matthew wise wrote: > > FlyBaby > > Will be wrapping the firewall soon with galvanized, > .018" most likely. Is there any other fire retardent > material required, or recommended, between the > galvanized and plywood or will just the metal suffice? A lot of homebuilts use a product called "Fiberfrax" between the metal firewall and the aircraft structure (wood in the Fly Baby's case). It's an asbestos-like material that withstands 2,000 degree heat. It'll help insulate the wood from the metal. It's pretty cheap... about $4 a running foot in the two-foot-wide rolls. The FAA certification standard for firewalls (FAR 23.1191) says that the firewall must resist flame penetration for at least 15 minutes when subjected to a 2000-degree flame over a 10 inches square area. However, the FAR does list the "standard" materials: FAR 23.1191 h): "The following materials may be used in firewalls or shrouds without being tested as required by this section: 1) Stainless steel, 0.015 inch thick 2) Mild steel sheet (coated with aluminum or otherwise protected against corrosion) 0.018 inch thick 3) Terne plate, 0.018 inch thick 4) Monel metal, 0.018 inch thick 5) Steel or copper base allow firewall fittings 6) Titanium sheet, 0.016 inch thick." While the flame won't penetrate, one must assume the backside of the metal firewall will be as hot as the front. And that's where the Fiberfrax comes it...it insulates the wood from the hot firewall. Ron Wanttaja