[NSRCA-discussion] Snaps

[Ed Alt]

To Doug's point re. the long tail moments & added stability of Pattern designs, this can be overcome pretty well with enough control throw.  Granted, it's not going to be just like a Scale Aerobatic design, but real snaps can be done and barrel rolls can be avoided.  I remember the angst that was generated by the reverse avalance in Masters in '05.  Fears of bent wing tubes, busted wings etc.  Locally at least, there were several examples where very good pilots had to re-do their setups to get enough throw to make this maneuver happen properly and not bend their airplanes.  Well, not a single airplane in the district was damaged that I know about, but I do remember having discussions about upping the elevator and also rudder throws to get the autorotation to happen properly. Hey, I admit to having only a short 2.25 year Pattern flying history, but as far as I can tell, it doesn't seem to be part of the Pattern "DNA" to set airplanes up with enough throw in alot of cases.  Having the deal with a schedule including the loaded snap in the reverse avalanche has advanced the knowledge because guys had to figure it out.

Ed
  ----- Original Message ----- 
  From: Doug Cronkhite 
  To: 'NSRCA Mailing List' 
  Sent: Saturday, July 08, 2006 8:54 PM
  Subject: Re: [NSRCA-discussion] Snaps


  The INBOARD wing dumps lift as a result of the increases angle of attack AND the rapid reduction of airspeed (by a sharp yaw moment - rudder input). The outboard wing's lift and drag increase rapidly. If the outboard wing dumped lift you'd get no rotation at all or very little. Some airplanes actually snap much better with no aileron usage as the changes in angle of attack on the inboard wing causes it to keep flying and not dump the lift from the yaw input.

   

  I think the biggest problem pattern aircraft have with performing proper snaps is the long long tail moments keep things so stable that it's very hard to generate the critical angle of attack required to get the stall to happen. So you see barrel rolls with VERY high G-loads on the aircraft. 

   

  In full scale aerobatics, there is nearly no G-loading once the stall occurs, except for the rotational forces of the autorotation of the aircraft. There is some G leading up to the break, but once that happens, it's all kind of non-stressful. 

   

  -Doug

   

   


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  From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Rcmaster199 at aol.com
  Sent: Saturday, July 08, 2006 12:45 PM
  To: nsrca-discussion at lists.nsrca.org
  Subject: Re: [NSRCA-discussion] Snaps

   

  In a message dated 7/8/2006 2:09:25 PM Eastern Standard Time, natpenton at centurytel.net writes:

    Matt

    Regards. Two comments. 

    Snap characteristics are independent of scale. The only thing that changes is the clock ( due to changes in moments of inertia ). 

    When the rudder is applied it is the outboard wing that exceeds the stall AOA and dumps. Actually it is not much of a lift dump but a huge jump in drag.

  Nat true. Moments of inertia are design parameters. So are several other key parameters that may make or break a model's ability to perform snaps. That was my point.

   

  I agree in terms of AOA (outboard aileron low) and drag increase but I am not as sure regards to lift. I know what you are saying though. 

   

  One question: how does the outboard panel lift over the top if its lift has been dumped?

   

   



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