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Need some tail rotor setup help for my XL CDE

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Need some tail rotor setup help for my XL CDE

Old 11-29-2006, 10:42 PM
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Default Need some tail rotor setup help for my XL CDE

I am pretty much finished with my build and have run into a snag that is not really covered in the manual. I noticed that my tail does not have as much pitch (travel) on right rudder deflection. I centered the servo arm several times with no luck. Can anyone give me a sure fire way to set up the tail? Also, the manual does not give any mention as to how much pitch should be present on the tail rotor. I have searched on here and have also watched "the videos" as well. I want to make sure I have the correct amount of travel on the tail before I fly it for the first time.
Thanks in advance for the help!
Rob
Old 12-01-2006, 01:17 AM
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Default RE: Need some tail rotor setup help for my XL CDE

You won't have much pitch travel to the right on the tail rotor pitch slider. I was worried about this too but it's OK. You should set the tail servo's neutral position (and the pitch slider) so that you need no trim to keep the nose straight with the gyro in SR mode in a normal hover. This will set the tail rotor pitch slightly right of neutral, and it will look like there is a lot less travel to the right than to the left for the tail pitch slider.
This is normal. In flight the gyro takes care of yaw rates in SR mode and should lock the heading in HH mode with no trim (well, as the battery decays you might need some right rudder trim, but very little if the system is set up right.)
You will get even yaw rates to both sides.
Old 12-01-2006, 01:47 AM
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Default RE: Need some tail rotor setup help for my XL CDE

I tried to take a picture for you but camera is out of batteries. But I measured it--from the pitch slider to the tail rotor hub there's about 3 mm shaft showing. On the other side, from the slider to the tail case bearing, there's about 7 mm. Servo arm is centered. This is neutral for me--the tail blade is pitched a couple degrees to thrust the tail left (nose right) and I can hover in Normal flight mode with zero trim. The yaw rate is snappy and equal in both directions when I push the left stick, and in HH mode the nose holds like it was on a rail, even with the roughest collective inputs.
I thought it looked strange too but at 10,000 rpm you don't need much pitch to be effective.
Which hole in the servo arm you use depends on the gyro and the servo. Use the closest one to the servo that you can use and still get tail-twitch behavior. That is, if you cannot make the tail twitch by setting the gyro gain too high, then you need to move out one hole on the servo arm and try again.
Old 12-01-2006, 08:24 AM
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Default RE: Need some tail rotor setup help for my XL CDE

Thanks for the help! Now it makes sense...
Coming from a Blade CP, this is a lot more complicated. I just wanted to make sure that everything was correct before I got it in the air.
Rob
Old 12-01-2006, 08:45 AM
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Default RE: Need some tail rotor setup help for my XL CDE

I just noticed another thing--on the standard TRex setup the tail blade pitch links are rigged on the leading edge of the blades/grips, while on the MX400PRO/MX450 they are set up on the trailing edge. I think this will make a difference in the "Left-Right" relationship--in other words, the pitch slider travel to the right will make your tail blades pitch the opposite way, depending on the way you have your pitch links rigged.
When I put the TREX tail rotor assembly on my MX400PRO I rigged it like the original. I don't think it makes any aerodynamic difference. Maybe someone with more experience can comment on this.
Regardless, the tail will move away from the direction of the trailing edge of the tail rotor blades. That is, if the TE is to the right of zero, the tail will want to move left, and vice versa.

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