I built my Rebel a long time ago, but still remember that after flying it, I
wished I would have lined up my fairing box and wing tips with the reflex
position since that is where the flaperons spend most of their time. My
assumption is that you would save a bit of drag in reflex cruise then. Just
remember, though, that due to flexing, your inflight reflex position is not
the same as on the ground, just as is the case with the flaperon position.
If you want it to look good on the ground, you can leave them there, too.
Walter
-----Original Message-----
From:
mike.davis@dcsol.com [mailto:
mike.davis@dcsol.com] On Behalf Of Ron
Shannon
Sent: January 30, 2009 2:43 PM
To:
rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Ailerons-neutral position
[VERBOSITY ALERT: Read at your own risk of boredom, etc.]
Here's how I analyzed this "neutral" issue for purposes of setting the mixer
arm travel. Reasonable minds may differ, but as discussed below, in the end
it may be more a question of semantics than anything else.
When setting the mixer arm travel, Ch. 20, p. 28, calls for alignment of the
aileron trailing edge 5-1/4" up from neutral. However, Ch. 20 doesn't
clearly define neutral, except to the extent it is shown and specifically
labeled in Fig. 20.6.2. If this isn't immediately apparent to your eye, put
a straight edge on that diagram and you'll see the aileron in "neutral"
position is quite clearly angled up a bit from the line across the bottom of
the wing. The same slight up angling is shown in Fig. 10.12.3. As far as I
can tell, that's as close as the documentation comes to definitively
defining "neutral". However, FWIW, as discussed below, the documentation
does clearly show a "0 deg." line.
The method of defining aileron neutral, adopted by some here, is to make a
straight line across the bottom of the wing and the bottom of the aileron.
This results in the aileron trailing edge lining up more or less with the
fairing and cabin top at "neutral". However, if "0 deg." is the same as
"neutral", it's not possible to use the bottom lines _and_ pass through the
aileron hinge as shown in the figures cited above where the "0 deg." line is
clearly defined, because the hinge is not on that line.
Ch. 10.12, pp 1-2, Fig. 10.12.2, shows the 0 deg. position drawn from the
center of the aileron hinge pivot to the trailing edge. The questions are 1)
is this "0 deg." line the same as "neutral" -- most would think so -- and 2)
if so, where is the forward extension of that line? What is clear is that
the "0 deg." line cannot be congruent with a line along the bottom of the
wing because the hinge is well above that line. Although the documentation
is less than crystal clear on this point, the 0 deg. line (from aileron
hinge to aileron trailing edge) when the aileron bottom is angled up
slightly, aligns perfectly (?) with a line from the hinge to the wing
leading edge, i.e., a line from the wing leading edge, through the aileron
hinge to the aileron trailing edge -- which is also geometrically the
maximum chord line, though the difference in chord length between these
methods is certainly insignificant. Adopting the "0 deg." line as "neutral"
places the aileron trailing edge about 1/2" above cabin roof and fairing at
"neutral."
What this boils down to is that if you think the 0 deg. line shown in Fig.
10.12.3 is the same as the manual's "neutral", you may end up with the
"neutral" aileron trailing edge roughly 1/2" above the cabin top. On the
other hand, if you think the manual's "neutral" must be "aerodynamic
neutral" and that "aerodynamic neutral" _must_ be with the bottom line of
the aileron in line with the bottom of the wing (not necessarily true), then
"neutral" ends up with aileron trailing edge at fairing and cabin top.
"Neutral" is not mentioned in the fairings chapter. "Neutral" is mentioned
in the wing tip chapter. I haven't done my wing tips yet, but I suspect
they're sufficiently maneuverable to accommodate the small difference
between either method discussed here -- but there's no need to quibble over
that. There's no question that aesthetically, it looks best to have the
tips, ailerons, fairings and cabin all lined up together when parked on the
ramp. However the "0 deg."method can be used for setting mixer arm neutral,
and wing tips still can be set at "aesthetic neutral" without affecting any
flying qualities, per se, because....
As a practical matter, I think the only real significance of the "neutral"
definition for builders is that it's used to mark and set the mixer arm,
before measuring and installing the push-pull tubes, etc. Where you set
"neutral" thus affects what absolute top and bottom travel you will have for
flaperon movement at the mixer arm, regardless of how you label the
positions. Except for that, it doesn't really matter which method you use to
define aileron neutral because for aesthetics, you can line things up
regardless.
FWIW, I used the "0 deg. line" method which more closely approximates
Figures 10.12.3 and 20.6.2 and came out with _possible_ available travel of
about 10 deg. up, and about 20 deg. down -- which is the outside range of
what I would ever want -- so it worked great for me. I think that regardless
of whether "neutral" in the manual means "aerodynamic neutral" or not, and
regardless of where that is -- the manual at least means "travel neutral",
for purposes of setting upper and lower limits of travel.
I believe it was Bob P. who confirmed that the manual's "neutral" has
aileron trailing edge slightly above cabin roof. If not, he can and no doubt
will defend himself. <g>
Your mileage may vary, and maybe it should! :-)
Ron
http://n254mr.com
On Fri, Jan 30, 2009 at 12:31 PM, Rebecca Brownell <
brownell@cottagecountry.net> wrote:
Great jeff thanks.Is one supposed to build the fairing boxes and the
wing tip to line up with the aileron when in neutral position?that
would make the fairing box come up at a bit of an angle from the cabin
roof.not a problem if that's the way its supposed to be.appreciate the
input.
Jason
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