Most airfoils have an aerodynamic center located around 25% – 33% of the mean aerodynamic chord (MAC) from the leading edge, so 25% is often used as a reference point on our models. Locating the CG at 25% is a safe bet for a maiden flight. Remember, it’s always better to have a nose heavy plane than a tail heavy one.

As the CG moves rearward, less tail-down force is required and the stalling speed decreases. However, moving a CG too far aft reduces pitch stability. Less tail-down force with an aft CG also means less tail trim drag, resulting in higher cruising airspeed and better fuel efficiency.

A correctly balancing rc airplane, sitting on your fingertips, will either be level or have the nose pointing slightly downwards. If the tail points downwards then the plane is tail heavy and you need to do something about that.

Balancing a low wing from the bottom of the wing creates an unstable balance point because the weight is on top of the cg wanting to make the plane fall in either direction. Put the weight under the cg and it creates a stable balance point. Alternatively you don’t have to actually balance it at all.

Add weight to either the rear or front depending on where it’s needed. Use just enough glue to hold the weight from moving, then check the balance by lifting the plane with your fingertips. Repeat the process until the airplane is balanced. Then glue the weights securely to the airplane.

between 2.5 and 3.5 pounds

To calculate the center of gravity, divide total weight distance moment by total mass of the system. Thus, the center of gravity is 13 meter from left-hand side.

Start by standing up and placing the tip of your index finger just below your navel. The height of your center of gravity is three finger widths (about two inches) below that point. Move your index finger to that point.