Throt/ Rud

[John Ferrell]

Or IF gyros would become legal....

John Ferrell    
http://DixieNC.US

  ----- Original Message ----- 
  From: Keith Hoard 
  To: discussion at nsrca.org 
  Sent: Thursday, January 27, 2005 1:21 PM
  Subject: RE: Throt/ Rud


  I guess if you guys were REALLY serious about pattern models, you'd design counter-rotating props for the engines. . .

   

   

   

  Keith L. Hoard

  Cordova, TN

  khoard at midsouth.rr.com

   

   

   


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  From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On Behalf Of Rcmaster199 at aol.com
  Sent: Thursday, January 27, 2005 12:17 PM
  To: discussion at nsrca.org
  Subject: Re: Throt/ Rud

   

  Bob, this is exactly how I feel. Why not learn to use the sticks? 

   

  On the money with P-Factor (not to be confused with K-factor) and GP also. Slipstream is the key and it could be significantly straightened by doing something similar to what Nat has done with the Xpress series of models. Strakes surrounding  the CG help reduce the effects. This is a design feature tha belongs on all pattern models. IMHO

   

  MattK

   

   In a message dated 1/27/2005 8:18:27 AM Eastern Standard Time, bob at toprudder.com writes:

    Ed,

     

    I am a very firm believer (no one will convince me otherwise) of exactly what you describe. Slipstream effect is the whole reason we put right thrust in our engines. It has NOTHING to do with torque, P-factor, or gyroscopic precession.

     

    The issue of transitioning from vertical to horizontal (either to inverted or upright) is a gyroscopic precession issue. The best way to counter that is to use lighter weight props turning at lower rpm -- less spinning mass and less gyroscopic effect.

     

    P-factor only exists at high angle of attacks, which does not happen in a vertical climb. 

     

    Torque tries to roll the plane, and some schools of thought are that, to counter the torque-induced roll, the left wing has to lift more than the right, causing more induced drag on the left. While this may be true for a lot of planes while taking off, this does not apply to pattern planes in a vertical climb since both wing panels would be fighting the torque equally.

     

    Gyroscopic precession only occurs when the airplane is moving around its pitch axis, as when pulling or pushing a corner. It is most noticeable when the airplane is slow, since there is less aerodynamic stabilizing force available from the rudder/fin.  IMHO, no throttle-rudder mix is going to correct this. It might be possible to mix elevator to rudder, and enable/disable the mix based on throttle position.

     

    When I flew a Cap21 in pattern, I had to use left rudder when pulling an inside corner at the top of square loops. I had to use a TON of right rudder when pushing a corner, and this was with about 5 degrees of right thrust.

     

    IMHO, learn to do it with your thumbs. Practice enough and it will become automatic. Just my 2CW.

     

    Bob R.



    Edward Skorepa <edsko at xmission.com> wrote:

      I'm confused too. I know, I know I shouldn't argue with someone like chip but I believe the main reason we're putting right thrust is an asymmetric vertical fin. On most conventional airplanes the area above thrust line is much greater then area below. So, the spiraling slip stream  will hit the top portion of the vertical fin from the left pushing tail to the right thus right thrust. When inverted, the spiraling slip stream will hit vertical fin from the right because fin is now on the opposite side and  pushes tail to the left. To straighten the flight path, we need now the left thrust which is already there. During inverted push ups, why do we need to use left rudder? The spiraling slip stream misses completely vertical fin and the right (left when inverted) thrust is causing airplane to yaw left. If you have a big gasser, turn on smoke, do inverted push up and watch where the smoke goes. However, Chip's approach of fixing the inverted push ups problem is quite interesting and I'll try it on my new bird I'm working on right now.

      ed

   
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