Empennage Attach

Today was a big day, as I was able to attached the Vertical Stabilizer and hang the rudder on the aft fuse. I then added the elevators and finished up section 11. Well, it’s not really done, as there is some electrical routing that still needs to be done, but that can wait for now.

First I installed the VS attach bracket, then the Vertical Stabilzer itself. I used temporary fasteners, as this is all coming apart again soon.

With the VS on, I attempted to hang the rudder. Everything looked good except the gap on the top hinge was too narrow for the rod end bearing to fit. I took the rudder off and attempted to bend out the Ganges on the hing using a small wooden block. Measuring with my calipers, I found it to be about a millimeter narrower than the middle hinge. After several attempts, and with Jen’s help, I was able to get it to fit.

With the rudder on, I installed the elevators. This required supporting the tips of the HS so that the elevator counterweights didn’t cause the fuse to roll over as I installed these one at a time.

With the elevators on, I measured the clearance between the rudder and corner of elevator and trim tab. It was 3mm more gap than the minimum, so I left it as-is.

I had been stuck for a few days, as I didn’t have the right drill bits to finish enlarging the holes on the rear spar. I did have a 1/4 inch drill, but I really wanted a reamer. I reached out to my friend Murlin who offered to lend me some bits while mine were in-route from Aircraft Spruce.

Using a #C drill bit, and a 1/4 inch reamer, I drilled a perfect hole in the top right side of the spar. The bottom two holes were positioned such that I needed a longer drill bit to clear the aft fuse. Rummaging through my box of used tools, I found a 12 inch long 1/4 inch drill bit, and a 12 inch long 3/16ths bit. This was quite lucky! I practiced with them on some scrap to ensure they worked ok, then drilled two more great holes through the spar. Not as clean as the reamer, but close enough.

With the holes drilled, I bolted on the Horizontal Stabilizer.

Today I rearranged the benches in the shop, then installed the HS on the aft fuse. It’s neat to have this attached and to see how it all fits beautifully together.

Yesterday I reoriented the HS and attached the elevators so it’s sitting vertically on the bench. This makes it easier to drill these important bottom holes on the elevator horns. I marked and center punched the location for the first hole, then drilled it. The right hand elevator horn is slightly aft of the left, as expected, per the plans.

Tonight I clamped up the trailing edges, and then spent time shaping up a drill block.

Once I had a perfect fit on the drill block, I clamped the elevator horns and drilled the hole in the left elevator horn. These came out quite well I think.

I found that my trim tab is indeed twisted, which was causing most of the misalignment. I discovered this after removing the tab and setting it on a flat surface.

With the trim tab set aside for now, I clamped up the trailing edges of the elevators, and found I still had a difference of 3/16ths between the counterweight arm and the HS, when holding one elevator counterweight arm flush with the HS. from the research I’ve done, I’m going to leave this as-is, and move on. Provided the trailing edges are flush, it shouldn’t be a problem.

While waiting for new drill bits, I skipped ahead and installed the rod end bearings on both elevators and the rudder. First I made a tool out of PVC pipe, as these are fairly stiff and need some kind of tool. The PVC does a good job avoiding scratching the bearing, while still providing enough torque.

Measuring the distance between the spar and the center of the bearing was easy, but not super accurate. I got these with 1/32 of the plans, then finger tightened the jam nuts. These will need to be torqued up once I have some crowfoot attachments for my torque wrench. I’m going to wait on that until I’m sure I have these set correctly.

I also made some blocks that I will be using to drill the alignment holes in the elevator horns. Today I also picked up a couple of 8 foot lengths of aluminum angle so I can clamp the trailing edges while locating and drilling the elevator horn holes.