[NSRCA-discussion] pitch

[jivey61 at bellsouth.net]

Well Georgi I think you did a good job of starting some hackles,hehe.
Jim Ivey
----- Original Message ----- 
From: "George Kennie" <geobet at gis.net>
To: <nsrca-discussion at lists.nsrca.org>
Sent: Wednesday, February 01, 2006 11:45 AM
Subject: [NSRCA-discussion] pitch


> I'm having some problems with this one. Nothing serious, mind you,
> but just a little confusion.
> If we take this stab/fuse joint pressure build up to be causative,
> then it should logically follow that in order to achieve
> equilibrium, the rudder area above and below the stab should be
> equal.
> Then if we take the Stick, everything (area) is above the stab,
> which lends credence to the hypothesis, but if we go back to the
> Cap, the area is now closer to equal, but probably weighted slightly
> in one direction or the other, but closer to the equality that we
> are seeking, and yet the reaction is just as violent except in the
> opposing direction.
> Therefore, we must assume that the point of equilibrium is at some
> point between the two locations.
> With our thoeretical airplane with it's adjustable stab, we end up
> determining that indeed the point of equilibrium appears to be at a
> much lower point (relative to the rudder area) than we would have
> originally anticipated. So we, at this point find ourselves doing
> some serious head scratchin'.
> On the other hand, if we take the two airframes together and analize
> the force arrangements we find that they are basically inverted
> mirror images of one another,i.e., Stick, ........wing on top, stab
> on bottom. Cap, wing on bottom, stab on top. And yet the rudder area
> intersect points are definitely not mirror images.For that to be the
> case, the Cap would have to be a T-Tail. Something doesn't jibe!
> Here we have the Cap with close to a balanced area scenario and yet
> we have the dreaded pitch to the belly. If we now turn the Cap
> upside down and cut off the canopy and glue it to the belly
> pretending that the belly is now the top and fly the airplane it now
> pitches to the canopy( new top, but still really to the belly). The
> problem with this scenario is that, in this inverted position the
> Cap's fin and rudder become equivalent to the biggest sub-fin,
> ventral, strake, whatever you want to call it and yet it doesn't
> correct the pitching problem.
> I have strong feelings that the dynamics are located in a different
> area and would contend that a poorly designed force arrangement
> cannot be corrected with a band-aid approach.
> This is not intended to raise anybody's hackles, just my two cents.
> G.
> 
> 
> 
> 
> 
> Since were still guessing at cause of pull to top in knife edge,
> Here is my Suspect -
> Stab is on bottom of fuse- true with this design?
> When rudder is applied, air pressure builds at intersection of fuse
> & Fin,
> with the top of the stab.  Pressure on top of stab creates a nose up
> condition.   There is no equivalent pressure on bottom, cause there
> is little or no fuse and fin.
> 
> If that is the cause, adding a strake to bottom might improve it.
> 
> Later, Ron Lockhart
> 
> 
> _______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion