Summer 2007 Issue

Airborne Radio

Motorless Flight

By Del Schier, K1UHF

The basic slope launch.
(Photos courtesy of the author)

Perhaps the most enjoyable way to fly is without a motor, whether it is a full-size glider that you can fly in or a model that you fly from the ground. This month’s column is a quick overview of RC (radio-control) soaring—how it is done and the necessary equipment.

Gliders are the simplest form of aircraft. They also have many advantages over more complicated types. They are less expensive, easier to build, and more reliable. In general, they also are easier to fly. However, the skill it takes to keep an aircraft such as this in the air without a motor is an endless challenge.

Personally, I find soaring fascinating, a challenge similar to using unusual radio propagation for working DX on VHF and above. You will never be bored with our infinitely changing atmosphere! Both flying and radio propagation are highly dependent on the atmosphere.

Two Forms of Soaring

There are two basic forms of soaring— slope soaring and thermal soaring. The term soaring refers to keeping a glider aloft longer than it would remain in still air, which is the whole point of flying a glider. Wikipedia® defines soaring as a mode of flight in which height is gained slowly by using air that is moving upwards.

Slope soaring is simply flying in air that is being displaced upwards by some obstacle to the air flow, such as a hill or cliff. When horizontal air flow (wind) hits the side of a hill, it has no way to go but up. If the vertical component of this upward flow exceeds the rate at which the glider descends, you can stay aloft.

It sounds simple, but finding a good place to slope soar requires a variety of factors, such as the wind speed and direction, the shape of the hill and also the amount of turbulence in the air. The ideal hill would have a wide expanse of steep, but not vertical, slope with wind hitting it directly at a perfect 90 degrees. You will never find this perfect slope. Therefore, making do with what you can find is what makes it interesting. It is important that the wind hits the hill without being disturbed by some obstruction in front of the hill. Cliffs along lakes and oceans are ideal, especially if they face the prevailing wind. Depending on where you live, there may or may not be a good place for this type of soaring. I drive to Cape Cod, Massachusetts and have flown at the Marconi site and also at Mt. Greylock, both of which are excellent VHF operating locations.

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