Mpilot,
Check out http://www.spadtothebone.com and don't miss the showcase for some of the best examples of what can really be done with Coroplast. It is the same stuff that U.S. Air Core makes their airplanes out of, but it is more commonly known as corrugated plastic sign board...you see it in the form of pop, beer, and cigarette signs every time you drive past a gas station. Building airplanes out of it is getting popular...from simple basic designes to some incredable scale designs. Thanks to RCU, there is also a topic here just for the Coroplast airplanes! The best part is that it's CHEAP!!! Signs are free and thrown in the dumpsters across the nation every day...they can usually be had just by asking...and if you buy Coroplast, it's usually around $8-$10 for a 4' x 8' sheet...and comes in a variety of colors! It's totally fuel proof, and no covering is required. It's also strong as heck, so very little internal support is needed. Properly built, a Coroplast airplane rivals the weight and performance of a balsa or foam plane...but much more durable...the stuff is a scratch builder/designer's dream! I converted from Balsa to Coroplast 5 years ago (after 20 years of Balsa and foam) and am having a blast with the stuff!