Images 1 and 2 show me match drilling the Flap Drive Bracket to the Inboard Flab Rib. Because the inboard rib sits at an angle to the lower Flap Skin edge, you can use a standard length drill bit for the holes closer to the trailing edge but you have to use a longer drill but for the holes closer to the flap spar. I used my 12-inch long #30 drill bit for those. Image 3 shows me using a center punch on the shims I made for the aft tab on the flap ribs. Using the center punch will leave a small dimple in the center of where I've marked the hole so that the drill bit will have less tendancy to walk when I drill the hole. The shims are clamped between two pieces of scrap 1x4.
Match Drilling the Flap Drive Bracket to the Inboard Flap Rib
Match Drilling the Flap Drive Bracket to the Inboard Flap Rib
Using a Center Punch to Keep Drill Bit from Walking
