Zn-Line Alliance trimming question

[Troy Newman]

If the rudder induces a pitch to the belly when on knife edge...It should also induce the same pitch to the belly upright, inverted, and on 45's of roll. If it is different upright-inverted and knife Its not a very good design. I have come across this on some models. In the past couple years I have noticed it...These models would act different in roll couple with rudder Upright vs. Inverted. I have my own ideas as to why this is the case...but its an aerodynamics thing and according to the experts it makes no difference. I have just noticed that all the models with this design feature seem to do it and the models without this feature don't. This is just a interesting thing that made go hmmmm in the past year or so.

Back to the question, if you have it mixed and on all the time this coupling is counteracted and overcome by the mixing all the time.  However this mixing does become speed sensitive as the slower you get the less effect the Elevator "trim" will be be...Also if you setup the mix at full throttle for knife edge and then don't use full throttle for the knife edge it will not have enough "elevator trim" to fly at a lesser speed....Same goes for mixing at half power and then flying it at full power...you will now have too much mix (elevator trim),

This is the problem when you start running mixes.....Also its rare that the amount of mix needed if linear to the amount of rudder input...Many times the mix to maintain knife is nearly nothing but the mix to counter the coupling at full rudder deflection will not be even close to proportional.

Again depends on the model...But mixing is not a bad thing, and if you model doesn't have pure yaw then you should mix it so that it does. If mixed out properly then you will not see its effects. Of course it is possible that some things can be solved with other physical parameters that can trim the model. It is best to trim with the mechanical changes in the model rather than electronically...I don't have and have never had a model that required nothing in terms of a mix...Many models use a little down elevator at idle for the downlines. Some don't. Also most model need some roll mixing for rudder too. 

Even if your class doesn't fly knife edge, and even if its a little bit of coupling mix it out to lower the work load on you the pilot. I guess bragging rights about a model being zero mix are just too important. I can say that I have mixing in every single model I own. Some have more than others...but they all have some. It makes it easier to fly the model. But if not done correctly it will make things worse too.

TN
  ----- Original Message ----- 
  From: Mark Hunt 
  To: discussion at nsrca.org 
  Sent: Sunday, August 22, 2004 5:00 PM
  Subject: Re: Zn-Line Alliance trimming question


  I have a question regarding pitch mix with rudder.  If you mix some up with rudder, won't it appear when trying to wind/yaw correct when flying inverted?...causing the plane to drop the nose?

  I wondered about stall turns also, but I guess the airspeed (nearly zero) would nullify any elevator deflection while using full rudder.


  -mark
    ----- Original Message ----- 
    From: Troy Newman 
    To: discussion at nsrca.org 
    Sent: Sunday, August 22, 2004 6:43 PM
    Subject: Re: Zn-Line Alliance trimming question


    I have flown several Alliances and all of them needed some pitch mix...Specifically they pitched belly with rudder. And to be quite honest most of them pitched more than I would like...BUT When this was mixed out they were extremely great flying models. 

    I would setup a curve type mix for the rudd-elev mix....This way you can mix out the coupling at different rates depending on the amount of rudder deflection. I usually stick 3 points on each side...Say 1/3-2/3-full rudder stick...

    Then go out and fly it and set the mix value for each rudder deflection. It works well. Some people think the model is trimmed when they get their mix to zero. Personally I don't really care what values the mixes are...the question is do they interfere with other things.  My experience with the Alliance is that when its mixed out properly it flies extremely well and you don't see it.

    From the sounds you are happy with CG, up and down lines so mix it out properly so that at any rudder deflection its properly corrected and you will never see it in flying it.

    Good Luck with it

    TN
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