Locating firewall on forward fuselage
Note: the firewall is very thin Stainless Steel and slightly soft. Edges can very sharp. Use care when handling to avoid cuts or damage to the firewall
1. Place lower firewall P4309 on front of fuselage. The flanges of the firewall should be between the bottom and side skins and the fuselage frame as shown below. Place a sacrificial 0.032” thick shim between the fuselage frame and the lower flange of the firewall. Note: shim can be poster board, scrap Al or anything approximately .032 thick that can be drilled. Normally, the lower flange of the firewall will be below the bottom skin, but for transfer drilling, the bottom skin should be placed below the flange.
2. Check that the holes in the firewall for the engine mount bolts are aligned with the holes in the fuselage. If necessary, holes in the firewall can be enlarged. Do NOT enlarge holes in fuselage frame.
3. Drill #40 holes around perimeter of firewall.
4. The pads for the engine mount will cause the firewall to be offset from the front face of the fuselage tubes. The skins/firewall are riveted into SIDE of tubes so this not an issue. At the center “V” tubes a small gap will also exist. When riveted this may cause a very slight pucker in the firewall which is normal. That can be seen in the picture below.
5. Drill #40 holes through the firewall into the diagonal “V” fuselage tubes and along the top of the firewall.
