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Airplanes yaws left uncontrollably when hovering

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Old 06-19-2011, 08:54 PM
  #1
cyborg1
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Default Airplanes yaws left uncontrollably when hovering

Hi,

I just bought a 3dhs extra 330sc and it's powered with a turnigy 5055 580kv motor, 80a esc, turnigy 3000mah 22.2v lipo, and a 14x7 prop. It flies well, very light and responsive, but I have a problem when hovering. The airplane yaws to the left and even full rudder is not enough to stop it from doing so. The rudder throw is maximum according to the recommended setup, but once the plane starts to yaw left, no amount of rudder will bring it back, even when I'm blipping the throttle. Is this a mechanical setup problem or is it something else? I have another sbach 342 57" that exhibits the same tendency...any suggestions would be greatly appreciated. My 3D skills are just at the beginner/intermediate stage.
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Old 06-20-2011, 03:26 AM
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Default RE: Airplanes yaws left uncontrollably when hovering


Quote:
ORIGINAL: cyborg1

Hi,

I just bought a 3dhs extra 330sc and it's powered with a turnigy 5055 580kv motor, 80a esc, turnigy 3000mah 22.2v lipo, and a 14x7 prop. It flies well, very light and responsive, but I have a problem when hovering. The airplane yaws to the left and even full rudder is not enough to stop it from doing so. The rudder throw is maximum according to the recommended setup, but once the plane starts to yaw left, no amount of rudder will bring it back, even when I'm blipping the throttle. Is this a mechanical setup problem or is it something else? I have another sbach 342 57'' that exhibits the same tendency...any suggestions would be greatly appreciated. My 3D skills are just at the beginner/intermediate stage.
cyborg1,

How much right thrust on the motor do you have?
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Old 06-20-2011, 06:28 AM
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Default RE: Airplanes yaws left uncontrollably when hovering

just what it had on the firewall, which is a small amount.
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Old 06-20-2011, 04:38 PM
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Default RE: Airplanes yaws left uncontrollably when hovering

How does it fly inverted? I would set trims and CG to fly hands off for both upright and inverted flight. Then try from there.
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Old 06-20-2011, 05:54 PM
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Default RE: Airplanes yaws left uncontrollably when hovering

are you hovering dead straight into the wind?
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Old 06-20-2011, 06:42 PM
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Default RE: Airplanes yaws left uncontrollably when hovering

yes, I've tried it both ways - into the wind and the other side as well. The same thing happens. It stays straight for a while, then it starts to lean to the left. Even with full rudder deflection, it just keeps going to the left.
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Old 06-21-2011, 10:49 AM
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Default RE: Airplanes yaws left uncontrollably when hovering

As asked in your other thread of the same name, how much total rudder throw do you have? You really need 45 degs or better. KWJ48's question is good, if you are too far forward on the CG it will behave this way. Do a vertical upline with the canopy facing you, wings perpendicular to your line of sight, and see if yaws to the left. If so you need some more right thrust as others have suggested. I have moved the thrust angle in my 50cc Extra and it makes a difference flying but not much when hovering. I've moved it between 0 and 4 degs and when hovering I won't say you can't feel it but it's not difficult to hold in a hover with it at zero or 4 degs. Certainly not enough change as to make it hard to hold. On the 50cc, CG affects it more in a hover than anything else but I do have 48 degs of rudder, 46 degs of elevator, and 39 degs of aileron travel so controlling the tail in a hover isn't an issue with that much throw. In the picture I've posted here the thrust angle is 0-0.
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Old 06-21-2011, 01:05 PM
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Default RE: Airplanes yaws left uncontrollably when hovering

Yep, it shouldn't be a thrust issue. Most of my profiles have 0 degrees of right thrust and hover just fine. Right thrust does help a little. The 3dhs plane should have plenty of r/t built in already, unless something really screwed up at the factory.
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Old 06-21-2011, 05:31 PM
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Default RE: Airplanes yaws left uncontrollably when hovering

do you fly at a club ?

I would let someone eles fly the plane who's decent at 3D


I have the smaller SHP and it doesn't seem to have the same problem .. plus you said your Sbach does the same thing

another club member would help narrow this down I dout it's right thrust 3DHS motor boxes have them built into it stock so maybe if you crashed the plane or really went wrong with the the standoffs it should be dead on
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Old 06-25-2011, 06:37 AM
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Default RE: Airplanes yaws left uncontrollably when hovering

check overall thrust by measuring from the prop tips to a fixed point on the fin to check that the fuse doesn't give it a left thrust
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Old 06-25-2011, 11:20 AM
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Default RE: Airplanes yaws left uncontrollably when hovering

Is the rudder servo the same torque as recommended? Also check the rudder linkage for bending/failure under load.
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Old 06-26-2011, 01:21 PM
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Default RE: Airplanes yaws left uncontrollably when hovering

Thanks for all the suggestions...to date, I have done several things. I've added 2mm shims to increase right thrust, balanced the plane until the CG is neutral which makes it fly straight and level right side up or inverted, and balanced the wings. I have also crossed the pull pull rudder slings as recommended in the manual (which I overlooked). Result? A better flying plane but still with tendencies to yaw left when hovering. Rudder input is better now, but it still doesn't respond as good as my Katana .46. Is there anything else that I'm missing out on?
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Old 04-17-2012, 01:05 AM
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Default RE: Airplanes yaws left uncontrollably when hovering

try a smaller prop, have you a video?????

http://www.youtube.com/watch?v=GTtxStJJyFI
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