Advise how to reduce rudder to roll coupling

[PPandelaers]

Thank you Georgie

 

I will not convert my CAP into an Edge :-)

But I will apply some dihedral,

 

Waiting for Nat to tell me what he means with "Slaunch" the wing tips.

 

Regards

 

Patrick

 

-----Oorspronkelijk bericht-----
Van: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]
Namens George Kennie
Verzonden: zondag 7 augustus 2005 3:03
Aan: discussion at nsrca.org
Onderwerp: Re: Advise how to reduce rudder to roll coupling

 

Patrick, 
What you're experiencing is known as "adverse roll couple"! You can prove
this just by flying right side up and applying full rudder deflection in
either direction and you will see that the airplane will roll in the
opposite direction to whatever rudder you are applying.The cause of the
phenomenon is that the wing is located too far below the Datum line without
sufficient dihedral to compensate for the offset. Aside from trimming it out
with your radio, the only alternative is to saw the wing in half and adding
the correct amount of dihedral which is the better alternative to achieving
a correctly neutral flying airplane. However you will still have to deal
with the pitch condition and if you decide to do whats aerodynamically
required to correct this anomaly you will no longer have an airplane that
you can honestly call a Cap! 
The easiest solution, if you must persist in flying a "scale type" airplane,
is to sell the Cap and buy an Edge, as it has a much better force
arrangement (very close to a neutral flying airplane). 
Georgie 

PPandelaers wrote: 

  

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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