I recently read an article that the Royal Caribbean have just given the go ahead for the largest ever cruise liner to set sail, it’s nearly 1200ft long and has something ridiculous like 5 water slides and a zoo on it (maybe that’s an exaggeration, but you get the point).
It got me thinking – is there a ceiling to how large a boat can be? Does buoyancy have a limit? If you ignored the impracticality of mooring and getting into smaller bodies of water, is the capacity of Ship building limitless?
In: 2380
The only limit would be the physical resistance of materials. But if you manage to build something like a very large plate, for instance, with high borders, you can make it an insanely large ship. You merely have to get materials which will resist the huge torsion forces from having parts dangling, while other are pushed by waves, the parts in question changing with the underlying waves.
So, the current sizes are determined both by the sizes of the bodies of water / harbors (because, if you need 150m underwater and 800m abreast to be able to navigate, it *might* cause a few problems to reach a harbor, or to use channels, etc.), and by the economical use. If you plan to take 10k passengers, a ship maybe 20 or 30% larger than what we currently have will be enough. If you want to take 250k passengers, you’ll build larger.
Same for cargo: If you need to take 100 times the number of “boxes” a very big container transport does today, then yep, maybe you’ll build larger. But, then again, you’ll need facilities which can accommodate such a giant ship. And unless several ports invest in order to be able to do so, you won’t be able to use your ship, in practice. Considering the cost of a ship, you don’t want to build a giant you cannot use.
So, the limits are more because of economical and practical constraints, than physical ones.
Other considerations are ports large and deep enough. Height would be limited to any bridges it would need to navigate beneath – or canals it needs to traverse.
As many others pointed out “Sea Worthy” and “will it float” are not the same thing. Also at some point you start to strain the idea of calling it a ship.
The ocean is not flat, it moves around a lot. At some point you run into mechanical limits of a rigid structure, if you had a “ship” that was 10 miles long and the front end encountered a storm that blew it violently in one direction while the back end was still like an hour away, if your vessel as rigid or even semi-rigid, it would tear in half.
But if you don’t limit yourself to what we normally think of as a “ship” you could, at least in theory, do all kinds of crazy large scale things. For example you could create a series of large floating “nodes” connected by flexible pathways and spooling/retracting cables that allow it to bend and move and change shape with the ocean conditions. If it could very very slowly move around the oceans using some combination of sails and motors, a kind of large floating migratory city, that could become enormous. But is that really a “ship” at that point? And of course even if you could do it, is it feasible?
When the hull is dragging along the bottom of the Mariana Trench, you’ve reached your limit.
ELI5 – MONEY, ECONOMICS, EFFICIENCY, INFRASTRUCTURE, STABULITY restrict how big they can get.
Not a naval architect but used to work in the merchant navy on container ships.
To my understanding, there’s no real theoretical limit, they can keep getting bigger and bigger on paper. I worked on MV Erving, which was 366m long (~1200ft) and could hold 16000 containers.
Back when it was built it was about getting as much cargo from one place to another as fast as possible. It had a huge engine (2 stroke diesel that created 75000kw of power) cause back in those days that is what the goal was. Now it’s all about economics and saving money. Most high streets still need the demand of things getting from one country to another as fast as possible, but it isn’t money efficient and its better for shipping companies to take a little longer but in the meantime save on fuel. My ships was spending roughly $2.5m every 2 months to refuel.
Money aside, there are other major infrastructures to be majorly aware of, such as the Suez and Panama canal. They save the shipping companies a lot of time and therefore money on fuel, and allow shipping companies to make more money by being able to deliver their cargo and get new things in the shop a lot quicker than going round the capes of South America and South Africa. Ships are often restricted to the dimensions of these canals and ships are even named after this such as PANAMX containers, meaning the maximum size of a ship to fit through the Panama canal.
Another issue with making bigger ships that a lot of people aren’t aware of is the depth of water around ports. The ship I worked on was so big that we were restricted into what ports we could enter due to fear of grounding so if ships were made bigger, they would have a greater draft and therefor would run higher risks.
While larger ships can potentially carry more cargo or passengers, there are limits to the efficiency gains. Beyond a certain size, the economies of scale may diminish, and other factors such as loading and unloading times, port infrastructure, and operational complexity may offset the benefits of increased size.
Lastly is overall stability, even the ship I was on, when it was fully loaded, and we had some bad weather, it would roll like crazy. Like most things made from metal, they are designed so that they bend and flex. I imagine there comes a limit to this, longer something is, the more it can bend/flex but yeah, within limits for it to still remain safe.
Unfortunately I don’t know much about cruise ships, personally I think they are unnecessary and would advise people to read up on how much they pollute, but yeah hopefully that helps give a bit of insight for you!
Royal Caribbean keeps making basically the same ship but a couple meters longer, so each is the new “largest ever” cruise liner…
Couple of things… since I’ve been tangentially involved with several of Royal’s new builds…
If you’re talking about *Icon of the Seas*, they didn’t “just give the go-ahead”, that ship is less than 3 months from completion and will enter service in January. They take about 3 years to build following another 4-5 years to design and do the engineering on (which is why when they design one, they usually build at least 3 of them. Designing a ship is expensive af).
In terms of size, Icon Class is only a few feet longer than their existing Oasis Class ships, and a few feet narrower (called “beam”). In terms of overall size, it’s comparable to some of the very large container ships.
The only real constraints to size are needing a dry dock big enough to accommodate the construction (and later, repair and maintenance), and you have to be able to get it from the yard to the sea – Icon is being built at the Meyer yard in Turku, Finland, and getting from the Baltic to the ocean involves getting under a bridge on the west side of Denmark that has a maximum clearance (also called “air draft”) of 57m. Ships built in other yards don’t have that limitation.
The ships also have to be able to put into the various ports of call, where the channels need to be deep enough to accommodate the approximately 9 metres of ship that is below the water line (called “draft”) and be able to maneuver the ship in those conditions.
For some ships, they also have to be able to fit in the locks of the Panama Canal.
When you see a measurement like “Gross Tons”, that’s not a measure of weight, but rather one of *volume* (of the enclosed portions of the ship). This is more of an administrative metric that guides things like number of lifeboats, passenger capacity, minimum crew, taxation, and so forth.
The actual weight of a ship is considerably less since most of the enclosed space of the ship is just empty space filled with air. A surprising amount of that space is actually dedicated to air handling and ventilation throughout the ship.
A ship the size of Icon probably has an actual mass of a little over 100,000 tons.
Ships that size have been traversing the seas for years. [Ultra Large Crude Carriers](https://www.wikipedia.org/wiki/TI-class_supertanker) carry around 400,000 tons of oil and are around 1200 ft long. They are so large that they are effectively at sea their entire lives and can only moor to pipeline piers further out.
To be useful in the Northern Hemisphere a ship needs to fit through the Panama Canal. Recently upgraded locks allow for ships up to 51.25m/168 feet wide and 366m/1201 feet long.
the ice at the north pole is floating. it’s pretty big, I’d say. so no, you can have a really big thing float.
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