C Earnest

Let me explain to you why the CG position has an effect on the G load vs. lift requirements of the wing. For a conventional aircraft (tail aft), static stability occurs when the center of gravity is ahead of the center of lift. To maintain level (1G) flight, the tail must generate a downward force to offset both pitching moment of the airfoil and the forward CG.

Pylon racers generate very high G loading in the turns. This is evidenced visually by the nearly 90 degree angle of the wings when pulling at the pylon. The actual load depends upon both the speed of the aircraft as well as the radius of the turn. Use 170 mph (about 250 feet/second) and a radius of 71 feet for the radius of the loose turn at pylons 2&3, or a radius of 50 feet for a tight turn at pylon 1 for your own calculations.

Now as the CG is moved forward, the down force from the tail must increase. As you increase the G loading, this force multiplied. This means that the wing must also increase the amount of lift generated. Greater lift generated corresponds to greater induced drag. Therefore, for minimum drag, it is common knowledge that you fly with the CG as far back as possible. Typically, the trailing edge of the elevator will only move about 1/8” from neutral to full up elevator. I have flown some with even less throw.

BTW, Dr. Dolittle wrote a rather nice article on the concept of balance and speed of aircraft back around 1928. Who was Dr. Dolittle? He was kind of well known as the first pilot to hit 300 mph, and flew the Tokyo raid in 1942. His first name was Jimmy, he raced the GeeBee and he was also a General in the Army Air Corp.