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Reading Selection, Lesson 9

Choosing Materials for Pedal-Powered Flight

Illustration of Daedalus flying.

Daedalus made wings from wax and feathers to escape King Minos.

In Greek myth, Daedalus made wings out of wax and feathers. Daedalus used the wings to escape from the prison of King Minos on the Greek island of Crete. He flew more than 100 kilometers to safety.

In the mid-1980s, airplane engineer John Langford decided to do in real life what Daedalus had done in myth. However, Langford didn’t use wax and feather wings. Instead, he put together a team that built an ultra-lightweight, pedal-powered airplane. He called the plane Daedalus, after the mythological Daedalus.

Kanellos Kanellopoulus, a Greek Olympic bicyclist, was the pilot. He flew the plane 115 kilometers from Crete to another Greek island, Santorini. As of 1998, the plane still held the distance record for human-powered flight.

It is easy to see where the myth of Daedalus came from. Almost everyone, at sometime or another, dreams of flying like a bird. Through the centuries, many would-be eagles have strapped on homemade wings and tried to fly using only their own muscles. They flew like bricks.

The problem, says Langford, is that people are not very good engines. To fly the Daedalus 115 kilometers would take several hours. For that length of time, even the best athletes can sustain only the same power output as a bright lightbulb. Because of this lack of power, the plane had to be very light. “Every gram mattered,” says Langford.

When Langford and his team set out to build Daedalus, they needed materials that were very strong and very light. Fortunately, new materials had been developed that fit the bill.

The Daedalus craft with wings upturned

The Daedalus pedal-powered plane follows the route of the Daedalus of mythology.

For the plane's frame, Langford chose tubes made of a carbon composite. This material is composed of thin, very strong carbon threads embedded in plastic. The wings were made of solid foam building insulation cut to the proper shape. The plane's skin was made of Mylar™, an extremely thin but sturdy sheet material that is also used in videotapes and shiny helium balloons.

These materials are said to be "lightweight". But one pound of the lightest carbon composite still weighs as much as one pound of steel. The materials used to build Daedalus were special because of their combination of high strength and low density. This combination allows these materials to pack a lot of strength into relatively little weight.

Map showing the Daedalus' flight path.

The Daedalus was flown from Crete to Santorini in 4 hours—a feat of airborne cycling!

Even though they used the most advanced materials, the builders of the plane couldn’t make it any stronger. To make it stronger, they would have had to use denser materials, which would have made the plane too heavy to fly the distance. Despite a wing span of 34 meters—almost as wide as a passenger jet—the plane weighed only 31 kilograms. It was so fragile that the flight could only succeed on a completely windless day. But succeed it did.

At 7:00 a.m. on April 23, 1988, Daedalus took off from Crete and arrived at Santorini about 4 hours later. Once there, the plane’s fragility caught up with it. While being maneuvered to land on the beach, it was hit by a gust of wind. The plane broke into pieces, and pilot Kanellopoulus cooled off with a short unscheduled swim.

Langford still dreams of having another try at human-powered flight. “It would be great fun to try to make a plane using only the materials the ancient Greeks had,” says Langford. It would be a tough job, though. “I think I could make one that would fly, using thin silk for the skin and bamboo for the skeleton,” he says. “But without modern lightweight materials, you could never go as far as Daedalus.”

QUESTIONS

1.  What two properties did the designer of Daedalus look for in the materials he needed to build a human-powered airplane?

2.  Imagine you have been asked to design each of the following items:

  A.  A raincoat
  B.   A bullet-proof vest
  C.  A milk bottle
  D.  A fishing weight (sinker) What three properties would you look for when selecting the materials to make each item? What materials would you use to make each item? Write a reason for using each material you choose.

Early photograph showing a man standing on a raised step behind an ornithopter hung from a frame on wheels.

Many early attempts at human-powered flight, like that made in this ornithopter, failed because of poor design and the lack of strong, low-density materials.

 


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