Sailplanes/Gliders
A radio-controlled sailplane, or glider, is a type of radio-controlled airplane that normally does not have a form of propulsion. They are able to sustain continuous flight by using the lift produced by slopes and thermals. They can be made from a variety of materials, including wood, plastic, polymer foams, and composites, and can vary in wing loading from very light to relatively heavy, depending on their use.
Launching a Glider
In order to get the glider off of the ground, the plane must be launched. It can be launched by any one of the following methods:
Hand Launch
Hand launching is the simplest way to get a model into the air. All the pilot needs to do is throw it horizontally, giving it sufficient speed. This method is usually combined with slope soaring, so the glider can gain altitude.
Discus Launch
A discus launched glider (DLG) is simply catapulted into the air with a spinning motion, much like throwing a discus.
Towline Launch
In this method another person runs along the ground, pulling a long (50 – 100m) piece of string with the glider attached to the end, while the pilot steers it. It can be performed on any flat piece of terrain, as the glider is given sufficient altitude during the launch.
Bungee Launch
This launch is a variant of the towline launch, only it is performed alone. The running person is replaced by a piece of elastic band attached to the ground.
Winch/Hoist Launch
This launch is also a variant of the towline launch and is also typically performed alone. The running person is replaced by a steel cable attached to an electric powered winch, which is controlled by the pilot via a foot pedal.
“Piggyback” Launch
A powerful radio-controlled airplane tows the model glider into the air, not unlike the method in which real gliders are launched. Although this method is spectacular, it requires a very experienced pilot to steer the towing airplane.
Flying Sailplanes/Gliders
In order to keep the plane in the air, we have to use the air to keep it soaring. There are several terms for methods one should familiarize themselves with in order to understand how sailplanes/gliders are flown:
Slope soaring uses the lift produced by wind blowing up the face of a steep slope on hills, mountains, and cliffs.
Dynamic soaring is a relatively new style of flying model gliders whereby the wind shear just downwind of certain slopes can be used to create high speeds. It involves gaining altitude, then soaring into a patch of dead air, then back into the lift to gain speed. Dynamic “slope” soaring, which utilizes the leeward or “backside” of a hill, has recently become very popular.
Thermal soaring uses columns of warm rising air, called thermals, to provide lift for the glider.
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