Did you ever see a bird or an insect fly? Before you answer, “Of course,” let us define more exactly what we mean by “see.”
Byvoorbeeld, many people, when they see a bird, notice only a beautiful array of feathers. But a cat, seeing the same bird, may see a good dinner. Dan weer, a farmer seeing a bird, say a swallow, might see a sign of the approach of spring. So “seeing” can mean much more than just receiving an image on the retina of the eye.
Consider, byvoorbeeld, an experienced watchmaker examining an expertly made timepiece. What does he “see”? His view goes deeper than just a look inside the watchcase. He judges its timekeeping qualities, weighing the pros and cons of the method of construction used and assessing its efficiency. His “seeing” might reach into the mind of the watch’s designer, as he equates the result he sees with the problems the designer had to overcome. He might even strike up a kind of respectful acquaintanceship with the maker by means of his product.
This example of “seeing” will prepare us for an in-depth “look” at the flight of birds and insects. Without a doubt their flight is graceful, but just how good are they as flying machines?
When you last saw, say, a dragonfly, what did you actually see? Perhaps your attention was drawn to it as it hovered before your eyes. You probably admired it for its beautiful colors glistening in the sun. Then it may have darted off suddenly at surprising speed in a seemingly unpredictable direction. If you had been interested in the science of flight, you might have wondered how that little fellow was able to combine the peculiar hovering qualities of a helicopter and the high-speed stability of a fixed-wing plane. What versatility!
The more you pondered, the more it may have impressed you. Without a doubt the fiercely competing military strategists of the major powers of this world would give a king’s ransom to be able to apply the secrets held by that little insect. So if you had “seen” with a discerning eye you would have observed, not just a beautiful insect, but a wonderful example of versatility in a flying machine.
This coveted quality of versatility is common throughout creation. Take, for instance, the sparrow hawk, which has a wing structure and mechanism bearing no close resemblance to those of a dragonfly. Yet it, ook, is able to hover in one spot and dart off at high speed, two qualities of flight for which man continually strives.
It is worthy of note that a master designer takes all things into account, including environmental effects. He refuses to be enslaved to vested interests or some narrow aspect of technical efficiency. In werklikheid, a skilled designer is recognized by the way he nicely balances technical and aesthetic requirements and then painstakingly extracts the maximum from each aspect.
With this in mind, consider another aspect of flight. Have you noticed that flying creatures do not disturb the senses? The sounds made by them, byvoorbeeld, are generally welcomed sounds. But how different are the nerve-shattering sounds that come from either a fixed-wing plane or a helicopter. Ook, man-made flying machines pollute the air we breathe, causing sickness and disease. What a contrast there is!
But how does a bird stand in comparison with a plane in aerodynamic efficiency? Let us consider the wing. How efficient is it?
That depends a great deal on its shape. After much effort involving higher mathematics and experiments in wind tunnels man has been able to design a wing that provides acceptable flight efficiency. maar, as we might have expected, the bird’s wing also has just the ideal shape for the type of life the particular bird lives. Byvoorbeeld, the albatross and the hawk live widely different lives, and their wings are designed perfectly to meet their varied requirements. Really, who has ever seen an airplane that is able to do what a bird is able to accomplish with its wings?
Wel, dan, what about the method of propulsion? For simplicity we will consider the propeller, of, more specifically, the airscrew. How does this method of propulsion work?
As its name implies, it screws its way through the air, thus giving the required pull to the aircraft to which it is attached. Maar, it differs from a metal screw working in a solid nut because the air slips as it were, thus constituting a continual loss that the solid nut would not have.
To visualize this kind of loss we might think of an angler winding in a large fish. If his boat were rigidly anchored to the river bottom or seabed, the only work done would be in winding in the line with his arms. Maar, if the boat were not anchored, and he wished to retain his exact position, he would have to run his boat engine just fast enough to prevent being pulled toward the fish. All the power used by the engine would thus be pure loss due to the fluidity of the environment.
But what about the wing of the bird? Hoekom, it sidesteps virtually all the slip losses of a propeller due to its marvelously coordinated flapping movements and gliding techniques. Nor is the jet-propulsion method employed by modern aircraft nearly as efficient as the propulsion achieved by the wings of birds.
The flapping and gliding means of propulsion employed by the bird can, in a sense, be compared to the movements of a skater. Try to imagine the skater coasting down a slight incline and then, just before reaching the end of the incline, being able to step up on to the crest of another incline running alongside. In normal skating this principle is employed, except that the legs are thrust sideways to give the body propulsion. In the case of a bird, the downward movement of the wings propels the creature.
What a truly marvelous and efficient flying machine a bird is! Hoekom, it seems to ooze with evidence of ingenuity. en, in particular, what a wonderful instrument that wing is!
Have you seen two gulls dive for the same tidbit and have a near collision? But note, it is only near, for they seem to flow around each other in a flurry of wing flaps as the loser takes evasive action.
Or have you watched a crow landing on a wire fence? Stalling holds no fears for him. As he comes in for a landing it seems as though he will overrun his mark, but around comes the tip of that powerful wing, which had recently done such efficient service as a propeller, and into a stall he goes. And what a stall! How beautifully controlled, as he slides down gently toward the wire! But likely as not, because he is such a suspicious fellow, he will not even land, but pull right out of the stall and nonchalantly flap away, cawing as he goes, quite oblivious to the remarkable feat he has just performed.
Aircraft designers generally recognize the many benefits of moving wings and wings of variable shape, whether to gain added versatility, or to achieve the difficult movements needed to execute landing maneuvers like a bird. But the pitiful results that human engineers have attained with flapping wings and wings of variable shape suggest how far man yet has to go before he can even approach the aerobatic performances seen in creation.
Thus the more we observe and ponder over flying creatures, whether from the aspect of versatility, aerodynamic efficiency or maneuverability, the more we can appreciate what a master of his craft is their Creator. Seeing how beautiful flying creatures are to the eye, as well as how quiet and graceful, we are drawn in appreciation to their Grand Designer.
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