Control Installation - Part 2

My quick build kit shipped with the aft torque tube already installed, which at the time I thought this was great, less work for me!

 

After spending many hours working to get the main elevator torque tubes moving with minimal resistance my expectations for the rest of the control system were much higher.

The same problems existed on the aft elevator short torque tube, which means I needed to disassemble this part and get to work.

For those building from the flat pack definitely spend the extra time before you fully assemble this section to get this control section exactly how you want it.  Trying to fix this later in the build is quite difficult and getting access to the rivets in this location are a challenge without custom tools.

To reduce overall friction in this section I removed the close-out ribs and started working on sanding the ribs to allow the bushings more room to seat properly.

I also slightly enlarged the bushing locking plates to keep the bushings aligned on the same axis as the torque tube.

The torque tube was wet sanded to reduce surface friction where it rests inside the bushing.

I reassembled everything with some white lithium grease and Cleco's and turning resistance was significantly improved.

With these steps complete I needed to rivet the locking plates the hold the bushings in-place but I hadn't considered just how little space there was to even get a hand-pulled riveter in this section.

I found a drill operated rivet attachment that I could use with a 90 degree drill fitting to get the last few rivets pulled.

Pop Rivet Gun Tool Rivet Drill Attachment 

 

Prior to riveting everything in place I needed to secure the locking collars to the elevator tube.

The last step during final riveting of the close out ribs was to add J-B Weld on the bushings to lock them in place so that they didn't rotate with the torque tubes.

Control Installation - Part 1

 Elevator torque Tube Assembly

This installation task was one of the most time consuming and frustrating parts of the build.

Placement of the control bushings is still incorrectly printed as of version 8.1 of the KAI, I will cover this later in this section.

I found that initial installation of the elevator torque tube to be simple and that movement was unencumbered and smooth.

What transpired next was over a month of assembly and disassembly trying to determine what was causing various binding locations in the controls.

The first hurtle was confirming with the factory the location of the inner bushing.

The KAI clearly shows it in the picture below.

My initial fitting using this location for both the inner and outer bushings depicted in the picture above was nice and smooth with little to no binding. (WRONG)

 My confidence in this location was confirmed because there was no way the bushing would fit in the inner bushing as shown below. (WRONG)

Consulting with other builders on the Facebook builders group I learned that it has to be installed on the center console rails and this location was confirmed by the factory. When I asked other builders how they were installing the bushing the feedback was to bend the parts to allow the bushing to slide down into the channel.

I didn't think this was the correct approach, and so began the journey to determine how to install these bushings with minimal bending and zero damage to this section.

The problem is this section was way too rigid and did not allow for any significant flex that would accommodate the bushing, especially considering the amount of times I needed to install and remove this torque tube and bushings.

The solution was staring me in the face and it was actually very simple.

Removing the rivets circled in red changed everything.

My kit is a quick build, these rivets were installed at the factory and builders with flat pack kits might not have even installed these rivets yet.

Removing these three rivets allows the channel to flex just enough on both sides of the center channel that you can relatively easily install/remove this torque tube and slid the bushing into place.

With this piece of the puzzle solved I could move on to next unexpected challenge, the excessive binding of the bushings and the close-out ribs that lock the bushings in place.

Many builders have struggled with this section and I have sat in a number of completed planes and there seems to be a wide variance in the amount of resistance still remaining in the controls.

I wish I had a magic solution for the this problem but unfortunately for me it was a lot of trial and error, and sanding.

I sanded each of the ribs walls to give each of the bushings more room to sit squarely in the ribs which was a big improvement.

I placed the torque tube on the rib without seating the bushing and found that some of the ribs were slightly taller than others which was causing some misalignment.

By slightly move the torque tube back and forth I could see which ribs were making contact with the tube and which ones weren't.  From there, I reshaped the lower valley of the ribs until each was making contact with the torque tube.

The rib closeouts were the next problem. 

When you Cleaco the rib close out panels in place they also changed the alignment of the bushings especially the more Cleacos that are used.

The walls of these parts were also slightly sanded down where they made contact with the bushing and in the case of the inner close out plates on the center console I sanded the surface to thin out the aluminum just enough so that the bushings would stay squared up and result in very little twisting of the bushing off axis.

These steps got me about 75% there but it was not friction less.

At this point I was still extremely frustrated and kept searching for any clues to reduce friction that would meet my expectations.

I removed the torque tube again for what seemed like the 50th time and was looking at the condition of the tube where the bushings were making contact.

The bushings had worn away some of the Bonderite (gold color) and the surface had a few scratches and bumps that I could feel with my finger.

I decided to polish the sections of the torque tube where the bushings make contact with the aluminum until I had a smooth finish.  I think I used 1000G and wet sanded this section to dull mirror finish.

Reassembled everything once again saw marginal improvements but wasn't quite the breakthrough I was hoping for.

I found a few builders mention that these Vesconite bushings are self-lubricating yet they had added some white lithium grease further reduces overall surface friction.

I bought too much grease...

By adding grease to these bushings and the mating surfaces on the torque tubes this was the piece that I was missing.

I was able to fully install both flap and elevator torque tubes, bushings and close-out ribs and Cleaco at least 50% of the rivet holes with negligible resistance in the system.

Successes at last, and it felt good.

Prior to riveting everything in place I needed to secure the locking collars to the elevator tube.

My first attempt unfortunately reintroduce some friction into the mechanism because the collars were rubbing against the bushings. (FACE-PALM)

I drilled the rivets out and was able to rotate the collar 180 degrees and that gave me a little extra space and everything worked out.

The last step during final riveting of the close out ribs was to add J-B Weld on the bushings to lock them in place so that they didn't rotate with the torque tubes.

I know others have been able to lock or pin the bushings in place but I had already committed to using adhesive. (not ideal but can be removed if necessary)

Rudder Pedal - Assembly

Rudder Pedal Assembly

I opted for the standard rudder and hand-brake for my Sling, I found that operation took a little bit of time get used but ultimately determined that adding toe brakes would not have significantly improve ground handling characteristics.

My current aircraft is a Vans RV-12 with a castering nose wheel, and mastering that takes quite a bit of time and finesse but provided maximum turning capability in either direction. The sling having a steerable nose gear means that you are going to get the same tuning radius without the need for multiple brake cylinders and a lot of hydraulic lines.

My left and right rudder pedal tubes were painted black at the factory, so I opted to have the bushing close-out plates powder coated as well to protect these surfaces and have consistent finish.

 

Tip #1

If you are going to paint or powder coat these parts only paint the outsides or keep the paint thickness to a minimum.  I powder coated both sides and when all of he parts were assembled they put a lot of strain on the bushings and caused binding in the rudder tubes. This meant that I had to remove nearly all of the power coating on the inside of the closeout brackets to provide sufficient clearance.

I removed paint where part #7 and most of the inside and outside paint on with the lower section in turquoise as shown below.  I ended up taping off the paint I wanted to keep and removed the rest with a Dremel and an abrasive wheel.

 

Tip #2

I recommend some white lithium grease on the bushings, to remove as much friction as possible.

I used CRC SL3660 Super White Multi-Purpose Lithium

I test fit everything after removing the power coating getting in my way.

I used a reamer to cleanup the holes so that I could insert rivets easily through the rudder tube mounts into the bottom of the fuselage.

In most cases is was quite easy to pull rivets where my Milwaukee riveter would fit, in some instances I used a hand-pull riveter for some tight spaces.

 I was cool getting to install the rudder tubes into the fuselage, it made the inside feel like an airplane.

I will be switching to the Sling branded rudder pedals in the future, but for now I installed the bar pedals that came with the kit.

I have the same bar configuration in my RV-12 and I find that this small amount of surface area can be tricky to keep your feet on and even a little dangerous if your feet happen to be wet due to a rainy day.

I have mitigated this with wing walk tape so that my shoes get sufficient grip.

Something I sought clarity from the engineering team at the factory was the removal of material on the rudder control stops.  They sent back the following pictures of what they are doing at the factory.

Some builders are shaping these parts similar to what is shown below and I think a few builders bent their brackets to allow more clearance without the need to cut.

 Another view without the markup for visibility.

I temporarily assembled everything until I was ready to connect the rudder cables, and push/pull tubes for the nose gear steering.