Illustration from The World Record Paper Airplane Book by Ken Blackburn and Jeff Lammers.
Earning a world record allows paper-plane designers to own football teams and marry Russian oil heiresses. And according to aerospace engineer and record holder Ken Blackburn, you need master only three things in your quest for paper-plane glory: good folds, a good throw and good design.
Let’s polish off the first two in a couple words: Good folds are extremely crisp, reducing the plane’s profile and thus its drag. They also make the plane perfectly symmetrical. And a good throw means different things for different planes (we’ll get into specs later), but for a world-record attempt, you use a baseball-style throw to launch the plane straight up, as high as possible — there’s video of Blackburn’s Georgia Dome launch and subsequent 27.6-second, world-record flight online at paperplane.org.
Now to design, wherein lies the true geekery of paper planes.
“Long, rectangular wings are for slow speeds and long glides, and short, swept-back wings are for high speeds and maneuverability,” said Blackburn, when I interviewed him for my book, Brain Trust. You can see this in the difference between the condor and the swallow. The first is optimized for slow soaring, while the second — assuming an unladen European swallow — is optimized for quick dips and dives. You can also see these swept-back wings on the space shuttle, and because these high-speed wings have very little lift at low speeds, the shuttle needs to keep an aggressive, nose-up angle of attack even when landing. A straight-winged Cessna can land almost flat to the runway.
These triangular wings certainly have a paper plane design purpose. “I make pointed airplanes myself,” says Blackburn. “They certainly look cooler, and if you’re just throwing a paper plane across the room, you might as well have something that looks cool.”
But a world-record plane needs both the ability to act like a dart during launch, and like a glider after it levels off — a tricky balance. “People don’t realize how desperately I would love to fold my plane the long way,” says Blackburn, which would allow him to make wings from the 11-inch rather than 8.5-inch side of the paper. But so far he’s been unable to find a design that has both long wings and the ability to withstand the force of the nearly 60 mph launching throw.
Wing shape defines other aspects of design, too.
“For a rectangular, or nearly rectangular, wing, the center of gravity should be a quarter of the distance from tip to tail,” says Blackburn, “but for a plane with triangular wings, the center of gravity should be right at the midpoint.” Basically, this is because the additional lift of a rectangular wing requires additional weight up front to keep the plane from pulling immediately nose-up and flipping instead of flying. “The further forward your center of gravity, the more your plane acts like a weather vane,” says Blackburn. But you don’t want to hang an anvil off the nose — that would negate the effect of lift. So optimal design is a balance between stability and lift.
Mathematically, it means that in a square-winged plane, you need exactly half the plane’s weight right up front on the nose to make the full center of gravity rest a quarter of the way back. For example, in the super-simple plane made by multiply folding down the 8.5″ side of a piece of paper and folding wings, you’d want to fold exactly half the paper into the plane’s leading edge.
Recreationally, you can adjust your paper plane’s center of gravity with a paperclip. A cheater clip also helps ensure your plane’s center of gravity remains below the wing, on the fuselage, making your plane stable right side up. But world-record rules disallow any additions to the paper, so creative folding is required. Instead of adding aerodynamically beneficial ballast, fold your wings slightly up, so that when you look directly at the plane’s nose, the fuselage and wings form the letter “Y,” not the letter “T” (horizontal wings) and certainly not like an upward-pointing arrow or three-line Christmas tree (downward angled wings).
Blackburn also gently folds up the wing’s trailing edge to make his launchable dart a little more like a glider once it levels off. Flaps-up means that air pushes down on the trailing edge, slightly rotating the plane around its center of gravity and keeping the nose up. Like the space shuttle, which is forced to land with its nose high in the air, an increased angle of attack creates increased lift (as long as it doesn’t make the plane flip).
Notice all these design features in the plans for Blackburn’s world-record paper airplane, shown above. But also notice that there might be room for improvement — can you lengthen the wings while still allowing a dartlike launch? If so, the paper plane world record and all its glory could be yours.
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