Brief Description: Drill F-7127D Doubler to Firewall
The F-7127D doubler goes inside the firewall, but to drill all the holes I wanted to use the doubler as a drill guide from the outside to avoid interference with the rudder mechanism. I carefully measured and marked the location for the second bolt on the master contactor and drilled the firewall #40 at this location. I also used measurements from plans to mark this hole on the doubler. I verified this mark lined up with the hole in the firewall then drilled it #40 also. I marked the starter contactor location on the firewall and drilled #40. Cleco'd the doubler on and marked this hole on the doubler, then drilled the doubler. Now I had the doubler secured by two cleco's and could drill the four remaining mounting holes. With these complete I used a step drill to open the bolt holes, then used a nutplate as drill guide to drill the doubler for the nutplaate rivets.
