Written some years ago by Gordon Whitehead, "The Winning Formula" has Gordon deriving a formula for calculating the center of gravity position for a model aircraft where the Static Margin, or degree of stability in the pitch axis, is ten percent of wing chord. Gordon derives the Winning Formula from the fuller aerodynamics formula in the standard equation for Static Margin, detailed in Martin Simon's book Model Aircraft Aerodynamics and elsewhere. The original formula originated in an old Aeromodeller plans handbook but it's origin was lost, until Gordon showed it to be the standard formula with some nifty algebra.
The Winning Formula reduces the number of variables to locate the CG from nine to four.
The formula and it's big brother, full neutral point, are available from this website as free software which the aeromodeller can use to ensure his CG placement is optimum.
The article itself, from Radio Modeller all those years ago, is so interesting, it is included here for those who are interested.
10 per cent Static Margin equates to a separation distance between the CG and Neutral Point of 10 percent of wing chord, with the Neutral Point being aft of the CG. It is a good starting point for model aircraft. Reducing the Static Margin to values lower than 10 per cent, is OK providing care is taken, along with the aeromodeller knowing that the shorter the separation, the "hotter" the aeroplane.
Related Articles:
Neutral Point and Static Margin. 1. Visualisation.
Neutral Point and Static Margin. 2. The Winning Formula.
Neutral Point and Static Margin. 3. Software.
Neutral Point and Static Margin 4. Tucking In
Neutral Point and Static Margin. 5. Stall On Landing Approach
Neutral Point and Static Margin. 6. Aircraft unstable about the Pitch, or lateral Axis.
