Note 5 — VIII EXPERIMENTS OF 1904-’05

The Wrights carried 70 pounds of iron bars in many of the flights of 1904-’05, and could fly with less power than if that load had not been carried. Here is the explanation: The center of gravity of their machine was so far back of the center of pressure on the wings that an air pressure of 70 pounds was required on the top side of the horizontal elevator in front, to make the center of lift and center of gravity coincide. Any downward pressure on the elevator, the brothers reasoned, regardless of whether produced by the air or by a weight, would have to be supported by the main planes. But if the downward pressure is obtained by use of the elevator, then two drags are created, one on the elevator itself, and the other on the wings, in consequence of carrying that extra pressure on the elevator. On the other hand, an equal downward pressure produced by a weight, carried at the same distance as the elevator in front of the wings, would add little to the drag on the elevator, because it would dispose of the necessity for a downward pressure on that part of the machine, and there would then be only the drag on the wings.