Ch 6: Installing the Lower Firewall...

Tape measure running straight from f-22 (extended outward) to the
firewall (extended outward) to ensure the 101.75" dimension

The lower firewall install took a lot longer than I thought it would, mostly because I'm too anal about some of the measurements.  The initial fitting was fairly good but I had to find a way to make sure the 101.75" dimension from F-22 to the firewall was maintained when floxed in place.  After leveling the fuselage upside down on saw horses, I clamped an extra 4 ft level to the aft side of F-22.

This allowed me to extend the back face of F-22 out to the side of fuselage far enough to allow for a tape measure to be pulled straight to another extension used at the firewall.  Without doing something like this your measurement will get distorted by bending around the fuselage or over the landing gear bulkheads and won't be accurate.

Using finish nails to hold
firewall in place while curing

I used small finish nails to hold the firewall in place once I got it where it was straight and square to everything else.  After many trial and error installs to get it square, my install process after putting on the flox was...

1. install firewall loosely and gently tap into position which I had marked on the longerons; install holding nails
2. adjust height by tapping with rubber mallet to ensure the proper water line positioning of the top of the lower firewall (w.l. 13.2") and the center of the motor mount hard-points (w.l. 4.5") using the top of the upper longerons as the known reference of w.l. 23"
3. check the F.S. 101.75" position at the bottom longeron and tap to adjust as needed
4. using a smart level, adjust the top of the lower FW (which is on the bottom now) until perpendicular (0.0 degrees or % slope which seems to be a slightly higher resolution)
5. clean up excess flox and stand back so as not to accidentally hit it and move it

It took a while, but I think I ended up with a very accurately installed firewall.

Onward.

cab