marble like substance

[my other east]

hey guys,
what is this stuff that Bertram used in between the engine beds and the stringers? I'm softly chiseling it off as i prep for the dreaded "grind". it's anywhere from 1/8" to 1/2" thick.

[CaptPatrick]

Bondo, or something similar. Usually blue... Carefull with your chisel and try not to cut any fiberglass strands. I've even put a dull air chisel to it.

[my other east]

Yes, i have been very careful not to cut any strands, but the stuff is so thick in a few places that it has popped a little fuzz off the fiberglass.
it's white w/ a little blue in it, and has very sharp edges when chipped off.

Thanks again Capt. Pat,
Eric