Edith Cowan University Open Day brought Aboriginal crafts and science closer together. You could learn how to throw a boomerang, and realize the complexity of the aerodynamic design. I discovered that there is more than one shape for boomerangs.
In fact boomerangs don’t all come back. If you want to eat a kangaroo, you don’t want to throw a boomerang at it and miss because the silly thing circles back to you.
A hunting boomerang is aerodynamically designed to fly straight to the target over a large distance, so the Aborigines must have known something that the Wright Brothers discovered many centuries later.
The returning boomerang was used by some tribes to knock down birds, though other tribes treat it as a toy. If you throw your boomerang over a billabong (water hole) to catch flying waterbirds, it saves you diving in to get back your boomerang when you miss.
Now I don’t want to confuse you with the mathematics of the boomerang flight (well… The real reason is that I don’t know them) but here is what I picked up at the exhibition.
The lady here is the instructor. Notice that she is holding one wing and the next one reaches back over her wrist. If there were only two wings, that would mean that the “elbow” goes first you throw it. Everyone was taught to use the “trimarang” because the field was too small to throw a two-winged boomerang. In other words, it is a clever toy, but no use for hunting birds.
The instructor showed many people – even little children how to throw the boomerang, so it must be easy. I only saw it come back to the hand of the thrower once, however. You see… You must balance the aerodynamic lift, circular motion, and torque against the force of gravity and gyroscopic precession. OK. I admit that I don’t understand it either, but what it amounts to is that you must throw it at just the right angle to get the perfect return that you need for competition work.
I can’t promise that cheap plastic boomerangs will work. Here is how to tell if they are shaped well.
The wings must be contoured like the wings of an aircraft. If you have a two-wing variety, you should hold it with the elbow upward. The near edge wing that you are holding should be thick, tapering to the edge farther from you. The top of the wing that goes back over your wrist should be thick, tapering towards the bottom. Of course, the thick edges are rounded like an aircraft wing.
In the photo on the right, the little boy has just thrown a three-winged boomerang correctly. It will make a roughly circular path because the shape of the wings keeps pushing it to the center of a big circle.
It won’t, however, return to his hand because he hasn’t the experience to throw it with just the right lean sideways to counteract the force of gravity.
Oh, by the way, one advantage of cheap plastic boomerangs is that if several are in the air at once, and you can’t watch them all, it won’t hurt much when one of them hits your skull. These watchers don’t intend to learn the hard way.
The little girl on the right is just going to put a second boomerang in the air.