April 18, 2016 – I think I lost a few hairs doing this one. Really needed to make sure I didn’t mis-drill, and I measured, re-measured, and so on.
The first part of this was to trim the front spar of the stabilizer. The plans called for 5/8″, but I kept it at 1/2″ for now.
I marked edge distance on the splice plate and clamped it into place.
I clamped the stabilizer into place.
I made the angle that ties the stabilizer to the top deck of the fuselage. I ended up making another one, because it turned out just a bit too short. I wanted some more edge distance for the outboard bolts.
I drilled the bolt holes, which have to go through the longerons, and edge distance there is critical. The center three holes are for rivets that attach to the deck.
There are several measurements that have to be made:
- the distance from the tips of the horizontal stabilizer to the tip of the vertical. This ensures that the vertical is truly vertical. My measurement came out to 62 5/16″
- the vertical is displaced 1/4″ to the left of the aircraft centerline. This compensates for engine torque. The splice plate at the forward spar is “joggled” to the left to allow for this.
- the rudder hinge brackets had to be in line. This is adjusted at the forward spar splice plate. This took me the longest time to figure out. I though the center bracket was somehow incorrect, because it was just forward of the top and bottom brackets. I was able to straighten the stabilzer vertically by pushing the forward spar down lower on the splice plate.
I drilled two bolt holes on the angle at the aft spar and the deck.
Once I had everything measured and located properly, I back-drilled the holes for the splice plate. Had to use an angle drill, and I couldn’t get to all the holes with the stabilizer in place.
I took the stabilizer off and drilled the rest of the holes on the table.
Remember when I said that the plans showed to trim the stabilizer spar 5/8″ and I just trimmed 1/2″? Here’s the situation I had:
The spar interfered with the bend in the splice plate. So I marked good edge distance from the rivet holes and trimmed another 1/8″ off the spar. Now it fits like a glove.
The last thing I had to do was drill the bolts attaching the aft spar of the stabilizer to the fuselage. These bolts also go through the tailwheel mount.
To give myself better access, I lifted the tail up onto a box.
I used the tooling hole in the fuselage frame just above the tailwheel mount. I used a #30 with a drill bushing, then back-drilled from inside, and took the hole up to final size.
I also measured the hole locations in just the frame, with the stabilizer off. Triple-checked everything because I’d be drilling blind through to the tailwheel mount and I needed good edge distance. I drilled the holes to #30, reinstalled the stabilizer, and back-drilled from the inside.
I think it came out pretty good…:
That did it. Here’s a few shots of the drilled front assembly: