Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/254584
EAA Experimenter 29 feet) and 18-meter (59 feet) spans are common in competition sailplanes, with more than 100 feet in the largest open-class competition sailplane. Sailplanes are called "sun ships," as the energy for natural lift comes from the sun. Wind is the result of solar energy combined with the rotation of the Earth. The fi rst kind of lift used by the glider pioneers was wind against a slope, called ridge lift. The second kind of lift that was discovered was thermal lift. Solar radiation heats the ground and thus the air immediately above the ground. Bubbles or columns of that hot air break loose and rise in the cooler surrounding air. This is how hot-air balloons work and why you see hawks circling, using solar energy to fl y. The soaring birds always have been the living models for sailplanes. The third type of lift that was discovered was wave lift. Under certain atmospheric conditions, wind at more or less right angles to a mountain(s) will set up vertical waves that go high into the atmosphere and have several cycles downwind of the mountain(s) that trigger them. By fl ying in the up- traveling part of the wave, very high altitudes can be achieved. The current sailplane altitude record is more than 50,000 feet. The Perlan Project will attempt to take the record to 90,000 feet. If you have the right mountains, such as the Andes, very long sailplane fl ights are possible in wave conditions. I believe the current record is more than 1,500 miles. There are dif erent ways of launching gliders. One of the earliest was picking up a hang glider and running down a hill or of a clif . That gave way to a bunch of guys pulling at the ends of a V-shaped rope and accelerating the glider to the launch point. Later, bungee cords were used to catapult the gliders. Cars and—even on occasion—horses with towlines were used. Today, ground launching using engine-powered winches is the favored method in many countries for its low cost, low noise, and suitability for fl ight training. In the United States, tow- planes are the most common launching method. Each method has its advantages, disadvantages, and training requirements. There also are gliders and sailplanes with engines. The main reason is to give independence of operation as there are rela- tively few airports that have provisions for launching gliders. Engine-equipped gliders can operate from almost all general aviation airports. The two main types of powered gliders are the self-launching sailplanes (SLSs), which look like conven- tional sailplanes but have retracting props on masts that pop out behind the wing for launching and the occasional save from an out landing. The other type of powered sailplane is a motorglider. Unlike the SLS, which typically have two-stroke engines and look like sailplanes, the motorgliders look like long-winged light planes and have four-stroke engines. There are some that are blends of the two types. Sometimes called touring motorgliders, they can be used for very efficient powered flight, and when there is natural lift available, the engine can be shut down for silent flight. Efficiency is the reason why some light-sport aircraft look like short-wing motorgliders. Efficiency is also the reason airframes of powered sail- planes are used for many of the pioneering efforts at electric-powered flight. DIFFERENCES BET WEEN GLIDERS AND LIGHT POWERED PL ANES The long wings of a glider/sailplane make it more reluctant to roll and more dependent on an ef ective use of the rudder for coordinated fl ight than its short-winged brothers. While skids under the nose are still sometimes used for brakes in the light- est gliders, almost all now have a mono wheel near the center of gravity and equipped with a brake; some have tail wheels, some nose wheels, and some both. Tip wheels or skids are used to protect the wingtips when roll control power is lost on landing. The mono wheel landing gear has become standard because of its simplicity, light weight, and low drag. Most high-performance sailplanes have a retractable main gear. Due to landing gear ge- ometry and very low stall speeds, gliders are normally fl own onto the ground at above stall speed, like a wheel landing in a powered taildragger. The touring-type motorgliders have the normal light plane types of landing gear. One control that is normal on gliders/sail- planes but rare on conventional light planes is spoilers. Gliders/ sailplanes can be so ef cient that they do not want to come down, which makes landing dif cult. Spoilers are drag and lift- reduction aerodynamic surfaces that can be used like the power plane's throttle to control the descent rate without airspeed changes. Almost all sailplanes are designed to be relatively easy to disassemble for trailering and compact storage. THE GLIDER'S ROLE IN THE EARLY DEVELOPMENT OF FLIGHT Sir George Cayley, an English gentleman, was one of the fi rst to look at fl ight in a scientifi c manner in the 1800s. He built a man-carrying glider in the 1850s. A young family member is reported to have been the fi rst glider passenger in recorded The Silent II Electro has a small electric motor in the nose and has self- launching capabilities. Electric fl ight is available now! E A A E X P _ F e b 1 4 . i n d d 2 9 EAAEXP_Feb14.indd 29 2 / 3 / 1 4 3 : 1 7 P M 2/3/14 3:17 PM