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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'>Bob, I like your theory. Years ago, </span></font><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>Don</span></font><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> Lowe published some test
reports in RCM where he rigged an Extra to have a moveable stab. He
claimed that that was the ultimate cure to the pitching problem – move the
stab, in the directions you indicated. Only have tried it on two planes –
a CAP, where it did resolve the problem, but made it un-scale like, and
currently a Funtana that’s still on the bench waiting for other mods.
Can’t say what bad things this does to other flight characteristics, as
the CAP had a host of other problems……which is why it is gathering
dust in the corner of the shop as I type this! If I ever get my home-brew
pattern plane done, that’s one of the adjustable features it will have –
a stab I can raise or lower, to see really what the effects are on the flight
envelope.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<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></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<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>
nsrca-discussion-bounces@lists.nsrca.org
[mailto:nsrca-discussion-bounces@lists.nsrca.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Bob Richards<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, January 30, 2006
1:41 PM<br>
<b><span style='font-weight:bold'>To:</span></b> NSRCA Mailing List<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [NSRCA-discussion]
Trimming question</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>I don't like to get involved with knife-edge trim
discussions since I don't feel that I am an expert on the subject. However, I
developed a theory about it years ago that seemed to fit most problems I have
seen.</span></font></p>
</div>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>The vertical placement of the wing and stab on the
fuselage has a lot to do with it. With a top-wing and a bottom stab (such as
the Ultrasticks) the tendency would be to pitch nose-up during knife edge.
OTOH, a Cap 21 has a bottom wing and a top mounted stab, and I know only too
well that this pitches severely to the belly in knife edge - my old Cap21 took
35% mix to fly straight.</span></font></p>
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style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>My theory is that, when the fuselage is presented to
the relative wind at a given angle of attack, there is pressure built up on the
side of the fuselage (has to be, to fly knife edge). This pressure will
naturally wrap around the fuselage, so there will be a separation line along
the fuselage where the air separates, just l! ike at the leading edge of a wing
-- some goes over, some goes under. The stab should be placed near this natural
separation line. If it is far below this line, the plane will pitch to the
canopy, if far above, it will pitch to the belly. This is due to the stab
trapping some of the pressure.</span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>I don't think the wing incidence change can correct
anything other than a very minor pitch coupling problem. For really bad
situations, a change in the stab location is probably what is needed.</span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Anyway, that is my story and I am sticking to it. :-)</span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Bob R.</span></font></p>
</div>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><br>
<br>
<b><i><span style='font-weight:bold;font-style:italic'>John Ferrell
<johnferrell@earthlink.net></span></i></b> wrote:</span></font></p>
</div>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>My Guess:<br>
The sum of the drag vectors is well above the vertical CG. You MIGHT be able <br>
to help the condition with really big wheels generating some dr! ag down low. <br>
Its anybody's guess what the turbulance might trigger.<br>
<br>
The wing is not lifting in knife edge, but it is still draggin'.<br>
<br>
John Ferrell<br>
http://DixieNC.US<br>
<br>
----- Original Message ----- <br>
From: "John Pavlick" <br>
<JPAVLICK@IDSENG.COM>To: "NSRCA Discussion" <br>
<NSRCA-DISCUSSION@LISTS.NSRCA.ORG>Sent: Friday, January 27, 2006 11:31 PM<br>
Subject: [NSRCA-discussion] Trimming question<br>
<br>
<br>
> Ok here's a good one. The owner of the L.H.S. asked me what I thought <br>
> about<br>
> this and I couldn't come up with a good answer. He has a Hangar 9 Ugly<br>
> Stik - the real big one. I can't remember exactly what it's called. Guess <br>
> it<br>
> has a gas motor in it. It's big. He says he has it trimmed so it will fly<br>
> inverted with just a very slight bit of down elevator (almost none). Ok, <br>
> so<br>
> it's not nose heavy, maybe even a little tail heavy. Now, when he flies it<br>
> knife edge (either side) it pulls s! everely to the canopy. I mean like it<br>
> will fly a complete circle. It needs almost 3/4 down elevator to fly<br>
> straight. It's beyond a mix - fix. He also says that it has a bit of roll<br>
> couple when flying level (not knife edge) but it doesn't pitch severely up<br>
> or down under these conditions. Any thoughts? I guess you can rule out <br>
> C.G.<br>
> because if anything it should pull to the belly considering how it's <br>
> trimmed<br>
> to fly level upright and inverted. I haven't flown it so I can't add too<br>
> much more. He builds OK so I don't think there's anything way out of<br>
> alignment, but again I haven't seen it yet so maybe there is. What should <br>
> I<br>
> look for if I get my hands on it to try and help him?<br>
><br>
> John Pavlick<br>
> http://www.idseng.com<br>
><br>
> --<br>
> No virus found in this outgoing message.<br>
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><br>
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<br>
<br>
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http://lists.nsrca.org/mailman/listinfo/nsrca-discussion</span></font></p>
</blockquote>
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