[NSRCA-discussion] Odyssey CG

[Nat Penton]

Tom
Thanks for the input. I use a CG formula from Gordon Whitehead's book "How 
to Make Scale Models Fly". Since there are only two variables, % stab and 
stab moment arm, for pattern airplanes it reduces to 36% MAC. I have never 
found a need to move the Cg after test flying. If anyone is interested in 
the formula they can let me know.

My opinion is that 95% of trimming is best taken care of in the shop.

BTY I question Sutherland's determination of the MAC of an elliptical wing. 
Maybe RVP can shed some light.      Nat

----- Original Message ----- 
From: "Tom Simes" <simestd at netexpress.com>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
Sent: Tuesday, May 01, 2007 1:09 PM
Subject: Re: [NSRCA-discussion] Odyssey CG


> On Tue, 1 May 2007 10:40:01 -0800
> Tom Simes <simestd at netexpress.com> wrote:
>
>> On Tue, 1 May 2007 14:13:54 -0400
>> "Ken Velez" <kvelez at comcast.net> wrote:
>>
>> > Anthony I think the 3 inches will not work for you that is not 30%.
>> > That holds true if it was a straight wing like in a trainer. In a
>> > taper wing you have to figure out the center of the wing compensated
>> > for the taper and them measure and figure out your 30%. There is a
>> > few different ways to do this but I think the easiest is to add the
>> > root length to the tip and the tip length to the root. Any way I
>> > attached the figure so you can see it, If you have any questions
>> > just ask. Hope it helps.\\
>>
>> I agree with Ken, I believe the good Dr. is referring to 30% aft of
>> the leading edge on the Mean Aerodynamic Chord (or MAC) as opposed to
>> 30% aft of the LE on the root chord. Here is a good explanation of the
>> the method Ken was referring to:
>>
>> http://www.lferc.com/Tips/mean_aerodynamic_chord.php
>
> Just for the archives, here are a couple more good links on deriving a
> resonable CG range for a model by finding the Mean Aerodynamic Chord (or
> MAC):
>
> http://www.airfieldmodels.com/information_source/math_and_science_of_model_aircraft/formulas/mean_aerodynamic_chord.htm
>
> Here's a good drawing explaining the various measurements as well as a
> web based tool to figure it all out for you:
>
> http://www.geistware.com/rcmodeling/cg_calc.htm
>
> (just enter data in the top 5 boxes and hit the calculate CG button)
> Tom
>
> ======================================================================
>   "Z-80 system stack overflow.  Shut 'er down Scotty, the system's
>         sucking mud" - Error message on TRS 80 Model-16B
>
> Tom Simes                                       simestd at netexpress.com
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