Where should the CG be on an RC plane?

A plane balanced in the wrong place is the most common reason a maiden flight ends in a crash. Here is how to find the right point for any layout.

Start with the MAC

On a straight wing, the CG sits about 25–33 % of the chord back from the leading edge. A tapered or swept wing has no single chord, so we use the mean aerodynamic chord (MAC). On a swept wing the MAC sits further back, so the CG moves back too.

Check the static margin

The tail pushes the neutral point back. A big tail on a long arm lets you balance further aft. A flying wing has no tail, so its CG must sit close to the quarter of the MAC, usually 15–20 %.

Worked example: Koonj 1650

Root chord 270 mm, tip 170 mm, 1650 mm span, a small sweep. The MAC is 224 mm long. At 27 % MAC the CG is 81 mm behind the leading edge at the fuselage side, with about 20 % static margin. That is a stable, safe setting for a first flight.

Try it in the CG calculator