Here's the skinny on finding the CG. Finding the Center of Gravity or CG of a wing section is a fairly simple process. Simple straight wings with no sweep only require you to go back about 1/4 of the way back from the leading edge to find the CG. For more complicated wing sections, you will need to find the Mean Aerodynamic Chord or MAC. The MAC is a line that runs along the chord that defines the average chord of the wing section.

The drawing below shows a swept wing section.   One way to find the MAC is to add the tip chord dimension (y) to the leading and trailing edge of the root. Then add the root chord dimension (x) to the leading and trailing edge of the tip. Finally, connect the end points with diagonal lines as shown below. Draw a line, along the wing chord, where the lines intersect - this is the MAC line. The CG for most aircraft will be located at about 25% or 1/4 back from the leading edge along the MAC line.