How to Make a Balloon‐Powered Boat

Using a Sponge

Cut a slit in the middle of a kitchen sponge. Find the center of your boat by drawing an X on it, from corner to corner. Use a craft blade to cut a small slit in the center of that X. The slit needs to be big enough so that you can slip the end of your balloon through it. The thicker the sponge is, the better. Make sure that the sponge is smooth on both sides and does not have a scrubbing pad.

Cut one of the narrow ends of the sponge into a point. Find the center of one of the narrow ends. Use a pair of scissors to cut both of the corners off towards that point so that you end up with a ^-shaped point. This will make the front of your boat.

Pull the end of the balloon through the slit in the sponge. Keep pulling until the body of the balloon touches the top of the sponge. The tail should be on the underside of the sponge. Don't blow up the balloon just yet!

Slide a short piece of plastic tubing into the balloon's tail. Find a short piece of plastic tubing, about 3 inches (7.62 centimeters) long and ¾-inch (1.91 centimeters) wide. Stick the tube into the tail end of the balloon not not into the sponge. You want the sponge to be pinching the balloon shut. It's okay if the tube is a little flexible. You can find such tubes in your local hardware store, aquarium store, and pet store (fish section).

Blow the balloon up. Hold the balloon firmly by the tail and tube. Blow into the balloon through the tube, then quickly cover the opening of the tube with your finger. Keep holding the tail end of the balloon.

Set the boat into a body of water. You can use anything, from a sink to a bath tub to a swimming pool. Keep your finger over the tube; you're not ready to release the boat just yet!

Angle the tube back and let go. Hold the sponge steady with one hand. Angle the tube towards the back of the boat with the other. Release the tube, and watch the boat propel itself forward!

Using a Milk or Juice Carton

Slide the tail end of a balloon over a short piece of plastic tubing. The tube needs to be big enough to fit into the tail end of the balloon with a little stretch. Look something that is about 3 inches (7.62 centimeters) long and ¾-inch (1.91 centimeters) wide.

Cut one of the side panels out of a plastic milk carton using a craft blade. If your carton has a handle attached, you want to cut out the side with the handle. Leave the top and bottom of the carton intact. Save the panel that you cut out for later. You can also use a plastic juice carton instead. If the carton is dirty, take a moment to clean it.

Cut a hole in the bottom of the carton. Place the plastic tube against the bottom of your carton. Make sure that it is centered, then trace around the plastic tube using a pen, the set the tube aside. Cut the hole out just inside the outline using a craft blade.

Insert the plastic tube into the hole. Place the tube, along with the balloon, into the carton. Push the end of the tube out through the hole you just cut out. The balloon should be on the inside of the carton.

Angle the tube downward and glue it in place. Push the tube downward as far as it can go without actually bending anything. Draw a ring of hot glue around the seams both on the inside and outside of the boat. This will also help create an airtight seal and prevent any water from getting into the boat.

Duct tape a bent paper clip to the bottom of your boat. Straighten out a paper clip, but leave one of the ends bent at a 90-degree angle. Duct tape the paper clip to the bottom of your boat, just below the plastic tube. Make sure that the bent part is flat against the bottom of your carton. You will attach the rudder to this, which will help make you boat go straight.

Duct tape a 2-inch (5.08-centimeter) plastic square to the bottom of the paper clip. Cut a 2-inch (5.08-centimeter) square out of the plastic panel you cut out earlier. Place it against the paper clip, just below the bottom edge of the carton. Make sure that it is perpendicular to the bottom of the carton, then wrap a piece of duct tape around the paper clip and the plastic square. If there is ay paper clip sticking out from under the rudder, you can cut it off with a pair of wire cutters. You can also fold it up against the rudder instead.

Blow the balloon up. Hold the balloon's tail firmly against the plastic tube. Blow into it, then place your finger against the end of the tube.

Place the boat in a body of water and let go of it. You can use anything for your body of water, as long as it is big enough for your boat. Bath tubs and swimming pools make great choices. Set your boat down onto the water, then let go of it, both hands at the same time. Watch it go!