How to Make a Water Bottle Rocket

What you need

  • Two 2-liter bottles
  • Scissors
  • Cardboard
  • Duct tape
  • Clay

Step 1: Make the nosecone

  1. Cut one of the bottles in half. The top portion will be the nosecone.
  2. If you want to experiment with nosecone length, you can start by cutting the nosecone longer. Later, you can trim the nosecone shorter to experiment with flight behavior.

Step 2: Add clay to the nosecone

  1. Screw the bottle lid onto the top of the nosecone.
  2. Pack clay up inside the top of the nosecone.
  3. Clay adds weight to the nose of the rocket in order to move the center of mass in front of the center of pressure for stable flight. Too much clay, and you sacrifice height. Too little clay, and you sacrifice stability.
  4. Don’t worry. You can add and remove clay later.

Step 3: Tape the nosecone onto the body.

  1. Wait to tape on the nosecone if you don’t have your own clay. We have clay for you at the park.
  2. If you do have clay already packed into the nosecone, tape the nosecone to the bottom of the second bottle.

Step 4: Tape fins to the rocket.

  1. Cut a fin from a piece of sturdy cardboard.
  2. Use this first fin as a pattern to cut additional fins.
  3. Tape the fins toward the bottom of the rocket body.
  4. Fins add drag to the bottom of the rocket, putting the center of pressure behind the center of mass for stable flight. Too much “finnage”, and you sacrifice speed. Too little “finnage”, and you sacrifice stability.
  5. Bring extra cardboard to experiment with fins.


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