[NSRCA-discussion] Odyssey CG

[Tom Simes]

On Wed, 2 May 2007 06:21:33 -0700 (PDT)
Anthony Abdullah <aabdu at sbcglobal.net> wrote:

>   Simple question:
>   Does the 13.5 in the below example refer to the distance out from
>   the center of the fueslage or from the root rib? As I understand it,
>   if I go out 13.5 from that point (fuse center I believe) and draw a
>   perpendicular line that will be my MAC. Setting the CG from there is
>   just a matter of taking 25% to 30% of the MAC distance out (13.5 for
>   example) and marking that on the fuse at the root rib?

Mike is describing a quick way to estimate the MAC - and has RVP noted
earlier in the thread, there are lots of ways to arrive at a flyable CG
you can then fine tune from.

If you just want a number you can work with, just plug the Odyssey's
measurements into this calculator:

http://www.geistware.com/rcmodeling/cg_calc.htm

NOTE!!  The numbers Mike tossed out in his example are likely off the
top of his head and are not applicable to the Odyssey.

With that out of the way, if I understand Mike correctly, his estimate
(27/2 = 13.5) is for the dimension of the MAC itself.  The way you would
locate it is to take a ruler held parallel to the fuselage and move
along the span of the wing until the chord (including aileron) of the
wing measured 13.5 inches on your ruler.  Now that you have located the
MAC on your wing planform, measure 30% of 13.5 inches (4.05 inches) aft
of the wing leading edge at the MAC this is your starting point for the
airplane's CG.  For convenience you can project that point perpendicular
to the fuselage back to your root rib.  


Tom
 
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Tom Simes                                       simestd at netexpress.com 
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