Build a balloon-powered mini-hovercraft

Description:

A hovercraft works because of air pressure: it uses a motor to create a cushion of air. The hovercraft floats on this cushion, allowing it to move over land and water.

Build your own balloon-powered mini-hovercraft. It’s a great way to demonstrate the basics of how a hovercraft works. It also demonstrates the concept of air pressure.

Here’s what we’ll build: our balloon-powered hovercraft, all ready for launch:

Equipment needed:

Balloons

Duct tape

A plastic plate with raised edges. The edges themselves should be smooth if possible, not ridged. (Notice that the plate used in the pictures below has ridged edges. It works, but not as well as one with smooth edges.)

A straw

A sharp knife

The Digital Bits Science Lab Experiment:

Cut a straw in half. Stick the straw into the balloon. Duct tape around where the straw meets the balloon mouth. Test for air-tightness: you should be able to inflate the balloon by blowing into the straw. After you inflate the balloon, pinch the straw closed. If you hear the hiss of air, there’s still a leak - add more duct tape or pinch around the seal to close all leaks.

Cut a hole in the middle of the plate. It should be no bigger than the straw.

Turn the plate upside-down. Place the straw/balloon part into the hole in the plate. The straw can extend into the other side of the plate, but shouldn’t be lower than the plate’s edges. (When the plate is sitting upside-down, it should rest evenly on its edges. The straw should NOT be pushing the plate into the air.) Here’s a shot of the bottom of the hovercraft:

Use duct tape to make a seal where the straw enters the plate.

Your final product looks like this:

Here’s detail of the bottom of the hovercraft (which is actually the top side of the plate):

Get another straw. This will be our removable inflater for the balloon.

Crimp the end of the inflater straw. It should look similar to this:

Shove the crimped straw into the balloon-attached straw. If you push firmly, you’ll have a pretty good air seal between the two straws. Blow to inflate the balloon. When you’ve inflated it, you can pinch the straw/balloon part to hold the air in until you’re ready to run the hovercraft.

Here’s a shot of me pinching the hovercraft straw to keep air in the balloon. The inflater straw is still inserted:

Place the hovercraft on a very flat surface, like a table or counter-top, and release the pinch.

The balloon will start pushing air under the plate. The air pressure under the plate will build until the plate floats on a cushion of air. When that happens, the plate will skitter back and forth by itself, until the balloon runs out of air. When the balloon is empty, you can “refill” it again with your inflater straw.

Try different things when you launch the hovercraft: Try spinning it. Try putting it on a hill. Put it in water. Try building hovercrafts with different balloons, and enjoy the results!

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• Learn about air pressure from a leaky bottle
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