Final assembly: vertical stabilizer and rudder

TLDR

• Assembled the vertical stabilizer and rudder onto the airplane.
• Connected tail section wires
• Connected rudder cable
• Installed rudder cable anti-chaffing plate in the center channel

Details

Today’s work might not seem to be related to avionics, but it is :) In order to install the top skin and dash etc, I want to make sure a few things are done: rudder cables are connected, nose wheel pushrods are adjusted, anti-chaffing plates are installed. All of these require the rudder to be mounted onto the airplane.

So, I spent today to install the vertical stabilizer and rudder.

Vertical stabilizer

Wiring

Before installing, I needed to finish the wiring on the VS so the harness can connect to the tail lights. The wire running through the VS has 4 wires, matching to T2 connector from midwest panel builder’s wire diagram.

I found my previous blog entry for the wiring, and crimped the 4 wires into a GT150 connector. Easy enough. Can’t believe the original wiring was 1.5 years ago! That was one of the first things I built when started this project :)

Installing

The vertical stabilizer are connected to the airplane via 12 AN3 bolts. I aligned the it to the fuselage and did a quick test fit. Most bolts went in just fine, but 2 of them did not want to go in. They were blocked by the primer I spray painted into the bolt hole. So I took the VS off and did a quick clean up with a reamer. The reamer barely shaved anything off, but the fitting became much better.

When torquing the bolts, several of them were super difficult to reach. I needed to grind down my wrench to be able to reach the bolts.

Then I did a bunch of cleaning up between the horizontal stabilizer and the vertical stabilizer so the metal parts movement does not go anywhere near any wire cable.

Rudder

Then there is the rudder.

The rudder is connected to the VS through 3 AN4 bolts. Installing them is a big PITA. I spent close to a full day just doing that. I had to redo a few times because either I forgot to first connect the wires between rudder and VS, or I dropped the bolt into the rudder (multiple times).

Anyways, the sequence was roughly: connect the wire, shove the connector into the VS, then connect the center bolt, then top bolts, then bottom bolt. That’s the only sequence I found working for me. If I connect the top and bottom first, the middle bolt just won’t align.

Also, inserting the washer for each bolt was super painful too. Each bolt needed 4 washers. The top and bottom ones were easy, but the center 2 that needed to be sandwiched between the parts was simply not accessible by hand. I again used the 3D printed washer holder with a dab of glue for help. It required a bit practice, but after having to redo this part 50 times, I got pretty good at it.

Torquing the bolts

Torquing was not easy either. I had no trouble torquing the bottom one. But there was no space for torque wrench on the middle bolt and the top bolt. I tried crowfoot, couldn’t insert either.

So I improvised a homebrew crowfoot using standard wrenches.

You can see in the picture above, I connected the torque wrench and a regular wrench through a common AN4 bolt. This obviously extended the torque arm significantly. I measured the new arm (from torque wrench handle to silver wrench tip), and calculated the new torque to be 55 in-lbs.

Testing the tail light

With the rudder finally installed, I did a quick test on the tail light power. And it worked. I did the test by sending 12v power to the tail harness pin 14 and pin 16, as described by Midwest Panel Builder’s wire drawing.

Rudder cables

With the rudder installed, I pulled the rudder cable and connected them to the rudder.

At first, the cable was 2 inches short. I searched around on Facebook builder group and also on the maintenance manual, and found out that the tension is controlled by the nose wheel pushrod. The longer the pushrod gets, the less tension there is. So I loosened he pushrod a bit, and the cable became longer. I connected them to the ruder uneventfully.

Rudder cable anti-chaffing plate

This was the last piece of the puzzle for today.

While the rudder cable is pulled tight at both ends, I got to get an accurate positioning on the cable inside of the center channel.

I then drilled a few holes on the channel where the rudder cable is rubber, and riveted the nylon anti-chaffing plate in place.

To be honest I am a little skeptical about Sling’s design on this part. It shouldn’t be too difficult to make the center channel a few millimeters wider. Then the cables won’t rub on the channel at all, and I will have more space to run my wires. But with the nylon anti-chaffing plate I’m sure the rudder cable will eat right through it. This will for sure be an annual replacement item.

Video

And I made a quick video to summary the work in the last few weeks.