For pure grace and beauty—as well as for a stirring example of the wonder, symmetry, and constancy of nature's laws—the delicate, balanced, and bird-like flight of a boomerang is hard to beat. Even when the forces acting upon the device are explained and understood, its dramatic soaring is—as things controlled by nature tend to be—still, in essence, a mystery.
Once thrown, a "return" boomerang travels in a rising, circular flight. If the wielder is right-handed, it will fly up and around to his or her left (throwing a boomerang with the left hand reverses the circle), reaches its peak at a point about 45° from the line of the direction in which it was thrown, then begins a gradual, circling descent, and either glides gently to the ground or hovers for a few seconds before dropping. The commonly made comparison of its flight to that of a predatory bird is quite accurate. In fact, some primitive tribes, by throwing return boomerangs into the air while imitating a hawk's cry, are able to keep small birds on the ground and thus drive them into nets.
Generally, however, the return boomerang is used as a toy. It will typically weigh less than five ounces, and the angle of its limbs—each of which is no more than a foot long—can be as extreme as 90°. The approximately pound-and-a-half hunting versions, on the other hand, have gradual curves and overall lengths sometimes surpassing three feet. They can travel up to 250 yards in a straight line and are used by Australian aborigines for felling animals and birds.
How It Flies!
Return boomerangs operate on the principle of the airfoil. Their upper surfaces are curved, much like the top of an airplane's wing, while the undersides are flat. As one of these aerodynamic implements slices through space, the air flows faster over the greater surface area of the curved top, and (since, as the velocity of air increases, its pressure decreases) a partial vacuum is created. Therefore, the greater air pressure against the flat side pulls the boomerang up, around, and back to its starting point (the hunting boomerang is shaped to provide some lift in straight flight).
As the return boomerang leaves the thrower's hand, both its rotational and linear momentum are very strong. The airfoil principle is acting to move the device around to the left, but at first the linear momentum is great enough to resist this pull, and the device travels pretty much in a straight line. However, since linear velocity decreases much more quickly than does rotational velocity, the toy soon begins to circle. The whirling motion then causes the boomerang to tip over on its side so that it rises, still circling, like a bobsled going up and around a banked curve. Finally, the rotation slows so much that the air pressure can no longer hold the weight of the boomerang up, and the device begins to drop—though it continues to curve—until, if the throw is good, it lands near its starting point.
Most folks who aren't familiar with boomerangs assume that they're thrown sidearm, but that's not the case. When pitched in such a manner it will rise to a great height and then come crashing back down to the ground , sometimes even breaking apart on impact.
The proper method is to take a few short steps and throw the device straight overhand, snapping your wrist at the instant of release. The wrist snap greatly increases the boomerang's rotational velocity, making it appear almost as a solid round object when it leaves the hand. Be sure to hold the "aboriginal Frisbee" so that the curved surface is facing the body, and throw hard, with authority, as if you were trying to hit a fencepost 50 yards away.
How to Make One
It's probably a good idea to buy a boomerang and become familiar with it before trying to make your own. You can find the fliers for as little as $2.00 in sporting goods stores, but some of the best I've been able to locate—and they're available in both right- and left-hand models—are sold by Col. Gerrish Boomerangs.
[EDITOR'S NOTE: Another source of truly excellent boomerangs is The Boomerang Man]
Using a ready-made version as a guide, you can then try to produce your own homemade designs. Just trace a pattern onto a piece of good-quality 1/4" or 3/8" plywood. (Never try to fashion a boomerang out of inexpensive or inferior plywood, because—even at the end of its flight—the boomerang is spinning quite fast and could break after only a few throws unless the material is tolerably strong.) Each limb should be about a foot long and approximately 1 1/2" wide near the center, tapering slightly toward the end. Once you cut out the basic design, the most difficult part begins: shaping the airfoil with a rasp and sandpaper.
The limbs should be formed so that the curve rises sharply from the leading edge and then tapers gradually toward the trailing edge. Remember that the leading edge for one "wing" will be on the inside of the angle formed by the two limbs and on the outside of that angle for the other.
How to Play
Once you've mastered the technique of throwing a boomerang, there are any number of games that can be played with the toy. The simplest and most obvious is to try to make it land close to you after its flight. You might, for instance, mark out a series of concentric rings and score points as you would in archery. It's also possible to catch a boomerang after throwing it, though I wouldn't recommend trying to do so until you're thoroughly familiar with its flight pattern.
But of all the various games that can be invented, the most pleasurable (because, perhaps, it's the quietest and simplest) is throwing a boomerang just to watch it fly. The device will seem to ignore all laws, act outside the realm of possibility, and soar free by its own volition. Knowing that it is actually trapped by the very forces it seems to defy only adds to the wonder and increases the enjoyment of he game.