Advise how to reduce rudder to roll coupling

[George Kennie]

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,
>
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> 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.
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>
> Thx!
>
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> Patrick
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