Rebel Flaperon limits when reflexed
Posted: Sat Feb 18, 2012 1:43 pm
Like others, I find that I have limited left aileron travel when the
flaperons are fully reflexed due to the control horn (at the fuselage
hanger) hitting the bulkhead (just inside the fuselage) that the rear
wing attachment bolts onto. I'm sure there was a previous discussion
about this but I couldn't find it. Anyway, shortening the vertical push
pull tubes that go from the mixer up to the wing torque tubes alleviates
the interference but also aggravates the negative differential aileron
which means more rudder will probably be required to coordinate any
aileron control inputs, especially when the flaps are extended. Figure
20.6.2 in the controls section of the 1999 manual shows the torque tube
hanger positioned 4 1/8" from the fuselage side. FWIW if I did this
again I would increase that distance to at least 4 3/4 (maybe even 5")
to get the horn farther away from the bulkhead which curves down toward
the fuselage side. Interestingly that would make the specified length of
the short left torque tube inside the fuselage about right whereas I and
some others have had to shorten that tube. I'm not saying anyone should
deviate from the manual without MAM's blessing but I think this is a
common problem and it does not become apparent until after the torque
tubes are cut and fitted. Wayne has some comments in the archives
regarding the strength of the hanger mount that should probably be read
as well. A search under "flaperons" should find those.
As a side discussion - I notice that instead of differential aileron,
the rebel has the forward edge of the aileron protrude down into the
airstream in cruise. Since that doesn't happen once the flap(erons) are
lowered and since lowering the flap(erons) causes more negative
differential, I'd guess that the rebel needs definate rudder inputs
along with any aileron inputs when the flaps are extended?? Part of its
character I'd guess and it probably makes for better STOL performance
;) Differential aileron means that the upgoing aileron would move
farther than the downgoing aileron to counter the adverse yaw. Adverse
yaw occurs because for equal deflection the downgoing aileron usually
causes more drag than the upgoing aileron.
Ken
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flaperons are fully reflexed due to the control horn (at the fuselage
hanger) hitting the bulkhead (just inside the fuselage) that the rear
wing attachment bolts onto. I'm sure there was a previous discussion
about this but I couldn't find it. Anyway, shortening the vertical push
pull tubes that go from the mixer up to the wing torque tubes alleviates
the interference but also aggravates the negative differential aileron
which means more rudder will probably be required to coordinate any
aileron control inputs, especially when the flaps are extended. Figure
20.6.2 in the controls section of the 1999 manual shows the torque tube
hanger positioned 4 1/8" from the fuselage side. FWIW if I did this
again I would increase that distance to at least 4 3/4 (maybe even 5")
to get the horn farther away from the bulkhead which curves down toward
the fuselage side. Interestingly that would make the specified length of
the short left torque tube inside the fuselage about right whereas I and
some others have had to shorten that tube. I'm not saying anyone should
deviate from the manual without MAM's blessing but I think this is a
common problem and it does not become apparent until after the torque
tubes are cut and fitted. Wayne has some comments in the archives
regarding the strength of the hanger mount that should probably be read
as well. A search under "flaperons" should find those.
As a side discussion - I notice that instead of differential aileron,
the rebel has the forward edge of the aileron protrude down into the
airstream in cruise. Since that doesn't happen once the flap(erons) are
lowered and since lowering the flap(erons) causes more negative
differential, I'd guess that the rebel needs definate rudder inputs
along with any aileron inputs when the flaps are extended?? Part of its
character I'd guess and it probably makes for better STOL performance
;) Differential aileron means that the upgoing aileron would move
farther than the downgoing aileron to counter the adverse yaw. Adverse
yaw occurs because for equal deflection the downgoing aileron usually
causes more drag than the upgoing aileron.
Ken
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