[NSRCA-discussion] Annhedral Stab

[Nat Penton]

Thanks Matt, as with any other design change it needs to be tried to understand the effectThe anhedral stab tips should be done like most trainer wing tips, slaunched <G>.                   Nat
  ----- Original Message ----- 
  From: J N Hiller 
  To: NSRCA Mailing List 
  Sent: Monday, April 21, 2008 3:45 AM
  Subject: Re: [NSRCA-discussion] Annhedral Stab


  Can you tell me more about "stab tip treatment" and why?

  Thanks.

  Jim

   

  -----Original Message-----
  From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Nat Penton
  Sent: Sunday, April 20, 2008 11:34 PM
  To: NSRCA Mailing List
  Subject: Re: [NSRCA-discussion] Annhedral Stab

   

  Anhedral creates problems only for high yaw rate manuevers. It is difficult to do an inverted spin - you can't get the nose up. Proper treatment of the stab tips solves this problem, however.                  Nat

  ----- Original Message ----- 


  From: J N Hiller 

  To: NSRCA Mailing List 

  Sent: Sunday, April 20, 2008 6:20 PM

  Subject: Re: [NSRCA-discussion] Annhedral Stab

   

  Thanks Matt, as with any other design change it needs to be tried to understand the effect. I always felt that the bottom running stab in knife-edge or the outer stab when the fuselage is yawed is more effective than the other side and dominate. In the old days I was able to balance knife-edge pitch by adjusting one elevator up and the other down. When an annhedral stab is yawed it becomes unbalanced resulting in a pitch force change towards the top of the fuselage. If this were true it should also produce a slight roll with yaw. I will probably never understand as much about pattern plane design as I would like, I just try things. It either gets better or it gets worse and this is only one of many design considerations.

  OH that rolling circle stuff makes my head hurt. An analog processor would probably help or one about thirty years younger.

  Jim 

   

  -----Original Message-----
  From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of rcmaster199 at aol.com
  Sent: Sunday, April 20, 2008 12:43 PM
  To: nsrca-discussion at lists.nsrca.org
  Subject: Re: [NSRCA-discussion] Annhedral Stab

   

  Jim,

   

  Most would say that anhedral stabs are hype......

   

  I prefer to call them a viable option for pattern models and here're my thoughts on the subject. First off, fundamentally, they don't change how the wing is stabilized in pitch compared to a flat stab...same physics apply. Anhedral area however is the resultant of two component areas, horizontal which dominates and a vertical which adds to the already eixsting vertical stabilizer area. It may be thought as area added to the ventral side of the fuse without adding a subfin. This often helps settle some unwanted thrust vector forces namely the much cussed and discussed dredded pitch to belly with top rudder. Does it always work as prescribed? Does anything in our sport ever always work as prescribed?

   

  Rolling circles may be helped with anhedral in the stab. When the anhedral angle is "just right", there is no region during rotation (X degrees from horizontal) that completely blanks out the stab as can happen with flat stabs. Does is do wonders? I don't think so but it certainly does not hurt.

   

  My new design will have anhedral in its stab (7-8 degrees)

   

  Cheers,

   

  MattK

   

   

  -----Original Message-----
  From: J N Hiller <jnhiller at earthlink.net>
  To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>
  Sent: Sun, 20 Apr 2008 2:01 pm
  Subject: [NSRCA-discussion] Annhedral Stab

  

Can I open a discussion on why some designs have an annhedral stab?  Was it to lower the effective flying height of the stab to reduce the wing  to stab vertical offset and knife edge belly pitch, or is there some other  reason?  Jim Hiller    _______________________________________________  NSRCA-discussion mailing list  NSRCA-discussion at lists.nsrca.org  http://lists.nsrca.org/mailman/listinfo/nsrca-discussion  
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