Elevators on PL models (still)

[Earl Haury]

Elevators on PL models (still)John

I've not come to any conclusions regarding hinge line angle either, perpendicular to the fuse seems OK. 

I do find it interesting that small elevators tend to be more sensitive around neutral than larger elevators. I've experimented with changing the elevator size on several airplanes. In all cases the smaller the elevator, the more sensitive around neutral (not necessarily more total authority). The most dramatic demonstration was an airplane with a flying stab arrangement that was numb around neutral and became "normal" with conventional stab / elevators. In fact, most fun-fli (3D) airplanes are quite tame around neutral with pattern type control systems/ travels while having huge elevators. One interesting aspect of moving the hinge line on the same airplane to effect elevator size is that it also changes the pitch control moment arm, however this seems too small to influence "feel". 

Of course "feel" is very subjective. I've flown a couple of Quique's designs with his recommenced control travels and find that the feel he's comfortable with is more sensitive than I prefer. I suspect his thumb resolution is 2048 while us mere mortals are still 512 (and getting coarser with age)!  

Earl
  ----- Original Message ----- 
  From: John Ferrell 
  To: discussion at nsrca.org 
  Sent: Monday, November 15, 2004 9:44 AM
  Subject: Re: Elevators on PL models (still)


  I have given some thought to the hinge line angles but I can never reason it out to my satisfaction.
  If you would sweep the hinge line forward I would think it to be a little like adding toe in on an automobile. 

  A little squeeze on the centerline might be a good thing. On the other hand, you are dealing with spanwise flow on the control surface as well. It is easier to think about if you make the control surface rectangular, with the hinge line and the trailing edge parallel. But that is definitely not the best way to build a "stiff" elevator.

  I always put the whole question back on the shelf because I cannot think of any way to evaluate the different examples. I will never have the flying skills to do it myself and I really don't know what I would be looking for. 

  I find it easier for me to understand characteristics by considering what a given model does or does not do well and look for the underlying flying cause/effect relationship.

  Please keep us advised of your experiences!

  John Ferrell   
  My Competition is not my enemy! 
  http://DixieNC.US

    ----- Original Message ----- 
    From: Koenig, Tom 
    To: Discussion 
    Sent: Sunday, November 14, 2004 4:59 PM
    Subject: Elevators on PL models (still)


    Hi again all, 

    Sorry to rabbit on about this, but I have some more questions...or should that be, seeking ideas. I realise that I am probably getting caught up on something that really doesn't matter ...but here goes anyway.

    Like I said in an earlier post..I will simply build two sets of stabs and see for myself...but I cant help trying to get inside Quique's or the Matt's head on this one. Or should that perhaps be Monsieur Lemmonier?

    On the weekend, I realised I made a small measurement error, when reverse engineering the plan form of the stabs. I can live with the fact that they arrived at a small elevator design, but I can see no relationship other than area.

    What has me rattled is that the hinge line of the elevators is swept forward....on both the Lazulite and the Partner, there is no relationship between chord percentages, the area's kind of work out..but how did they arrive at the distribution???

    So I assumed that they jigged the stabs up wrong when boring the stab tube hole..but this appears to not be the case, as the root( fuz) angles are correct. So I looked at the aileron hinge line angle to see if there is a relationship there, but there appears not. 

    On elevators, I have either always used chord percentages or placed the hinge line square to the Fuz CL, with great success. Using ( even) chord percentages results in a hinge line being swept back...not forward ( depending on plan form ofcourse)

    So does anyone out there talk to Quique? Could someone ask him about this? 
     As the once famous Professor Julius Summner Miller said..'why is this so'? Did they make half a dozen stabs and try them empirically. I have not seen a Smaragd..did it have a square hinge line? 

    My limited knowledge has me baffled on this one...its not that important...I just want to know why! 

    Thank you again to all of you who have contributed to this one. 

    best regards 

    (curious) Tom 

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