Glossary

Here are some terms and their clarification:

EPP Expanded Polyproplyene, the stuff the latest foam gliders are made of.  Very resilient, bounces back to its original shape when smashed.  Great for plane wings, but has drawbacks such as cost and being difficult to cover.
EPS Expanded Polystyrene, basically the stuff styrofoam cups are made of.  Cheap, but not as durable as EPP.
Fuselage The body of a plane
Built-up A term used to describe a glider that is built using balsa ribs and pieces and then covered with a heat shrink film such as monocote.  The traditional way of constructing a glider.  Very labor intensive.