ACTION OF A SKIPPER.--When the skipper leaves the hands of the thrower it goes through the air in such a way that its fiat surface is absolutely on a line with the direction in which it is projected.

At first it moves through the air solely by force of the power which impels it, and does not in any way depend on the air to hold it up. See Fig.

1, in which A represents the line of projection, and B the disk in its flight.

_Fig. 11. A Skipper in Flight._

After it has traveled a certain distance, and the force decreases, it begins to descend, thus describing the line C, Fig. 1, the disk B, in this case descending, without changing its position, which might be described by saying that it merely settles down to the earth without changing its plane.

The skipper still remains horizontal, so that as it moves toward the earth its flat surface, which is now exposed to the action of the air, meets with a resistance, and this changes the angle of the disk, so that it will not be horizontal. Instead it a.s.sumes the position as indicated at D, and this impinging effect against the air causes the skipper to move upwardly along the line E, and having reached a certain limit, as at, say E, it automatically again changes its angle and moves downwardly along the path F, and thus continues to undulate, more or less, dependent on the combined action of the power and weight, or momentum, until it reaches the earth.

It is, therefore, clear that the atmosphere has an action on a plane surface, and that the extent of the action, to sustain it in flight, depends on two things, surface and speed.

Furthermore, the greater the speed the less the necessity for surface, and that for gliding purposes speed may be sacrificed, in a large measure, where there is a large surface.

This very action of the skipper is utilized by the aviator in volplaning,--that is, where the power of the engine is cut off, either by accident, or designedly, and the machine descends to the earth, whether in a long straight glide, or in a great circle.

As the machine nears the earth it is caused to change the angle of flight by the control mechanism so that it will dart upwardly at an angle, or downwardly, and thus enable the pilot to sail to another point beyond where he may safely land.

This changing the course of the machine so that it will glide upwardly, means that the incidence of the planes has been changed to a positive angle.

ANGLE OF INCIDENCE.--In aviation this is a term given to the position of a plane, relative to the air against which it impinges. If, for instance, an aeroplane is moving through the air with the front margin of the planes higher than their rear margins, it is said to have the planes at a positive angle of incidence. If the rear margins are higher than the front, then the planes have a negative angle of incidence.

The word incidence really means, a falling upon, or against; and it will be seen, therefore, that the angle of incidence means the tilt of the planes in relation to the air which strikes it.

Having in view, therefore, that the two qualities, namely, speed and surface, bear an intimate relation with each other, it may be understood wherein mechanical flight is supposed to be a.n.a.logous to bird flight.

SPEED AND SURFACE.--Birds which poise in the air, like the humming bird, do so because they beat their wings with great rapidity. Those which soar, as stated, can do so only by moving through the atmosphere rapidly, or by having a large wing spread relative to the weight. It will thus be seen that speed and surface become the controlling factors in flight, and that while the latter may be entirely eliminated from the problem, speed is absolutely necessary under any and all conditions.

By speed in this connection is not meant high velocity, but that a movement, produced by power expressed in some form, is the sole and most necessary requisite to movement through the air with all heavier-than-air machines.

If sufficient power can be applied to an aeroplane, surface is of no consequence; shape need not be considered, and any sort of contrivance will move through the air horizontally.

CONTROL OF THE DIRECTION OF FLIGHT.--But the control of such a body, when propelled through s.p.a.ce by force alone, is a different matter. To change the machine from a straight path to a curved one, means that it must be acted upon by some external force.

We have explained that power is something which is inherent in the thing itself. Now, in order that there may be a change imparted to a moving ma.s.s, advantage must be taken of the medium through which it moves,--the atmosphere.

VERTICAL CONTROL PLANES.--If vertically-arranged planes are provided, either fore or aft of the machine, or at both ends, the angles of incidence may be such as to cause the machine to turn from its straight course.

In practice, therefore, since it is difficult to supply sufficient power to a machine to keep it in motion horizontally, at all times, aeroplanes are provided with supporting surfaces, and this aid in holding it up grows less and less as its speed increases.

But, however strong the power, or great the speed, its control from side to side is not dependent on the power of the engine, or the speed at which it travels through the air.

Here the size of the vertical planes, and their angles, are the only factors to be considered, and these questions will be considered in their proper places.

CHAPTER III

THE FORM OR SHAPE OF FLYING MACHINES

EVERY investigator, experimenter, and scientist, who has given the subject of flight study, proceeds on the theory that in order to fly man must copy nature, and make the machine similar to the type so provided.

THE THEORY OF COPYING NATURE.--If such is the case then it is pertinent to inquire which bird is the proper example to use for mechanical flight.

We have shown that they differ so radically in every essential, that what would be correct in one thing would be entirely wrong in another.

The bi-plane is certainly not a true copy. The only thing in the Wright machine which in any way resembles the bird's wing, is the rounded end of the planes, and judging from other machines, which have square ends, this slight similarity does not contribute to its stability or otherwise help the structure.

The monoplane, which is much nearer the bird type, has also sounded wing ends, made not so much for the purpose of imitating the wing of the bird, as for structural reasons.

HULLS OF VESSELS.--If some marine architect should come forward and a.s.sert that he intended to follow nature by making a boat with a hull of the shape or outline of a duck, or other swimming fowl, he would be laughed at, and justly so, because the lines of vessels which are most efficient are not made like those of a duck or other swimming creatures.

MAN DOES NOT COPY NATURE.--Look about you, and see how many mechanical devices follow the forms laid down by nature, or in what respect man uses the types which nature provides in devising the many inventions which ingenuity has brought forth.

PRINCIPLES ESSENTIAL, NOT FORMS.--It is essential that man shall follow nature's laws. He cannot evade the principles on which the operations of mechanism depend; but in doing so he has, in nearly every instance, departed from the form which nature has suggested, and made the machine irrespective of nature's type.

Let us consider some of these striking differences to ill.u.s.trate this fact. Originally pins were stuck upon a paper web by hand, and placed in rows, equidistant from each other. This necessitates the cooperative function of the fingers and the eye. An expert pin sticker could thus a.s.semble from four to five thousand pins a day.

The first mechanical pinsticker placed over 500,000 pins a day on the web, rejecting every bent or headless pin, and did the work with greater accuracy than it was possible to do it by hand.

There was not the suggestion of an eye, or a finger in the entire machine, to show that nature furnished the type.

NATURE NOT THE GUIDE AS TO FORMS.--Nature does not furnish a wheel in any of its mechanical expressions. If man followed nature's form in the building of the locomotive, it would move along on four legs like an elephant. Curiously enough, one of the first road wagons had "push legs,"--an instance where the mechanic tried to copy nature,--and failed.

THE PROPELLER TYPE.--The well known propeller is a type of wheel which has no prototype in nature. It is maintained that the tail of a fish in its movement suggested the propeller, but the latter is a long departure from it.

The Venetian rower, who stands at the stern, and with a long-bladed oar, fulcrumed to the boat's extremity, in making his graceful lateral oscillations, simulates the propelling motion of the tail in an absolutely perfect manner, but it is not a propeller, by any means comparable to the kind mounted on a shaft, and revoluble.

How much more efficient are the spirally-formed blades of the propeller than any wing or fin movement, in air or sea. There is no comparison between the two forms in utility or value.

Again, the connecting points of the arms and legs with the trunk of a human body afford the most perfect types of universal joints which nature has produced. The man-made universal joint has a wider range of movement, possesses greater strength, and is more perfect mechanically.

A universal joint is a piece of mechanism between two elements, which enables them to be turned, or moved, at any angle relative to each other.

But why multiply these instances. Like samples will be found on every hand, and in all directions, and man, the greatest of all of nature's products, while imperfect in himself, is improving and adapting the things he sees about him.

WHY SPECIALLY-DESIGNED FORMS IMPROVE NATURAL STRUCTURES.--The reason for this is, primarily, that the inventor must design the article for its special work, and in doing so makes it better adapted to do that particular thing. The hands and fingers can do a multiplicity of things, but it cannot do any particular work with the facility or the degree of perfection that is possible with the machine made for that purpose.

The hands and fingers will bind a sheaf of wheat, but it cannot compete with the special machine made for that purpose. On the other hand the binder has no capacity to do anything else than what it was specially made for.

In applying the same sort of reasoning to the building of flying machines we must be led to the conclusion that the inventor can, and will, eventually, bring out a form which is as far superior to the form which nature has taught us to use as the wonderful machines we see all about us are superior to carry out the special work they were designed to do.

On land, man has shown this superiority over matter, and so on the sea. Singularly, the submarines, which go beneath the sea, are very far from that perfected state which have been attained by vessels sailing on the surface; and while the means of transportation on land are arriving at points where the developments are swift and remarkable, the s.p.a.ce above the earth has not yet been conquered, but is going through that same period of development which precedes the production of the true form itself.

MECHANISM DEVOID OF INTELLIGENCE.--The great error, however, in seeking to copy nature's form in a flying machine is, that we cannot invest the mechanism with that which the bird has, namely, a guiding intelligence to direct it instinctively, as the flying creature does.

A MACHINE MUST HAVE A SUBSt.i.tUTE FOR INTELLIGENCE.

--Such being the case it must be endowed with something which is a subst.i.tute. A bird is a supple, pliant organism; a machine is a rigid structure. One is capable of being directed by a mind which is a part of the thing itself; while the other must depend on an intelligence which is separate from it, and not responsive in feeling or movement.

For the foregoing reasons success can never be attained until some structural form is devised which will consider the flying machine independently of the prototypes pointed out as the correct things to follow. It does not, necessarily, have to be unlike the bird form, but we do know that the present structures have been made and insisted upon blindly, because of this wrong insistence on forms.