Soda Bottle Submarine
1-3 hours
Ages 8+
What Will You Make?
Make a simple, self-propelled submarine out of soda bottles and other household items.
What Will You Learn?
Explore buoyancy, forces and motion, and why submarines need stabilizing fins as you use common hand-toosl to upcycle a soda bottle into a submarine.
Build Your Submarine
Assemble the Submarine Interior
Drill a hole in the bottom of your bottle. Using chopsticks, feed a paper clip through. Hook paper clip into second hole for stability. Use chopsticks to hook the rubber band to the paper clip.
Add the Stabilizer
Connect ruler stabilizer fins with 2 rubber bands.
NOTE: Why you need stabilizer fins: Without fins, prop and bottle both spin in opposite directions. With stabilizing fins, the prop spins and the bottle moves forward.
Make the Propeller
Crush, then cut a bottle in half. Trim around the bottom, and cut through the middle of each high and low point. Drill a hole in the bottle cap. Straighten paper clip, and feed through bottle cap then through propeller’s center hole. Bend a hook into second hole. Attach loose end of rubber band to paper clip hook.
Test It Out
Spin the propeller to twist the internal rubber band. Place your submarine in the water and release the propeller. What happens?
What Is Happening Here?
Propeller
Propeller blades displace water, to create the forces that move a submarine forward. The rubber band creates the torque, or energy required to turn the blades. But, the design of propeller blades is what creates the displacement of water. The displacement of water is what creates forces that move a boat forward.
Try changing the size or shape of the propellers to see how it affect the motion of your submarine.
Stabilizing Fins
We added a ruler as a stabilizing fin to the submarine. Without this fin, the bottle and propeller will spin in opposite directions. But with it, the propeller spins and pushes the submarine forward.Â
Try different materials for the fin, or change its width or length.
Buoyancy
With lots of air inside, the sub has positive buoyancy and will rise under water to float on top. With just the right air inside, the sub will have neutral buoyancy and will stay under water. With little or no air inside, the sub has a negative buoyancy and will sink under water.
Experiment with different amounts of water to get your sub to move nice and straight in the water.
What' Next?
Materials:
- Water bottles, plastic (2)
- Ruler, 6"
- Rubber bands (3)
- Chopsticks (2)
- Paper clips (2)
- Needlenose pliers
- Scissors
