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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Very interesting Bob! A few years
ago I was messing around with a 3D animation program (Bryce 3), and tried my
hand at making a clip showing a plane tracing out a basic loop while following
a “ribbon in the sky” – ie, the path looked like those shown
in the maneuver descriptions in the AMA rule book. It allowed for perspective
effects, placement of viewpoint and all the other usual stuff a 3D program can
do. So, on to my point: When I mathematically made the loop
perfectly round, it had a distinct egg shape to it when the view point was
moved from the same level as the center of the radius, to a more typical 5 ft
from the ground, looking up. In order to get a loop that looked round
from a typical judge/pilot position, I had to squish it from the top a fair bit
– indicating to me that as we fly our planes over the top, it’s not
enough to keep the radius consistent, we actually have to pull harder on the
top side, to keep everything looking right – in other words, we don’t
actually fly a true constant radius loop, because of perspective effects.
Makes it all so much harder than just keeping airspeed and angle of attack
constant – because we have to vary the shape to make it look right.
While I didn’t go back to look at other maneuvers in more detail, it has
always stuck with me that this effect also rears it’s head everywhere
else too. Kind of the visual version of the upwind/downwind debates –
so much depends on the frame of reference. Would be interesting to hear
others take on this subject……</span></font></p>
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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Ted Sander</span></font><font size=2
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color:navy'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>-----Original Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> discussion-request@nsrca.org
[mailto:discussion-request@nsrca.org] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Bob Pastorello<br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, August 17, 2004
6:14 PM<br>
<b><span style='font-weight:bold'>To:</span></b> NSRCA<br>
<b><span style='font-weight:bold'>Subject:</span></b> Some Diagrams</span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>After getting some feedback about
geometry, I thought I'd draw out a few of my more problematic ones. They
may help you, too....</span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><a
href="http://www.rcaerobats.net/ManueverDiagrams.htm">http://www.rcaerobats.net/ManueverDiagrams.htm</a></span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><br>
Bob Pastorello<br>
<a href="mailto:rcaerobob@cox.net">rcaerobob@cox.net</a><br>
<a href="http://www.rcaerobats.net">www.rcaerobats.net</a></span></font></p>
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