For our DEEP experiment, we built a submarine and compared the speeds of a submarine with a nose cone, and without. We combined hydrodynamics, and engineering. We chose to make our submarine rubber band powered instead of electrically, because we did not want to have to worry about waterproofing anything.
Our results show a comparison between a pointed nose on our submarine, and no nose at all. On average, when the submarine had the nose on, it went about 3.7 inches per second, compared to no nose at all, which had an average of 5.5 inches per second. Our results proved that having the water flow openly through the submarine allows for the submarine to move faster than having a coned nose which does not let water flow openly through it. Although a pointed nose goes smoothly through the water, it does create some drag which led to the higher speed on the submarine with the nose.
Our results relate to scuba diving, because the depth affected the submarine. After it started moving forward, it would slowly ascend. This is because it is very hard to keep something neutrally buoyant (like Greg). Our submarine was about four feet underwater, so the foam was still buoyant. It had more of a chance of floating up from the bottom than if it was deeper. Also, the propellors moved much slower in the water than in the air. We cut the propellors shorter so they would work better flowing through the water.
In our experiment there was a great deal of error. When the submarine had the cone nose, there was 9 percent error with the nose, and 25 percent with no nose. With no nose, the submarine traveled about 56 inches. Because there was a 9 percent error, that error could be 9 percent higher, or lower than 56. If it’s higher, it would be about 60 inches. With the nose cone, it traveled 82 inches. The percent error was 25. That too could go higher or lower. If it went lower, it would also be about 60 inches. However, there is a 50 percent chance that it would be higher or lower for both. Therefore leaving a 25 percent chance that they were about equal.
There was not an exact control, because the submarine had different weights. With the nose cone, it was a little heavier than without.
We already changed our project, because our first submarine fell apart. Alex kicked it at long beach..... (Don’t use hot glue for underwater projects!) We used hot glue to hold some of the parts together, and it easily fell apart in the water. We used metal to hold the three pvc pipes together, and the epoxy held the metal strips together well. However, our old submarine was too heavy. The wire mesh that held the weights was unstable. The weights would easily slip out. The flat nose moved around too much, and was top-heavy (the front of the submarine was tilted down). The propellors were too big, and so we cut them down on the new submarine.
Our new submarine was made entirely from pvc pipes,
with “T connectors” used to attach the different tubes. Inserted
in the center was a piece of foam for floatation.* The only things we could
have done better on our new submarine would be to give the rubber bands more
so they could move easier in the water, and maybe add a rudder to allow for
a straighter path.
What we Learned
Obviously, we learned how to scuba dive. For our project though, we learned about hydrodynamics, and what propellors would work better in water. Since we had to make a new submarine, we learned about error, and how to “cope” with it. You should always get more supplies than you think you need in case you mess up. You also need to make sure if you are doing engineering, that you need to use stable materials. We learned a lot about underwater engineering, and how to make the most out of our project.