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Other › Tail Rotor Setup: lead vs lag control
08-30-2013 04:54 PM  5 years agoPost 1
Santiago P

rrProfessor

South West, Ohio

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Since the 1st build and for over a year I have been using trailing control method on the tail with absolute excelent results,

No tail blowouts even in super fast funnels, or sideways loops, and no vibrations.

Recently I had to rebuild the tail at the Jamboree and used lead control on the grips.

Results were quite interesting. With the control on the lead side I noticed with the pitch slider at the center of the travel the tail blades incidence was to favor the torque instead of countering it. Also at the pitch slider limits I had much more left instead of right.
I did not make much of it, just readjusted the tail pushrod, and servo to have the right incidence for tail and to the air we went.

Once I started flying hard I started experiencing constant tail blowouts. Never before I had this out of my Diabolo, specially with radix 110mm blades and turning 2K on the head.

I when home and decided to dig more into why is this happening. Measure the tail travel with a pitch gage to see why there seem to be a bias with respect to the geometry.

I laid the sucker sideways, placed the tail blades 90 degrees to the tail boom, and zero the pitch gage:

So here it is in trailing mode


Neutral Stick

Full left stick

Full right stick

With the tail arm at 90 degrees, trailing tail control, and pitch slider in the middle you get perfect geometry for tail compensation.
The numbers simply reverse for leading tail control.

It is my PERSONNAL recommendation that you setup your tail this way IF you are having any issues with the tail holding if you are using lead control.

Santiago

Team Minicopter - PeakAircraft.com
bavarianDEMON- Team Kontronik - Scorpion Motors-

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09-01-2013 05:08 AM  5 years agoPost 2
Magneto 3D

rrNovice

Boston MA.

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Sounds Good Santiago!! I had some blow outs but they were from a vibe I had that is fixed now but a smoother tail sounds attractive ill give it a try Thanks!!

Team Kontronik Germany

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09-01-2013 10:01 AM  5 years agoPost 3
hndaluvr

rrNovice

Delaware

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Very interesting... fore the manual shows that it should be assembled "leading edge".
I've built my Diab per the manual... and flying Vbar.
I've adjusted my control rod to provide me with equal throw (along the length of the tail shaft... results in more counter-torque pitch than with-torque pitch) in both directions (not sure of the actual blade pitch, 'cause i don't own one of those new RCLogger kits) but my tail has ALWAYS been rock-solid regardless of head speed.
Theoretically, regardless of leading or trailing connection, the blade grip ball is centered on center of the blade (pitch-wise)... so pitch-leading should be the same as pitch-trailing correct? The only factor that would make a difference is if the control rod was adjusted differently with each setup.

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09-01-2013 03:02 PM  5 years agoPost 4
KevinB

rrKey Veteran

Earth

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The trex450 Pro is the same way. With leading edge connection to the tail grips (as per the manual), centered pitch slider results in approx. 0 degrees and you have excess "with torque" pitch and not enough "counter torque" pitch. Flip the grips and with a centered pitch slider, you have approx. 5-10 degrees of counter torque pitch with equal movement in either direction.

Your tail may still hold well, but try doing left and right piros while in mid to fast forward flight and you will see if you have enough tail pitch in each direction. If not close, you will get an outright stall in the piro and your heli will stop at approx. 90 degrees to the direction of flight even though you are still holding the stick left/right. If you have almost enough tail authority, it will continue the piro but you will get a whipping action (uneven piro rate) as it goes around.

On my Embla, I actually needed to grind out the back of the tail hub a little as it didn't have enough "with torque" pitch to maintain a constant rate left piro in fast forward flight. Now it does .

KevinB

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09-02-2013 02:19 AM  5 years agoPost 5
Santiago P

rrProfessor

South West, Ohio

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Theoretically, regardless of leading or trailing connection, the blade grip ball is centered on center of the blade (pitch-wise)... so pitch-leading should be the same as pitch-trailing correct? The only factor that would make a difference is if the control rod was adjusted differently with each setup.
But is not

Disconnect the pushrod, move the slider to the ends of its travel, and measure the angles.

Unless you shorten (cut) the ball links going to the tail grips on the lead side you will get more travel in favor of torque than to counter it.

===============================================================

If your tail is build per manual and you are not experiencing any blow outs, then please disregard my entire post.

but if you are getting tail blow outs then you should try this.

S

Team Minicopter - PeakAircraft.com
bavarianDEMON- Team Kontronik - Scorpion Motors-

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09-02-2013 02:18 PM  5 years agoPost 6
hndaluvr

rrNovice

Delaware

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<If your tail is build per manual and you are not experiencing any blow outs, then please disregard my entire post.

but if you are getting tail blow outs then you should try this.>

----------------------------------------------------------------

Good advice!

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02-20-2014 06:32 PM  4 years agoPost 7
ymuraki

rrApprentice

Tampa, FL

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Santiago,
My tail blow out on cross wind with 95mm blades.
I went back to gyro setup and found your point right side rudder is not enough.

I shortened ball links at tail blade grip about 2mm. That will give more right rudder command without dealing with reversing all kind of things. (As you said.)

Futaba/Hobbico
Morgan Fuel
Peak Aircraft
Kontronik

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02-20-2014 07:10 PM  4 years agoPost 8
Santiago P

rrProfessor

South West, Ohio

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I shortened ball links at tail blade grip about 2mm
YES!
That's the other way of doing it, and actually better than going to the trailing side.

I know YOU are an oustanding craftsman, but for others who may try this method, use a pitch gage to verify the pitch on both tail blades is even after cutting the links.

Great finding Nob, THANKS!

Santiago

Team Minicopter - PeakAircraft.com
bavarianDEMON- Team Kontronik - Scorpion Motors-

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