Reflections on a Wandering Life.....

Monday, March 08, 2021

Science Night - How does a Sailplane Work? 

In the previous lesson, we introduced the glider as an aircraft that flies without an engine. We also talked about the difference between a conventional glider (or perhaps I should say “pre-Treaty of Versailles” glider) and what we have come to call a “sailplane.” As mentioned in the previous lesson, the Treaty of Versailles is important, because it is the historical event that motivated the Germans to focus on developing super efficient gliders.

In this lesson, we want to focus on how sailplanes work. To begin, then, we want to be sure we understand how a sailplane differs from a regular glider. Both sailplanes and regular gliders need to be towed aloft, usually by a powered airplane. The difference between them is that once they are released, the regular glider will simply glide back to earth, while the sailplane will search for rising air currents and try to use these rising air currents to stay aloft or even to gain altitude. The process of floating back to earth is called “gliding.” The process of using rising air currents to stay aloft is called “soaring.”

The video above explains how sailplanes use air currents to stay aloft. There is one error I should point out do you. He says, “gliders, also known as sailplanes.” That’s not correct. That implies that “sailplane” is just another term for glider. No. A sailplane is a specific type of glider. All sailplanes are gliders, of course. But all gliders are not sailplanes. But aside from the fact that he keeps saying “glider” when he should be saying “sailplane,” this video is the best technical description of how sailplanes work that you will ever see. It is excellent.

After you have watched the video above, take a look at the one below. The video below is interesting, because it shows a modern version of the gliders from 1930 that we introduced at the beginning of the previous lesson. Very similar. Essentially the same design. So why would anyone want to have such an old fashioned glider like the one below (that is no good for soaring) in the modern age when high performance sailplanes are available? The reason is that these old style gliders are very good as trainers, because they are so easy to fly. A kid could fly one. Mind you, you still need training, and you should limit your flying to days with almost perfect weather, but training gliders like this are very good for learning. So science takes a giant step backward. This is why there will always be a difference between gliders like the trainer below (which is also built by a German company) and high performance German sailplanes like the one we introduced in the video at the end of the previous lesson. So the need for conventional gliders is not going to go away, but It is probably also true that future innovations in powerless flight, especially the ultra light variety, will focus on taking advantage of rising air currents to extend flight.

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