RMS Titanic: How (Not) to Build a Ship

By: Adam Tseng

“I cannot imagine any condition which would cause a ship to founder… modern shipbuilding has gone beyond that.” - John Edward Smith

Boy, was he wrong. As the first and only captain of the RMS Titanic, Smith would pay for his words with the lives of 1500 other passengers and crew, including himself.

The Titanic was one of the most modern passenger ships for its time and a leviathan of a vessel. At 46,328 tons, she was 882 feet and 9 inches wide and 104 feet high. She displaced 66,000 tons of water and traveled at a top speed of 21 knots. Construction on the Titanic was completed at Belfast Harbor and she set sail from Portsmouth, England in 1912. Bruce Ismay, the brainchild of the Titanic, put all of his effort into the project, hiring one of the most innovative shipbuilders, Thomas Andrews, and spending 400 million dollars in today’s currency. Upon completion, he told the eager press that it was “practically unsinkable.” Few disagreed. After all, how could such a massive ship, fitted with the most modern technologies, result in a large maritime disaster?

To answer that, we’ll have to look into the science of buoyancy - or how objects float.

When an object floats in a liquid, there are two forces acting upon it: the gravitational force, which acts downward, and the buoyancy force, which acts upward. The buoyancy force is what keeps the object from sinking, and it is determined by the amount of fluid that the object displaces. Ever notice how placing a rock in a beaker or cup raises the water level a little bit? It’s because some of the space taken up by the water is now displaced by the space taken up by the rock. Thus, to offset that, the water level rises to gain more space.

The amount of fluid displaced depends on the object’s density, which is the mass of the object divided by its volume. A low density means that the object will displace more fluid with its high volume and be lighter due to its lower mass. This allows the buoyant force to be greater than the gravitational force, keeping the object from sinking. Generally, an object has to be less dense than the fluid surrounding it in order to float. That’s why a styrofoam cup might float in the water, while a hard rock would sink. The rock is more dense than the water, while styrofoam is less dense.

Remember shipbuilder Andrews? He was terribly afraid of the ship sinking - so much so that he decided to change the whole structure of the ship’s bottom to combat the sinking problem. While the top and middle sections of the ship were filled with rooms, recreation areas, crew spaces, and engine rooms, Andrews made sure to fit 16 empty watertight compartments into the bottom of the ship. This increased the ships volume and only slightly increased its weight, allowing it to displace more water and float. If for some reason the hull was breached, water would flow into a compartment. The flooded compartment would be filled up and sealed shut. By this design, Andrews hoped to contain the flooding to a few of the sixteen compartments at most, leaving most of the ship water-free. He reasoned that this would mean that the ship could only gain a certain amount of weight, and it would be offset by the buoyant force due to the other empty compartments.

It’s a seemingly well thought design, so, why would the Titanic still sink? When the ship struck an iceberg 400 miles of Newfoundland, the hull broke and water rushed through the breach to fill five watertight compartments. This might not seem like a big deal, as the overall amount of fluid displaced was still greater than the weight of the ship and the water it took on. However, by breaking the Titanic up into compartments, Andrew had inadvertently created a weight imbalance. While the flooding was limited to a few compartments for the time being, those compartments were much heavier, leading that portion of the ship to be more dense than the surrounding water. This caused the ship to tip over at an angle. While the bulkheads - big internal walls that separated the compartments - were massive, they only extended a few feet above the waterline. Thus, as the ship dipped downward, water was able to go over the top of the bulkheads and spill into the next compartment, which caused the ship to dip down even further, eventually plunging the entire front of the ship, or bow, into the water. This cycle continued until the ship was so heavy on one side that it broke in half, dooming it.

Ultimately, the Titanic sunk because its designers had made quite a few mistakes in simple logic. In compartmentalizing the ship, they somehow failed to recognize that those compartments had to be high enough to stem rising water and seal off everything below the deck. Ironically, without compartments, the ship would have floated or sank much slower because the water would spread out in the hull and even out the ship, preventing it from tipping over.

So is the lesson to never overthink a problem? Maybe, because you might just make it worse.


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Edward D Walker Marine Artist. (n.d.). Retrieved from http://www.edwalkermarine.com/

Silverman, J. (2019, December 05). 10 Scientific Laws and Theories You Really Should Know. Retrieved from https://science.howstuffworks.com/innovation/scientific-experiments/10-scientific-laws-theories7.htm

Tikkanen, A. (2019, October 13). Titanic. Retrieved from https://www.britannica.com/topic/Titanic

Why Did the Titanic Sink? An Engineer's Analysis: SimScale Blog. (2019, November 04). Retrieved from https://www.simscale.com/blog/2018/01/why-did-titanic-sink-engineer/

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