Mid County R/C Club

Construction Tools

 

Adding or Shifting Weight Effect On A Given CG Location

Formulas to calculate the effects that adding

or shifting weight will have on the CG

Mean Aerodynamic Chord (MAC) Calculator

A tool that will calculate the MAC of a

given wing in reference to the CG

Center of Gravity Calculator

A tool that will calculate the CG

 

 

 

 

 

 

 

 

Center of Gravity (CG) Calculator 

The Center of Gravity Calculator Shown Here Is Used With The Permission of

And Provided Courtesy of The Blue Max R/C Flying Club (www.BlueMaxRC.com)
 

  This will give the wings Center of Gravity (CG)  as measured from the leading edge of the Root Cord.

Enter Root Cord (A): 

CG Graphic
Enter Tip Cord (B): 
Enter Sweep Distance (S):
Enter Half Span (Y):
Enter %MAC Balance Point:

Sweep Distance @ MAC (C) =
Mean Aerodynamic Cord (MAC) =
MAC Distance from Root (d) =

Balance Point @ Root Cord (CG) =

The Equations

For S<>0 Forward or Rearward Swept

For S=0 Straight Leading Edge
C = (S(A+2B)) / (3(A+B)) C = Zero
MAC = A-(AC/S)+(BC/S) MAC = A-(2(A-B)(0.5A+B) / (3(A+B)))
d = YC / S  d = (2Y(0.5A+B)) / (3(A+B))

For all Values of S

CG

= %MAC B.P.*(MAC) + C 

   

 

 

 

 

 

 

 

 

 

Mean Aerodynamic Chord (MAC) Calculator  

The Mean Aerodynamic Chord Calculator Shown Here Is Used With The Permission of

And Provided Courtesy of The Blue Max R/C Flying Club (www.BlueMaxRC.com)

This will calculate the wings Mean Aerodynamic Cord (%MAC)

for a given position of the CG.

Enter Root Cord (A):  MAC Graphic
Enter Tip Cord (B): 
Enter Sweep Distance (S):
Enter Half Span (Y):
Enter Center of Gravity (CG):

Sweep Distance @ MAC (C) =
Mean Aerodynamic Cord (MAC) =
MAC Distance from Root (d) =
%Mean Aerodynamic Cord(%MAC) =

The Equations

For S<>0 Forward or Rearward Swept

For S=0 Straight Leading Edge
C = (S(A+2B)) / (3(A+B)) C = Zero
MAC = A-(AC/S)+(BC/S) MAC = A-(2(A-B)(0.5A+B) / (3(A+B)))
d = YC / S  d = (2Y(0.5A+B)) / (3(A+B))

For all Values of S

%MAC B.P.

= ((CG-C) / MAC)*100 

 

 

 

 

 

 

 

 

 

The Adding, Removing, or Shifting Weight Chart Shown Here Are Used With The Permission

of And Provided Courtesy of The Blue Max R/C Flying Club (www.BlueMaxRC.com)

Adding, Removing or Shifting Weight (Effect on CG)

The following formulas are used to determine CG location

after adding, removing or shifting weight.

The best results occur if you use weight in ounces and distance in inches.


For reference:
 Moment = weight (in ounces) x distance from CG (in inches)
Original Moment = weight of model (in ounces) x the CG location (in inches)

Adding Weight

(Effect on C.G.)

  Orig moment + added moment
  ------------------------------------------ = new CG
  Orig weight + added weight
 

Removing Weight

(Effect on C.G.)

  Orig moment - moment removed
  ---------------------------------------------- = new CG
  Orig weight - weight removed

Shifting Weight (Effect on C.G.)

Original moment ± moment change
                   -------------------------------------------------  = new CG
Original weight