Do you guys employ aileron differential on your 3D airframes? If so, why? The reason i'm asking is that I was in a heated debate with a friend and fellow flyer today. I'm definitely no aerodynamicist but I just don't see a need for differential on a plane that spends most of it's life in a stalled state.

The need for differential is determined not when the plane is in 3D (stalled or semi-stalled) mode, but when the plane is actually flying on the wing. If the wing has a tendency to "walk" when doing an aileron roll, resulting in a sort of cork screw effect versus an axial roll, then differential is probably needed to correct this. This should be corrected for even if the plane is going to be used for mostly 3D style flying.

[QUOTE=columbo;2005211]The need for differential is determined not when the plane is in 3D (stalled or semi-stalled) mode, but when the plane is actually flying on the wing. If the wing has a tendency to "walk" when doing an aileron roll, resulting in a sort of cork screw effect versus an axial roll, then differential is probably needed to correct this. This should be corrected for even if the plane is going to be used for mostly 3D style flying.[/QUOTE

That makes perfect sense although I was led to believe that the symmetrical airfoil of a 3D flyer, in theory compensated for that effect based on the speed at which 3D maneuvers are executed, is that true?

That is a straight forward answer. Nothing to add to that.

A symmetrical wingl will create lift when the aileron is down because the wing then has a camber. The drag of the aileron is created not by the aileron resisting the air, but because of the lift it generates, and it does so because by being down, it creates a camber in the wing surface making the profile semi-symmetrical.

Also, 3D has a different meaning now and has become more of an extreme aerobatic freestyle than what it was a few years ago, which was a lot of hovering. There are probably 60 maneuvers that I know of that are considered part of the 3D repertoire, and seems to grow every week. I'm still working on the first dozen.

Originally Posted by Aeroplayin

A symmetrical wingl will create lift when the aileron is down because the wing then has a camber. The drag of the aileron is created not by the aileron resisting the air, but because of the lift it generates, and it does so because by being down, it creates a camber in the wing surface making the profile semi-symmetrical.

Also, 3D has a different meaning now and has become more of an extreme aerobatic freestyle than what it was a few years ago, which was a lot of hovering. There are probably 60 maneuvers that I know of that are considered part of the 3D repertoire, and seems to grow every week. I'm still working on the first dozen.

Hence my confusion. A wing doesn't know whether or not it's upside down. so on a full symmetrical airfoil, wouldn't the amount of lift generated by an equal aileron deflection be equal on both wings? Does the wing's incidence change that?

Originally Posted by mizm75

wouldn't the amount of lift generated by an equal aileron deflection be equal on both wings? Does the wing's incidence change that?

No. If both ailerons move by equal amounts, the downward deflecting aileron creates more drag and lift than the upward deflecting one creating what's called adverse yaw. Hence the need for differential.

in an aerobatic plane... Aileron differential is used to firstly negate the slight positive incidence between the wing and tail all planes need to be stable....

Secondly it is used to try and tune out other minor peculiarities that might exist.....

But generally speaking... a truly Pitch-Neutral plane with symmetry should not need differential

As per the original question. Yes, I generally always use differential whether its a "3D plane" or not. Why? Because I'm never flying 100% "3D" and I don't think anyone really is. Unless you never do any sort of axial roll (which are a part of a lot of 3D maneuvers anyway) you can benefit from it. It doesn't hurt to set it up either way.

Originally Posted by columbo

No. If both ailerons move by equal amounts, the downward deflecting aileron creates more drag and lift than the upward deflecting one creating what's called adverse yaw. Hence the need for differential.

+1

You are looking at lift vs drag when playing with aileron differential.

You'll have to experiment with your programming, determine what works best for your style of flying and your airframe's tendencies.

Of course I assumed you have you geometry set correct to begin with.

Jeff

Originally Posted by columbo

No. If both ailerons move by equal amounts, the downward deflecting aileron creates more drag and lift than the upward deflecting one creating what's called adverse yaw. Hence the need for differential.

But that would imply that lift is exclusively relative to the ground. I'm completely confused now.

LIFT IS RELATIVE TO THE PLANE...
(rasts.. stupid caps lock!!)

Try a little experiment.... do a roll and hold just a smidge of up elev.... see how it barrels around....
Differential simply negates the "Up" trim a plane needs to be stable....

Originally Posted by 401HITMAN

+1

You are looking at lift vs drag when playing with aileron differential.

You'll have to experiment with your programming, determine what works best for your style of flying and your airframe's tendencies.

Of course I assumed you have you geometry set correct to begin with.

Jeff

I've never used differential on my 3D birds but i'm up for experimenting. Never considered an axial roll a "3D" maneuver but times change I guess. Also do you guys use diff in low and high rates?

[QUOTE=Mithrandir;2005291]LIFT IS RELATIVE TO THE PLANE...
(rasts.. stupid caps lock!!)

LOL! I'm fully aware of that. I once gave "up" input while inverted.

Originally Posted by mizm75

I've never used differential on my 3D birds but i'm up for experimenting. Never considered an axial roll a "3D" maneuver but times change I guess. Also do you guys use diff in low and high rates?

Picture full roll rate loops. It beats correcting with the elevator all the way around the loop while the plane is rolling at 600 degrees per second.