Container ships transport... containers. But what is a container? A container is a standardized "box", into which one can load almost any freight one would like to transport.

A key idea of a container is that it can be used for different modes of transportation: it can be loaded on train cars, on trucks, and on ships. That's why they are sometimes called intermodal containers. This way large numbers of items (say, a shipment of new mobile phones or clothes) can be transported by train from a factory to a harbor, transported by ship across an ocean, and hauled by truck to its destination, all without having to be individually loaded and unloaded.

To ensure that a container fits and can be properly attached, a whole bunch of international standards specify all the relevant aspects, such as the exact length, width, and height. Because these standards are released by the International Standards Organization (ISO), the containers are also known as ISO containers.

There are different kinds of ISO containers; the most common type is the 1AA container, which is 40 feet long, 8 feet wide, and 8.6 feet tall. Another type is the 1CC container, which is half as long.

The size of the 1CC container is used when talking about the capacity of container ships. There is even a unit for this, called TEU (Twenty-foot Equilvalent Unit). If a container ship can transport 100 40-foot containers, its capacity would be indicated as 200 TEU.

The MSC Ajaccio, shown above, is not the largest ship by far. It can carry about 9400 20-foot containers. The freight containers we know from trains and trucks in Europe are 40 feet (12.192 m) long. Thus, to transport as many containers as fit on the MSC Ajaccio, we would need 4700 trucks!

Now, the largest container ships as of 2023 are the MSC Irina, MSC Loreto, and MSC Michel Cappellini. They are 399.9 meters long and 61.3 meters wide. They have 24 bays (6 + 14 + 4), each of them 40 feet long, for holding containers. A bay can hold up to 24 rows of containers. It can stack up to 25 containers (above deck and below deck combined). Each of them has a TEU of 24346 -- they each can fit over 24000 20-foot containers! You would need 12173 trucks to carry the load of one of these ships!

Decomposition

Let's decompose a container ship. We can horizontally split the ship into two parts: below deck there is its hull (black and brown in the above photo), and above deck there is its superstructure.

Let's look at the ship from the side (like in the above photo); the front (bow) of the ship is on the left, the rear (stern) on the right.

Throughout the length of the ship there are spaces to place containers. Those spaces are called bays. The MSC Irina has 24 bays. Each bay contains a stack of 40-foot containers. Some of the containers are stacked below deck. They are covered at the deck with hatch covers (to prevent water from entering the bay). Other containers are stacked above deck, above the hatch covers. These above-deck stacks are supported by lashing bridges at either end of the bay.

Besides container stacks, the ship's superstructure includes a deckhouse (with a bridge on top, and accommodations for the crew) and a funnel for the exhaust from the engine. At the bow of the ship there is a foremast, which should remain visible from the bridge even when the ship is fully loaded.

Implementation

Now let's implement functions to compose the different parts of the ship.

Container

Before forcusing on the ship, let's compose the containers we will load on it. The measures of the containers determine most of the measures of the ship.

Let's model a container as a rectangle that is 40 feet wide and 8.6 feet tall. To allow us to scale our composition, we pass a parameter to the function that determines how big we want a foot to be. We want to allow different colors of containers, so the function takes a parameter providing the color.

Foremast

Funnel

Deckhouse

Hatch Cover

A hatch cover covers a bay of containers.

Lashing Bridge

At either end of a container bay there is a lashing bridge. The lashing bridges support the stacks of containers above deck. Often all the lashing bridges of a ship have the same height. They do not go up to the top of the container stacks, but only cover the bottom few tiers of containers.

Stack

The part of containers stacked below deck is not visible. We only see the containers stacked above deck. These stacks can have more than 10 tiers, and only the bottom few are supported by the lashing bridges. Containers are stacked on top of each other and are attached tightly with twistlocks at each corner. Because ships can roll quite a bit (typically up to 22 to 30 degrees), it can happen that a ship loses some of its containers (each year several hundred containers are lost at sea).

Hull

Superstructure

We use the term superstructure to refer everything located above deck.

What You Learned

You practiced composing graphics. In particular, you composed multiple graphics above and beside each other.

You also learned about container ships, an important mode of transportation in today's interconnected world.