I already had pilot holes in the longeron for the outboard attach bolts from my previous attempt at drilling the HS front spar to the fuselage (see fuselage log entry for 9/21/2018), so I had previously transferred them to the F-710C spacer so I could drill from underneath and not worry about missing the hole in the longeron. The fore/aft location of these holes is fairly critical, as my HS front spar is located 1/8” aft of the F-710B angle so there is a narrow range that will give proper edge distance on the HS-714 spar attach angle while allowing clearance for hardware from the vertical leg of the F-710C bulkhead angle. After back drilling the outboard holes through the aft deck (without the HS in place) I clecoed the previously pilot drilled shims in place and pilot drilled the inboard holes through the aft deck and F-710 spacer and angle.
I then positioned, aligned, and clamped the horizontal stabilizer onto the aft fuselage. I used a 3/16" center finding punch to set the spacing between the rear spar and the aft deck to set proper incidence. To square the HS to the fuselage I measured the diagonal on both sides from the hole in the top of the main longeron at bulkhead F-902 to the first rivet in the HS tip rib forward of the front spar. After about a dozen adjustments and trips around the airplane I convinced myself that the two measurements were within 1/32” of each other.
After pilot drilling all four holes in the F-714 from underneath, I fabricated a new left shim, slid it between the aft deck and the HS spar and opened up all four holes to final size, installing bolts as I went.
I then drilled the HS rear spar to the F-711 bars for AN3 bolts, which was a piece of cake compared to the four through the front spar.
A 3/16 center-finding punch used to space the rear spar off the aft deck.
