• 2L pop bottle
• small electric motor
• battery (AA)
• 1/8" dowel
• cork
• duct tape or glue
• electrical tape
• 1/8" diameter rubber tubing
• insulated wire (16 gauge)
• popsicle sticks
• 1/4" styrofoam

1. The Hull
   1. Draw a design of the boat on the 2L pop bottle. Be creative with your design but make sure to cut at least half the bottle away near the centre of the boat (this is where the motor will eventually be mounted).
   2. Cut out the boat and be sure to save the discarded plastic for the propeller and bottom of the boat.


2. The Propeller
   1. Drill a small hole through the centre of the cork for the drive shaft.
   2. Using a sharp knife, make four angle slits for the propeller blades to fit.
   3. Cut the propeller blades out of plastic. Experiment with different sizes and shapes (smaller blades allow the propeller to turn faster).


3. The Drive Train
   1. Glue a 3-4 cm piece of rubber tubing to the end of the motor so that the tube spins freely.
   2. Glue a section of 1/8" dowel into the tube. The length of the dowel will depend on the position of the motor. For now the dowel should be at least 12" long.
   3. Strip the ends of two 6" long insulated wires and attach a wire to each terminal of the motor.
   4. Bend a paper clip and attach it to the positive end of a battery. The "hook" of the clip should fit tightly around the positive terminal and be secured with electrical or duct tape. The other wire should then be connected to the negative terminal of the battery with tape.


4. Putting it together
   1. Around the centre of the boat use two popsicle sticks to form a bench for the motor to rest on. Secure the bench to the bottle with tape or glue.
   2. Melt a hole (only big enough for the dowel to easily fit) near the bottom of the rear of the boat.
   3. Slide the dowel through the hole and rest the motor on the bench. Tape or glue the the motor to the bench, allowing the central axis of the motor to line up with the dowel.
   4. Slide the cork onto the dowel and cut the excess dowel off.
   5. Put the blades of the propeller on and glue if necessary.
   6. Tape the battery to the bottom of the boat with the paper clip sticking up.
   7. Use some left over plastic and cut two curved strips about the same size (around 5 cm by 5-10 cm). Tape them together so that they curve away from each other. Then tape this fin to the bottom of the boat; this will allow the boat to steer straighter.
   8. (Optional) Cut two strips of styrofoam and glue them to the sides of the boat for stability.

5. Operation of the boat
   1. Slide the wire into the hole of the paper clip to turn the motor on.
   2. If the boat goes in reverse, the leads of the motor must be switched.
   3. The water durability of the motor will depend on the motor used.
   4. The test boat used an AA battery, but a larger battery (D) gives the boat a lot more power. Be careful not to overload the motor.
   5. Enjoy your boat and don't worry about losing it; the propeller causes it to turn in circles.

Archimedes' principle doesn't apply only to boats. You might have heard the legend of Archimedes leaping out of the bathtub and running naked through the town shouting "Eureka!". Archimedes was happy because he was able to save his King from being cheated. He found that his King's crown pushed aside more water than an equal weight of gold, proving that the goldsmiths had cheated the King by adding a less dense, cheaper metal to the crown.