Radio Controlled or "R/C" sailplanes are small to large usually engine-less model aircraft also known as gliders. The sailplanes are constructed from a variety of materials including balsa wood, different kinds of foam, maybe some plastic, kevlar, carbon fiber and epoxy, in various combinations of each. Sailplanes don't have or need engines to keep them flying, although many use electric motors or even gas engines to spin propellers lifting the sailplanes to a high altitude. As in real (human piloted) gliders, R/C sailplanes rely on the same mechanisms for gaining and keeping altitude: thermal and slope lift. Some people think that you can just toss a sailplane into the wind and the plane will just rise like a kite into the air. Instead, a sailplane that has no power will always be descending or falling downwards through the air. If the air below the plane is happens to be rising faster than the plane is falling, the plane will rise with the air upwards, and then the real fun begins...

Sailplanes have some very nice traits in that they're noiseless, don't produce gas exhaust, need to continually charge and recharged between flying sessions, or get a coat of 'slime' over every exposed surface of the airframe after being flown as in gas-powered planes.

Sailplanes have an advantage over motorized planes, either gas or electric, in that under certain conditions, can be flown for an hour or even longer. You don't just launch your sailplane and then glide down to the ground. You fly, fly, and fly until your eyes get tired or it's time to have lunch. The ultimate goal is to stay airborne and that means 'looking' for thermals or flying on the edge of a slope which gives the sailplane lift. Once your sailplane is aloft, regardless of how high, the sailplane may only remain in the air for a couple of minutes or less. However, if there is lift available and the pilot has gained a reasonable amount of experience, the sailplane can remain in the air continuously, riding on that lift...

Once you're in the 'lift', you rise or stay at the same altitude. There is something very special about launching a handlaunch glider in a small field, groping around for lift, finding some and then specking it (making the sailplane go so high that it is a 'speck' in the sky). Once you've done this with a sailplane, you will be hooked into this hobby for the rest of your life, so choose your hobbies carefully.

Sailplanes can be launched from the ground by merely throwing them to get altitude, known to the 'purest pilots' as Hand Launch Gliders or HLG, flying above the edge of windward facing slope, or by using a towing mechanism from the ground such as a long rubber band known as a hi-start or with an electric winch. (You can see a diagram of a hi-start here.) To get the sailplane to a high altitude means attaching your sailplane the line end of the hi-start with a ring on the hi-start and 'tow hook' on the bottom of the plane (just in front of the plane's center of gravity) and staking the rubber end into the ground. Start by stretching the rubber downwind and when there's enough tension (depends on the weight of the sailplane) releasing or sometimes throwing your sailplane up and into the wind. The hi-start will cause the plane to rise quite quickly depending on the weight of the sailplane, the tension on the hi-start, and the amount of wind that is blowing. Launches can be as high as the hi-start is long or even longer under good conditions.

Winch-driven launches can be higher than hi-start launches, and certainly are more convenient, but can also destroy a sailplane if too much force is applied to the sailplane during launch. Typically, there is a foot pedal that allows the pilot of the sailplane control over how much 'winching' occurs during a launch. Tapping the foot pedal can then modulate the force by turning on and off the winch.

Launching sailplanes from a slope can be much easier. You don't need a hi-start or winch, you don't really have to search out thermals, instead you just give the glider a good toss into the wind. The rising air on the slope face provides the lift to keep the sailplane aloft. Keep the plane in the lift and the plane will continue to stay at the same altitude or rise. On good days, the only limitation of duration of a flight is the amount of available daylight or battery power for the radio equipment.

All classes of thermal sailplanes will work well on in a slope environment. The only potential problem about flying, say a handlaunch sailplane, on a slope is the amount of available lift can be too much for a sailplane designed for extracting every breath of lift available. I.E. You can't get the plane down on the ground again easily! For a slope, you can sacrifice lightness of construction and other efficiency in the airframe for a plane designed for speed and strength. It is not uncommon for some slope gliders to fly at speeds in excess of 120 mph or faster as long as the conditions permit this.

Thermal sailplanes generally fall into one of four categories:

Slope sailplanes are in typically two categories:

Additionally, some of these planes can fall into multiple categories meaning that thermal planes can be flown equally well on the slope, handlaunch planes can be thermalled like open-class sailplanes, etc. Sometimes I like to fly my handlaunch planes on the slope when the wind is light and I fly some of my thermal duration or other open-class planes there too. Sometimes I even attach tow hooks on the bottom of my combat wings and shoot them into the air with a shortened high-start for a quick combat session, when I'm not on the slope or there's no wind.