Courtesy of the Scientific American
Testing a Gnome motor on a gun carriage. So great is the power of the engine that the tongue of the heavy carriage is buried in the ground to hold it in place
"Why can't we make a glider that would be a success?" the brothers asked each other. They were sure they could, and they got so excited in talking it over that it nearly brought back Orville's fever. When he got well they studied aeronautics with the greatest care, approaching the subject with all the thoroughness that later made their name a byword in aviation for care and deliberation.
Neither of these two young men was over demonstrative, and neither was lacking in the ability for years and years of the hardest kind of work, but together they made an ideal team for taking up the invention of something that all the scientists of the world hitherto had failed to develop. Wilbur was called by those who knew him one of the most silent men that ever lived, as he never uttered a word unless he had something to say, and then he said it in the most direct and the briefest possible manner. He had an unlimited capacity for hard work, nerves of steel and the kind of daring that makes the aviator face death with pleasure every minute of the time he is in the air.
No less daring is Orville, the younger of the two, who is a little bit more talkative and more full of enthusiasm than was Wilbur. He was the man the reporters always went to when they knew the elder brother would never say a word, and his geniality never failed them. He also is a true scientist and tireless in the work of developing the art of aviation.
First, the brothers read all the learned and scientific books of Professor Langley, and Octave Chanute, the two first great American pioneers in aviation, and the reports of Lilienthal, Maxim, and the brilliant French scientists.
They saw, as did Professor Langley, that it was out of the question to try to make a machine that would fly by moving its wings like a bird. Then they began with great kites, and next made gliders—that is, aeroplanes without engines—for the brothers knew that there was no use in trying to make a machine-driven, heavier-than-air flier before they had tested out practically all the theories of the earlier scientists.
They fashioned their gliders of two parallel main planes like those of Octave Chanute. The width, length, distance between planes, rudders, auxiliary planes and their placing were all problems for the most careful study. It was very discouraging work, for no big thing comes easily. As their experiments proceeded they said they found one rule after another incorrect, and they finally discarded most of the books the scientists had written. Then with characteristic patience they started in to work out the problem from first principles. "We had taken aeronautics merely as a sport," they wrote later. "We reluctantly entered upon the scientific side of it. But we soon found the work so fascinating that we were drawn into it deeper and deeper."
The Wrights knew that an oblong plane—that is, a long narrow one—driven through the air broadside first is more evenly supported by the air than would be a plane of the same area but square in shape. The reason for this is that the air gives the greatest amount of support to a plane at the entering edge, as it is called in aviation—that is, the edge where it is advancing into the air. A little way from the edge the air begins to slip off at the back and sides and the support decreases. Thus, it will be seen that if the rear surface, which gives little support because the air slips away from under it, is put at the sides, giving the plane a greater spread from tip to tip and not so much depth from front to rear, the plane is more efficient—that is, more stable, less subject to drifting, and better able to meet the varying wind currents. Scientists call this proportion of the spread to the depth the aspect ratio of planes. For instance, if a plane has a spread of 30 feet and a depth of 6 feet it is said to have an aspect ratio of 5. This is a very important consideration in the designing of an aeroplane, because aspect ratio is a factor in the speed. In general, high speed machines have a smaller aspect ratio than slower ones. The aspect ratio also has an important bearing on the general efficiency of an aeroplane, but the lifting power of a plane is figured as proportionate to its total area. In order to hold the air, and keep its supporting influence, aviators have tried methods of enclosing their planes like box kites, and putting edges on the under sides. This latter was found a mistake because the edge tended to decrease the speed of the flier and did more harm than the good obtained through keeping the air.
In aviation, as we know it to-day, aeroplane builders believe in giving their planes a slight arch upward and backward from the entering edge, letting it reach its highest point about one third of the way back and then letting it slope down to the level of the rear edge gradually. This curve, which is called the camber, is mathematically figured out with the most painstaking care, and was one of the things the Wright brothers worked out very carefully in their early models. Also, planes are driven through the air at an angle—that is, with the entering edge higher than the rear edge—because the upward tilt gives the air current a chance to get under the plane and support it. This angle is called by the scientists the angle of incidence and is very important because of its relation to the lifting powers of the planes.