I made the four F-704-L straps shown in Detail D, DWG 23.
Then I removed the forward six or seven clecos from the longerons and set the firewall in place. The rear facing “fingers” of the WD-602 brackets rested on the inside of the longeron angles. I clamped the firewall to the longeron.
I then drew a centerline on the flange of the aluminum firewall angle. I clecoed the F-772 Forward Bottom Skin to the F-704 bulkhead. Then I clamped the skin to the firewall with the line centered in the 2nd row from the front edge. Then I drilled a hole on each side of the fuselage, through the skin and angle. This set the distance between the firewall and the F-704 bulkhead.
I slipped some AN470AD4 rivets into all the holes in the skin and longeron between the firewall and the aft end of the WD-602. At this point, these holes had not been drilled through the steel brackets and the firewall was heavy enough to cause some sag in the longerons and make the holes mis-align.
I took a short break for a few minutes and returned to recheck that:
1. The forward face of the firewall was 5/8″ aft of the forward edge of the F-770 skin.
2. The webs of the longeron angles were clamped tightly to the Wd-602 brackets.
3. The 1/8″ holes in the F-770 skin and longerons were still aligned -in other words, 1/8” rivets slipped easily into the holes.
When all these things had come to pass, I drilled the F-770 skin to the flanges of the firewall, starting at the top longeron and working toward the bottom.
Adding another couple clamps to the longeron/bracket assembly I continued the holes already in the longeron and skin through the steel brackets and put a cleco in each hole as I drilled it.
Time: 4 hours.
Leonard's RV-7A Build 