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HomeAircraftHelicopterBeginners Corner › Can't get rid of this wag! HELP!!
09-07-2013 02:23 AM  5 years agoPost 1


South Jersey, NJ

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Howdy... Let me preface by saying I'm pretty much a novice at all this. I built a T-Rex 550 for myself - it was my first helicopter build. I had very minimal problems with it and got it dialed in pretty quickly. Many Flights on it and never had any real issues that I couldn't fix quickly. So my buddy wants to get one and he buys a 450 DFC. I think to myself "Hey, I did pretty well on mine - I must be good at this." (Wrong). I tell him I'll build it for him, which I did. It's all set, pretty much good to go, but for the life of me I can't get rid of a pretty wicked wag in the tail. I've tried everything I can think of to fix it. I've re-built the tail making sure there is absolutely no binding, and everything is nice and centered. I've changed the main rotor blades thinking maybe they were unbalanced or out of whack. I've messed with every setting on the transmitter (gyro settings, servo throw distance, etc.). I've re-set up the flybarless system (3gx) countless times. The wag only happens in one direction, not the other - so if I move the rudder one way, it rotates just fine. However, I move the rudder the other way and it starts wagging. It's so bad that I haven't even flown the thing yet. I've been tinkering with it for a few weeks now and I'm at my wits end. Anyone have any suggestions that I may not have tried? I'm about to destroy my friends new toy out of sheer frustration, which would not end well for me. Thanks in advance!

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09-07-2013 02:30 AM  5 years agoPost 2


Middle Arkansas

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This may sound trivial but just throwing this out there. First disconnect the servo from the linkage and make sure the linkage is silky smooth in both directions. Make sure you don't have a tail blade on backwards. Also check to make sure you don't have a thrust bearing on the wrong way if it has other than radials. Just a couple of things to check.
Spyder Batteries

09-07-2013 02:36 AM  5 years agoPost 3


Brewerton, New York

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Also check for leading edge control or trailing edge control on the tail blades. Check in that manual which way the slider should attach to the grips. Also did you play with the gain?

Bill Whittaker

09-12-2013 01:26 AM  5 years agoPost 4

rrKey Veteran

west seattle

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ws just gonna say maybe the gains too high, if it is turn it down till the wag stops but still holds the tail straight

CAUTION!!! politicians may be hazerdous to your well being

09-15-2013 01:03 AM  5 years agoPost 5

rrElite Veteran


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Head speed... might be too low. Main shaft bearings may be bad. I know they are brand new. Could be the 3GX unit, can you try another?

I am betting on head speed. Play with the throttle and pitch curves.

09-15-2013 11:37 AM  5 years agoPost 6


Geilenkirchen Germany

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Make sure you didn't crush the bearings on the tail spindle when you assembled them.

R.I.P. Roman

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09-15-2013 12:51 PM  5 years agoPost 7

rrKey Veteran

Planet Brooklyn, NY-USA

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How rigid are your tail blades? How far out is the ball on the rudder servo horn? Is the pushrod and pitch slider as smooth as possible? Is there any slop in the tail system whatsoever? Just a few things to look @.


RIP Roman Pirozek Jr.
Team Futaba USA
Team Kontronik USA

09-15-2013 01:24 PM  5 years agoPost 8


Lincoln, NE

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Ive been having the same issue with my pro v2 but a wag in both directions. I found that the outside bearing in the blade grip was coming apart. I replaced the bearing and flew fine the first flight then on the second flight it started doing it again. The new bearing inner race was coming out of the bearing. So i began looking at the screws that hold the grips to the hub and it appears one of the screws might be bent. Anyway, when i had the tail wag problem, the grip that had bearing problems was hard to rotate. Also check for racheting in your blade grip bearings.

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