CENTER OF GRAVITY BASICS

The secret to a plane that flies well

It happens too often, unfortunately: Someone with a brand new airplane shows up at the field and has everything working perfectly. The radio checks out, and all the controls move in the correct directions; the engine runs reliably and provides plenty of power. The model taxis out and runs down the field and becomes airborne. Right away, it starts to rock its wings; the nose points up sharply; and after several frightening seconds, it hits the ground—hard! The pilot did everything right except that he forgot to check the model’s balance.

To successfully test-fly a new model be absolutely certain that the model is balanced at the correct center of gravity (CG). Nothing can spoil your day more than trying to sort out a tail-heavy model after it has left the ground. It is a fair bet that improper CG location is responsible for more broken airplanes than engine and radio issues combined. Let’s look at some methods for determining the CG.

Editor’s note: Please note that these techniques are good for close estimations and will get your model balanced in the ballpark well within the proper CG range so that it is safe to test-fly. We’re not taking into account unusual configurations or lifting tail surfaces.

BALANCING ACT

While balancing a monoplane, use the location indicated in your model’s instructions or plans measured back from the leading edge. If you don’t have this information, it isn’t hard to figure it out yourself.