A boomerang is a curved throwing stick used chiefly by the Aboriginals of Australia for hunting and warfare. When thrown, the boomerang returns to the thrower if tossed correctly. They are a popular plaything with young children who marvel at how work. Boomerangs are also an internationally recognised symbol of Australia and are also works of art.
Boomerang throwing can be an enjoyable activity with a place in school physical education and/or outdoor education programs. Boomerangs are a great play thing and much more portable than something like a rocking horse or a play house.
History of the Boomerang
Native peoples in the Middle East and Australia have long had boomerangs, and they probably used them to develop throwing skills. Boomerangs were found in King Tutankhamen’s tomb in Egypt, and even older ones have been found in Australia. Although many cultures used throwing sticks as weapons or for hunting, the boomerang filled neither of these roles. It’s our guess that young hunters developed their throwing strength with boomerangs (it’s much easier to practice your throwing when you don’t have to walk across the field to retrieve your stick) and that later in life they used throwing sticks (that did not return) in battle and hunting.
How Boomerangs Work
The ability to spin and an asymmetric shape are essential for a boomerang. The thrower holds the boomerang vertically by one end and spins it as he or she throws it. The wing-shaped surface of each boomerang arm creates lift. Lift on the upper arm is greater since it spins in the same direction the boomerang is traveling. Lift on the lower arm is less since it’s moving the opposite way from the boomerang’s direction of travel. In other words, air speed measured on the upper arm is the sum of the boomerang’s forward motion plus the forward spin of the upper arm, but on the lower arm, the measured air speed is the boomerang’s forward speed minus the speed of rotation. The greater the air speed, the greater the lift. Because the boomerang is flying vertically, the increased lift on the upper arm causes the boomerang to lay over to its left side (assuming it’s thrown by a right-handed person). In addition, the spinning boomerang’s lift-generated torque causes the boomerang to turn to the left; this is the gyroscopic effect. This is the same effect you experience while riding a bicycle: if you lean to the left you put torque on the front wheel, but instead of falling to the left, the wheel itself turns to the left.
As the boomerang turns to the left in flight, it lays over so that it flies in a nearly horizontal position, and its lift causes it to rise. From the top of its trajectory, now about halfway around the circle, it falls back to the thrower. With some luck and skill the thrower can deftly catch (with one hand on top and one hand underneath) the still spinning boomerang.
Inside the Boomerang
Boomerangs are made of solid wood or plastic, so there isn’t much to see on the inside. What is interesting, however, is the boomerang’s shape. Almost every toy that’s meant to be thrown is symmetrical. You can’t tell one edge of a Frisbee, Aerobie, or baseball, from another. But a boomerang is asymmetric; you can see a left side and a right side. It’s the asymmetry that allows it to return.
Check out the cross section of a boomerang arm. It looks like the wing of a plane. The steeply climbing side is the leading edge, and the other side is the trailing edge. This shape generates lift. Try flinging a piece of wood that doesn’t have a wing-like profile, and you’ll see not only that it won’t return to you, but also that it doesn’t travel very far.
The other thing to notice is that, unlike an airplane wing, the boomerang has leading edges on opposite sides. The outside edge on one side is a leading edge, and on the other side it’s a trailing edge. This is because, unlike airplanes, boomerangs spin to fly.
How to build your own Boomerang
Balsa boomerangs are simple and quick to build. Here’s a way to make one in just half an hour. Cut two 11-inch-long, 1-inch-wide arms (1 inch by 11 inches) out of 1/8-inch-thick balsa wood or plywood. Sand the wings to create a 45-degree rise on the leading edges (on opposite ends of each arm), then sand a gradual descent to the trailing edges. The two arms should be identical.
Use a rubber band to hold the two arms in a cross, or drill a ¼-inch hole in the center and insert a short piece of ¼-inch dowel to peg them together with glue. When the glue is dry, follow the throwing directions below and notice the short diameter path that the boomerang takes. To throw a boomerang, hold it vertically in your right hand, with the flat side of the boomerang to the right. Face 45 degrees to the right on any wind and fling it with lots of spin. (If the wind is blowing strong enough to stand flags out from their poles, don’t throw a boomerang.) It takes patience and practice to become a good thrower.
Lefties need not be left out. They can throw a right-handed boomerang by following the same directions that righties do, but using their left hands. It will fly in a counterclockwise path, just as it does for righties. To make a true left-handed boomerang, just reverse the leading and trailing edges. Hold the lefty boomerang in your left hand, face 45 degrees to the left of any wind, and fling it with lots of spin. It will fly in a clockwise path.