Predicting roll moment coefficients using RASAero

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Ilya

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Looking for method\aeroprediction software to calculate roll moment coefficients of rocket with canted fins.

Here is my attempt
According to this work: https://www.dtic.mil/dtic/tr/fulltext/u2/a298617.pdf one can calculate roll moments coefficients using Cnalpha force coefficient. The idea of this method is presented at page 5. Cnalpha coefficient is the output of RASAero software so using RASAero I got Cnalpha for M829 projectile(test example from link above) for both body-alone-configurtion and four-fin configuration. Here is code in MATLAB
Code:
%m829
cal = 27.05e-3;
n = 6;
M = 5;
CNalpha = 11.313;
CNalphaBody = 3.7;

% %Basic finner
% cal = 20e-3;
% n = 4;
% M = 2.5;
% CNalpha = 10.44;
% CNalphaBody = 3.15;

CNalphaFin = (CNalpha - CNalphaBody)/2;
yc = .45*cal+cal/2;
Cldelta = n*CNalphaFin*yc/cal
Clp = -2.15*(yc/cal)*Cldelta
output
Code:
Cldelta =

   21.6971


Clp =

  -44.3162
Using this method I got 2x difference for range value of Clalpha for M829, and 1.5x difference for basic finner.
The question is if algo from pdf file will work correct with values of Cnalpha from RASAero? Is there any difference in Cnalpha coefficient calculation with code fromRref 7?
 

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