A sophisticated ultralight sailplane. Real cute, too.
With an empty weight of about 50 kg (100 lbs), the Archaeopteryx can be flown in many countries under the rules that govern hang glider flying.
This sailplane was just released by Ruppert Composite from Switzerland. It can be foot-launched, aerotowed by an ultralight, or even bungee launched.
It derives its name from Archaeopteryx, generally regarded as the oldest known bird. This bird lived about 150 million years ago in the area now known as Germany.
An old saying among soaring fans says that the thermals are always smaller than you would like. This is true for both full-size and model gliders. The core of a thermal has the strongest updrafts, and even the smallest turning radius always keeps you outside the center of a thermal core.
Wing loading is the primary factor that determines the smallest size circle that an airplane can turn in. A glider like the Archaeopteryx, with a very low wing loading, can turn very small circles of about 50 feet (15 m).
This small turning radius lets this glider take advantage of smaller weaker thermals closer to the ground. Recreational full-size flying is mostly about sightseeing, making this glider a great “fun” machine.
The downside of a low wing loading is that it also lowers the speed for best range (best L/D speed). These are not contest winning machines. Their strength is on weak thermal days or for flying very close to the ground working the weak thermals found there.
A low wing loading also translates into low take-off and landing speeds. It makes these gliders safer to fly. It also opens up many more potential airstrips.
By the time all is said and done, one of these babies will set you back close to $100,000. That works out to about a thousand dollars a pound. Even by full-size sailplane standards, that is very pricey. But I guarantee you that building a great looking scale model would set you back a lot less than that!
To build a scale model, I see no need to turn to composites. Keep it simple and keep it light. A two and a half meter wing span (about eight feet) sounds about right to me. Put a strong spar on it for winch launches, or just launch it like any other scale glider.
The key to a scale model like this is the pilot. Make sure the pilot is to scale. Get a nice looking one while you are at it. It will really put into perspective the ultralight nature of the full-size glider.