Science Project: Make a Soap Powered Boat

Experiment with motion and propulsion by making these soap powered boats. This is a great project for home schoolers or for anyone else who wants to learn a little more science at home.

For this project you'll need an empty milk or juice carton. You'll need the cardboard carton; not the plastic bottles. Cut a two-inch by three-inch piece out of one of the sides of your carton. This will become your boat.

Lay your rectangle on your work surface so that the two-inch side is closest to you and the three-inch sides are running up and down across the table in front of you. Make a mark in the center of the top edge and another mark one inch down from the top on each of the two side edges. Draw diagonal lines from the center mark to each of the two side points. This will mark off a triangle shape in each corner. Use scissors to cut on those lines so that the corners are removed. Discard the triangle pieces.

Now on the opposite end of the paper from the point you just created, you'll make the tail of your boat. Cut a small triangular slit in the center of the back end of your boat. The slit should be an inch or less long, and perhaps a quarter of an inch wide at the most.

If you don't already have a body of water (such as a lake) nearby, you'll need to create a space for your soap powered boat to run in. You can use the bathtub for this, or a plastic wading pool. Fill it with about a half an inch of water. You don't need to fill it up completely, because the boat isn't going to be down in the water. It is going to skim along the top. So, half an inch is plenty.

Lay your boat shape down on the top of the water; then using a bottle of liquid dish detergent squirt a drop of soap just at the point of the slit that you made on the back of the boat. Then stand back and watch your soap powered boat take off.

The soap is providing the fuel for your boat to move. When it runs out of fuel, it will come to a stop. You can add another drop of soap to get it going again.

After a while you'll find that adding additional drops of soap isn't working anymore. This just means that enough of the soap has gotten off the boat and into the water that the water is no longer clean. Your soap powered boat works best on clean water, not soapy water. If enough of your water is contaminated with soap, you'll simply need to dump out that water and put in fresh water. Then you can continue to enjoy your soap powered boat.

You can experiment with different shapes of boats changing the angle of the point on the front changing the length and width of the boat to discover which shapes move fastest or harder or easier to control in the water.

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