Next revolution in pattern planes?

[ray ayestaran]

does anyone have a Hanno Prettner article or articles describing research/development for curare and its anhedral stab? I remember at that time pattern contests were won and lost with loops which require just the right amount of rudder at the right time to keep them round, constant speed and not to loose heading upon completion was a big downgrade.  Hanno understood that the spiraling airstream from prop during straight and level flight bombards the tail group at a certain angle with maximum force pushing the nose to the left. right engine thrust angle is required to offset this. problem is right engine angle is fixed in a compromised position. the amount of right thrust actually required at any moment in time depends on throttle position, airspeed and angle of attack. during positive loops the spiraling airstream is redirected away from thrust line impacting only a small portion of top tail post/rudder reducing left force but since right engine angle is fixed you need some left rudder to hold your line.  you can see where this spiraling airstream is being directed by flying slow with smoke on. during an outside loop prop air is directed away from thrustline past out and away past bottom of airplane where no tail group exists - now you need even more left rudder to hold your line. lets fix the problem:

1. you can have as much tail group area below thrustline as above - prop airstream would push plane to right and left with the same force canceling this effect - plane would look funny and require extra long landing gear.
2. you can put in some fixed rudder trim or mix throttle to rudder but this doesn't address airspeed/angle of attack problems listed above only engine thrust.
3. you can chop off the top of tailpost/rudder (less tail area above thrustline for prop air to impact) you can drop down or flair out the bottom of tail group a few inches (more tail area below thrustline to offset area above) you can also put in some stab anhedral which adds tailgroup below thrustline and takes away from above. now add some more side area to fuse and especially in front of cg to setup a nice rudder pivot point and get back rudder authority you just cut away from top of tail and you have a curare! you have not spoiled that "pattern look" the judges want and you need only slight amount of right engine thrust offset. nothing loops better than a curare, only a handful of pilots with expert rudder skill can beat a curare with something else. pattern contests might be won with straight lines but more points are deducted in half loops/loops, snaps, looping maneuvers, etc. loosing your heading on the backside of a looping maneuver  or snap effects that manuever and the next. just my 2 cents - sorry for long post.      




     
  ----- Original Message ----- 
  From: Rcmaster199 at aol.com 
  To: discussion at nsrca.org 
  Sent: Friday, December 31, 2004 7:35 PM
  Subject: Re: Next revolution in pattern planes?


  Anhedral stabs are affected by crosswind more than flat stabs. At least for the kind of flying we demand. The Prettner Curare design, World Champ around 1976 or so, introduced the feature to models. By virtue of its being World Champion model, everybody copied it. Sort of the way fixed gear took over from retracts, except fixed gear have persisted far longer and serve the intended purpose well. 

  Curares and other anhedral stab designs flew well into the 80's but eventually the fad died down. 

  Naruke san is possibly trying to cure some aerodynamic inadequacy by employing the feature again. Or maybe just likes the look. It does look Kool as hell. I doubt that this is a revolution though; more like evolution....in reverse

  MattK

  In a message dated 12/31/2004 6:54:03 PM Eastern Standard Time, rcaerobob at cox.net writes:
    Beautiful plane, but planform is BTDT, remember Hanno??? And the Bridi UFO?  And others.  The anhedral stab really introduce bizarre characteristics, if I recall.  It was abandoned as an "innovation" about as fast as *somebody's* "Split Rudder "airbrake"....

    Man, we are O-L-D...

    Bob Pastorello
    NSRCA 199  AMA 46373
    rcaerobob at cox.net
    www.rcaerobats.net


      ----- Original Message ----- 
      From: Adam Glatt 
      To: discussion at nsrca.org 
      Sent: Friday, December 31, 2004 4:54 PM
      Subject: Next revolution in pattern planes?
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