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Old Feb 23, 2012, 04:49 AM
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Torque-induced roll w/ HK Tuff Trainer

Hi everyone-

I'm not a beginner in RC, but this is definitely supposed to be a beginner plane so I thought it was appropriate to post here. The plane is the Hobby King Tuff Trainer, an EPP 4 channel trainer. The elevator and rudder move quite slowly due to poorly routed (lots of friction) control rods. The ailerons are fine (not much force needed to move them).

Problem: During any significant throttle (<10% or so), the plane rolls very hard to the right. So hard that at about 25% throttle or greater, I cannot make a lefthand roll at all. At 80% throttle the thing basically does a barrel roll nose dive.

If I manage to gain altitude, then kill the throttle completely, the plane behaves very well. Stalls very easily and a bit "see-saw" in nature, but for no-power it's ok.

The plan has a large amount of downthrust "built in" (the motor and mount comes fully installed). I dont think this is a mistake, as the angle is clearly molded into the foam. Also, I dont see why downthrust would have the rolling effect. Most importantly, it doesnt appear to have any left/right bias.

I am considering putting in some washers behind one side or another of the motor screws to give it some left thrust. But I thought motors were supposed to have RIGHT thrust to compensate!?!

Any advice is appreciated...as always...
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Old Feb 23, 2012, 05:23 AM
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First give it a really good eye-ball for any warps, twists etc. That include both the wing and the fuselage and tail, sometimes foamie models can get 'bent' in transit.

If it look good, next time you fly, climb highish, cut the throttle and glide. Get the nose down slightly to build up a little speed and see if it still wants to turn on it's own, and whether the controls seem equal for lefts and rights. That's to check out the models aerodynamics.

If it glides Ok, then it probably is a motor trust line problem.

Usually there should be some right thrust showing. Hold the model vertical, nose up, the prop should look like it's pointing to the right a bit. I wouldn't have thought the motor and prop size was enough to give that much torque effect.

Sorting the controls out so they all work smoothly is well worth the effort, it reduces the load and current on the servos and BEC just for a start.

Here's a thread on that model, though you may have seen it - Hobbyking Tuff Trainer
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Old Feb 23, 2012, 06:47 AM
fmw
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Torque roll works in the opposite direction. It causes the plane to roll left, not right. Try the washers. Also check the trim.
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Old Feb 27, 2012, 06:15 PM
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Wouldn't adding washers only change the yaw of the plane? I know it's common to tilt the motor to the right, though I don't understand why this would help the plane from rolling. Seems like it would only affect the yaw-rotation, not the roll.

By the way, I checked trims again, totally neutral. During flight, I end up maxing out the trims as far to the left as possible. : (

I suppose I need to try the washers next!
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Old Mar 03, 2012, 09:11 PM
DJO
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Check to make sure the wing is centered. I glued the wing down instead of the elastics. How many elastic bands are you using?
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Old Mar 06, 2012, 03:18 AM
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roll and general poor performance tuff trainer

I bought one of these and had exactly the same trouble - on takeoff it would roll to the right. Only rarely could I get a decent flight out of it. Finally concluded the wings with ailerons fitted were not up to scratch. Previous users without ailerons (3 channel version) did not report similar problems. I swapped the wing for a non aileron version - similar wingspan but more lift - from an ezi flyer I think - gt it at the hobby shop for $15 - the problems went away. I suspect the wing is just flopping about too much when in flight causing erratic trouble.
Fit a 3 channel wing from another trainer and it is a beaut plane - I just do not think it was designed from the ground up to be a 4 channel plane
good luck
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Old Mar 06, 2012, 07:03 AM
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Doug: looking down from the top and from the back, as sitting in the cockpit, the motor should be a little to the right. You say when flying, the trims are all the way to the left to fly straight. You should readjust the linkages on the surfaces so the trimmers on the trans are back to the neutral position. If they're to the left with power off, it's a warp problem. If it turns right with power on, put washers under the right side of the motor.

Gord.
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Old Mar 15, 2012, 11:04 AM
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Hmmm....all very interesting. I've put some washers under the left side to tilt the motor right--we'll give it a test flight tomorrow and see how it goes.

Phil--what plane exactly did you take the wing from? An ezi flyer?

Thanks
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Old Mar 15, 2012, 05:01 PM
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Don't do too much, there is such a thing as too much. I know!
Don
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Old Mar 31, 2012, 03:43 AM
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Quote:
Originally Posted by doughpat View Post
Hmmm....all very interesting. I've put some washers under the left side to tilt the motor right--we'll give it a test flight tomorrow and see how it goes.

Phil--what plane exactly did you take the wing from? An ezi flyer?

Thanks
For the person who wanted to know what wing I fitted it was the Electrafun wing - about 40 inches. If you just add that wing to the tuff trainer, glue it on (I do not like rubber bands) and consider it a 3 channel beginners plane it is beaut - very stable, easy to fly and glides pretty well too - ideal for a beginner. I am convinced the 4 channel version of this plane is not well engineered
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Old Mar 31, 2012, 08:50 AM
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Now that I think about it, I thought that I just had to trim out the plane to get it to fly straight... but that wasn't the case. I didn't even notice at the time that it always went to the right except for when I did this flight.

http://www.youtube.com/watch?v=2c7P3hCJT6Y

Dan
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Old Mar 31, 2012, 07:32 PM
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Quote:
Originally Posted by doughpat View Post
Hi everyone-

I'm not a beginner in RC, but this is definitely supposed to be a beginner plane so I thought it was appropriate to post here. The plane is the Hobby King Tuff Trainer, an EPP 4 channel trainer. The elevator and rudder move quite slowly due to poorly routed (lots of friction) control rods. The ailerons are fine (not much force needed to move them).

Problem: During any significant throttle (<10% or so), the plane rolls very hard to the right. So hard that at about 25% throttle or greater, I cannot make a lefthand roll at all. At 80% throttle the thing basically does a barrel roll nose dive.

If I manage to gain altitude, then kill the throttle completely, the plane behaves very well. Stalls very easily and a bit "see-saw" in nature, but for no-power it's ok.

The plan has a large amount of downthrust "built in" (the motor and mount comes fully installed). I dont think this is a mistake, as the angle is clearly molded into the foam. Also, I dont see why downthrust would have the rolling effect. Most importantly, it doesnt appear to have any left/right bias.

I am considering putting in some washers behind one side or another of the motor screws to give it some left thrust. But I thought motors were supposed to have RIGHT thrust to compensate!?!

Any advice is appreciated...as always...
If the plane stalls easily and see-saws when gliding with no throttle ( and no wind ) it's tail heavy and you should move the battery forward or add weight to the nose .
If you've ruled out warped wings etc. , then check how much built in RIGHT thrust there is - it might be too much , and you'll need to decrease it .
Another remote possibility is that your transmitter has right aileron or right rudder mixed in . If that mix is set up whenever you increase throttle the transmitter mixes in right aileron or rudder .
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Old Apr 01, 2012, 07:18 AM
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WOW that's some take off !!

SLOW down !! that's a take off that is way way too fast and no chance for you to have control of her.
She's banged of to right before you can say Holy S*** ...

With that much power and speed - she may have too much right thrust on motor, but there's something else ... maybe a warped rudder ? A warped or insecure aileron ?

My Cessna when the ailerons were as out of box - one aileron had 2mm vertical movement via the tape ... useless ! If I'd tried to fly - that would have fluttered and that side of wing been affected ..

I would a) balance plane across as well as fore-aft (you could brung CoG forward a touch actually to calm that ballistic attitude it has !)
b) Check all surfaces are secure, no slop or tape loose .. c) Maybe even give a few clicks left aileron before flight ...... or a few clicks left rudder ? d) are you sure elevator halves are ok ?
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Old Apr 01, 2012, 10:07 AM
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I sure do agree! Apply the power is a linear manner, slowly add it. If you think your trim is OK, solentlife and I may agree on this ... look at the rudder trim. You never mentioned that. GL
Don

edit: slow down also. And find a place without so many tall things! Light poles and trees will get you!
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Old Apr 01, 2012, 04:05 PM
DJO
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I don't even have that plane anymore, it did that exact same motion in the air - "death spiral" into a very tall tree. I was able to hear the motor running, but could never see the plane.
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