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setting up rudder aileron mixing ?

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Old 06-30-2005, 03:22 AM
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martno1fan
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Default setting up rudder aileron mixing ?

hi ive just aquired a computer radio and want to set up the rudder aileron mixing for my trainer to combat the adverse yaw!!.im not sure of the %age .will it be 50-50%ive seen somewhere they use a y harness but seeing as ive now got a computer radio with mixing i was thinking of using 50%rudder to 50%aileron would this be right im not sure? .anyone have a clue?.any advice would be great thanks!!.
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Old 06-30-2005, 06:05 AM
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Default RE: setting up rudder aileron mixing ?

The best way to do it is trial and error. Put some % in and try it. If it needs more add some or subtract if too much until it flies to suit you.
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Old 06-30-2005, 06:58 AM
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Default RE: setting up rudder aileron mixing ?

First, everything gets plugged into its normal channel. Next, if you have a regular ARTF trainer, there won't be much adverse yaw so try 5% or 10% to start with. In most cases your rudder will be more powerful than the ailerons. High wing planes with a lot of dihedral have a huge amount of roll due to yaw. That's how 3-channel planes fly, right.

Unless you are using 2 aileron servos, you shouldn't need a Y-harness.
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Old 06-30-2005, 09:06 AM
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Default RE: setting up rudder aileron mixing ?

From what I have read, 50% is a way high figure for mixing due to adverse yaw. If I recall, it is more like 5 to 10%, but I have been known to be wrong.

DS.
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Old 06-30-2005, 09:40 AM
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Default RE: setting up rudder aileron mixing ?

Hi!
You should not use mixing at all on a trainer!!! WHY?
I have been teaching people to fly R/C for 25 or more years and I can assure you that mixing aileron to rudder is not a good thing on a normal size (around 1,5m-2m ) high winged trainer.
On planes like this you turn by using aileron and elevator.
You can use rudder too but please do not mix it with aileron. If you do, you will get a plane that acts in a weird way!
Of course you can use only rudder (and elevator ) to turn your plane but ailerons will make it turn more swifter and cleaner.
I personally do not use any mixing at all on airplanes.

Regards!
Jan K
Sweden
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Old 06-30-2005, 12:19 PM
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Default RE: setting up rudder aileron mixing ?

hi guys thanks for the replys,i was watching the one week to solo video and the guy on there says to allways use mixing to overcome adverse yaw on a trainer.that way you can just use one stick to manouver the plane!!.using the left stick only for throttle?.now im confused lol[]he says all trainers act weird without it?.HELP!!!!!!!!!!!!!!!!!!!!!!!!.[X(]
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Old 06-30-2005, 08:28 PM
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Default RE: setting up rudder aileron mixing ?

1fan,

Before messing with any mixing functions on a computer radio, my suggestion would be to first learn to fly your trainer proficiently using just the inputs from your own computer, the brain. If you are going to depend on the computer radio to make pretty turns, you will be missing out on some of the very basic, fundamental steps to becoming a good pilot. It's like trying to learn mathematics by only using a calculator. You will always get the right answer, but you won't really know how you got there.

Also, I hope you are not learning to fly just by watching a video. Please join a local club and get flying lessons from an instructor. That is your best path toward a successful solo flight.

After you have become a proficient pilot, go ahead and experiment with the mixing functions, at least now you will know from your own experience how much correction you might need.

Best of luck,

JC




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Old 07-01-2005, 02:11 AM
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Default RE: setting up rudder aileron mixing ?

can i just say 1stly i did learn to fly by myself and i soloed my trainer 1st time!!,i got the video to help me.i started by flying a firebird gold eagle 3 channel plane before moving to the tutor 40 glow plane.i was just wanting to know how much mixing i need?.i look at it this way why use the gear stick on a car when automatics are easyer?.anything that makes it easyer for me is a good thing!!after all thats what mixing was invented for wasnt it?.but i see where your coming from !!.im not a member of a club either but thats my choice!!.
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Old 07-01-2005, 12:42 PM
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Default RE: setting up rudder aileron mixing ?

I prefer the gear stick instead of automatic because I have total control over the gearbox. The automatic gearbox will shift up right before a hill where you need the extra power from the low gear. With manual shift you will stay in low gear because you see the hill. The same thing goes for airplanes. Ailerons and rudder are NOT (contrary to what many people believe) used at the same time all the time. Ailerons control bank angle, and rudder controls the direction of the tail/nose.

Flying with rudder mixed with ailerons will fix the adverse yaw problem partly, but learning to fly using rudder and ailerons INDEPENDENTLY is, in my opinion, the way to go. When entering and exiting the turn, more ailerons than rudder is generally required. During the turn, more rudder than ailerons are required. With rudder/aileron mix, you will end up somewhere in between, being unable to make a turn coordinated all the way through. Uncoordinated turns increase stall speed. If you can use the ailerons and rudder separately, you will with little extra practice be able to handle crosswind landings better, fly slowly safer (particularly takeoffs and landing approaches), and your plane will not "bounce around" when you turn.

Aerobatics will be VERY limited with rud/ail mixing. Even if you don't intend to turn the plane upside down for a few months, you will still have to unlearn (is that a word?) a couple of "bad habits" when you DO want to fly aerobatics.

To sum it up; Mixing ailerons with rudder will reduce adverse yaw, but IMO introduce other problems that are equally bad. Learning to use the rudder properly will reduce adverse yaw, but also make your flying safer and better in other aspects. Mixing is NOT bad, and many people do it, but flying manually opens a few other possibilities. It depends on what you want.

(BTW, I learned by myself too. 100+ hours on a simulator and THEN a 2-channel 2-meter glider (Gentle Lady).)
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Old 07-01-2005, 01:23 PM
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Default RE: setting up rudder aileron mixing ?

thanks for the reply mate!!,maybe im lasy but i just wanted to know how much rudder to aileron mixing is needed?.i just want to try it out to see if it makes life easyer thats all ,but i supose everryone has there own opinions lol.
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Old 07-01-2005, 05:08 PM
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Default RE: setting up rudder aileron mixing ?

You're not lazy. Experimenting and seeing what we like best is a nice part of this hobby. "What happens if I..." are my favourite questions.

How much rudder you need depends on the type of plane, CG etc. Some planes (typically Cubs) need a lot of rudder, others close to nothing. I would start with 15% and see how it flies. Look at the tail/nose when turning and try to see whether 1) the nose is pointing out of the turn and the plane is skidding sideways into the turn, or 2) the nose is pointing too much into the turn and the plane flies like a rear-wheel drive car in a power slide If 1, increase rudder mix, if 2, decrease it. If you got it right, the nose and tail should more or less fly the same path through the turn.

Setting up the transmitter (forgive me if you already know how to do it):
Most radios have aileron/rudder mixing preset. Enable the mix in the setup menu and enter the percentage rudder that you want. 20% means that full aileron deflection will make the rudder deflect 20%. Do not change the end point settings (usually called EPA or ATV).

If there is no preset ail/rud mix, you must program one yourself. Set the aileron channel (channel 1 on Hitec/Futaba) as MASTER and the rudder channel (ch 4 on Hit/Fut) as SLAVE. Then set the percentage.

Check that the rudder moves in the right direction according to stick input and aileron movement. Viewed from behind: Aileron stick left => left aileron up, right aileron down, rudder left. If the rudder moves in the wrong direction, use a negative percentage (like -15% instead of 15%) as rudder mix.

Do your ailerons move the same amount up and down? Often it can help to have twice as much travel up as down. (aka aileron differential)

I hope this helps, and good luck!
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Old 07-01-2005, 08:45 PM
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Default RE: setting up rudder aileron mixing ?

If adverse yaw is what you're trying to get rid of, or lessen, then you want differential in the ailerons, not a rudder mix. There are times you might want to bank without turning, and if you have rudder mixed, it will induce a turn. Mixing the rudder with ailerons is nice if you want to make coordinated turns using only one stick, but I can tell you from experience that it gets so easy, you forget that the left stick will move sideways.

You need to have the ailerons set up so that they move "up" more than "down". Adverse yaw is created because the "down" aileron creates more drag than the "up" one, causing the upward moving wing to slow more than the other one, yawing the plane opposite of the roll. I set my Cub up so I have twice as much "up" as "down", and there is very little adverse yaw when I bank. You can set up the servo arms on a single servo aileron setup to give some differential, but to give a lot requires a double servo setup using two separate channels on the radio, one for each aileron.
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Old 07-01-2005, 09:48 PM
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Default RE: setting up rudder aileron mixing ?

As Khodges says diff. ail. is the best correction. If you let your radio do the mixing, it's having all the fun There are times when you would use the rudder in the opposite direction from the ailerons, such as side slips and flat turns, but you'll have fun doing that later on down the line.
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Old 07-02-2005, 03:31 AM
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Default RE: setting up rudder aileron mixing ?

wow im so glad you all agree lol,but seriously guys i really apreciate the advice!!!.ill just need to try a few of the things mentioned and see how it goes?.thanks for the advice on setting up the radio,it does have preset mixes so thats easy enough also good tip about the rudder when banking inducing a turn!!!id not thought about that one!!.i think ill try to set up the ailerons to give more up than down!!.thanks again guys its much apreciated.
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Old 07-02-2005, 03:32 PM
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Default RE: setting up rudder aileron mixing ?

Aileron differential is way to go if you have one servo and channel per aileron and radio with ail diff function. Start with 3 - 5% mix. I am not sure but I think, by using a y harness, you are limited to mixing opposite rudder. With a high wing / dehidral trainer, you may need quite a lot of mix, and that can interfer with normal control, like maybe causing too much drag, which may cause a stall/spin crash. I would start with 10% and adjust as test flights indicate. Be sure to put the mix on a switch to turn it off if necessary, and to be able to experiment with different flight situations. Go to NSRCA Trimming Chart to help you understand all the different variables. Consider all this as an experiment where you will have to try several different settings before finding the best one. Using premixes to fix aerodynamic design problems can get complicated. But it is one of the things that make the difference between average pilot and great pilot.
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Old 07-02-2005, 04:44 PM
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Default RE: setting up rudder aileron mixing ?

Hi!
We all just use right stick (aileron and elevator) to control our airplanes...Well most of us (Mode 1).
You don't have to use rudder to control an model airplane.
Adverse yaw...you must mean having differential in the ailerons...not mixing??
Aileron differential could be used but is not necessary on most small (1,5-2m) highwinged trainers. On a 1/4 scale CUB, Yes! But not on most other airplanes.
I don't use it at all.
Regards!
Jan K
Sweden
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Old 07-02-2005, 05:53 PM
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Default RE: setting up rudder aileron mixing ?

"Please resist the urge to curse, flame, degrade, insult or embarass someone in your post."

Jaka, I feel that some of the information you give is incorrect, giving your personal opinions as hard facts, not providing the necessary how's and why's. I'll try to explain why I think so:

1: "We all just use right stick (aileron and elevator) to control our airplanes...Well most of us (Mode 1)."
I disagree, but I don't have the statistic data to prove it. In our club we teach all students to fly with rudder, particularly landing approach and takeoff. About 50-50 use rudder at our field. I guess things are different where you come from, where everyone uses 15% Motul Micro and 0-5% nitro. (BTW ail/elev on right stick is mode 2)

2: "You don't have to use rudder to control an model airplane."
You are right. You don't HAVE TO, but it makes quite a difference. If you have a fire-breathing MVVS in the nose and the left stick all the way forward, there won't be much difference, but at slower speed (read: normal speed), more rudder is necessary to keep the turn coordinated. A turn that is NOT coordinated will increase stall speed by more than people often think. Using the rudder to coordinate the turn will give you a safety margin in the landing circuit, or enable you to fly even slower. It looks better too, (my opinion), having the tail follow "the rest of the plane" properly instead of hanging down on the inside. And, martno1fan asked HOW to use rudder, not whether to do it or not. Obviously he too has seen the value of coordinated turns.

3: "Aileron differential could be used but is not necessary on most small (1,5-2m) highwinged trainers."
Where did you get this information? Generally, the wing with the aileron moving down will create more lift and thus more drag, whereas the other wing will create less lift and thus less drag. The wing that creates more drag is the outside wing in the turn, and this will cause the plane to yaw in the opposite direction of the turn. Aileron differential will reduce adverse yaw. Can you explain the aerodynamics behind saying that this principle doesn't apply to smaller airframes (below 2 meters)?

Moderators, feel free to arrest me.
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Old 07-02-2005, 06:38 PM
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Default RE: setting up rudder aileron mixing ?

Can't remember the number of planes i've seen go in dead slow,banked to the left with full right aileron cranked in, whereas right rudder would have saved it.
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Old 07-02-2005, 06:43 PM
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Default RE: setting up rudder aileron mixing ?

I think this is much ado about nothing for a 1st trainer. You dont need any mixes in a trainer, thats a fact. Just set it up as recommended, trim it and go fly it. The benefits gained by this mix FOR A NEW FLYER are unnoticeable. If you just want to mix it in for the sake of learning or to try out your computer Tx then go for it!, it wont hurt as long as you dont overdo it. Most mixes on control surfaces are there to mitigate poor design or setups on somewhat more advanced acrobatic planes. On a well set up, truly neutral plane you will find that you need no mixes at all, that is also a fact. My pattern planes have no mixes at all and are true and straight in any attitude, but it took a ton of work playing with thrust, weight, CG and incidence to get there.
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Old 07-02-2005, 06:45 PM
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Default RE: setting up rudder aileron mixing ?

First off you should really try to use all of the controls you have for any trainer. Leave the mixing out until you are completely confortable using each and every control

Yes, some trainers do have adverse yaw and the really true way to keep it in check is coordinating your turns with rudder. A good instructor will teach the proper use of the rudder and you should already be using it for you takeoff and landing rollouts anyway.

Granted learning the rudder is something to be done a little later in training BUT if you never learn to use it you are missing out on the most powerful control surface you have besides learning the proper use of the rudder will help allot for flying in the wind. If you never plan on flying in wind then you will not be flying much.

In my opinion, not using the rudder at all is just waiting for diaster when the time comes that you move to bigger airplanes with bigger props. Torque of the prop will pull the plane left and low airspeed high power settings and the only proper way to correct for this is the rudder. Think of aborting a landing, you slam full power, the plane yaws left and you have very little airspeed, now you decide to try to compensate for the yaw by using ailerons and if your speed is slow enough, isttant tip stall and cartwheel not ot mention that the torque of the prop may have just turned the plane towards people.

An easy way to learn is to do rudder turns. Get way up high and use the rudder to turn, then use the airlerons to keep the wings level. You may also need to use the elevator to keep the plane from dropping or climbing. The goal is to use the rudder only to do the turn and using all other controls to keep the wings level and the altitude constant. Pretty soon you will be doing it automatically and the wind will no longer bother you.

Besides your turns will look tons better

Now if you really want to mix it keep the numbers low, say around 5% to 10% rudder to ailerons
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Old 07-02-2005, 06:47 PM
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Default RE: setting up rudder aileron mixing ?

agreed[8D]
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Old 07-03-2005, 11:26 AM
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Default RE: setting up rudder aileron mixing ?

PHEWim glad thats all agreed then!!!,i think ill keep practicing with the rudder!!.i might try a touch of differential on the ailerons say 5% and see how she reacts.would the differential affect doing a roll?.ill await your replys before i try it!!.all your advice is greatly received.
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Old 07-03-2005, 03:19 PM
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Default RE: setting up rudder aileron mixing ?

yep, differential will effect the roll, just the right amount and they will become more axial, to much and the nost will raise in the roll, not enough and the nose will drop in the roll. The nose will drop normally after so many rolls but differential will make the rolls axial longer.
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