Author: Dave Garwood
Edition: Model Aviation - 2007/10
Page Numbers: 129,130,131
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Radio Control Slope Soaring

Dave Garwood <[email protected]>

Using nets to catch Slope Soarers in small or hazardous landing areas

Some of the slopes we fly from have plenty of height and steady winds from a favorable direction, but lack a clear area large enough to make safe landings that don't beat up our aircraft or force us to climb trees to recover our models. This is particularly true in mountainous terrain with forest cover, such as the Adirondack Mountains in the East and the Rocky Mountains in the West.

It's a shame for those who live in hilly, tree-covered terrain to be unable to fly locally just because available landing areas are small, rocky, or surrounded by trees. We can often find an open area that is large enough to launch and fly from but is way too small and obstructed to have much of a chance for a safe landing.

Of those who have faced this situation, who among us hasn't considered that if we had a net we could snag our sailplanes from the air after a flight and fly from smaller launch areas?

Last fall I observed and tried a recovery net deployed by Berkshire Flyers at the Mohawk Trail flying site in North Adams, Massachusetts. There was approximately a 1,000-foot rise above the valley floor, facing a prevailing west wind, and generally excellent lift, but the prospects of landing there were daunting. The small cleared area we launched from, roughly the size of two volleyball courts, featured some grass, many rocks, and was bordered on three sides by trees. Occasionally we could execute a precise landing, but it was all too common to put a model into rocks, bushes, or tall trees behind the launch point at the end of a flight.

On this day John Collins ([email protected]) brought his "recovery net": a soccer-goal net that travels neatly in a medium-size duffle bag. When ready for use it is held in position by two helpers standing approximately 25 feet from each other, reaching upward roughly 7 feet, giving a landing target of approximately 175 square feet.

Does that seem easy enough? Well, it's tougher to hit that target than you would think, but the sailplane is trapped safely when you do. Given that the net is located at the edge of the bluff, if a pilot misses an approach on the high side he or she can shoot back into the lift again and make another approach. If the pilot misses on the low side, the model plows into the grass and rocks, as we often do with no net. Shooting landings into the net takes some skill and practice, but it makes for big fun trying. It becomes a new slope-flying game in itself.

A few years ago I tried another recovery-net design built by Fred Stillman ([email protected]) and his nephew, Rick Stillman. These die-hard slope pilots live and fly in Colorado. As Rick observed, "The Rocky Mountains are definitely rocky." At the 2002 Midwest Slope Challenge in Lucas, Kansas, Fred and Rick erected their net in two locations on two days during the event. Plenty of fliers got the chance to try landing in it.

The Stillmans built a frame for a 12 x 20-foot (240 square feet) hockey net from PVC pipe. The netting material is 3.5 mm twine in 4 x 4-inch squares.

We learned by observing the first and second days' setups that leaving a little slack in the net, so that it forms a "belly," helps keep the sailplane in the net after it lands rather than having it bounce out.

Following is further advice from Fred's experience.

  1. Do not place the net too close to the lip of the slope. When too close, the gliders get back into slope lift and make hitting the net difficult.
  1. To make hitting the net easier, the pilot should stand behind the net and fly the slope sailplane in just as if you were going to catch it in your hand. This gives the pilot the best view of the plane coming in and you can set up a descent right into the net. We tried all kinds of places to stand, and standing behind the net gave us the least problems with depth perception.

Roughly 20 Kansas slope fliers who tried it also observed that it's not nearly as easy as you think it will be to land in the net, but it sure is fun practicing and learning to use it.

The advantage of the Collins net is that little equipment needs to be hauled around and set up, but two helpers are necessary to hold the net in position. The advantage of the Stillman net is that no helpers are needed when it's erected and in position, but there's more gear to store and truck around, and it still takes two to set up.

Either design works for recovering sailplanes in tough terrain, and, given the relatively low cost of the gear, my experience is that using a landing net is worthwhile.

How Fast Does My Sailplane Go?

It's common to wonder how fast your sailplane is going or can go. You may want to measure the result of an airfoil change or other aerodynamic modification. Sometimes you need to settle a bet or gain bragging rights.

For those who don't pack a radar gun, there is a miniature airspeed-recording instrument that works as airspeed indicators do on full-scale airplanes. Winged Shadow Systems' "How Fast Model Aircraft Airspeed Instrument" records airspeeds from 15 to 500 mph with 1 mph resolution.

After a flight the How Fast can report the highest airspeed attained by signaling flashes via an LED mounted on the tiny onboard recording instrument. To read the stored data (before turning off the receiver after the flight), wave your finger over the LED for maximum airspeed report and count the flashes emitted in a series for each digit of the airspeed.

When used with another Winged Shadow Systems device, the See How, the How Fast can record up to nine in-flight speeds, recorded at points controlled by the transmitter-stick command, and the See How extends the resolution to 0.1 mph. Both devices are available with metric (kilometers per hour) readouts.

Preparing to measure the speed of more than one slope sailplane, I mounted a How Fast, the pitot tube, and the static pressure tube on a small plywood frame designed to be attached to a fuselage with tape or rubber bands. I mounted the circuit board with double-stick foam—the kind used to mount servos.

The instrument needs a DC electrical source ranging from 3.2 to 12.0 volts and is shipped with a "universal" plug and designed to receive its power from a receiver. I plugged mine into a receiver, which was plugged into a 4.8-volt pack, blew gently into the pitot tube, and got a reading of 48.9 mph.

We had a warm, clear summer day with steady west winds, and I headed to the Mohawk Trail flying site to try the instrument. Andreas Mergner volunteered an aircraft, and with his Bowman Models JW in a long dive he hit an indicated 98.0 mph. This gear is cool. —MA

Sources

Transcribed from original scans by AI. Minor OCR errors may remain.