Incidence or CG?

[Thomas P. Fiorentino]

Symetrical airfoil wing design needs some AOA to create lift though...no?

I'll buy a dozen of those perfect planes if they are out there!
  ----- Original Message ----- 
  From: Ken Thompson 
  To: discussion at nsrca.org 
  Sent: Sunday, September 11, 2005 3:35 PM
  Subject: Re: Incidence or CG?


  You shouldn't need an aft CG to create lift, the wing design will do that for you.  If your "assumption plane" flies level, both upright and inverted, with no elevator input, I call that the "perfect" CG.

  At least that is my opinion.

  Ken
    ----- Original Message ----- 
    From: Thomas P. Fiorentino 
    To: discussion at nsrca.org 
    Sent: Sunday, September 11, 2005 8:51 PM
    Subject: Re: Incidence or CG?


    OK thats helpful Ken.  I have a pattern ARF that I am tinkering with and having some fun.  The downlines are really nice, but I hold too much down on inverted flight.  I'll move the CG aft a little and see where that takes me.

    Here is my follow-up question because I can't help myself.  Lets assume you have a plane with wing and stab at 0 degrees.  Lets assume further that you have no elevator trim and the engine has no thrust adjustments.  If this assumption airplane actually flew level...would an aft CG be responsible for creating the right AOA on the wing to create lift?  Am I understanding this correctly?

    Thanks for your input!

    Tom
      ----- Original Message ----- 
      From: Ken Thompson 
      To: discussion at nsrca.org 
      Sent: Sunday, September 11, 2005 6:38 AM
      Subject: Re: Incidence or CG?


      If you had a little positive incidence in the main wing, to fly level in upright flight, you would have it corrected by incidence in the stab or possibly elevator trim.  When you roll inverted the correction remains constant.

      Ken
        ----- Original Message ----- 
        From: Thomas P. Fiorentino 
        To: discussion at nsrca.org 
        Sent: Sunday, September 11, 2005 12:29 PM
        Subject: Incidence or CG?


        Bear with me on this question guys...

        I know the test for CG is to roll inverted and watch for nose down or tail down.  But relative to everything else why wouldn't wing incidence screw you up inverted?  Seems to me that all things remaining equal, if you had a little positive wing incidence and level flight upright that the nose would drop when inverted....Where is the blind spot in my logic?

        Tom Fiorentino
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