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hang glide

There’s a photo on Wikipedia of two gleeful brothers flying hang gliders they’ve made from duct tape, plastic sheeting, and bamboo. We at the Tinkering School had been kicking around the idea of making a hang glider for a couple of years, and this picture convinced me that a group of 12- to 16-year-old kids could do it.

The photo shows a design referred to as the Bamboo Butterfly, but try as we might, we could only find one low-res scan of a handmade copy of the original plans. No matter — we had the picture and a dab of collective knowledge of aerodynamics to convince us that it was possible. Some might call this hubris, but we like to think of it as gumption.

The first hurdle was that we didn’t have any bamboo, but we did have plenty of ¾-inch PVC pipe. The tinkerers immediately clued in to the fact that PVC is not a great substitute for bamboo. Compared to a 10-foot stick of bamboo, a 10-foot PVC pipe is like a heavy cooked noodle. They would have to figure out how to deal with that in the design.

The next big problem was scale. Trying to deduce dimensions from the photograph, they quickly discovered that the perspective was really distorting things. A note in the unintelligible plans implied that we wanted a “wing-loading” (the weight of the craft and pilot, divided by surface area of the wing) of between 1 and 2 pounds per square foot of wing. Some math ensued and we arrived at our first fixed dimension: the keel of the craft would be 15 feet long. We started cutting PVC.

As it took shape, the idea that someone was going to fly down a hill in this overgrown kite seemed alternately exciting and ludicrous. We couldn’t stop laughing at how noodly the whole contraption was. Someone pointed out that we didn’t have to keep it from drooping, we only needed to keep it from bending up. In a few moments the gang had tied dozens of guy wires from the leading-edge poles to the pilot cage. We were ready to fly!

While Tywen Kelly donned his protective gear, I tied a leash to the keel. I didn’t want the kids getting more than a foot or two off the ground. After a brief discussion of technique, he ran down the hill — and didn’t leave the ground. The wing was either stalling or nose-diving. This was going to take some real finesse.

Everyone took turns running down the hill at full speed. It was thrilling, and big hops were accomplished, but no real flying. After some discussion they decided that the pilots just weren’t getting their weight far enough forward — the nose would go up and not come back down.

Back in the shop, they got the cage moved forward, and padded the cage bars that had given everyone armpit bruises. Then it was back up the hill for more tests.

Leo Berez made the first real flight on the very first run — the new cage position was helping! Not everyone who tried it before it started to fall apart actually flew, but everyone felt that it could fly, and some short glides were accomplished. At the end of the day, we were exhausted and happy. And that’s all you really need from a project like this.


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