Built F-790 aft elevator pushrod. I don't have a tubing cutter that will handle that 1.5" pipe, so I ended up having to carefully cut it with a hacksaw. I cut it to the exact length specified on the print, but wish I had bumped it up by about 3/8" or so. When assembled, the length turned out okay, i.e. when rigged each end had more that 1/2 of the threads engaged, but not a ton more. If a jamb nut gives it up and it the rod unscrews itself until it bottoms out in one direction I still have about 1/4" of threads engaged on the other, so there's no way they can unscrew themselves far enough for one to fall out, but if I had made the rod 3/8 longer, teh margin would have been more like 7/16."

Installed elevators with rig pins, stacked up the appropriate hardware at the center aft bearing per print. This requires several washers stacked up to fill in the gap between the control horns and the center bearing and I've got to say I'm not crazy about this arrangement. I may eventually try to have some steel tube machined to make spacers for this area for a cleaner installation.

The print tells you to deal with the extra gap at the pushrod to control horn bolt the same way, but also says alternately you can take up the gap by by making appropriate shims from AT6 tube stock. The stackup would take about 4 washers per side, which looks really cobbled together and hard to assemble without dropping washers everywhere, so I took the time to build spacers.

I cut them to .25" each and then turners then down by chucking them up in my drill press and bringing them down on a file to mill off the end. I continued the process with lots of trial fitting until I was happy with the fit. For future reference, each side ended up being about .230" which is a snug fit without prying the horns apart.

One more thing about rigging. The build instructions tell you that the way to rig this is to clamp the elevator balance horns so the elevators are in trail, then adjust the length of the F-790 pushrod until the F-635 elevator bellcrank is vertical. However, there there is no detail about how to determine vertical on this component other than to say that you can get it close (but not perfect) by slipping a socket through the hole in the supporting structure onto the lower bellcrank bolt.

I went to the VAF to see what others had done. That, combined with a close review of a bunch of different prints, determined that "Vertical" meant parallel to the F-728A channel.

After tinkering with this for a while, I determined that the easiest way to determine this was to put a bolt in the lower bellcrank hole and then just measure from the top and bottom bolts to the channel. In my case, this dimension is approx. 3 3/16" from the fwd side of each bolt to the fwd face of F-728A.

Had a little bit of time still available, so I cut the F-789 pushrod tube to length (making this one 1/8" longer than called out on the print) ran a green scotchbrite pad wetted with acetone through it a few times and also prepped the exterior, then primed it. I'll let the primer dry overnight and then finish this assembly tomorrow.

I also marked the F-781 vertical stabilizer attach plate and clamped it in position. Then I measured between rivets to determine the tailcone centerline and marked a reference in preparation for installing the vertical.