Objective

To find out how a submarine uses a propeller and a stabilizing fin for forward movement.

Introduction

Although the submarine you have seen in a movie seems to be gliding along effortlessly, it is actually fighting the forces of gravity, pressure, friction and buoyancy. Have you ever encountered these terms in previous science fair experiments? Among all other science fair experiments, this is one of the best, as you will understand how these forces are overcome by the submarine.

Materials

A 500ml water bottle, a soda bottle (2 liter), knife, scissors, 2 large paperclips, needle-nose pliers, chopsticks, 3 rubber bands, stiff ruler, a silicone sealant, a bathtub or pool

Preparation

The Propeller

This is one of those science fair experiments in which you will need the assistance of an adult.
Cut a soda bottle (2 liter) in half. Take the bottom for making a propeller with 5 curved separate blades. Two holes are to be drilled in the propeller, in the centre and a little off-centre. Cut a small plastic circle out of the remaining 2-litre soda bottle. Bore a hole at the centre of this circular piece of plastic and the submarine bottle cap. The free end of a straightened paperclip should be passed through the cap of the bottle, the circular plastic and the centered propeller hole. The free end should be bent back and passed through the non-centered hole in such a way as to keep the cap, the plastic piece and the propeller in close contact with each other, but allow the propeller to rotate freely.
The Submarine
Drill two holes at the bottom of a 500 ml water bottle similar to the propeller holes. Now feed the straightened end of a paperclip from the inside of the bottle through the central hole. Bend the free tip and pass it in the non-centered hole. Secure the paperclip in such a way that it will not turn. This part is very tricky, so use a chopstick. Attach a rubber band between both the paperclip hooks. The rubber band must be tightly stretched between the hook at the bottle’s base and the hook on the cap. Attach the ruler perpendicular to the water bottle body in the centre with the help of two rubber bands in the form of an “X”. The ruler is your stabilizing fin. Now use a waterproof sealant to close all the paperclip holes in the bottle.

Your submarine is now ready.

Testing your Submarine
Fill three-quarters of the submarine bottle with water and put the cap on. Turn the propeller to build potential energy in the rubber band. Science fair experiments require that you write down all your activities. So count the number of turns and write this number in your lab book. You must turn the propeller that many times in future.
Procedure

Now you will position the stabilizing fin in the front, center and the back in different ways and have some fun observing how your submarine moves. Record your observation each time. Use the below-mentioned ten positions.
No fins- Middle: Fin Centered- Middle: Fin moved to the right – Middle: Fin moved to the left – Front: Fin Centered- Front: Fin moved to the right – Front: Fin moved to the left – Back: Fin Centered- Back: Fin moved to the right – Back: Fin moved to the left –

The observations will allow you to answer the following questions:
What would happen if there was no stabilizing fin? What is the best position for the fin? Why is a stabilizing fin important in a submarine?

If you’re ready to get started with your submarine experiment, your next step is to download a free copy of “Easy Steps to Award-Winning Science Fair Projects” from the link below right now.

By: Aurora L.