RC Gliders

RC gliders provide more than just an economical way of learning to fly RC,
they are arguably the most addicting type of RC airplane!

For some it’s the challenge of seemingly defying gravity by keeping their sailplanes aloft for hours at a time. For others, it’s the thrill of riding a thermal so high the glider becomes merely a dot in the sky. And some thrive on the pure adrenaline from reaching speeds of nearly 400 mph!

If you have a glider or two, be sure to share them with the rest of us.

Glider Basics

Great Planes Fling
(Popular Entry Level DLG)

Yeah, there really are RC gliders that fly that fast! We’ll get to that in a second. But first it is important to understand the “physics” of how gliders stay afloat.

In the absence of any moving air, all gliders will loose altitude until they hit the ground. It’s that pesky law of gravity at work. Some gliders will sink faster than others. The speed at which each glider descends in completely still air is called the Minimum Sink Speed of the glider.

In order for RC gliders to gain or maintain altitude it must find a column or pocket of air that is rising faster than the glider is sinking. This rising air is called lift. There are two types of lift associated with gliding, which are thermal lift and ridge lift.

Thermal Gliding

A thermal glider stays aloft by the same principle that pulls hot-air balloons high into the sky. Both are pulled upward by the force of rising warm air. A hot-air balloon basically hangs from a huge bag of hot air, where as a thermal glider floats on top of a rising mass of warm air.

The source of hot air for the hot-air balloon comes from a controlled fire in the basket. The source of warm air for the thermal glider comes from nature. Finding a naturally occurring thermal to ride into the heavens is the magic of thermal gliding. More information on catching thermals.

Slope Soaring

Slope soaring involves riding atop the rising air that comes from wind blowing directly into a ridge or hill. When a strong wind hits a hill straight on, it really has nowhere to go but up. This is called ridge lift. Ridge lift is much stronger and more uniform than thermal lift.

For this reason, RC gliders designed for slope soaring are generally built a little heavier than thermal gliders. They usually have shorter wings and are turned by aileron control as opposed to rudder control for better aerobatic performance. Learn more about slope gliding.

The conventional method of slope gliding is to float atop the rising air from ridge lift in the same manner as thermal gliders utilize thermal lift.

A relatively new type of slope soaring harnesses the energy difference between the stagnant air on the backside of the hill and the fast moving air coming over the hill to reach unbelievably fast speeds. Yes, some can go nearly 400 mph! You gotta take a second to check out dynamic soaring!

Launching Gliders

Since most RC gliders don’t have a motor or engine, they must be launched into the air. There are several different ways that RC gliders are launched.

Hand Launching

Smaller gliders with a wingspan of 1.5meter or less and considered Hand Launched Gliders (HLG’s). Although other methods can be used, HLG's are generally launched the old fashioned way, by hand.

For years the typical method for hand launching a glider was to give it a firm over head “javelin style” toss. stronger more athletic pilots had a huge advantage in competitions being able to launch their RC gliders to much higher altitudes than the older or out of shape guy. Not to mention the fact that a few too many launches could lead to a painful back in the morning!

Nowadays discus style launching with Discus Launched Gliders (DLG’s) is the more standard way of hand launching gliders. This involves holding onto one of the wing tips while whirling around in a circle and releasing the glider much like a track and field discus. This method of launching puts the glider much higher in the air with much less effort! More on discuss launched gliders.

Bungee/Hi-start Launching

A “Hi-start” or bungee launch is basically a gigantic sling shot that can launch RC gliders several hundred feet into the air. An elastic chord or stretchable tubing is attached to a longer section of ridged line. The elastic end

Curtesy of Ed Anderson

of the line is attached to a solid stake in the ground; the ridged end is attached to the glider by a tow hook with a parachute.

Dynaflite Up Start Kit

The pilot pulls the glider back stretching the chord. When released the glider immediately zings high into the sky. Once airborne, the tow hook releases and floats back to the ground via the parachute.

Varying lengths and strengths of tubing are used depending on the size of your glider. Some people even make their own bungee launching systems.

Winch Launching

This method of launching a sailplane uses a relatively high speed winch.

Curtesy of Ed Anderson

The winch sits on the ground next to the pilot. A cable extends from the winch to a return pulley staked into the ground severally hundred feet in front of the pilot. This cable goes round the pull then back to the pilot where it is hooked to the glider’s tow hook, which has a parachute.

The pilot uses a foot pedal to control how quickly the winch reels in the cable. As the cable is reeled in, the glider is swiftly pulled towards the return pulley as the glider races to the air. The tow hook releases and parachutes down.

Hand Towing

Instead of using a winch, hand towing involves having a buddy or two take a hole of the end of the line and run like crazy to get your glider airborne.

Some people stake one end of the line to the ground and run the line through a hand pulley. This method actually launches the glider twice as fast as the launcher runs.

Tow with another RC Plane (Aero Tow)

With this method of launch, you attached your glider to a larger "powered" RC airplane via a tow line. The tow plane pulls the glider high into the sky, around 200 M altitudes, where it is released.

Electric Motor Launch

Many RC gliders, like Parkzone's Radian shown to the right, are equipped with small electric motors to pull them into the sky. The propellers actually fold back when the motor is stopped to prevent the prop from acting as a brake. These types of RC gliders are great when you’re just learning to catch thermals.

Fédération Aéronautique Internationale (FAI) Designations

If your surfing the net or shopping for a sailplane chances are you’ll see people throw around terms like F3F glider or F3J glider or what have you. This can totally throw you for a loop if you don’t know what they heck they’re talking about!

The FAI is the world governing body for air sports and aeronautical world records for both full scale and model aircraft. The CIAM is a branch of the FAI that is specifically dedicated to model aviation.

The "RC-Soaring Subcommittee" of the FAI developed the following radio controlled glider classes. Here is a summary of those classes.

F3B - Multi Task Thermal Soaring Gliders – This class of competition has three formats including thermal duration, speed, and distance. What makes this more interesting is that each task must be done with the same glider!
F3F - Slope Soaring Gliders – This is a slope soaring event where each participant flies their RC gliders over a 1000 M course in the shortest amount of time. At least four rounds are completed to determine the winner.
F3H – Slope Soaring (cross country) – This is a cross country event where participants race from one point to another, as apposed to completing a circuit.
F3I - Aero-Tow Soaring Models – This event utilizes a second “tug” model to tow the competing glider to an altitude of 200 M where it is released. This event is judged on both distance and speed.
F3J - Thermal Duration Gliders – In this event pilots attempt to keep their gliders aloft for exactly 10 minutes, then land the glider as close as possible to a designated spot. The gliders are launched by hand towing.
F3K - Hand Launched R/C Gliders – This class of competition involves hand launching of relatively small 1.5 meter or less wingspan gliders. As mentioned above, discus style launching is the most popular way of hand launching these days. The task involves several short duration flights per round while attempting to utilize thermal activity close to the ground.

RC Glider AMA Classes

RC gliders can be broken down into the following categories based upon there size and functionality.

Class A Hand launched (HLG) – Sailplanes with wingspans of 1.5 meters or less.
Class B Two Meter - Sailplanes with wingspans between 1.5 and 2 meters.
Class C Standard Class - Sailplanes with a wingspan great than 2 meters but less than 100 inches...
Class D Unlimited Class - Sailplanes that have wingspans greater than 100".
RES Class Sailplane – Sailplanes limited to three control inputs which are Rudder, Elevator, and Spoilers.(RES)

Generally most RC gliders are controlled with two channels with one being elevator. It is important to keep the wings level as much as possible when thermal sailing to increase lift. For this reason most thermal gliders use rudder for turning and have no ailerons.

On the contrary, slope gliders are much faster and more aerobatic due to the more powerful lift of the wind. For this reason you’ll find that the majority of slope gliders use ailerons for control and do not have a moveable rudder.

Obviously all gliders are designed to provide as much lift as possible. By design they are built to float. This sometimes makes coming in for a landing rather difficult. This is why some pilots used spoilers to change the shape of the wing to increase the drag when landing.

An experienced glider will also uses spoilers to their advantage throughout the flight for moving more quickly through downdrafts etc. Gliders that use spoilers are in the RES class of sailplanes and are limited to only those three channels or control inputs.

Special Interest Groups for RC Soaring

The following are special interest groups that are dedicated to RC soaring. I am sure there are many more, please drop me a line if you have one you'd like to ad to the list.

League of Silent Flight (LSF) SIG to the AMA for Soaring
League of Silent Flight of Australia
League of Silent Flight of Norway
Canadian Soaring Society

Tell us about your gliders

I'd imagine there are more different variations and types of RC sailplanes than any other RC aircraft. Everything from slope speed demons to graceful thermal gliders, and even stand off scale.

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