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Gliders | |
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Gliding or flying has been a wish of mankind for thousands of years.
Many myths and legends have been told about man trying to fly.
The first person to actually leave a written record was Sir George Cayley.
He realized that trying to copy the flapping wings of birds was a waste of time. Instead he looked at how birds soared or glided. 
By 1799 Cayley made a very important discovery. He found that air flowing over the top of a curved, fixed wing will create "lift". Lift is what makes flight possible. The wing needs to be big. The airflow needs to be fast. This gives the best lift. He also decided that a tail was needed to steady the glider. 
Cayley actually built a glider. His assistant flew in it. Later Cayley wrote about his experiences. This was very important. For the next 100 years people interested in flight would study his writings.
Another important person was Otto Lilienthal. Eighty years later
Lilienthal started building hang gliders. He lived in Berlin, Germany.
Lilienthal flew off a hill near his home. His glider was a wing with a
hole in the middle.
Lilienthal would stick his head up through the hole. He would hold onto
the wing and run down the hill. He could glide 150 feet or more! He
did this more than 2000 times.
He learned that he needed a tail on the glider. The tail helped keep it steady. He learned about: roll - tipping from side to side; pitch - the nose moving up and down; and yaw - turning right to left. This helped him control the glider much better. There was one problem. At the end of each flight the glider would suddenly dive down into the ground. Lilienthal didn't know why. He finally learned that it was because of the angle of the wing to the wind. This is called a "stall". Lilienthal died in 1896 when his glider stalled and dove to the ground. Why does an aircraft stall? Remember, the top of a wing is curved in the front and flat in the back. When the air moves over the top of the wing it must move faster because of the curve. The air under the wing moves slower. One of the results is that lift is created. When the wing is at the wrong angle lift can not be created. This is a stall. There is no more lift. The glider goes down nose first. Today, thousands of people "glide". Many build their own gliders. They jump off mountains, cliffs and hills. Some gliders are towed by an airplane up to 5000 feet or more and let go. There are many competitions and meets all over the world. If you want to find out more ask your local library or school. See if there are any glider clubs in your area. There are magazines and you can find out more on the Internet.
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