Goodwin’s voice aroused Harry from his absorption. “No questions answered after the train leaves,” he said. Harry felt very much at home with him already. Here was a man, unaffected, simple, offhand, competent, self-assured, and levelheaded. Nothing of the crank or the visionary,—the kind of man who helps to advance the science of aviation.
“I thought the propeller looked pretty big across the field,” said Harry; “but it doesn’t look so big now. That all there is to the motor,—just that that’s on the propeller?”
“That’s all, but it’s enough,” Mr. Goodwin answered.
“It makes a whole lot of fuss, anyway.”
“Right you are, and she fits like a suit of clothes. It isn’t wholly a question of how much power you have, you know, but does the power fit? That’s the question. See?”
“But doesn’t more power mean more speed?” Harry asked.
Goodwin laughed. “No, not exactly. The motor sustains the machine in flight. Now, if there’s a good big supporting wing area, why, the engine can be smaller—it’s got to be, in fact.”
“I’m afraid I’ll have to go to the foot of the class,” laughed Harry.
“So? Why? You never studied the subject? Well, see here, now, I’ll give you the A B C of it and then we’ll hop in. The more spread there is, the less supporting work the propeller has to do. So a powerful motor fits a small machine, and a big machine takes less power to get the same results. Now, you take Curtiss; he cuts down his planes, makes his machine small, and what’s the answer? Does he get along with less power? No, he needs more. You see, it isn’t a case of more power, more speed. It’s having your power to fit your machine. The propeller is more than a propeller,—it’s a sustainer as well. Stop the propeller of a boat, and the boat stands still. Stop an aero propeller, and down she comes. Propeller keeps her up and keeps her going—two jobs. If you lessen your support in one way, you must make it up in another. An aeroplane is sustained by its speed with help from its planes. Well, now, the more area you have, the less the motor has to do. You’ve heard aviation compared to sailing, and that’s just the very thing that it isn’t a bit like. Did you ever skate on thin ice? Well, there you have it. If you want to keep from going in, skate fast. Now, if you put a large motor on a large machine, you don’t get a normal increase of speed, by any means. So you see, it’s not a question of power—it’s a question of a nice, neat fit, as you might say.”
Harry remembered this later, when he saw more than one model aeroplane lurch and flutter to the ground, to the amazement and disappointment of its young maker. And when he returned to Oakwood, he remembered the words of his aviator friend, “It isn’t a question of power—it’s a question of nice, neat fit.”