I don't think you'll find any styrofoam in your glider's structure. The
R/C gliders, a different story... Most aircraft structural foams are
PVC. Some are urethane. Acetone used on the surface will not hurt
either the finish nor the structure. Don't get me wrong - please don't
pour a bunch of it on. A paper towel damp with acetone will not wet the
surface or structure sufficiently to cause damage... depending on the
finish. Most gel coats and urethane will be impervious to acetone. On
the other hand, if you're working on the original lacquer finish of a
Schweizer 1-35, leave the acetone in the can... don't ask me how I
know... at least I had the good sence to test it on a small, out of
sight spot. I'd recommend that before you use any solvent. MEK on the
other hand has such a bad reputation that I leave it alone. The only
time that gets used is in extremely small quantities of patch gel coat
I got from an RV dealer. Protect your health - we have too few glider
pilots already - use gloves and ventilation.

Regards

Jack Womack