I prefer sanding... flame and flammable plastic combined is not something I recommend.)