RC parachuters

Ever since Dr. Rogallo invented his "flying parachute," flight has no longer been limited to craft with big engines, solid wings and hinged control surfaces. High aspect ratio cloth "wings" produce enough lift for prolonged flights, and the timehonored, round parachute has been replaced by modern designs that provide controllable forward movement. This is recreated in miniature with RC precision parachute jumping.

I attended the latest Open German Championships and was impressed with the state of the art in RC parachuting. Most jumpers are about 1/4 scale and have multi-cell sails that allow a high degree of control. In the last 20 years, these competitions have become very popular, and several aspects of RC parachuting make it appealing to beginners: the jumpers are durable and crashes are infrequent, so breakage is minimal. Learning to fly them is quite easy because of their relatively slow speeds and self-correcting behavior, though mastering advanced techniques takes time.

HOW TO GET STARTED

Few things are required. The jumper's body is easily made as a simple plywood box, though most commercial models are fiberglass. You can buy a sail, or make it yourself, but this is somewhat more elaborate.

A 2-channel radio is enough to control flight, but most parachutists use a third servo to open the chute at the end of the free-fall.

Almost any plane can be converted into a jumper-carrier as long as it's large and powerful enough. Most jumpers weigh 3 1/2 to 4 pounds, so any 90-size plane could carry one. In Germany, most jumper-carriers are simple sport planes with removable carrying devices. The Zenoah 62 is the power of choice, and an 80- to 100-inch-span plane will carry two jumpers to altitude. The jumpers' berth is typically under the fuselage or in side pods.

FLYING A PARACHUTE

Control is the same as with a fullsize parachute: pulling more or less on a control cord changes the sail airfoil on the corresponding side. The jumper's arms can be controlled by regular servos, but it's more realistic-and more elaborate-to use double-action arms (upper and lower arm pieces hinged at the elbow). This allows more throw and therefore more control, as long as the sail was designed for it.

Lowering one arm increases the sail's curve on that side, and the increase in drag initiates a turn. Lowering both arms provides braking and allows a vertical descent, but speed and control input are critical. The "aircraft" is prone to oscillate because the jumper acts as a pendulum.

The length of the free-fall is used to control the jumper's altitude and distance from the landing spot, and it depends on the wind. If the sail and extraction parachute have been correctly folded (the most critical step, as with full-size jumping), the sail pops open in a fraction of a second and the jumper begins the landing approach slightly downwind. If all goes to plan, the jumper hits the center of the target, which is a mere 1 1/4 inches in diameter, and earns the maximum score.

If you try RC parachuting, I'm sure you'll soon be hooked. It's easy enough for beginners to enjoy right away, yet precision parachuting is challenging enough for experienced pilots. It's a great way to enjoy RC with the entire family.

For information on RC parachuting in the U.S., check out the R/C Skydive USA website: www.rcparachutes.homepage.com. 4

Copyright Air Age Publishing Jan 2001
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