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Disregarding how battleships are really big targets and not really viable in the modern era anymore, I would like to ask how big a battleship can be built before it starts being so large it sinks.

It doesn't have to be practical and I don't mind if sinks from a single torpedo or shelling neither does it matter if it takes a millennia worth of oil just to start moving. I would just like to know what kind of ludicrous size we can build a Battleship to set sail and fire bombardment with.

This question was inspire by the real-life battleship https://en.wikipedia.org/wiki/Yamato-class_battleship which was kinda useless, so I'm now asking how big of a useless ship can we make to rain death with. (sorry if there's actually an answer for this or there's no actual limit to how big ships can be made)

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    $\begingroup$ "I would like to ask how big a battleship can be built before it starts being so large it sinks." That's a fundamental misunderstanding of why things float. $\endgroup$ – RonJohn Oct 8 '18 at 13:19
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    $\begingroup$ In real life, men-o-war were rarely among the biggest ships of their time. The Yamato, for example, displaced 73,000 tonnes fully loaded; a modern large container ship such as the Maersk Triple E class displaces 250,000 tonnes fully loaded, and a TI-class supertanker displaces a whopping 500,000 tonnes fully loaded. And a ship "so large it sinks" makes little sense; ships do not sink under their own weight, that's sort of the main point of ship design. $\endgroup$ – AlexP Oct 8 '18 at 13:24
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    $\begingroup$ Are you after biggest 'battleship', or biggest 'ship' in general? If it is biggest 'battleship', then the criteria is no longer the ability to float, but the definition of 'battleship'. and the criteria for being called one. Once it gets too big, then it is properly classified as an 'aircraft carrier' and not a 'battleship'.. $\endgroup$ – Justin Thyme Oct 8 '18 at 15:48
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    $\begingroup$ You may wish to put in some constraints here. If you put a gun and a propeller on the north pole you could call that the largest battleship ever created! Some interesting constraints could be: "... where it can move at least x knots" "... where it takes the form of a traditional battleship, but is just scaled in size" "... costing under x $" "... that can be self sufficient for x days without nuclear power" "... that could still go through the suez canal" "... having a single hull" $\endgroup$ – BobtheMagicMoose Oct 8 '18 at 20:08
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    $\begingroup$ @Renan Size isn't really the distinction between "aircraft carrier" and "battleship". The smallest aircraft carrier is smaller than the largest battleship by a large margin (30-40%). Notable prerequisite to something being designated an aircraft carrier: it must carry aircraft. It's reasonable to think you could take any aircraft carrier footprint and build a battleship using the same footprint (instead of airstrip, layers of cannons; it may be taller than the aircraft design due to weight differences, though). $\endgroup$ – Delioth Oct 8 '18 at 20:51
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TL;DR: there is no realistic limit on size.

A ship stays afloat because while it is really heavy, its total weight is less than the weight of the water its hull displaces, so you could easily build a huge flat steel ship with a thin hull that is not very high and it would happily float. However, if the water were anything except for flat calm, then the movement of the water risks ripping it in half.

Or you could build it out of polystyrene, as that's lighter than the water itself. Again it would break easily though.

But…

Let's look at the Yamato, according to Google: 263metres long and weighed 65,030 Tons… pretty big, and pretty heavy.

How about the TI Class Super Tanker

380metres long and a fully loaded weight of 501,437 tons… Now that's heavy!!! But it still floats quite happily, in fact it's more stable when it's full than if it were empty

So...

The important factor is strength of materials and ship design. A multi-hulled ship has a stronger hull than a single thick hull (Within reason!!!) for the same amount of steel used. And then you wouldn't need to carry huge amounts of material that can slosh around compared to a super tanker carrying oil… probably a few nuclear reactors to power the props would do quite nicely.

A when you think about it, the wider the ship, the more room you have for additional props! so more speed... but then again an even bigger disaster if one or more of the reactors melt down.

The problems with big ships are what you have already mentioned, easy to hit, easy to find, and very costly to build and maintain. And no real need for them… But apart from that, nothing is stopping us.

It's also interesting to know that the real limit in modern terms is actually if it will fit in through the Panama Canal.

Tight Fit

It's a bit of a tight fit!

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    $\begingroup$ As a historic note, the size limit used to be the Suez canal, but during the Suez crisis that changed and ships had to be big enough to be worth sending round the Cape of Good Hope instead, $\endgroup$ – Separatrix Oct 8 '18 at 14:11
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    $\begingroup$ Panama Canal started being expanded in 2007. Your Answer is definitely correct, but the size limit may increase over time. $\endgroup$ – Christopher Hostage Oct 8 '18 at 16:44
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    $\begingroup$ My +1 is mostly for that last bit "if it will fit in through the Panama Canal." Similarly, there are many ships for which the build size is primarily restricted by the smallest area it needs to pass through. Often they are created slightly narrower and slightly shorter than the smallest lock they must pass through during their expected route. $\endgroup$ – Loduwijk Oct 8 '18 at 17:51
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    $\begingroup$ The problem with big ships is not only the width, it's the draft. For example, "New Panamax" limitation is 15.2 m, which makes more than a few (fully loaded) existing ships ineligible. Similar limitations won't allow supersized ships to enter harbors. $\endgroup$ – Alexander Oct 8 '18 at 18:42
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    $\begingroup$ Being able to fit in the Panama canal is only a concern if you want (rapid) transit between the Atlantic and Pacific. If you're Pacific only or Atlantic only, it doesn't matter. For example, the US's Nimitz-class aircraft carriers are 333 m long, about 44 m too big to go through the Panama canal (prior to 2016). That didn't matter, though, as the US Pacific fleets and Atlantic fleets don't swap ships, or when they do, it's no problem to go around South America. $\endgroup$ – R.M. Oct 8 '18 at 23:01
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I suspect that there is a fundamental limit based on material strength.

If we look at wooden ships, the longest you can feasibly get is about 150 meters. So the biggest wooden warship could be no bigger than that. So a similar limit must exist for steel ships, at which point the stresses of being at sea overcome any realistic structure. For example, a ship which could not turn without buckling would not be a practical ship.

Some research gives a maximum girder span of about 75m. Let's assume that we can't have more than 4 compartments across the ship, so our beam is limited to 300 meters. Scaling up from the Yamato gives us a length about 8 times that, so say 2.5km. Displacement would go as the square, so 64x64000 = 4 million tonnes.

I suspect that past that size, the need for internal reinforcement would make the ship impractical. It would certainly float, and be very, very hard to sink because, well, most current non-nuclear munitions would bounce off the 3 meters(!) of side armor. Likewise torpedoes would just flood a few compartments. And whatever guns it carried would be firing nuclear shells hundreds of kilometers..

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  • $\begingroup$ Unless you increase draft also, at some point the "ship girder" will be far too shallow and wide, and the ship will have serious structural problems. Draft is a possible limiting factor. $\endgroup$ – David Thornley Oct 8 '18 at 18:06
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    $\begingroup$ I think material strength really is the key factor here but I think we should also consider other materials such as carbon fiber, nanocarbons, and others we haven't even discovered or invented yet. Does the vessel need to withstand a storm? A hurricane? These use cases constrain the design as well. If we needn't worry about all those other items, moving it, defending it, etc. do we need to constrain ourselves with its seaworthiness? If not, building a flat, modular barge has no real limit as the other answers indicate. $\endgroup$ – Tracy Cramer Oct 8 '18 at 18:42
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    $\begingroup$ The big problem with wooden ships is that, as the length of the ship approaches the wavelength of the ocean surface, the difference in buoyancy between the ends of the ship and the middle cause it to flex in unpleasant ways. Steel ships can exceed that wavelength, and the buoyancy difference becomes merely a nuisance. $\endgroup$ – Mark Oct 8 '18 at 20:44
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    $\begingroup$ @Mark Sagging and hogging are still considerations with steel ships, and differences in buoyancy along the ship can be significant. The Iowa class of battleships were very thin for some distance forward, and seakeeping suffered from its lack of buoyancy. $\endgroup$ – David Thornley Oct 8 '18 at 21:17
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    $\begingroup$ @Mark, this is still very much a problem for metal ships. The reason why modern antiship torpedoes like the Mk. 48 is a "Bend over and kiss your ass goodbye" one-shot kill weapon isn't because of direct impact to the ship, but because it causes the hull to hog and then sag, breaking the keel. This can still happen to modern ships due to hull loading, either external or internal: MOL Comfort snapped in two off Yemen in 2013 due to bad weather, and it was a modern container ship. $\endgroup$ – Keith Morrison Oct 9 '18 at 5:58
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At least several km2

See Modular island wiki article. There are several proposals to make modular floating islands possible.

What? Do I hear that it does not count as battleship? Just add modules on edge with walls / shileding.

Does it fulfill your requirements?

It doesn't have to be practical

Check.

I don't mind if sinks from a single torpedo or shelling neither does it matter if it takes a millennia worth of oil just to start moving.

Check.

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  • $\begingroup$ tks, this is pretty cool :) $\endgroup$ – LuckyE Oct 8 '18 at 13:23
  • $\begingroup$ Please tell me one day they'll build a floating race track? $\endgroup$ – Blade Wraith Oct 8 '18 at 13:44
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    $\begingroup$ @BladeWraith because the surest way to have car crashes is to move the road on which you race $\endgroup$ – John Dvorak Oct 8 '18 at 17:06
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    $\begingroup$ @JohnDvorak: but surely having a racetrack that changes shape every lap is a surefire way to create one hell of a spectacular race! Obviously no one watches touring cars or rally cars hoping to see some crashes... :D $\endgroup$ – Blade Wraith Oct 9 '18 at 6:10
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There was a proposal during WWII to build an aircraft carrier out of frozen water mixed with wood pulp called Pyekrete. It was intended to be able to take multiple torpedo hits with no effective damage. You could build a battleship out of Pyekrete and put armor around the generators and chillers and guns. It would be slow (and probably best towed by tugs) but it would be hard to hurt. Maximum size is mostly limited by how many chiller hoses you want to run to keep it frozen.

Pyekrete is better than straight water ice for this because the wood pulp forms a fuzzy blanket as the ice melts and slows melting greatly.

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  • $\begingroup$ Downvoting because this doesn't address the question: How big can a battleship be? $\endgroup$ – Ghedipunk Oct 9 '18 at 23:50
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    $\begingroup$ Hint: The size of the arctic icesheet. Of course, it wouldn't be able to squeeze between continents without breaking up into battlebergs. $\endgroup$ – Don Qualm Oct 10 '18 at 12:44
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    $\begingroup$ I might question the usefulness of a battleship whose centrally mounted guns were in fact incapable of firing at anything not on the deck, but, hey, early battleships mounted guns at the edge of the ship in many cases (that went out of favor shortly before WWI). $\endgroup$ – David Thornley Oct 10 '18 at 16:47
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    $\begingroup$ The final product was estimated to be at least 1 mile (1.6km) in length. $\endgroup$ – Thucydides Oct 10 '18 at 18:43

protected by Community Oct 9 '18 at 6:21

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