Stick or Boomerang?
PURPOSE:
The pupose of this project is to find out why different boomerangs fly different ways.
HYPOTHESIS:
I think the shape of the boomerangs make them fly differently.
PROCEDURE:
First I read some books on boomerangs to find out why boomerangs fly. Next we picked four of my dad's boomerangs which flew in different ways. Then Dad told me how they fly. Next, I went through the books looking for things that would change the way a boomerang flies. As I found things that might be important, I checked the boomerangs to see if those boomerangs to see if those boomerangs had it.
RESULTS:
I found out that there are four different forces that effect the flight of the boomerang. They are lift, drag, thrust and gravity. Lift is the opposite of gravity and drag is the opposite of thrust. Lift is made by the shape of the boomerang wing. This shape is called an airfoil. An air foil is formed by making the top of the wing curved and the bottom flat. The air has to go farther and faster over the top of the wing, but it doesn't go quite as fast on the bottom. This means there is less pressure on the top than on the bottom; the greater pressure pushes, or lifts, the airfoil toward the lesser pressure.
An airplane wing is shaped the same way a boomerang wing is shaped. The boomerang is thrown vertically so the lift is on the side and pushes the boomerang to the side. But if an airplane wing is the same as a boomerang wing, why does the boomerang fly in a circle and an airplane just goes up?
A boomerang turns because it is spinning. A force called precession turns the boomerang. In a spinning object, when pressure is applied the effect of the force goes one fourth around the circle. Because the top of the boomerang is going forward faster than the bottom there is more lift, or force, on the top than the bottom. The effect of the lift is on the front of the spinning boomerang, causing the boomerang to go in a circle.
The following segments were on the display boards with the appropriate boomerangs.
Boomerang: Fast Catch Comp
Made By: John Flynn
Material: 5mm Finnish Birch Plywood
This boomerang is used for an event called "Fast Catch", where the object is to make 5 catches in the shortest amount of time (the boomerang must go a minimum of 20 meters). This boomerang will return in 4 seconds or less. It flies in a tight circle, staying low and remaining vertical throughout its flight. To adjust the distance traveled, one twists the leading arm slightly.
Lift is the force that causes a boomerang to turn. The more lift a boomerang has, the faster it will return. Adjusting the leading edge creates angle of attack. Angle of attack creates more lift. There are different ways to increase lift. Hollowing out the underside of the boomerang helps create more lift. The weight added to the leading arm helps in a couple of ways. It helps the boomerang keep its spin, so it keeps creating lift. The wight will also help the boomerang stay vertical; this helps the lift continue to turn the boomerang. The weight also helps keep the boomerang from climbing which would slow it down.
Twisting a boomerangs arm changes the angle of attack. If you add angle of attack, it increases the lift which will shorten the distance. If you take out angle of attack, it reduces the lift, increasing the distance.
Boomerang: Island Omega
Made By: Chet Snouffer
Material: 5mm Finnish Birch Plywood
This boomerang is used for an event called "Australian Round". This event awards points for distance achieved and accuracy of return. This boomerang flies a fairly typical pattern, but will achieve distances of 45-50 meters.
While more lift will make a boomerang return faster, less lift will allow the boomerang to go farther. Reducing the angle between the arms will create less lift. This boomerang also has less of an airfoil, which will create less lift. Adding weight to the ends of the boomerang's arms will increase the distance the boomerang travels. This boomerang has holes filled with lead to make the wing tips heavier, to increase distance. The wing tips are also larger which adds more weight to the wing tips.
Boomerang: Buzzhead
Made By: Chet Snouffer
Material: 5mm Finnish Birch Plywood
This boomerang is used for an event called "Trick Catch". This event involves catching the boomerang under the leg, behind the back and, even, with the feet. This boomerang flies about 25 meters and drops straight down at the end of its flight. THis makes it easier to judge its flight for the trick catches. If there is more wind, extra clips are added to the wings.
The clip on the leading edge of this boomerang is creating drag because it has a large blunt edge. This drag slows down the boomerang's spin. This makes it easier to catch without bouncing off the hands and causes it to drop at the end of it's flight, instead of hovering. If you add extra clips to the leading edges of the boomerang, in higher wind, you are creating more drag. The more drag, the slower the boomerang will spin and the less it will be pushed by the wind.
Boomerang: Bell'in Wind Dancer
Made By: Michael Girvin
Material: 6mm Finnish Birch Plywood
This boomerang can be used for several events. It only flies well in high winds. Rather than being blown away, it drops quickly after reaching its farthest point and is blown back to the thrower.
Drag is the main thing you need when throwing in the wind. Drag slows the spinning of the boomerang so it doesn't get affected by the wind as much. One way to make more drag is adding holes in the boomerang, like this one. Making all the edges blunt helps create more drag. The thickness of the boomerang amkes it heavier so it doesn't get tossed around as much, in the wind.
CONCLUSION:
Many different things make boomerangs fly the way they do. The two main reasons are lift and drag. Lift effects two things: speed of the boomerang and the size of the circle the boomerang makes. Drag is important because it slows down the spinning, which affects how long the boomerang can stay in the air and how much it is affected by the wind. I found out that this project was a lot harder than I thought. It is hard to remember and understand all the things that are involved with why boomerangs fly the way they do.
Q: What do you call a boomerang that doesn't come back?
A: A stick!
BIBLIOGRAPHY:
The Big Book of Boomerangs compiled and edited by H. L. Mayhew
The Boomerang Book by John Cassidy
An Introduction to Boomerangs by John B. Mauro
"How to Throw in Wind" an article from the web page of Mike "Gel" Girvin
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