[NSRCA-discussion] pitch

[Dean Pappas]

Hey Matt,
Yeah, and a buddy's lightly built Corsair rolled nicely too! 
You know, years ago, I had built three Pattern planes, before I ever realized that rolling trim was hard.
They all were as good or better than me. I have paid the price for those three planes, ever since.
Dean

	-----Original Message----- 
	From: nsrca-discussion-bounces at lists.nsrca.org on behalf of Rcmaster199 at aol.com 
	Sent: Wed 2/1/2006 6:40 PM 
	To: nsrca-discussion at lists.nsrca.org 
	Cc: 
	Subject: Re: [NSRCA-discussion] pitch
	
	
	
	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....).
	 
	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
	 
	Point is there are many ways to skin the kitty.
	 
	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. 
	 
	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.
	 
	regards,
	MattK
	 
	In a message dated 2/1/2006 11:58:29 AM Eastern Standard Time, jivey61 at bellsouth.net writes:

		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

	 

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