Advise how to reduce rudder to roll coupling

[Jerry Voth]

Thought first it had to do with dihedral, but in knife edge, the wing doesn't fly? What could it have do with it?

The wing may not fly in knife edge, but when you apply top rudder, the tail drops and if there is dihedral, the top of the upper wing and the bottom of the lower wing are exposed to the airstream which will roll the airplane back toward level flight or if it is correct, will hold the wing vertical.

Jerry Voth
  ----- Original Message ----- 
  From: PPandelaers 
  To: Mini IAC (Mini IAC) ; Discussion at Nsrca.Org 
  Sent: Saturday, August 06, 2005 11:09 AM
  Subject: Advise how to reduce rudder to roll coupling


  Hi folks,



  Got a Cap 232 ARF of some unknown brand "Hype" in Europe. Many problems, first of too heavy, wing profile weird but symmetric. High speed stalls at a blink.

  Size 80" wingspan.



  Now the question. Can make it fly pretty good with a DA50, but there's this enormous roll-coupling anytime you touch rudder. Also some pulling to the gear, but nothing unusual.. Best way to test it is to fly knife edge, it rolls on it's back in both directions, very quickly!  The wing has NO dihedral. CG is definitely OK, falls nicely straight down on stall turns



  Thought first it had to do with dihedral, but in knife edge, the wing doesn't fly? What could it have do with it? Tried on simulator AFPD, roll-effect by lack of dihedral is minor.

  So, I thought it's the shape of the rudder, I have to increase the bottom portion. So I did to a very significant amount, lowering the center (balance of the surface if you cut it out in cardboard)  of the rudder-surface about 1 ", I noticed some real improvement, but still far from OK. I had hoped that this much would have reversed the rolling direction. 



  Any ideas on what I could do? Mixing my radio, 20%  rudder to roll, still way insufficient.



  Thx!


  Patrick




















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