Southern Ontario Glider Group Inc.
a Charter Club of the Model Aeronautics Association of Canada
Types of R/C Sailplanes
Tongue-in-cheek, we refer to ourselves as the Southern Ontario "Glider" Group, but our aircraft are more properly called "Sailplanes". The sophisticated design of Sailplanes permits them to routinely exceed initial launch height by exploiting rising air.
We fly a variety of model sailplane types for fun, and for competition. We encourage the construction of models from kits. It's also possible to purchase Almost-Ready-to-Fly ("ARF") sailplanes.
Some sailplanes are self-propelled to reach their initial launch altitude, at which point their electric propulsion motor is shut off. These "Electric Sailplanes" typically employ a lithium polymer (LiPo) battery and brushless electric motor with folding propeller.
To participate in Electric Sailplane contests, your "Electric Sailplane" must have an onboard device to shut the motor off at a specified altitude and within a specified motor-run duration. This ensures that every competitor begins the search for lift from the same initial launch height, focussing the competition on soaring skill, rather than on propulsion capability.
Alternatively, you can fly traditional "Pure Sailplanes" which have no on-board propulsion motor. Instead, to gain their initial launch height, an external launching device which is not part of the aircraft is used. Eliminating the on-board propulsion system improves soaring performance by reducing the aircraft's weight. But if rising air cannot be found, a forced landing may result, sometimes at some distance from the launch point.
The most common types of external devices for launching Pure Sailplanes, are the electric "Winch" powered by a lead-acid automobile battery, or a "Hi-start", which is a catapult powered by stretched rubber. Either device is coupled to the aircraft by a long towline, which is jettisoned when the aircraft reaches its' launch altitude.
Other Pure Sailplane types include Discus Launched Gliders ("DLG's") and "Slope Soarers". DLG's usually operate from flat fields, and are pitched "side-arm" into the air by their pilots. DLG's are smaller than line-launched sailplanes, and are very lightly built to make best use of the available human launch energy.
"Slope Soarers" are launched from the top of a hill with an overhand throw. For slope soaring, windy days are preferred because the lift is created by wind deflected upward by the face of the slope. Landing a Slope Soarer on a hilltop requires considerable skill, particularly in high winds or gusty conditions. Slope Soarers must be very rugged to withstand rough landings.
For competition, model sailplanes may be further categorized by wingspan, and by the quantity of their radio controlled functions.
In contrast to "Slope Lift", "Thermals" are columns of warm air that typically rise up from flat fields on relatively calm days.
The location of thermals can be predicted by paying attention to subtle changes in air temperature, windspeed and wind direction. A host of additional telltales exist, including the behaviour of nearby soaring birds, the motion of tree leaves, flying insect behaviour, and the formation of clouds. By rising or sinking, the sailplane itself visibly signals if it is in a thermal. On-board variometers are also available to measure and report rate-of-climb (or sink) via radio downlink from the aircraft.
High performance sailplanes can glide in dead air at relatively high speeds for a long, long time. This enables them to search for thermals over a wide territory. Lower performance sailplanes fly slower, sink more quickly, and cover less territory. Essentially, low performance sailplanes must wait for rising air to come to them. Either way, unless rising air is encountered, even the best sailplane will eventually be forced to land.
The pilot steers his model in order to find Lift. Once Lift has been detected, strategic manouvers are employed to insert the aircraft into the Lift, to locate the boundaries of the Lift, and to keep the aircraft centred in the Lift, and rising.
SOGGI's "Thermal Workshop" has become a popular annual event. This Workshop for club members and visiting pilots, teaches thermal hunting theory mixed with thermal hunting practice time.
Some Examples of the Technology