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Indoor activity

Rubber Band Speedboats

Engineer a high-speed paddle boat powered entirely by elastic energy, and race them across the bath!

Ages 7-12 0-1 hours Education 10/10

Materials

  • Cardboard Boxes
  • Rubber Bands
  • Scissors
  • Tape
  • Water

Illustrated Steps

1

Construct the Racing Hull

Cut a pointed boat shape from cardboard with two rear arms, and wrap it completely in waterproof tape.

2

Build the Paddle Wheel

Slot two small cardboard rectangles together to make a '+' shape, and wrap it in tape to keep it dry.

3

Install the Engine

Stretch a rubber band between the boat's arms and carefully slot your paddle wheel into the middle of it.

4

Wind Up and Launch

Twist the paddle backwards to store up massive energy, place it in the water, and release!

What You’ll Create

Get ready for the ultimate shipyard challenge! 🚤 You will build a lightweight, water-skimming speedboat equipped with a functional rear paddle wheel. By winding up an elastic band, you’ll store kinetic energy that launches your boat across the water at top speed.

How to Set It Up

Step 1: Construct the Racing Hull

Take a flat piece of Cardboard Box and cut out a rectangle with a pointed front (like a real boat prow). Cut a square notch out of the back of the boat, creating two long ‘arms’ that stick out behind. Wrap the entire hull tightly in Tape to make it waterproof! 🛡️

Step 2: Build the Paddle Wheel

Cut two small rectangles out of cardboard (about 4cm by 3cm). Cut a slit exactly halfway up the middle of each one. Slot them together to form a ‘+’ shape, and wrap this wheel in tape too, so it doesn’t get soggy.

Step 3: Install the Engine

Stretch a strong Rubber Band across the gap between the two arms at the back of your boat. Carefully pry apart the rubber band slightly and insert your paddle wheel right into the middle, so the band grips it tightly.

Step 4: Wind Up and Launch

Time for the sea trials! 🌊 Wind the paddle wheel backwards towards you over and over until the rubber band is twisted super tight. Hold the paddle still, gently place the boat in a bathtub or sink of Water, and let go!

Have fun!

  • 🏁 Build two boats and host the ‘Grand Bath Tub Regatta’ to see whose design is fastest.
  • ⚖️ Experiment with cargo: How many coins can your boat carry before it sinks?
  • 🎨 Decorate the waterproof tape with permanent markers to give your speedboat racing stripes.

Why It’s Amazing

  • Physics in Action: Children visually experience the conversion of ‘potential energy’ (the twisted band) into ‘kinetic energy’ (the spinning paddle). 🔋
  • Engineering Iteration: If the boat spins in circles or doesn’t move, kids must problem-solve and adjust their design.
  • Water Confidence: A fantastic, engaging activity to make bath time incredibly exciting. 🛁

Pro Tips

For ages 8-12, challenge them to make the boat out of a plastic food container instead of cardboard for ultimate waterproofing! If the boat keeps flipping over, tape a single coin to the bottom of the hull to act as a stabilising keel.