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Balloon-powered boats are a fun science experiment that can teach kids about motion. They also make great toys for bathtubs and pools. All you need is something that can float, a balloon, a piece of plastic tubing, and a few extra supplies. You can even make several boats with different designs and race them!

Method 1
Method 1 of 2:

Using a Sponge

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  1. 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. [1]
    • The thicker the sponge is, the better.
    • Make sure that the sponge is smooth on both sides and does not have a scrubbing pad.
  2. 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. [2]
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  3. 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! [3]
  4. 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).
  5. 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.
  6. 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!
  7. 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!
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Method 2
Method 2 of 2:

Using a Milk or Juice Carton

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  1. 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.
  2. 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. [4]
    • 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.
  3. 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. [5]
  4. 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. [6]
  5. 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.
  6. 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. [7]
    • You will attach the rudder to this, which will help make you boat go straight. [8]
  7. 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. [9]
    • 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.
  8. Hold the balloon's tail firmly against the plastic tube. Blow into it, then place your finger against the end of the tube.
  9. 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! [10]
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Community Q&A

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  • Question
    If your finger is off the tube and you are not ready to release the boat just yet, then what is going to happen?
    Anselm
    Community Answer
    The boat will just sit and do nothing, unless you have blown up the balloon in which case it would deflate. But otherwise it would just float.
  • Question
    I think you should blow up the balloon with water, because air would make it go, but would go to the surface, but water would make it go better.
    Anselm
    Community Answer
    Yes, it would work but the balloon would have to be extremely full with water and the boat itself would have to be very strong or the weight of the balloon could cause it to tip over or sink.
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      Tips

      • You can also use a Styrofoam try instead of a sponge or milk carton.
      • If you can't find a plastic tube, use a straw instead. Wrap some tape tightly around the balloon tail to keep it in place and ensure an airtight seal.
      • If keeping your finger over the end of the tube is not enough to keep the air in, pinch the tail of the balloon instead, just below the body of the balloon.
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      Things You'll Need

      Using a Sponge

      • Balloon
      • Kitchen sponge (with out scrubbie part)
      • Small piece of plastic tubing
      • Scissors
      • Craft blade

      Using a Milk or Juice Carton

      • Balloon
      • Plastic milk or juice carton
      • Small piece of plastic tubing
      • Scissors
      • Craft blade
      • Hot glue gun and hot glue sticks
      • Duct tape
      • Paper clip


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