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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'>If a submarine had the shape of a pattern
plane with the CG up near the front third of the ship and a large amount of
side area near the rear fins then it would be an appropriate analogy. As
the sub is pretty symmetrical and likely has the CG near the center then I
would not expect it to water-vane<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Stu<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
nsrca-discussion-bounces@lists.nsrca.org
[mailto:nsrca-discussion-bounces@lists.nsrca.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Terry Beachler<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, October 12, 2007
10:59 AM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">NSRCA
Mailing List</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [NSRCA-discussion]
Weather Vane</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>The boat analogy previously used would only be valid for a submarine.
Wind force and water force are two separate forces. Wind shear in the air may
some application, but that is not what we are talking about. We'll have to ask
a submariner if a submarine weathervanes or er ah watervanes. It doesn't.<br>
<br>
Terry Beachler<br>
<br>
At 07:17 10/12/2007, you wrote:<br>
<br>
<br>
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>Hi Jim.<br>
<br>
Thanks for taking the time to post your reply. Wonder
how many will agree with your clarification. Some people are amazed with
magic also.. <tic> <br>
<br>
<st1:State w:st="on"><st1:place w:st="on">Del</st1:place></st1:State><br>
</span></font> <br>
<font size=2 color=blue face=Arial><span style='font-size:10.0pt;font-family:
Arial;color:blue'>----- Original Message ----- </span></font><br>
<font size=2 color=blue face=Arial><span style='font-size:10.0pt;font-family:
Arial;color:blue'>From: "Jim Alberico" <</span></font><a
href="mailto:alberji@charter.net"> <font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>alberji@charter.net</span></font></a>
<font size=2 color=blue face=Arial><span style='font-size:10.0pt;font-family:
Arial;color:blue'>><br>
To: "'<st1:PersonName w:st="on">NSRCA Mailing List</st1:PersonName>'"
<</span></font><a href="mailto:nsrca-discussion@lists.nsrca.org"> <font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>nsrca-discussion@lists.nsrca.org</span></font></a><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> <font
color=blue><span style='color:blue'>><br>
Sent: Thursday, October 11, 2007 11:19 PM<br>
Subject: Re: [NSRCA-discussion] Weather Vane<br>
</span></font></span></font><font face=Arial><span style='font-family:Arial'><br>
</span></font><font size=2 color=blue face=Arial><span style='font-size:10.0pt;
font-family:Arial;color:blue'>> Jim Oddino said:<br>
> <br>
>>>>> ====<br>
> Wish we had a real aero guy jump in here. ...<br>
> <br>
> Best Regards, Jim<br>
> ==== >>>><br>
> <br>
> OK, Mr. Oddino, I'll take the bait.<br>
> <br>
> I qualify as a real aero guy much more than as a pattern pilot. ;-)<br>
> <br>
> This whole thread started with the dynamics of a stall turn in a crosswind<br>
> (I think).<br>
> <br>
> Point 1:<br>
> Initial Conditions <br>
> -- steady wind from the right (constant velocity and direction).<br>
> -- constant aircraft velocity (or vertical rate of the cg)<br>
> <br>
> To track a vertical line, the fuse must be pointed to the right.
Under<br>
> these conditions, the thrust line counters gravity as well as the components<br>
> of drag in the vertical and horizontal directions.<br>
> <br>
> This is similar to the familiar "crabbing" in horizontal flight
to maintain<br>
> direction. However in the vertical geometric plane, gravity
complicates<br>
> things a bit. ...enough about that.<br>
> <br>
> Note that in crosswind, rudder trim is required to maintain the horizontal<br>
> line, as well as the vertical line. This is important.
Any "weathervane"<br>
> effect under these conditions is through control inputs. It doesn't
come<br>
> for free.<br>
> <br>
> Point 2:<br>
> Dynamics Near Stall (dynamics are always more complicated)<br>
> -- wind still steady from right<br>
> -- aircraft is decelerating to zero, then accelerating again.<br>
> <br>
> As the vertical speed (and overall velocity) decreases, the fuse must be<br>
> pointed more and more to the right to maintain a vertical track. Here is<br>
> where it is very hard to generalize. So much depends on the details
of the<br>
> aircraft shape, mass properties, control inputs (including throttle), the<br>
> wind speed, and etc. At zero speed, for example, the ONLY force
countering<br>
> the wind will be thrust. Sideslip forces certainly enter the picture
on the<br>
> final path up and the initial path down. <br>
> <br>
> Note also that the fuse must point leftward during the downward phase to<br>
> maintain the line (hence turning into the wind requires less than 180 deg<br>
> rotation). Again, pilot provides the rudder trim to maintain the
line.<br>
> Here fuselage side force plays greater role, as thrust is significantly<br>
> reduced. <br>
> <br>
> ...<br>
> <br>
> Regarding weathervane, the phenomenon is certainly present, but only in<br>
> dynamic situations. <br>
> <br>
> ... But again, depends on what you mean by weathervane ... In 3D, is a<br>
> steady angled hover in a steady wind considered weathervaning?<br>
> <br>
> I think not, but I also do not even think a weathervane
"weathervanes"<br>
> after steady state is established...<br>
> <br>
> I understand the physics fairly well...I just haven't learned to harness
it<br>
> nearly as well as just about everyone here. ;-)<br>
> <br>
> The graceful way you guys fly is amazing.<br>
> <br>
> Thanks for reading. Be sure to catch the movie version someday.<br>
> <br>
> Best regards,<br>
> <br>
> Jim A<br>
> (ultra-newbie pattern flyer)<br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> _______________________________________________<br>
> NSRCA-discussion mailing list<br>
> </span></font><a href="mailto:NSRCA-discussion@lists.nsrca.org"><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>NSRCA-discussion@lists.nsrca.org</span></font></a><font
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<font size=2 color=blue face=Arial><span style='font-size:10.0pt;font-family:
Arial;color:blue'>> </span></font><a
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