Rudder Alignment for Rigging

[Glenn Patterson]

This may seem like a dumb question but I did not see it anywhere. When installing the rudder cables where is the rudder position in the process? Is the rudder aligned with the centerline of the fuselage or is the top aligned with the top of the vertical stabilizer following the fin's offset line?
We have a difference of opinion and it would be good to have the alignment correct from the outset.
Thank you all in advance.

Glenn
BH727

[JakeP]

The rudder is aligned with the vertical stabilizer. One flat plane from the leading edge of the stabilizer, through the two spars, to the trailing edge of the rudder. Flat. Straight. If the stabilizer is offset, then the rudder is offset along with it in one flat vertical plane.

[edit] I "get" the argument though. With the vertical stabilizer offset to the left, aerodynamic pressure will always push back on the right pedal, so naturally you'd want to leave the right pedal loose to "flop in the breeze", so to speak. However, my attitude is: 1) can you really tell that small absolute difference off neutral with your clubby ankles/feet/toes? 2) if you can tell the difference, wouldn't you want to know what center actually was? You should be naturally kicking/leaning a little right anyway, right? So if your foot is resting a little heavy on the right rudder, that would be correct. So I say rig the rudder in-line with itself, as it was designed.

[edit 2] This is a good question by the way! I am interested in others views on this too.

[Glenn Patterson]

You are correct as there is very difference at the rudder horn and pedals between the two positions. Thank you.
Glenn

[Zzz]

Glad to see this topic come up. I had originally planned to just use the hard stop as my reference for cable length, i.e. left pedal forward to its stop, rudder full left, and adjust the length of the cable to that position, taught. Repeat for the right side pedal.

Doing it this way though will center the rudder by travel, not necessarily by a position that is aligned with the vertical stab. So we're agreeing that aligned with the vertical stab is the correct neutral position?

[alaskabearhawk]

On page one of the plans it has 30 degrees left/right for the rudder. The top of my vertical stab is just about aligned with the centerline and transitions from there to the 3/4 offset at the bottom. I did that on purpose because I have the airfoil-shaped ribs on the vertical stab and will provide more lift in that direction.

[Glenn Patterson]

We set the cables up aligned with the fin. One side just touches and the other side not quite. We are okay with as the cables will likely stretch some with time. We compared rudder angles on other airplanes at the flying club and the Bearhawk is generous at 30 degrees so missing a couple degrees is not worrying us.
Glenn

[mswain]

On page one of the plans it has 30 degrees left/right for the rudder. The top of my vertical stab is just about aligned with the centerline and transitions from there to the 3/4 offset at the bottom. I did that on purpose because I have the airfoil-shaped ribs on the vertical stab and will provide more lift in that direction.

Did you do anything different on the horiz. stab due to using airfoil ribs? ie. Can you take out a degree or two of negative angle?

[alaskabearhawk]

I took a degree out, so it's a neg 3 degrees per Bob B. I can possibly go to a neg 2 after flying it. If I remember right, Pat Fagan tried a neg 2 and went back to a neg 3 after he rebuilt his tail feathers. Here's the kitlog post and you can also look at entry 8 and 9 for a bit more info.

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=7248&log=166979&row=45

[mswain]

I took a degree out, so it's a neg 3 degrees per Bob B. I can possibly go to a neg 2 after flying it. If I remember right, Pat Fagan tried a neg 2 and went back to a neg 3 after he rebuilt his tail feathers. Here's the kitlog post and you can also look at entry 8 and 9 for a bit more info.

http://www.mykitlog.com/users/displa...=166979&row=45

thks, good info.

[Glenn Patterson]

We installed the airfoil ribs on the horizontal only & set it at 3 degrees to start as well. We had read that Pat went to 2 degrees and was content there so we were going to edge up to 2 degrees. Our intent was to start flying at 3. We were not aware that Pat returned to 3 degrees. I tried to find a thread on his stabilizer but no luck with this forum.
Thanks for the follow up.
Paul. I was looking at your floats on kitlog & was wondering what are the floats that you are installing?
Thanks,
Glenn

[alaskabearhawk]

I'm putting on a set of EDO 2870s. I thought he did go back to 3 degrees, but I could be mistaken. I'll check my archives...

[Glenn Patterson]

Paul,
Thanks. We were thinking 2870's as well. If you find it in you archives that would help. I squirrel away tons of info but did not file that conversation.
Glenn

[alaskabearhawk]

Hey Glenn...here's an excerpt from an email Pat sent June 2013:

"I made several flights with minimum weight and max forward CG to max gross and max aft CG and experimented with changing the tail plane incidence. Plans call for -4 degrees and Bob felt it could be set at -3 with the profiled tail surfaces. I made flights at the extremes with the tail plane set at -3 and -2 and have seen no difference in handling or controlability. I am going to leave the tail at -2. Even before making those changes the plane appeared to be faster than it was."

So he did leave it at -2 after all.

[Glenn Patterson]

Paul,
Thank you. That was my memory with one of Pat's postings once he was airborne again but one never knows if they missed a posting. I will clip this as well. I think that the airfoil tail and -2 degrees would be quicker. Down angle is like dragging a plow. Thanks again.
Glenn

[Mark Goldberg]

I might suggest you guys start with -3 degrees on the hor stabs for first flights. Then experiment with -2 degrees later. Mark

[Battson]

I might suggest you guys start with -3 degrees on the hor stabs for first flights. Then experiment with -2 degrees later. Mark

Having been there and done that, I agree with Mark. Incidence at -3 is a good starting point for the aerofoil h-stab, and needs no modifications for the standard kit.

[Battson]

Glad to see this topic come up. I had originally planned to just use the hard stop as my reference for cable length, i.e. left pedal forward to its stop, rudder full left, and adjust the length of the cable to that position, taught. Repeat for the right side pedal.

Doing it this way though will center the rudder by travel, not necessarily by a position that is aligned with the vertical stab. So we're agreeing that aligned with the vertical stab is the correct neutral position?

I aligned with the vertical stab when the pedals are neutral, but that didn't work out exactly, I needed a small trim tab on the rudder. BUT, that doesn't align it with the axis of travel of the aircraft, it's still largely offset, just not quite so large as the the vertical stabilizer's native angle.