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Old Nov 27, 2009, 12:50 AM
TyFlies is offline
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Basic Aileron / Rudder Mixing Question


I've got a Dx6i tx. I've never done much programing with it except dual rates. Somebody recommended setting up a mix so that a little rudder is mixed with aileron.

Is this a good idea for intermediate level flying, and if so how much of a mix is recommended?

Any specific advice about Dx6i mixing would be appreciated.

I'll initially be doing this on the Horizon corsair.
Thanks.
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Old Nov 27, 2009, 02:48 AM
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I, for one, do not generally recommend a rudder-aileron mix. Sure, rudder is required in many models to correct for adverse yaw, but that is what the rudder stick is for.

Some airplanes, a J3 Cub comes to mind, will benefit from a rudder-aileron mix. But, make it switchable so that it can be disabled for take off and landing. In a crosswind situation, an independent rudder is a necessity.

Bill
Old Nov 27, 2009, 02:55 AM
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Quote:
Originally Posted by TyFlies View Post
I've got a Dx6i tx. I've never done much programing with it except dual rates. Somebody recommended setting up a mix so that a little rudder is mixed with aileron. Is this a good idea for intermediate level flying, and if so how much of a mix is recommended? Any specific advice about Dx6i mixing would be appreciated. I'll initially be doing this on the Horizon corsair. Thanks.
On power planes and on sailplanes, it is normal to add rudder to aileron input. This is called a co-ordinated turn and is easily input manually on non-computer radios, and is especially required for the likes of a J3 for natural looking scale flight. Computer radios can be set up to do this automatically which results in a smoother, more efficient turn. Given the relatively small ailerons on a Corsair, rudder input is a must if flying to succeed in competition. Most planes would use a positive mix of moving the rudder in the same direction as the ailerons. However, this is just the opposite when the model uses a V-tail.
As with full size aircraft, the amount depends largely upon the length of the fuselage or tail moment. A short fuselage requires more input say 40% whereas the rudder on a longer tail moment has a larger impact so usually only needs 20% -30%.
Good notes regarding mixing and how to implement them can be found in
Hitec Optic 6 - Tutorial (good to learn mixing and other computer functions irrespective of brand) with Rudder <> Aileron on page 14.
Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links
Old Nov 27, 2009, 06:36 AM
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This can easily be done manualy that programming it is not a waste of time but you will find that if you and depending on the type of plane you want to this. You are going to want to be able to just roll without the rudder so you are going to have to program it on a switch and now you will find yourself always flicking a switch before turning where you can just manualy add a little rudder when turning.
Old Nov 27, 2009, 07:24 AM
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Originally Posted by freechip View Post
This can easily be done manualy that programming it is not a waste of time but you will find that if you and depending on the type of plane you want to this. You are going to want to be able to just roll without the rudder so you are going to have to program it on a switch and now you will find yourself always flicking a switch before turning where you can just manualy add a little rudder when turning.
With the correct amount of aileron-rudder mix you will not have to flick the switch during flight at all.
Fly overhead and roll from side to side and watch for the nose to yaw out of the turn. If it does add a bit of rudder mix until it stays straight as you roll.

The mix will not really help to coordinate a banked turn because you will not be holding aileron and in fact might be giving opposite to keep it from spiralling in. (Very common with gliders)
But it will ensure that you enter and exit the turn more smoothly.


Pat MacKenzie
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Old Nov 27, 2009, 10:19 AM
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If you program RUDDER with with ailerons to smooth out turns of for what ever reason, what happens when you go into a climb and want to roll as mush as you can before leveling out. The rolls wont be as tight as they would be if they were done without the rudder, so in this case one would want to have that mix turned off.

Anyways I guess it depends on the plane and the pilot because having flown HELI I am use to inputing rudder so turning with my plane and adding a little rudder at the same time is no big deal.
Old Nov 27, 2009, 10:42 AM
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Thanks for the great comments. And thanks for the detail and link, A.T.
More tradeoffs to consider. I'm thinking that for right now I'll work on manually adding a little rudder in my turns -- It will do me good to use my left stick more. If I program later it will be with a slight mix and probably on a switch.
Old Nov 27, 2009, 11:37 AM
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Well being a full scale pilot as well as a modeler, I never understood why virtually all computer radios came with a native aileron/rudder mix.

Then I started flying RC with some club members including the guy who got me started (an old pattern flyer) and I found out why... lol

There are way too many folks who don't know that the left stick on a mode 2 radio goes left and right besides going forward and back. Most also fail to realize that the rudder will continue to work at slower air speeds than the ailerons, will produce a slight skid if necessary (can anyone say crosswind landings) and can actually cause a roll if deflected some distance. This usually results in the nose dropping as well although some aircraft will pitch up.

This is known as roll coupling and is an undesired characteristic for most IMAC birds which compete in precision aerobatics. There you'll find lots of guys dialing in a rudder/aileron mix (opposite of the OP's mix question) and that is to "dial out" the the unwanted roll coupling during complex maneuvers.

So IMHO, you're on the right track with learning to use the rudder. Next step is flight trimming and you'd be surprised at how much easier it is to fly a well trimmed model and more fun....


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