Science Fair Experiments that get good grades – Experiment #9 - Submarine Science

Have you ever considered studying submarines when you thought about cool science fair experiments? Do you wonder why submarines need fins? In fact, most people think that submarines move very slowly when underwater, but they actually move fast! In this project, you will investigate how submarines use propellers and fins. You will do this by building your own miniature submarine and by testing different types of fins on your model.

 As far as difficulty levels in science fair experiments, this project is about average. You will not need any special skills and it should only take a few days to complete the experimentation section of your project. Also, the cost is pretty low because most of the material you will need is readily available. However, you will be using some cutting utensils and power tools, so you will need some adult supervision.  

Introduction

Did you know that the world’s fastest submarine can move over 46 miles per hour? It’s true! As you can imagine, moving a submarine under the water is pretty tricky. For a submarine to move underwater, there are several forces involved such as gravity, pressure, friction, and buoyancy.  

Do you know it’s like to try to run in a pool? It’s not that easy, is it? Well, that is the force of friction. It’s difficult because the water is much more dense than the air, and as you are moving the water is actually pushing against your body. This makes for much friction. Submarines are made to minimize friction by possessing a bullet-like, hydrodynamic shape. Plus, they are made of strong materials, such as steel, in order to resist these high-pressure forces as it moves through the water. 

If submarines are made of such heavy material, how can they float? They are able to do that because of buoyancy. That means a submarine displaces a certain amount of water that equals the amount of weight of a ship. So this makes for an upward force that is opposite the force of gravity. That force is called the buoyant force. This explains the way that a submarine can move up and down in the water. How does it go forward or backward, though? By using a propeller. 

When the propeller rotates, it can make the submarine spin. This takes away any of the forward movement. So submarines require stabilizing fins. Without them, it would merely be a tube that spins. Stabilizing fins fight the spinning by combining the force of friction. This cancels out the rotating motion, and lets the propeller begin to push the submarine’s body forward. To go backward, the propeller just spins in a different direction.

Science fair experiments always require you to become acquainted with certain terms and concepts. Before you begin the project, you ought to know the following: submarine, friction, stability, buoyant force, hydrodynamics and stabilizing fins.

By the way, getting a free copy of Easy Steps to Award-Winning Science Fair Projects will help you through your own project.

What you will need for this experiment:

•    one empty soda bottle, two-liters

•    an empty water bottle

•    a knife or a razor blade

•    a drill that has a 3/32-inch bit attached

•    scissors

•    a needle or a pen

•    needle-nosed pliers

•    2 big paper clips

•    chopsticks

•    ruler

•    3 rubber bands

•    a waterproof sealer like silicone

•    a pool or a tub that is full of water

•    lab notebook

Steps for submarine science fair experiments:

1.    First you’ll make a propeller. You will cut off the bottom half of the soda bottle to create a propeller shape. You need to have five individual curved blades. Ask an adult to help you use the knife or razor blade, because this can be tricky and difficult.

2.    Ask an adult to drill the hole into the water bottle’s cap. Drill 2 holes into the propeller, the first in the middle and the second just off of the center. Make sure you wear safety goggle when you use power tools.

3.    Carefully with the scissors, you need to cut out of the plastic soda bottle a small circle. Try to cut it about the same shape and the same size as your water bottle cap. It is going to go between your bottle’s cap and your propeller. It serves as a washer because the propeller must spin up against a slippery surface. Now, use the needle or the pen to create a hole in the center of your washer. Make sure it can fit a paper clip’s tip through it.

4.    Straighten out an end of a paper clip.  Feed it into the holes you made in the water bottle cap, your matching sized plastic washer and the center of your propeller.  Make sure your propeller’s fins are facing downward.

5.    Using the needle-nosed pliers, you need to bend the paper clip’s inside end until you can loop it in through the propeller’s hole that is just off centered.  This will make sure that the two pieces of your submarine are securely fastened together.

6.    Now you will craft the submarine. You need to ask an adult if they can help you drill two small holes into the bottom of your water bottle, similar to what you had to do for the propeller (one that is in the middle, the second just off of center).

7.    Bend out straight one end of your second paper clip. Using chopsticks or something else long and straight, you need to push the straightened end of the paper clip down and through the small hole that you created in the water bottle, into the mouth on the bottle and then through the hole in the center at the water bottle’s end.  This can be tricky, so take your time!

8.    Once the straight end is out, you will use your needle-nosed pliers and bend the free paper clip end over and then stick it through the second off-centered hole.

9.    Use your chopstick to lower a rubber band down to the hook that you made from the paper clip down in the bottle. Who ever thought you would use chopsticks in science fair experiments?

10.    Now, careful not to release the rubber band, you need to hook the opposite end of the rubber band’s loop through your paper clip’s hook that is inside the bottle cap. Be sure that the rubber band is taut because if there is a lack of tension, your submarine will not move.

11.    Next, you will use two of the rubber bands to make a fin for stabilization. Put the ruler perpendicular to but centered with the submarine. Making an “X” with two of the rubber bands, attach them around your bottle and your ruler.

12.    Let’s test the fin now. Fill your submarine’s bottle up approximately three-quarters full of water. Affix the bottle’s cap. Make sure to tighten it, because the cap should not move with the propeller.

13.    To build up energy, twist your rubber band a few times around. Why does the propeller work? How come the submarine will move forward and not backward?

14.    Be sure to count and write down how many times you twisted your rubber band around. Be sure to repeat this number of twists for each trial you run.

15.    Place your submarine underwater and release it. What does the submarine do? If it sinks, you should let some more water out. If it floats to the surface, you need to add some more water. If it moves forward, then you are all set to start!

16.    Next you will run a series of trails in which you should change the location of your stabilization fin. Try 10 various positions and take note of the results every time. Be sure to record them down in a notebook. You will test the submarine with no fins at all, with the fins directly centered, located off to the left, and finally, just to the right. Then, those three different positions (centered, left, right) will be tested in the front, middle, and in the back of your submarine. You will be running nine different tests and one more for your submarine that does not have a fin. Make sure you record all data in your notebook. 

Some things to think about are the effect that the stabilizing fin has on the way your submarine moves. What fin position was the optimal? Finally, why is it important to use stabilizing fins for hydrodynamics of submarines? I hope you enjoyed studying the hydrodynamics of submarines!  

To help you with your own project, take a look at some of the links next to this article. Good luck!