ISR

Center of  Gravity Calculator

How to use the calculator

 

  1. Input your root chord.
  2. Input your tip chord
  3. Input the sweep distance (see the picture below)
  4. Input the wing half span (1/2 the wingspan)
  5. Input the desired balance point percentage. (for normal planes it should be between 30-33%, flying wings will be 20-25%) This should get you in the ballpark. Other factors that will effect CG position are tail area, tail moment and airfoils. Always set your plane up a little nose heavy for first flights!!!


     The calculator will give you the CG at the wing root! Plus a
     few other numbers you might be interested in.

 

 
 

 

The Center of Gravity Calculator  

  
This will give the wings Center of Gravity (CG)  as measured from the leading edge of the Root Cord. If you want to find out the percentage of the Mean Aerodynamic Cord (MAC) for a given position of the CG you should use the form on

  
 

Enter Root Cord (A): 
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