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OBJECTIVES:
In this activity you will shape and balance
your own boomerang and learn about the aerodynamics of boomerangs.
Aerodynamics affects sports balls and projectiles,
like the javelin and boomerang.
Unlike its historical predecessor, the killer-stick,
a boomerang returns to its thrower due to its aerodynamic shape.
You will learn about:
the origins of the boomerang and early usage in hunting;
the basic aerodynamic forces on a boomerang (why it turns)
types of boomerangs;
right versus left hand boomerangs;
shapes;
competitive boomerangs such as MTA (maximum
time aloft versus long distance);
materials used in construction and the characteristics
imparted to the boomerang (bendable,
humidity resistance, strength, stiffness).
STEPS TO FOLLOW:
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Review the information in the
background section.
(The background section
is five pages long.
Continue to click "Next Page" to see all five pages.)
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Your boomerang still needs to be shaped. Both a
right-handed and left-handed
template are provided. The template is smaller than your rough-cut boomerang. Trace the template onto the upper surface of your boomerang. You will first file and then sand the upper edges of your rough-cut boomerang to these traced lines.
Right-Handed Boomerang
Left-Handed Boomerang
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MATERIALS:
1/4" Tag Board
Boomerang Pattern
Right-Handed Template
OR Left-Handed Template
Hobby Knife
File
Sandpaper
Transparent Tape
Pencil
Colored Pens Or Stickers (Optional)
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This is an airfoil shape. The blades of a boomerang have this (or a similar) shape. The airfoil shape on the top would be used for a right-handed boomerang (for a right-handed person). The airfoil shape on the bottom would be used for a left-handed boomerang (for a left-handed person.
Airfoil Shape For Right And Left-Handed Boomerangs
Using your file, shape the boomerang into the airfoil pattern. (If you are right-handed use the right-hand pattern and if you are left-handed use the left-hand pattern.) Use the sandpaper for smaller changes and finer shaping.
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You can decorate your boomerang.
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Filing a boomerang into a perfect shape can be a challenge. How do you know if both sides are identical (or close to identical)?
Find the center of rotation of your boomerang. Lay your boomerang flat near the edge of a table. Keeping one blade tip stationary, slowly begin to push the other blade tip toward the edge of the table. The boomerang's elbow will be over the edge of the table. Keep pushing, slowly. As you reach the point where the boomerang will fall off of the table, stop pushing. Place a dot at the two inner boomerang edges which cross the edge of the table.
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Repeat Step 6 for the other blade tip.
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Using the transparent tape, connect the two marks made in Step 6.
Repeat this process for the marks made in Step 7.
Note where the two lengths of transparent tape intersects. Mark that spot. This is the center of rotation.
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Examine the center of rotation. Is the center of rotation symmetric to the right and left sides of the boomerang? (Is there an equal amount of space from the center of rotation to the right side of the boomerang as there is to the left side of the boomerang?)
Discuss in class how the center of rotation affects the performance of the boomerang and how changes might be made to the boomerang.
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