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<DIV>One of the better knife-edging models and pretty fair all-around
sport fliers in recent past was.... of all things, a Stuka Divebomber with slats
fully deployed. It was an ARF (which annoyed me to no end....).</DIV>
<DIV> </DIV>
<DIV>It had this tiny fin with all rudder area above the stab, and a wing that
was mounted to the very bottom of the fuse and with a bunch of dihedral. It
showed virtually no roll couple and no pitch couple with either top rudder. It
would slow roll and point roll from horizon to horizon. Designer was either very
lucky or had pattern design experience in spades. Only faults I found was its
inability to do clean snaps and easy stalls.... rudder was possibly too small
and stab too large for its wing</DIV>
<DIV> </DIV>
<DIV>Point is there are many ways to skin the kitty.</DIV>
<DIV> </DIV>
<DIV>But I must admit, trying to make an UStik knife edge and make it perform
like a pattern model is a little like putting lip-stick on a pig. No offense
intended to owners of UStiks; these model types have their place. </DIV>
<DIV> </DIV>
<DIV>The designer of the original UStik for those new to the sport, Phil Kraft,
pattern competitor extraordinaire, intended the model for testing equipment and
not much else.</DIV>
<DIV> </DIV>
<DIV>regards,</DIV>
<DIV>MattK</DIV>
<DIV> </DIV>
<DIV>In a message dated 2/1/2006 11:58:29 AM Eastern Standard Time,
jivey61@bellsouth.net writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>Well
Georgi I think you did a good job of starting some hackles,hehe.<BR>Jim
Ivey<BR>----- Original Message ----- <BR>From: "George Kennie"
<geobet@gis.net><BR>To:
<nsrca-discussion@lists.nsrca.org><BR>Sent: Wednesday, February 01, 2006
11:45 AM<BR>Subject: [NSRCA-discussion] pitch<BR><BR><BR>> I'm having some
problems with this one. Nothing serious, mind you,<BR>> but just a little
confusion.<BR>> If we take this stab/fuse joint pressure build up to be
causative,<BR>> then it should logically follow that in order to
achieve<BR>> equilibrium, the rudder area above and below the stab should
be<BR>> equal.<BR>> Then if we take the Stick, everything (area) is
above the stab,<BR>> which lends credence to the hypothesis, but if we go
back to the<BR>> Cap, the area is now closer to equal, but probably
weighted slightly<BR>> in one direction or the other, but closer to the
equality that we<BR>> are seeking, and yet the reaction is just as violent
except in the<BR>> opposing direction.<BR>> Therefore, we must assume
that the point of equilibrium is at some<BR>> point between the two
locations.<BR>> With our thoeretical airplane with it's adjustable stab, we
end up<BR>> determining that indeed the point of equilibrium appears to be
at a<BR>> much lower point (relative to the rudder area) than we would
have<BR>> originally anticipated. So we, at this point find ourselves
doing<BR>> some serious head scratchin'.<BR>> On the other hand, if we
take the two airframes together and analize<BR>> the force arrangements we
find that they are basically inverted<BR>> mirror images of one
another,i.e., Stick, ........wing on top, stab<BR>> on bottom. Cap, wing on
bottom, stab on top. And yet the rudder area<BR>> intersect points are
definitely not mirror images.For that to be the<BR>> case, the Cap would
have to be a T-Tail. Something doesn't jibe!<BR>> Here we have the Cap with
close to a balanced area scenario and yet<BR>> we have the dreaded pitch to
the belly. If we now turn the Cap<BR>> upside down and cut off the canopy
and glue it to the belly<BR>> pretending that the belly is now the top and
fly the airplane it now<BR>> pitches to the canopy( new top, but still
really to the belly). The<BR>> problem with this scenario is that, in this
inverted position the<BR>> Cap's fin and rudder become equivalent to the
biggest sub-fin,<BR>> ventral, strake, whatever you want to call it and yet
it doesn't<BR>> correct the pitching problem.<BR>> I have strong
feelings that the dynamics are located in a different<BR>> area and would
contend that a poorly designed force arrangement<BR>> cannot be corrected
with a band-aid approach.<BR>> This is not intended to raise anybody's
hackles, just my two cents.<BR>> G.<BR>> <BR>> <BR>> <BR>>
<BR>> <BR>> Since were still guessing at cause of pull to top in knife
edge,<BR>> Here is my Suspect -<BR>> Stab is on bottom of fuse- true
with this design?<BR>> When rudder is applied, air pressure builds at
intersection of fuse<BR>> & Fin,<BR>> with the top of the
stab. Pressure on top of stab creates a nose up<BR>>
condition. There is no equivalent pressure on bottom, cause
there<BR>> is little or no fuse and fin.<BR>> <BR>> If that is the
cause, adding a strake to bottom might improve it.<BR>> <BR>> Later, Ron
Lockhart</FONT></BLOCKQUOTE></DIV>
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