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Biplane rolls violently left on takeoff

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Biplane rolls violently left on takeoff

Old 10-02-2003, 03:53 AM
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cosmospho
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Default Biplane rolls violently left on takeoff

I have a Bipe .46 and on my first takeoff the plane rolled violently to the left, managed to land it and since I'm not a builder I am wondering what happened. I also tried removing the top wing and flying with the bottom wing only but then it needs much more elevator to take off and nearly enters a spin to the left again. I have to apply nearly all aileron control to the left to keep it flying straight and haven't been able to roll right yet.

Any clues as to what is happening with the bipe and what can be done ?
Old 10-02-2003, 06:13 AM
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Default RE: Biplane rolls violently left on takeoff

cosmospho,

You will get much more expert opinion here than I can offer, but ...

Have you checked the wing incidences? Bipes must have these well in harmony or flight is tough at best. There is much debate on the relative incidence between top and bottom wing, but that is not your problem, yet.

Apart from this, you may be taking off too early, without enough airspeed. A hard roll left will occur when doing so.

Good luck! Let us know how you solve the problem.

Bedford
Old 10-02-2003, 08:27 AM
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Flypaper 2
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Default RE: Biplane rolls violently left on takeoff

If you neen full right aileron to fly straight, sounds like the wing may be warped. Looking at the plane from the rear, level it so you can just see the bottom of the wings. Should be obvious if one panel is lower than the rest. If you take off the top wing, will become very nose heavy and half the wing area. If a panel is warped, may be able to take it out with a heatgun. Engine should have a bit of right thrust, looking at it from the top. Let us know what you find.
Old 10-02-2003, 09:39 AM
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LesUyeda
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Default RE: Biplane rolls violently left on takeoff

Sounds like in the "biplane" configuration, there was not enough air speed at take off, and the engine torque turned the plane over. This is typical. Extend the ground roll until there is enough air flow over the flying surfaces for control.

Les
Old 10-02-2003, 09:46 AM
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cosmospho
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Default RE: Biplane rolls violently left on takeoff

Ok guys the low speed probability at take-off is totally out of the question since it took off and flew quite high, only i had to keep my TX totally left, killed the engine and glided it in making a circle since i almost couldn't fly straight. I am betting on the warped wings but how would I go about straightening, and making sure the wings are straight ? Trial and error ?

Thanks
Paulo Poinha
Old 10-02-2003, 10:16 AM
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David Cutler
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Default RE: Biplane rolls violently left on takeoff

I also tried removing the top wing and flying with the bottom wing only but then it needs much more elevator to take off and nearly enters a spin to the left again.
?

You could try taking both wings off and see if that helps!

No, seriously though, it sounds like a warped wing.

-David C.
Old 10-02-2003, 12:21 PM
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Default RE: Biplane rolls violently left on takeoff

Paulo:
You said it rolled to the left, but took left aileron to fly straight. Probably just a brainfart. But if you want to check incidence without an incidence meter, stick a pin in the leading edge of the wing in the furthest forward part of the curve of the wing. Stick a pin in the trailing edge opposite the one in the leading edge. Do this in all four corners of each wing panel. Prop the tailwheel up till the pins, front and back at the root of the wing measure the same height from the table. When you measure at the tip, front and back pins should be the same height from the table. Hope this is understandable. This is how we did it before incident meters were ivented.
Old 10-03-2003, 09:38 AM
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LesUyeda
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Default RE: Biplane rolls violently left on takeoff

If it is a flat bottom wing, you can rubber band a long dowel chordwise along each wing tip, and eyeball to see if the dowels are in the same plane. If it is not a flat bottom wing you could make some standoffs to glue the dowels to, and do the same thing.

Les
Old 10-03-2003, 09:56 AM
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Default RE: Biplane rolls violently left on takeoff

Forgive me if this is too simple, but did you clear out any mixing from your transmitter before you set up this biplane? I only ask because this happened to me, once and it took a long time to figure out that the model was OK but the tx mixing wasn't!
Old 10-03-2003, 10:04 AM
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cosmospho
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Default RE: Biplane rolls violently left on takeoff

Yeah I checked the TX and no mixing was activated ! Here is a pic of the plane for you guys to check it out !!! I'm gonna spend the weekend checking the wings and maybe if the weather allows it I will fly next weekend since its winter and it rains all the time.

regards
Paulo Poinha
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Old 10-03-2003, 11:12 AM
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Default RE: Biplane rolls violently left on takeoff

Nice job Paulo. What is the plane called? Let us know how you make out.
Old 10-03-2003, 04:54 PM
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Default RE: Biplane rolls violently left on takeoff

Sounds like it may be a wing warp. If one or both of the wings is warped to the right, the left wing(s) will tend to stall first at low airspeed, and the increased drag on the left side will tend to turn the model left. At higher speed and lower lift coefficients, the model will tend to roll in the direction of the warp, requiring left aileron to hold it level.
Old 06-14-2005, 09:24 AM
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Default RE: Biplane rolls violently left on takeoff

[8D]Some stuff to check, as though you dont have enough already, (some times the simple things are the one's we overlook, and they come back to bite us in the @$$%$%) These are a few I've had issue with in the past.

Lateral balance. Check the plane by putting one finger under the prop hub, and one under the rudder fin and see if it dips to one side or the other more than it should. Easiest solution is to put a small amount of weight on the opposite wing tip if it drops one way or the other.


As mentioned above, be sure to get ALOT of taxi run in so the plane won't snap on pull off. (I dont think this is your problem).

Depending on your plane weight and engine size, you could have torque issues at play here. Adding right thrust to the engine will cancel out its innate desire to turn left on an aircraft with a horsey engine.

Pre flight your controls and be sure the left aileron goes UP when you turn left, and vice versa for the right. Seems stupid, but a lot of people including myself have made this error in a haste to get airborne. Hence, you tell the plane to go right, and it goes left even MORE!!

And do what the guys mentioned before and check to besure your wings aren't severely warped. If you run through all of these, you'll probably find the problem.

Good Luck!!!

ZZ.


Old 06-14-2005, 12:10 PM
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Rodney
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Default RE: Biplane rolls violently left on takeoff

Most probably a warped wing, this should be quite evident if you look at the plane from the aft end and see if both left and right wing panels give you the same view. Also, make sure you have about 3 degrees of right thrust and probably about 3 degrees of down thrust.
Old 06-14-2005, 11:51 PM
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Default RE: Biplane rolls violently left on takeoff

Check that you haven't got aileron/rudder mixing turned on. If this mixing is on and mixing in the wrong direction then it will cause your symtoms.
Old 06-15-2005, 09:32 AM
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Villa
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Default RE: Biplane rolls violently left on takeoff

I have a similar size biplane with an OS 46. It is balanced a little more tail heavy than I prefer, but I manage OK since I hate to add any more weight to the nose. I believe because of this tail heavy condition it is a handfull to handle on takeoff. Wants to track left hard, and if lift off is early it will be a handfull till air speed builds up. If I have not flown it for a while I have to concentrate exceptinally hard on the first takeoff. Once in the air everything is fine. Very, very aecrobatic due to the slight tail heavy condition. Check you CG and settle for more nose heavy.
Old 06-16-2005, 10:33 AM
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Default RE: Biplane rolls violently left on takeoff

[8D]Very good point Villa. That could definately cause some of these symptoms, and it is often overlooked. So you like flying your bird tailheavy!? You just lookin for an extra adrenaline rush or something!!?? haha.

ZZ.

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