aec12

Can someone explain aileron differential to me? The way I understand it, there is less drag on the ailerons in the up position than there is in the down position. Therefore, in order to execute a good roll you have to have more throw in the up position than in the down position to create an equal amount of drag. Is this correct or am I way off base here?

NOTE: I am just leaving my trainer and am getting into my new Tiger 2, so I am definitely a rookie at R/C.

Allen

MHawker

My Feedback: (16)

I hope someone can answer your question, but for now, just set your Tiger with equal throws both ways and have fun flying.

aec12

Thanks Mike

Rodney

aec12, you have it right. I have found it especially helpful on high wing planes like the Cub. However, if you also use that left thumb and put in some rudder with the ailerons, you do not need it.

aec12

Thanks for the info Rodney. One question though. How do you determine how much more throw you will need?

Allen

Mike Ledbetter

start with 100% ATV for up and 80% ATV for down.

Or use your dual rate function if available.

SST

My Feedback: (2)

Think about what you're doing. The wings are creating lift, and you're asking the inside wing to fight against this lift, while the outside wing is working with the lift. Naturally, the inside wing must create more down force than the up force the outside wing needs, hence the extra up deflection needed.

aec12

Thanks guys for the info. I have already learned a lot from your inf.

SST: That makes toal sense. I never looked at it that way. So it really has to do with lift more than drag.

Thanks again
Allen

iowanspctr

Lift pretty much equals drag, what you want to do is reduce lift on the inside wing more than you increase lift (and drag) on the outside wing. That will minimize adverse yaw and reduce the amount rudder you need to add to be co-ordinated in the turn. It's easier to see and feel from inside a full-scale than in a model, but you can see the tail sagging in the turn if you're un-cordinated. My Cub needs the rudder, my Senior Kadet with differential really doesn't need rudder at all.

aec12

Thanks for the info iowan. All the info has been very helpful. I understand it more clearly now. Any additional info would still be welcome.
Thanks again.

Allen

Time Pilot

I don't think this is quite right. The reason for the differential, is that especially for flat-bottomed, high wing planes, the up going aileron creates more drag than down force. The way I've seen it rigged, differential aileron gives more down than up.

barto

I don't think I agree with that.

The example you give, flat-bottomed wings. Well, the down-going aileron (the right one when making a left turn) has a greater influence than the up-going aileron because there's more air flowing directly over it. That's why the down-going aileron needs less deflection than the up-going aileron.
So it's the opposite of what you are saying, differential aileron gives more up than down.

Anyway, that's the way I think it is, if I'm mistaking please correct me.



Bart

rccrazedman

My Feedback: (10)

barto is correct you need more up then down

barto

Thanks for confirming!!!
I was sure of my case when I started typing but nearing the end I started getting some doubts. It seams as they were unnecessary.



Bart

britbrat

Agree with barto. The down deflection increases the effective AOA of the wing, thus creating more lift, & hence, more drag. The up reflexion decreases the effective AOA, thus decreasing lift & drag. This is what causes adverse yaw, & it can occur in high, mid & low wings, plus with flat bottomed, semi-symetrical & symetrical airfoils. Some designs are much more prone to yaw than others, so the amount of differential required obviously varies. The optimum (if any is needed) can be determined by a series of test flights with progressive amounts of differential dialed in, starting from zero.

aec12

Again, thanks everyone. Keep the info coming.

Allen

Mike Ledbetter

As I said above, 100% up and 80% down works in many cases. As Britbrat said, the proper amount could be as little as zero differential. You will need to try different settings until the plane exhibits a level attitude (neither nose-up nor nose-down) in turns.

Regards

DadsToysBG

My Feedback: (35)

With a trainer with a flat bottom wing the diff will have no effect on the roll. Save the fuction for Extra's. About 20% is what i found to work best, but each plane is different. Dennis

J_R

Hi Guys

I will go along with the explanation barto gives. I have another thought for you to consider, however.

If you are flying a scale plane, or a warbird, differential is important in setting up coordinated turns. On the other hand, if you are flying an aerobatic plane, such as an Edge, or a pattern bird, differential is not desirable.

If you are cruising along inverted, and want to make a turn while inverted, and you have differential dialed in, where are you now? What was the upgoing aileron is now the downgoing aileron and the induced yaw is exaggerated by differential in the wrong direction. On aerobatic ships, there should be no differential, unless you are planning to spend all your time right side up.

Such a set up can actually cause the plane to turn in the opposite direction, due to the adverse yaw.

ho2zoo

My Feedback: (5)

I have been flying for about 15 years now and have flown 3 or 4 planes with differential ailerons (mainly trainers while instructing). I am no engineer but I know that I did not like the 'feel' of the airplane with d/a. My biggest problem is that the ailerons would lose all effectiveness when the plane was slowed down. I first noticed this when I asked a student to slow down so they could see how the plane would handle when slow (like on a landing). My student was alarmed and said that he could not turn the plane at all! I took control back and he was right! It was going about at landing speed (I estimated, we were about 100 feet up). As soon as I brought the throttle up and got some speed it would turn as normal again.

I fly mostly .40 and .60 size sport models and stand-off scale models. My largest is a Pica 1/6 scale Spitfire with an OS .91 4-stroke. None of my planes has differential ailerons and I wouldn't want it. So I guess my point is why would anyone want d/a? Is there really a big advantage to it? Maybe if you are flying big aerobatic, contest planes, but for us ordinary guys?

SST

My Feedback: (2)

I don't know what's causing the loss of control of the trainer, unless it has small barn-door ailerons that are getting no prop wash at low speed and are ineffective in the reduced airflow, but I doubt if aileron differential is causing it. I have differential on all my aileron-equipped planes, which includes everything from 1/2a sportplanes to .40 size to powered slope planes & trainers. Wouldn't even consider setting one up without it...

britbrat

I generally don't use it because I enjoy very sharp snap rolls, & ail. diff. blunts the snaps & messes up inverted flight response in some of my models. However, for some models it can be usefull (if that particular model type needs it). In no case is it critical, & the appropriate use of rudder generally hides or eliminates the adverse yaw "problem".

barto

Totally disagree with this.

Differential is desirable on trainers with flat bottom wings. It's is absolutly not wanted on extra's or other acrobatic airplanes because these usually have fully symmetric wings. This means there is no difference in the effect of an aileron moving up or down, since there is just as much air flowing over them.
Like J_R said, the differential works against you when you are inverted. That's why it is not wanted att all. An acrobatic airplane should fly the same both in upright and inverted position.



Bart

SST

My Feedback: (2)

Barto, I would agree with you in the case of a midwing plane. With thrustline, symmetrical wing & tail inline, there is likely no need for diff. However, I disagree that just because you have a symmetrical airfoil that you don't need any diff. My Sig Ninja is a high wing symmetrical airfoil that has a Norvel .074 installed on the nose, and it rolls very axially with differential, and it has no rudder. My other planes are semi-symmetrical highwings. If the wing is not on the thrustline, the plane will benefit from some degree of differential, though the amount or lack of dihedral, airfoil shape and height above thrustline, as well as the height of the CG in the airframe will all combine to decide how much is necessary.

Ho2zoo: I find that adding tip plates improves stability and aileron response at low speeds. I add them to all my non-scale planes. At least all those with straight wingtips...I think they'd make my Quaker's eliptical tips look funny...

barto

I see what you mean.

Thanks for the extra info, didn't know this had something to do with it.



Bart