DIY Balloon Helicopter

Materials you'll need

• Strips of cardstock or stiff paper (for the wings)
• Bendy straws
• Small plastic cap (like a marker cap or bottle cap)
• Round balloon
• Scissors
• Craft glue
• A drill or another tool (for poking holes)

 

Step-by-step tutorial

Step 1: On a strip of cardstock, draw a wing shape — rounded at the top corner and angled to a point at the bottom — then cut it out. Repeat two more times so you have 3 matching wings.

Step 2: Glue a bendy straw along the straight edge of each wing, running the full length of the blade.

Step 3: Once the glue is dry, trim the extra bit of straw poking past the bottom of each wing so it's flush with the blade's edge.

Step 4: With a grown-up's help, poke 3 evenly spaced holes around the sides of a small plastic cap.

Step 5: Add a dab of glue to the straw end of each wing and press it into one of the holes in the cap so all 3 wings fan out into a propeller.

Step 6: Blow up the balloon and pinch the neck closed to hold the air in — don't tie it off!

Step 7: While still pinching the neck, push it snugly into the opening on the bottom of your propeller cap. Head outside, let go, and toss your helicopter into the air.

Learn more

This helicopter uses a clever trick called a tip-jet design. Instead of air just leaking out of the balloon's neck, it travels up through the hollow straws and squirts out through a tiny opening at each blade tip. Every time air jets out sideways from a spinning blade, it pushes back on that blade — the same idea behind Newton's third law, which says every action has an equal and opposite reaction. It's a lot like how a spinning lawn sprinkler works: water squirts out sideways from the arms, and that push spins the sprinkler around. Because the blades are also tilted at an angle, they scoop the air as they whirl, creating lift that helps the helicopter climb.