1 Model, one of each
8" Dowel, 1/4"
3 Popsicle sticks
2 Rubber bands
2 liter bottle for wings
File folders or stiff paper
3/4" PVC, 1/2"
15/64 bit for drill (sharp)
Nail for punching hole to start drill
PVC cutter (or hack saw)
Large pliers to hold PVC piece while drilling
Cut a helicopter shape out of thick paper or file folder. The simplest can be a rectangle with a slit cut down the center. The blades are the pieces on each side of the slit. You can make the blades any size you like.
On the other end of the piece, fold the corners of the rectangle in towards the center. Then glue a Popsicle stick on the center.
Glue one or two or more pennies to the other end of the Popsicle stick. Throw it up and it should spin on the way down.
Cut a piece of 1/2” PVC, about 3/4”. Drill a 15/64th hole onto the center of the PVC while holding it tight with pliers. You can punch a shallow hole in the PVC with the nail to get the bit started.
Cut about 8” of a 1/4th dowel. Hammer it into the hole in the PVC.
Put some hot glue around the stick, especially inside the tube. This will keep the stick from flying out when you are launching it.
Draw slanted lines on a 2 liter bottle. Cut along the lines on the bottle until you have two strips. These will be the blades.
Put hot glue on the dowel. Allow the glue to cool for a few seconds so it does not melt the plastic. Then press the blades onto the glue.
Tape around the blades to reinforce the glue. Fold the wings a bit toward the outside and make them symmetric.
Tie two rubber bands together.
Tie the rubber bands to the tip of the Popsicle stick. This is the launcher.
Launch the helicopter like a slingshot. The hand with the launcher is up in front. The hand pinching the blades is down in back.
The rubber band is looped around the end of the tube toward your body. To launch, let go of the blades and move the launcher hand slightly so that the helicopter does not hit it. If the helicopter does not spin on its way back down, make sure the blades are symmetric, twisted slightly and bent opposite each other.
A Bit More Info:
As this toy helicopter falls, the blades encounter air. The blades are at an angle, so that each little bit of air that hits them bounces off and pushes them to the side. If you have them bent correctly, each one will be pushed in the opposite direction, causing the helicopter to spin. The air also pushes up the blades, causing the helicopter to fall slower than if it were just tumbling randomly.
Real helicopters do this in emergencies. If a helicopter’s engine fails, the recovery procedure is to begin “autorotation.” This simply means that instead of the engine turning the blades, the air flowing past the falling craft will turn the blades. In most cases, this provides enough upward force to insure a slow decent, allowing the pilot to find a suitable space below for an emergency landing.
This toy requires air to function. If you tried it on the moon, here is what would happen: It would rise to six times the height it rises to on earth, because the moon’s gravity is six times less than the earth’s. Then it would fall back to the earth without any spinning at all, because there is no air on the moon.
Let’s follow the energy used in this project. You provide the original energy to stretch the rubber band. Your body got this energy by metabolizing the food you ate earlier. When the rubber band is stretched, it holds potential energy. When released, it gives this energy to the helicopter. The helicopter begins accelerating upward. As the helicopter leaves the rubber band, it is traveling as fast as it will go during its flight. The potential energy of the rubber band has been converted into kinetic energy (KE = 1/2 mv 2 ).
The helicopter slows down as it continues upward because gravity is pulling steadily downward on it. It loses kinetic energy as it gains potential energy of height (PE = mgh). At its highest point, it stops moving up and has lost all kinetic energy. It holds the maximum potential energy of height it will have. It then returns down, exchanging that potential energy back for kinetic energy as it accelerates toward the ground. If the blades spring out properly, they encounter air. Some of the helicopter’s potential energy goes into pushing the blades around through the air, so the speed (and kinetic energy) of the helicopter is less on the way down. Since it is rotating though, it also has rotational kinetic energy. Upon impact with the ground, all remaining energy is converted to heat. You won’t feel this heat because there is not much energy involved. But if you clap your hands together hard, you’ll feel the heat of impact.
Air is real. You can’t see it, but it moves things.
The rubber band gives the force making the helicopter go up. Gravity gives the force making it come
back down. The air makes it spin around and fall slower.
If the blades are bent correctly, the air pushes them to make the helicopter go around.
What do you think would happen if you made the helicopter heavier at the bottom?
How could you make the helicopter go up farther?
What are some differences between this helicopter and a real helicopter?
What could you change to make the helicopter spin faster?