Science Project: Make a Balloon Powered Boat

Learn about propulsion and steering by making these fun balloon powered boats at home. This is a great home school project, or it can be used as a rainy day project in the bathtub.

For this project you'll need a milk carton; not a milk jug, but a cardboard milk carton. Actually, you'll only need half of it. Cut it straight down the middle from top to bottom so that the top closing is split in two. You should end up with two pieces, each of which is five-sided; a rectangle that comes to a point on one end. Since you could make two boats out of each carton, this is a great opportunity to make an extra boat so that you can race them with your children, or let your children race against each other later on.

The back of the boat will be the short flat end. Punch a hole in the center bottom of the back end of your boat. The hole needs to be just big enough to fit a drinking straw through. The straw should fit snugly and not slide up or down. If you accidentally make the hole too big, use a bit of tape to close it off some so that the straw will still be held snugly.

Using tape, attach a balloon to the end of your drinking straw. Then, putting your mouth on the opposite end of the straw, blow the balloon up. Use your fingers to pinch the point where the balloon fits unto the straw to keep the air from leaking out while you move it into position.

Push the open end of the straw down through the hole you made in the back of your boat, and into the water underneath it. Your water can be in your bathtub, in a wading pool outdoors, or even in a nearby lake or calm river. Once the straw is fully under water let go of where you've been pinching on the balloon.

As the air in the balloon is forced out through the other end of the straw, it propels the boat forward away from the escaping air. It even makes a soft 'putt, putt, putt' noise just like a real motor might.

Experiment with different sizes of balloons, different shapes of balloons, and different lengths of straw, to see how it affects the movement and speed of your balloon powered boat.

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