Also, boomerangs are a great project to build with family members you’ve wanted to introduce to woodworking. And when you are done you get to go to the park and spend time together throwing them.
I have just one warning: Boomerangs will draw a curious crowd of onlookers.
Boomerangs operate on the principle of “gyroscopic precession,” which is similar to riding a bike no handed and attempting to initiate a turn. In bike riding, the spinning (gyroscopic) motion of the wheels gives the bike stability. To execute a “no hands” bicycle turn, you simply lean the bike in the direction that you wish to turn. The wheels have a delayed reaction to the force of the leaning action. This way, the wheels actually feel the force a quarter turn from where the force was applied. So instead of falling over, the bicycle turns in the desired direction.
Unlike riding a bicycle with “no hands” while turning, the boomerang experiences a continuous turn as the force is applied for the duration of the flight. The boomerang is thrown with a slight tilt from vertical (more on this later). The gyroscopic nature of a spinning boomerang and the release angle (called the “layover angle”) causes the boomerang’s flight angle to flatten out as it turns. Thus a well-balanced, well-contoured and well-thrown boomerang will return to the thrower in a horizontal hover. Most people expect that this will take practice though.
The duration of flight is determined by the force with which the boomerang was thrown as well as the spin applied at launch. As with any object flying through the air, a boomerang is subject to drag its own weight as it makes its flight pattern. This drag slows the boomerang down, thereby limiting the flight time. However, given enough spin and initial velocity, the boomerang will circle above the thrower’s head a few times before landing.
Choosing a Shape and a Material
A practical, quality and easy-to-work-with material for this project is plywood. However, the plywood at the big box stores isn’t a good choice. Boomerangs are essentially flying wings, and better grades of plywood are more durable. In fact some plywoods are engineered for flying projects.
When I teach high school physics students to build boomerangs, I prefer to use 1/4″-thick Baltic birch or Finnish birch. Baltic birch costs less, but Finnish birch is laminated with waterproof glue so it can hold up better outdoors. The two plywoods are easy to tell apart. The glue lines for Baltic are similar in color to the wood. The waterproof glue used in Finnish birch is a dark chocolate color.