The Murphy Builders Site

Fabulous CAVU flight here today, lolling about at 7500 ft. overlooking
the snowy Olympic Mtns. to the south. We don't get a whole lot of
these days in the Pacific NW, and really appreciate them when we do.

The best part was that after switching the outer left flaperon section
with the inner right one, 254R now flies hands (and feet) off for
25-30 seconds at a time, perfectly trimmed. The right wing was always
a little heavy before, probably because the flaperon sections had
gotten mixed up at some point since the original builder did the
skeletons, and aligned them and their horns in pairs, of course.
Naturally, I had put off making this change for a long time because,
as anyone who's done it knows, taking them off and on again is an
onerous task, and I had planned to leave it until disassembly for
painting. Well, painting has been delayed, but not Oshkosh, and a
multi-day cross country with a heavy wing is at best, suboptimal.

There were two clues to the cause of the heavy right wing. First, the
two flaperon sections that were slightly lower ( ~ 3/16") than others
were the outboard section on the left, and the inboard section on the
right. The theory was the left wing had more lift due to the greater
arm, or leverage, of the extra lift from the lower, left outboard
section. Second, in reflex it flew hands off level anyway. Thus the
corollary to the first theory was that in reflex the mis-matched
flaperon sections were less "in play", making the slightly greater
lift on the left insignificant. I wouldn't be surprised if the
flaperon sections were properly marked in matched pairs to begin with,
but the banana brain novice who took over the project never noticed.
That would be me, of course, but it's all better now.

So the moral of the story is A) keep your pairs marked and identified
along the way (Duh!), and B) if you take over a project make sure you
know what pairs up with what (not quite such a Duh!)

Ron

PS - The A/P roll servo needs some minor gain & response adjustments
which I didn't want to do on a first flight, but it's working well
too, whether by itself, or driven by the GPS, or by the EFIS. Another
flight or two and the dynamics should be tuned up. More on that when
the pitch servo is in.



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Hmm. I think I screwed up describing this, but will take another crack
at it. Originally, both inboard sections were relatively high compared
to their outboard companion. I swapped left outboard for the right
inboard and ended up with a much better match on both sides, as well
as reduced lift on the outboard (longer arm) left while adding lift to
the inboard (smaller arm) right.

Hopefully you got the drift.

Ron



On Mon, Jul 4, 2011 at 4:42 PM, Ron Shannon <rshannon@cruzcom.com> wrote:

Fabulous CAVU flight here today, lolling about at 7500 ft. overlooking
the snowy Olympic Mtns. to the south. We don't get a whole lot of
these days in the Pacific NW, and really appreciate them when we do.

The best part was that after switching the outer left flaperon section
with the inner right one, 254R now flies hands (and feet) off for
25-30 seconds at a time, perfectly trimmed. The right wing was always
a little heavy before, probably because the flaperon sections had
gotten mixed up at some point since the original builder did the
skeletons, and aligned them and their horns in pairs, of course.
Naturally, I had put off making this change for a long time because,
as anyone who's done it knows, taking them off and on again is an
onerous task, and I had planned to leave it until disassembly for
painting. Well, painting has been delayed, but not Oshkosh, and a
multi-day cross country with a heavy wing is at best, suboptimal.

There were two clues to the cause of the heavy right wing. First, the
two flaperon sections that were slightly lower ( ~ 3/16") than others
were the outboard section on the left, and the inboard section on the
right. The theory was the left wing had more lift due to the greater
arm, or leverage, of the extra lift from the lower, left outboard
section. Second, in reflex it flew hands off level anyway. Thus the
corollary to the first theory was that in reflex the mis-matched
flaperon sections were less "in play", making the slightly greater
lift on the left insignificant. I wouldn't be surprised if the
flaperon sections were properly marked in matched pairs to begin with,
but the banana brain novice who took over the project never noticed.
That would be me, of course, but it's all better now.

So the moral of the story is A) keep your pairs marked and identified
along the way (Duh!), and B) if you take over a project make sure you
know what pairs up with what (not quite such a Duh!)

Ron

PS - The A/P roll servo needs some minor gain & response adjustments
which I didn't want to do on a first flight, but it's working well
too, whether by itself, or driven by the GPS, or by the EFIS. Another
flight or two and the dynamics should be tuned up. More on that when
the pitch servo is in.

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