Fuselage


Fuselage 34 – Aft elevator stop

First, an update. After the last post, I was very concerned with a slight discrepancy between the alignment of the elevators. I posted to Rivetbangers and contacted Van’s support. The response from Van’s was:

Actually, that’s darn close to perfect alignment.  Nail it down before it gets away.

So, I’m still a little annoyed that its not perfect, but I guess I’ll have a beer and forget about it for now. If it still bothers me, I can fix it when its flying. I think it will likely be forgotten and a non-issue.

So tonight it was time to turn my attention to the rudder stops. The amount of travel that the elevators are supposed to have is 25 to 30 degrees up, and 20 to 25 degrees down. I used the digital level method to measure the travel. Before any modification, I only had 21.4 degrees up, so not even at the minimum. The down deflection is 23 degrees, so thats square in the middle of the range. Today I decided to work on the up travel, which means working on the aft stop.

Here you can see the aft elevator stop before modification. In addition to setting the correct amount of travel, you also should make sure that both elevator horns contact the rudder stop at full deflection. As most people’s horns are not symmetrically aligned, this means the stop will be different on each side.

I started by using a dremel, but it became quickly apparent that I would need more material moved to get the travel where I wanted it. This meant I needed to remove the rudder stop and use the bench grinder and scotch-brite wheel. 

Here is the end result. You can see the right horn further aft than the left. The final reflection is  27.5 degrees up. I may take off just a little more tomorrow to get closer to 30 degrees. Luckily, the front stop won’t require much adjustment. I will only take off a little bit for the left side of the stop to try to make both of the horns contact the stop at the same time. That should also get me pretty close to 25 degrees. 

Session time: 2.5 hours 


Fuselage 33 – Rudder & Elev Travel

Two projects for this evening. First, I wanted to check the travel of the rudder. The best way I could figure to do with was with a couple of plumb bobs and a protractor. I set a plumb bob at the hinge line and on the trailing edge. I then marked all points of the resulting triangle of movement on the floor.  
  

Using a straight edge, I connected the lines.
  

I used a protractor to measure the exact angles. 33 degrees in either direction. They need to be 30 – 35 degrees so this is right where it needs to be. I may file the stops slightly to get the full 35 degrees, and measure the distance to the elevators. Or I might not. We’ll see.
  

I removed the rudder and the vertical stabilizer. Next, I had two things to deal with on the elevator. First, alignment. There is a very slight mis-alignment.

With the elevator horn drilled, and bolted at both ends I clamped the right elevator at the counterweight. The result is a slightly high left counterweight arm. It only about 1/16th to 3/32″ max. It is most likely a slight misalignment in the elevator horn, but it could also be the counterweight arms, or the elevators themselves. Hard to say. I figured the trailing edge was more important, so I decided to examine that.

The best way I could figure to examine the trailing edge was to compare its level with one side clamped to the horizontal stab. I played around with multiple configurations. Using both a regular level, and a digital level.
  

Here’s the digital level on the horizontal stab. It reads 0.2 degrees high on the right.

On the elevator it reads 0.4 degrees high on the right. So thats a 0.2 degree difference. So the question then becomes, what to do about it? I checked the alignment of my buddies airplane. His isn’t perfect either, but better than mine. Although with the fiberglass done, its hard to tell. My instinct tells me to build on, but I’m trying to be as perfect as possible on the control surfaces and alignment. My options are either leave it as is, or repair, likely by welding and re-drilling the elevator horns. I could also possibly hide the slight disparity when I do the fiberglass work. I decided to email Van’s to see what they say.  

I also measured the up and down travel of the elevators. Both the fore and aft stops will need to be filed to match the offset horns, and to achieve full travel. Currently 23 degrees up (supposed to be 25 – 30) and 21.5 degrees down (supposed to be 20 – 25 degrees).


Fuselage 32 – Control System

Today was a relatively slow day. First I needed to interrupt my session for both a Lowes run, and a run out to my paint booth. Additionally, I was significantly slowed down by the weather, as its rainy with high humidity and my priming and painting was going slower than I’d like. I tried to get some other tasks done in the mean time, but it still killed my pace.

The first thing I did when I got to the hangar was check the elevator travel. I used my digital level and set the elevators to neutral. I then zeroed the level while resting on the elevator. I then put the elevator through its full travel to see if any adjustment would be required for the elevator stops. Yes, adjustment will be required to both the fore and aft stops. Luckily nothing is over, so I only need to file away some of the stops. I will return to this project in the near future and be sure to document it thoroughly.

Next, it was time to turn my attention to the control system. First up is the part for connecting the two control sticks to the elevator and aileron push rods. This needed to be final drilled in several locations. Quick work.

Next, the two bronze bushings had to be sanded down, and shaped to match the taper of the part.

Here you can see that there are two tapers to deal with. The part tapers forward to aft.  

It also tapers top to bottom. The method I used was simple. I clearly marked the top of the bushing and then slowly shaped and shorted the part as appropriate using the scotchbrite wheel. I took my time going back and forth to check on progress. When it got really close, I would mark the high and low points with the pen for minor adjustments. The result is spot on perfect. The reason you want to do this, is to prevent bending of the bushing under the tension of the bolt. This will prevent binding of the controls.

Here are photos of the bushing for the rear pilot’s stick.   

I did some additional work to the controls. I mounted the rear stick. This requires two measurements. One on the bottom portion of the stick, and one on the stick itself. Van’s tells you to drill them together, but I used a drill press and did them separately. First I did the bottom portion careful to keep 1/2″ and a perpendicular drill. Then I marked the stick itself with a line and made sure the line was centered in the bottom portion. I then taped the two together and drilled on side. Placing a bolt in that side, I match drilled the other side. The result is perfect. Perhaps a little more time that the Van’s method, but I don’t like match drilling circular items with the drill press, particularly when its difficult to see measurements and hold the parts together. This method prevented any error. Unfortunately, it looks like I didn’t take any pictures.

Some of the control columns are bright orange, and other parts are going to be smoke grey. The interior of my plane will have three primary colors. A very dark grey as the primary, and a lighter grey for certain accent parts like the control stick. Very small parts will be done in bright orange. The control rods, which will only barely & rarely be visible are orange. Orange is a good accent color, but if you overdo it, or haphazardly do it, the result will be tacky. Hopefully I get it right.

  

 

Session time: 6.0 hours