[NSRCA-discussion] Odyssey CG

[Dr. Mike Harrison]

Anthony,
They are all correct.  That is 30% of MAC or mean aerodynamic chord.  A reasonable estimate with double taper wing is to add root chord plus tip chord divide by 2 and take 30% of that.  For example  if the root is 18 inches and tip is 9 inches that adds to 27/2 equals 13.5 as your MAC.  Go to your wing and locate it.  It is about halfway out.  Take .30 equals 4.05 inches, mark it and go perpendicular to the root rib and mark on the root rib.  There is a very specific formula for this in Ron Van Putte's old articles, but this is quick and dirty and will get you there in the shop or at the field.

Mike
  ----- Original Message ----- 
  From: george w. kennie 
  To: NSRCA Mailing List 
  Sent: Tuesday, May 01, 2007 1:27 PM
  Subject: Re: [NSRCA-discussion] Odyssey CG


  Anthony,
  Not trying to start a war here, but if that thing has a tapered leading edge, I think you might want to move out almost half way on the panel and then go for your 30%. If you start at the root, you may find yourself flying a brick. Trimming on KE on a 45 degree upline might also be a worthwhile addition to your trimming regime.
  G.




    ----- Original Message ----- 
    From: Anthony Abdullah 
    To: NSRCA Mailing List 
    Sent: Tuesday, May 01, 2007 1:46 PM
    Subject: Re: [NSRCA-discussion] Odyssey CG


    Dr. Harrison,
    Thank you very much for the information! I agree with you completely that the CG is pilot specific. I tend to like my planes just a hair tail heavy compared to others. What I was afraid of was having the CG so out of whack that the plane would not survive its maiden flight.

    I know that 30% is the rule of thumb and I wanted to make sure that applies to the Odyssey. Just to summarize and for example, If I am looking at the wing root of one panel and the chord is 10 inches, I wand to start with the CG roughly three inches from the leading edge at the root (fuselage)?

    I will follow that and let you know how it turns out.

    Is there anything else I should know about the Odyssey?

    Thanks again
    Anthony

    "Dr. Mike Harrison" <drmikedds at sbcglobal.net> wrote:
      Anthony,

      I designed the Odyssey and I can't tell you where it is, but I can recommend some guidelines.  First, however let me give some opinion as to the value of cg location.  I believe the optimum cg location is pilot sensitive, that is to say different flyers prefer different cg's based on how the plane is set up.  For that reason I recommend a range that is easy to find then fly the airplane and change the cg until you like the way it flies.  Some points to remember are to fly full speed then cut the throttle, the plane should descend very slowly.  If it descends rapidly, then it is nose heavy.  If it climbs, it is tail heavy.  That will get you close.  After that make very small changes to suit your style.  On your root rib mark from 28 to 32 percent of the rib.  That would be a recommended range.  You might start at 30% and work from there.  The stab is powerful on the Odyssey and requires expo for best results so don't confuse a powerful elevator as tail heavy.  

      Good luck
      Mike
        ----- Original Message ----- 
        From: Anthony Abdullah 
        To: NSRCA Mailing List 
        Sent: Monday, April 30, 2007 12:38 PM
        Subject: [NSRCA-discussion] Odyssey CG


        Does anyone know where the CG should be on the Odyssey?

        TIA
        Anthony

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