Over Sensitive Rudder

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Kyle Boatright, Jun 12, 2018.

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  1. Jun 16, 2018 #21

    Sockmonkey

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    Probably not directly. I think you just have to change the length of the control arms to fix the ratio.
    You might be able to get some damping by lengthening the arm the tail counterweight is on. Would that cause issues of it's own though?
     
  2. Jun 16, 2018 #22

    Dan Thomas

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    As with Pop's F-12, my Jodel's rudder is extremely sensitive and powerful. I think that the pilot who did that report onthe BD-4 might have had a lot of 172 experience and not much else. Just about any homebuilt would feel too sensitive to someone like that. A 172 barely has a rudder. The 150's is more powerful, and that's not saying much. The old Champs and Citabrias are way more powerful.
     
  3. Jun 16, 2018 #23

    Dan Thomas

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    The shimmy damper on the Cessna does not come into play in flight. There's a centering cam on the nosegear that locks it straight ahead once it's at full extension (no load on it), and there are spring bungees between the rudder bars and the nosegear steering collar that allow full and rapid rudder movement anytime, on the ground or off it. Those bungees are what make the steering so sloppy on the ground.
     
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  4. Jun 16, 2018 #24

    Kyle Boatright

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    Paul Dye did the flight report. He has 3 RV's and I assume, a fair number of hours in those and other experimentals in his role at Kitplanes.
     
  5. Jun 16, 2018 #25

    Pops

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    I have flown a RV-4 but not a RV-3, and the rudder on the F-12 was at least 30-40% more effective than the RV-4. The ailerons after I installed gap seals were as effective as the RV-4, but slightly heavier. Elevator about the same. The F-12 would spin ether direction very easy and out very easy. Could come out from a spin with in about 15-20 degs to the desired heading. Easy in and easy out. Everyone that flew it love it, but also had something to say about getting used to the rudder.
     
  6. Jun 16, 2018 #26

    BBerson

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    Right. But I think those springs damp the pedal motion a bit.
     
  7. Jun 17, 2018 #27

    Turd Ferguson

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    I would think at least 50% of the BD-4's built have a tailwheel landing gear configuration which means they have springs in the rudder loop.

    The steering tubes on a Cessna function as a return spring for the rudder when in flight. The nosewheel versions of a BD-4 undoubtedly have return springs in the rudder loop? I don't know enough about the design to know. Maybe this particular one that was labeled as having an "oversensitive rudder" did not?

    I think before making a claim that all BD-4's have an oversensitive rudder the details should be clarified. Perhaps Kitplanes should have limited the statement to this particular airplane unless they verified everything was built exactly to plans?
     
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  8. Jun 17, 2018 #28

    Kyle Boatright

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    They would have to create a disclaimer bigger than the article itself if they disclaim every objective or subjective observation. And nowhere was it written that all BD 4's have over sensitive rudders.

    Can we move the thread towards what the OP (me) was after - how to reduce rudder sensitivity?
     
  9. Jun 17, 2018 #29

    BBerson

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    Why was it sensitive?
    One thought. I remember Jim Bede wrote that the controls should be made thicker than the stabilizer for less drag. Did this BD-4 have this?
     
    Last edited: Jun 17, 2018
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  10. Jun 17, 2018 #30

    BJC

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    If rudder rebuild were an option, changing the rudder plan view section from either straight or convex to slightly concave would increase rudder deflection forces. The change would be less at lower speeds than higher speeds.


    BJC
     
  11. Jun 18, 2018 #31

    Dan Thomas

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    "Damping" involves rate control, as with a hydraulic shock or damper. The springs don't affect the rate. They just make the rudder pedal forces heavier.
     
  12. Jun 18, 2018 #32

    Rockiedog2

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    Somebody said change the ratios

    yeh we know you can change the ratio but then travel somewhere may become a problem. It's always a tradeoff.

    The rudder on my original design is too sensitive. Or is it?...the ailerons are heavy and slow, or are they? Each may seem that way only in comparison to each other. I've found that after a while we don't notice the "problem". Just fly the thing...now that's an easy fix.
     
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  13. Jun 18, 2018 #33

    BBerson

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    A bigger prop on the front could destabilize the yaw stability and make the rudder seem sensitive.
    Any number of things unrelated to the rudder such as CG might have some effect. I flew a seaplane with sensitive rudder because the owner didn't install the auxilliary vertical stabilizers for the floats. He didn't care.
     
  14. Jun 18, 2018 #34

    Pops

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    Old friend of mine hauled skydivers for a living. Someone make an offer to buy his B-18 that he couldn't refuse then he went plum crazy and bought a Cessna -411. I flew it on a short trip and it was one of the worse airplanes that I have flown and I ask him , " how in the heck can you put up with the way this flys. Like you said, he said , "Guess I have just got used to it".
     
  15. Jun 18, 2018 #35

    TFF

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    I think in general, the heavier the controls the happier the IFR pilot is for real IFR. If you want to fly fun VFR, stay away from the IFR trucks.
     
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  16. Jun 18, 2018 #36

    pictsidhe

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    Since I'm rather short on stick time, my guide to how controls is mil f 8785c. It doesn't seem to mention breakout force. So, what do you guys think is a good target?
     
  17. Jun 18, 2018 #37

    BJC

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    That depends on the airplane and why you are flying it. At one extreme is Sean Tucker’s modified Wolf Pro, with +/- 60 degrees of deflection. At the other is any serious IFR airplane.

    In the Pitts, one’s feet are very active, and I don’t notice any breakout force. But that may just be my feet.


    BJC
     
  18. Jun 18, 2018 #38

    Rockiedog2

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    I didnt notice any either BJC...just think about it and it's over. :)
     
  19. Jun 18, 2018 #39

    Pops

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    True, I always called them dump trucks, and I don't like dump trucks unless flying IFR. I need all the help that I can get :)
     
  20. Jun 18, 2018 #40

    Dan Thomas

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    Not only careless but illegal. The aux stabs or ventral fins are part of the float STC and are required. Cessna had a modification kit to eliminate the ventral fin; it involved a non-linear rudder return spring system that increased breakout forces enormously and improved directional stability while on floats.
     

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