Rebel Flaperon limits when reflexed

[Ken]

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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[Walter Klatt]

Without going and doing some measurements, I still remember that
indeed I have less travel available when in full reflex. I think
I fretted over it a bit, too, when rigging the controls. However,
I can now say when flying that I have more than enough travel
available when in reflex. Roll becomes a lot more snappy in
reflex, and it doesn't take a lot to really move those wings.
You're also going faster, which I guess helps it be more
responsive, too. The only time I use a lot of aileron is
sometimes on take-off and landing, and then of course you are not
in reflex.

As for adverse yaw, there isn't much with the Rebel, or maybe it
is just what I have got used to. I know there are other planes
that I fly that have a lot more, that's for sure. Also, you can
really go into some steep banks and still feel stable, and come
out real fast if you have to.

I was on another Wings Over Canada outing a couple of weeks ago,
and they had me doing some "aerials" for the camera, and I swear,
I had the Rebel (with floats) at what felt like near 90 degrees
(probably a lot less in reality) a few times. I would come down
to about 200 AGL to circle around the camera boat, bank as steep
as I dared, dropping the nose so I wouldn't overstress on the
G's, and come out at about 75 AGL. I kept it in reflex the whole
time, and was totally comfortable with whipping it in and out of
the rolls. Couldn't have done that in the neutral flaperon
position.

Walter

-----Original Message-----
From: mike.davis@dcsol.com
[mailto:mike.davis@dcsol.com]On Behalf Of Ken
Sent: Friday, September 23, 2005 3:21 PM
To: rebel-builders@dcsol.com
Subject: Rebel Flaperon limits when reflexed


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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