What Makes a Boomerang Fly?
Boomerangs used most famously by the Australian Aborigines use a very complex combination of physics and aerodynamics to perform their amazing returning flights. When thrown correctly, this type returns to the thrower though it cannot be aimed accurately.
It is the non-returning type which is used as an accurately aimed weapon for centuries, by the Australian Aborigines. The returning boomerang comes back to the thrower because of its shape, size, the manner it is thrown in, and also because of air pressure.
A returning boomerang is basically two wings joined at an angle of between 80 degrees and 120 degrees, although it can have more than two wings. The wings are arranged so they work best when the boomerang is rotating rather than flying straight like an airplane.
The combination of spin with forward motion causes uneven lift on the wings because at any given time, one wing is rotating forward in the same direction as the flight, while the other is rotating backwards, against the direction of flight.
This means the air flow over the wing on one side of the disk of rotation has a higher airspeed than the other wing and so generates more lift.
The uneven lift tries to tip the boomerang over, but just like leaning a moving bike over makes it turn, the boomerang’s spin twists the tipping force at right angles and gives the boomerang a curving flight.
Another tipping force, caused by the centre of lift being forward of the centre of gravity, is also twisted to make the boomerang “lie down” in flight. The name for both these twisting motions is gyroscopic precession.