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  • Context:

Because of a catastrophic war, a futuristic society was forced to use equipment similar to today's technology; and thus, use tactics and doctrines similar to today's military.

So, one of the ideas they had to make an efficient battleship taking missiles, torpedoes, water mines and other stuff into consideration, but without using advanced and expensive tech was to place everything as far apart as possible. Kinda like a long and small Oil platform just a few centimetres/meters under water, since the weight displacement would be as shallow as possible.

  • The Idea:

I know that are a lot of types of Oil Platforms, some are directly built on the sea floor, some are giant air filled metal tubes that float (thus the use of the term "like an Oil Platform"), but I will take the last one as an example.

enter image description here

Anyway, imagine a boat with a short column and a platform on top, not imagine a lot of them being connected until you have a weird battleship. The propulsion would be a water-jet engine inside the columns that would suck water and spill it out, not to mention that all of them could rotate indepedently.

enter image description here Kinda like this, but smaller and longer.

The idea is that even if the ship receives a torpedo hit, the explosion wouldn't destroy too much, and even if a missile hit one the platforms, it wouldn't be able to deal a lot of damage, because everything is as distant as possible. Not to mention that the quantity of columns are redundant and can be disconnected if it starts to spread fire to the rest of the ship.

I know it would be a maintenance nightmare with so many moving parts, but it would be somewhat of a "A-10" of the sea.

  • So, the question:

Would this many columns make too much turbulence in the water and instead create too much drag? Of course, taking into consideration it wouldn't be too much under water, only a few meters, or even a few centimeters.

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    $\begingroup$ That is one very slow moving battleship... What do you mean by "a few centimeters" under water? A typical battleship had a draft of 10 meters or more (32 ft or more). That's a thousand centimeters. Anyway, there is no such thing as an "efficient" battleship, mostly because there are no battleships any more. (And I don't know much about submarine warfare, but if I was in charge on the enemy submarine I would target those massive floating devices which are both essential and very hard to access and repair...) $\endgroup$
    – AlexP
    Jan 13, 2022 at 16:24
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    $\begingroup$ How much drag and turbulence is "too much"? Also, AlexP has some good points about battleship sizes, did you perhaps mean 'battleship' in a more loose sense (possibly as in 'ship meant for battle', or 'war ship')? I recommend adding more specific details for the overall size (height, width, length) of the ship, as well as what speed you're hoping to achieve, (or at least some ranges for these values), so we can better address the question $\endgroup$
    – Harthag
    Jan 13, 2022 at 17:52
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    $\begingroup$ Something like this would better serve as a simi-permanent force projection base, instead of a battle ship. In the right environment of course. $\endgroup$
    – Gillgamesh
    Jan 13, 2022 at 19:56
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    $\begingroup$ The big advantage of a semi-submersible platform is that submerging the pontoons below the wave action gives stability. When underway, they normally drain ballast so the pontoons are mostly above water and reducing drag. Putting the pontoons down only a few (centi)meters under would likely give most of the drag of fully submerged with most of the rolling waves of submerged. It would probably make a great gun platform when lowered though. $\endgroup$
    – jb6330
    Jan 13, 2022 at 20:02
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    $\begingroup$ You seem to have made a fleet of ships, and then nailed them together so they can't manoever like a fleet of ships. It isn't really obvious what this is supposed to gain. $\endgroup$ Jan 13, 2022 at 20:30

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It depends on the shape of the "columns"

If they're circular, or anything near it, you'll have trouble getting past about 5-7 knots (max towed speed of oil platforms is around 5 knots, I give it an extra 2 for military increases to durability and propulsion)

But if you usa a more ... loose ... definition of column, it starts getting much more plausible. A quick google search gave this definition of column: "an upright pillar, typically cylindrical and made of stone or concrete, supporting an entablature, arch, or other structure".

The key here is the word "typically", which gives leeway for it to have other shapes as well.

Again, a quick search of the word "pillar" (from the definition above) gives this definition: "a tall vertical structure of stone, wood, or metal, used as a support ... "

So, I'll take that to mean that the "columns" on your proposed battleship can be any shape, so long as they're vertical.

Operating on that assumption, this gets ship starts to become much more plausible. Enter the SWATH hull design. Ships with this design do exist, and are intended as combat vessels. They can achieve impressive speeds, Sea Fighter can make 55 knots, and impressive sizes, MV China Star is a full blown cruise ship, (but as with all ships and ship types, it's rare to have both size and speed at the same time).

Now, we have the issue that there are only 2 "columns" on these ships, one on each side, and each is nearly the full length of the ship. While the text of the question doesn't specify the number of columns, the images imply 4-6 should be used. Welcome the Skrunda-class to the conversation. They still have 2 sub-surface pontoons, but the superstructure is supported by 4 "columns". At less than a tenth of the horsepower of the Sea Fighter, I suspect the speed difference is much more related to the engines, not the number of columns.

Finally, combining the size of the MV China Star with the 4 columns of the Skrunda (and why not more if the ship is big/long enough, Skrunda is less than a third of the length of the Sea Figher), and then bringing in the military increases in durability and propulsion I mentioned back in the part about towing oil rigs, and evidenced in the speed of the Sea Fighter, you get a large ship, on at least 4 "columns", with decent speed (though it's almost certainly never going to be among the fastest in any fleet).

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    $\begingroup$ As a bonus, if you want to add more pontoons, they don't have to be side by side, or in a rectangular formation. Look at the Independence class with three pontoons in a triangle, and the center one is longer than the others. Opens the door to many configurations and possibilities. $\endgroup$
    – Harthag
    Jan 13, 2022 at 23:52
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Too much drag

The problem with the columns is as you say turbulence. Where the first column drags through the water the water will start churning. It can be imagined as two hands alongside something moving. If there is little churning you press the hands together only slightly, not causing too much drag onnan object sliding along your palms. If it is churning, you're putting a lot more pressure. This is because the churning water keeps putting pressure to the sides, as if you're pressing the hands together.

Your columns are only slightly in the water, but that begs the question of why. They aren't aerodynamic objects like the boat shape below. Even if each pilar is aerodynamic were it still offers potential problems. Only if they are far apart this can offer advantages. You need to offset the increased direct drag on each front of the pilar with the decrease in drag on the sides. This is difficult, as drag on the sides is much less than frontal drag. That is why it would be better to have the ship go all the way up above the waves before you start with columns.

As you have redundant columns this will immediately impact the efficiency, causing a lot of drag.

The propulsion can also be a big problem. Water jets can work in short tubes. But imagine drinking out of a straw if a meter. It takes too much effort. This is again because of side friction and turbulence. So if you have water jets through the columns you will habe too much drag because of the length. The saving grace here can be that they are mounted as far to the edge of a column as possible. Do note that as far as I know a water jet propulsion is never efficient.

Having so much real estate of the boat below the boat is also a waste. You seem to only use it as a floating device, while a normal boat It'll also house things like engines and such.

Conclusion

I do not know what your border of 'too much' drag is, but it seems an exceedingly inefficient method. It will float and move, no doubt about that. The energy required will be staggering, the speed will be low and you have a lot of wasted space only used for flotation.

Basically you've made something big and easy to hit, to prevent if it gets hit It'll fail. Real battleships have shown that they can take absurd amounts of damage before they sink, unless there's a lucky hit. It seems better to put your faith into multiple ships. They can be apart far enough, have less wasted space, are aerodynamic, have a ton more tactical advantages and have efficient engines for their purpose.

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