[NSRCA-discussion] Rudder mix instead of right thrust?

[George Miller]

That is the post that I remembered...I thought it was odd that the mix is for left at idle rather than right at full power....I'll print it and put the post in memory for future reference

Thanks Vincente!
  ----- Original Message ----- 
  From: vicenterc at comcast.net 
  To: NSRCA Mailing List ; NSRCA Mailing List 
  Sent: Sunday, February 19, 2006 11:54 AM
  Subject: Re: [NSRCA-discussion] Rudder mix instead of right thrust?


  Hi all,

  I have the information and I agree with Jason.  I had the opportunity to see Chips planes at the Nat and obviously he uses some right trust.  I just copied the Chip's old e-mail and pasted here so you can see details.  I found useful to mix throttle with left rudder as Chip explains below to improve the outside corners.  

  Vicente Bortone

  #####################################################
  I run almost no right thrust in my planes and use the thottle to rudd mix at 2% left rudd. to throttle at idle. Thottle is the master rudd the slave. This makes the planes fly so much better when inverted at idle, they do not have that funny yaw through the corners. I have all but stopped using right thrust and do it all with the mix. What happens is the fin moves to the opposite side when inverted but the engine and prop don't know it, so the plane starts to yaw really bad due to spiraling slip stream. 

  To set this up just go out and fly the plane straight away from yourself at full throttle and then go to idle and watch to see which way it yaws start with 2% and start it f! rom half throttle on down. 

  Trim it a full throttle with you rudder trim, and when you go to an idle if the plane yaws left you have to much mix, yaws right there's not enough. Have this screen up at take off and a buddy that can adjust it for you. Once you have it going nice and straight at idle and full go out and do a stall turn at the end of the box, on your way down do a half roll and exit inverted, you will be amazed how well it will go through that corner. 

  Do that first before any other trimming. After that go with CG(45 degree upline 1/2 roll and it should stay on that line with little or no down elev.) then ail differential(1 Degree More up the Down) verticals(wing incidence .5-1 degree positive, then put the stab where ever it needs to go get the elevators to be neutral, you will at this time mix 1-2% down elevator with throttle for your down lines), and knife edge last (start with 5% up elevator with rud! d.) 

  Let me know how it goes and remember trim smarter n ot harder<G>        

   

                                               Chip Hyde

   

    Copy & Pasted from RCU Thread on the Hydeaway

  Ed,

   Don't think about inverted / upright / right / left like that. It's all the same to the airplane. Upright the slip stream hits the left side of the fin causing Left yaw. For sake of argument: Right thrust will be used to counteract this. Inverted, the SAME THING happens. Don't think right / left in reference to YOU, think left / right in reference to the AIRPLANE. When inverted the slip stream hits the left side (still) of the fin - unless the motor suddenly starts turning the opposite way. Same thrust offset ("Right") required unless the slip stream goes away in a push. Now if there's right thrust, you need left rudder to offset the right thrust which is trying to make the airplane yaw right in the absence of the slip stream air on the fin. If you still want to think about it the "other" way, remember "left" rudder when inverted will make the plane yaw to the! "right" (in reference to YOU standing there watching the plane). Now I'm getting confused.

   If you think about what Chip described: Trim for straight flight at full throttle, mix left at idle. Another way would be trim straight at idle, mix right at full throttle. That's what I've been doing. Same difference. 

  John Pavlick

   

  ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Rudder trim is set by using a combination of things together. Thrust is a big player in the rudder trim game... Most pilots don't realize all that goes into getting a plane trimmed in the yaw axis, and stop once they have the plane trimmed to fly straight at full throttle. 

  Whether you use right thrust or not is irrelevant, you have to have throttle to rudder mixing as well, to completely trim a plane in yaw. This is required to compensate for the propellors affect on the model. 

  The main goal here is to end up with a plane that flies straight at any speed, or any throttle setting. So trim you model at full throttle flying straight away from yourself first. Once this is done, again flying straight away from yourself, go to an idle and watch which di! rection you plane yaws. If you are not already using throttle to rudder mix your plane will definitely yaw one way or the other. All you need to do is determine which way that is and then mix a couple of percent opposite rudder to your throttle, and try again. Once you get it set so there is no yaw when adding or reducing the throttle, your rudder is trimmed. 

  Chip 

  quote:

  ORIGINAL: Xrod 

  Hi Chip, 
  I can't get a straight answer on this one and decided to ask you and the other panel of experts here on RCU for a definative answer. What is the proper way to set rudder trim? How do you go about it, and what manoevers do you use to assess correct trim? 
  Thanks, 
  Steve 

  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

  The most common mixes are rudd to ail and rudder to elev for knife flight, and your carden edge needs the second one. Start with 5% and go from there. 

  As for some other mixes the rudder to throttle is one I have used for 10 years now and will continue to use until someone comes up with a light weight counter rotating prop. In order for a plane to be true upright and inverted it is the only way I can think of to even come close. THRUST IS NOT THE ANSWER. lol Finally I sometimes mix 1 or 2 percent down elevator at idle in order to get the downlines perfect. The reason for this is once you get your plane to go straight up ! you don't want to mess with anything that can affect that on the plane so I just mix out whatever is needed on the down lines. 

  Chip

  ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

  Start with none and trim for straight and level flight with the plane going away from you. Make sure you only have 1-2 degrees of right thrust at the most. once it is trimed at full throttle level flight, land and see how far your Rudder is off to the right< and then add the mix until your rudder is netral at Idle and off by however much needed at the full throttle setting. 

  Have a nice day 

  Chip

   


    -------------- Original message -------------- 
    From: "JShulman" <jshulman at cfl.rr.com> 

    Hi George,

    It's not my technique, it's Chips. I tried it and didn't like it, but Chip's been using it for many years. Basically, there is no right thrust in the motor, and he uses a Throttle-Rudder mix. At idle, the rudder is neutral, and at full it has about 3/16ths (3-5%) right rudder mixed in. It's just a straight mix. If you want to get a more fine tuned mix, use a point mix and set the trim at the different points.

    Regards,
    Jason
    www.jasonshulman.com
    www.shulmanaviation.com
    www.composite-arf.com 

      -----Original Message-----
      From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of George Miller
      Sent: Sunday, February 19, 2006 11:08 AM
      To: NSRCA Mailing List
      Subject: [NSRCA-discussion] Rudder mix instead of right thrust?


      Somewhere I've seen a description of Jason's technique to set up rudder mix instead of right engine thrust, but I can't find it.  Could someone please re-post this or re-iterate it.  I can't believe I didn't save the message!-DOH!

      I can set up the mix in the transmitter...what I really want to know is what starting percentages are reasonable, and how to fine tune the mix.

      thanks,

      George


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