On Wed, 25 Feb 2004 00:19:12 GMT, wrote:

:I've seen a few homebuilts with part of the fuselage panel that are flat
:aluminum that are quite wrinkly and tend to "oil can" and make noise in
:various flight attitudes. I haven't seen cross breaks used to stop this,
:although it is used in duct work to stiffen flat panels. (cross breaks are
:slight bends in the metal, done diagonally from corner to corner)
:
:Another thought to reduce this noise is to spray urethane foam on the panels.
:I know that this foam is combustable, but I figure for it to get on fire would
:mean the pilot and passenger cabin is already engulfed, so it wouldn't really
:matter.

Check out

http://www.eng.fiu.edu/pantherskin/

It's very interesting stuff. Especially the burn through test.