Throt/ Rud

[Edward Skorepa]

John,
we're talking model airplanes here (we're standing on the ground with transmitters in our hands) not a full scale where pilot sits in the cockpit. So, we have to THINK about inverted / upright / right / left like that. All in reference to us. It's all the same to the airplane (like you've said) but not to us (pilots on the ground). It's funny like a simple logic explanation (IMHO) can be turned into mess.

ed
  ----- Original Message ----- 
  From: John Pavlick 
  To: discussion at nsrca.org 
  Sent: Wednesday, January 26, 2005 8:13 PM
  Subject: RE: Throt/ Rud


  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
  http://www.idseng.com
    

    -----Original Message-----
    From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On Behalf Of Edward Skorepa
    Sent: Wednesday, January 26, 2005 8:15 PM
    To: discussion at nsrca.org
    Subject: Re: Throt/ Rud


    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
      ----- Original Message ----- 
      From: Nat Penton 
      To: discussion at nsrca.org 
      Sent: Wednesday, January 26, 2005 11:32 AM
      Subject: Throt/ Rud


      Cameron Smith relayed comments from Chip ( from RCU ) relating to how he uses a mix to eliminate the need for right thrust. I know Chip knows but he left me confused. Could someone clarify what he said?


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