I know dock space, canals, and coastal areas have hard limits on how big you can make a modern ship, but I also heard recently that it would be impossible to make a mile long ship that wasn’t just a series of floating platforms (similar to the Freedom Ship concept) because the heavier the ship the deeper the maximum draught and there comes a point that the ships draight would be so low that you’d effectively sink the ship since the ship would be too heavy to move without it keeling over.
I’ve heard of a max size of ships but I’m pretty sure that was not the reason given but for stress though the ship which the structure has to grow exponentially faster then the length does. Eventually you would need all structure which would make it a solid steal block which don’t tend to float so well. This also assumes a rigid construction and can be overcome by the the method you state, interconnecting smaller sections.
No, this isn’t correct. Ships are supported by their own buoyancy which is distributed along the wetted hull, so as long as they aren’t top-heavy or otherwise unstable you can make them as tall or wide as you see fit. Large ships are also obviously not rigid structures—you can see and hear the movement of large cargo vessels twisting and bowing in heavy seas—and are designed with adequate flexibility in the design, either through accounting for hull flexure or adding mechanical joints depending on the kind of vessel.
I suppose you could make a vessel as large as you want short of having to account for the curvature of the planet but the real limitation is being able to generate the power to move it through the water; the more wetted surface, the more viscosity has to be overcome and at some point you just wouldn’t be able to drive enough propellers to make it go. I doubt we’ve ever approached that limit, though; oil tankers, container ships, and aircraft carriers are all enormous and yet they can definitely get going and move at a strong clip; Nimitz-class nuclear powered aircraft carriers can and routinely do go at greater than 30 kts during flight operations.
I think the biggest barrier is economic: What purpose does this big ship serve, and can it serve it more economically than a number of smaller ships? If a large ship can carry twice as much cargo for three times the cost of a smaller ship, then there’s no reason to build it. Even if it can carry three times the cargo for twice the cost, there might still be a benefit to the smaller ships, that can go to multiple destinations at once.
Generally speaking, for cargo haulers bigger has been better for economies of scale. Even though container ships often return virtually empty it is still cheaper for a large ship to make one haul than a smaller ship to make multiple ones, and this has largely contributed to globalization and cheap international shipping. Of course, there are physical limits there; a cargo ship can only enter a channel and harbor that been dredged for its loaded draft, and terminals are only built to handle container ships of a certain size which has evolved over the years such that newer terminals are built to handle larger ships in deepwater ports, while shallow ports and those accessible by river systems have declined.
So I suppose, in the limiting theoretical case, you could build a ship with its bow in dry-dock in Japan while its stern in dry-dock in California. It wouldn’t require any energy to get those propellers turning. Just load the cargo into the hold via a hatch near the bow and unload the same via another hatch near the stern.
If you were really smart, you’d wait until one end was lifted slightly higher on the tide, and put your cargo on castors the they would be able to simply coast to the other end with a gentle push. Do the process in reverse when its high tide at the other place.
Maybe at some ridiculous point, currents and prevailing winds at cross purpose to the intended course might require more energy to overcome than is worth it? A HUGE rudder at right angles.
No idea at all if that is a real concept.
Yes, if you want to be able to get through the Panama and Suez Canals - if you can’t, then you are going to go bankrupt. That’s the economical limit, no idea about a physical limit.
Is there a limit to the size of an iceberg? I believe there is not, so there is no limit to the size of a boat. You just have to make it with pykrete:
Or hollow out an existing iceberg and attach some screws and rudders. It may not be practical, perhaps it does not make economic sense (though you regularly read stories about the water that could be transported to some Arabian desert from the poles that way) but I see no limit.
I recall a discussion on how big a space ship could be. IIRC there was a material limit on size. Eventually something would be so long that just turning it would put stresses on the overall structure and it would break no matter what you made it from.
So, there is a limit. I do not know what it is though.
Ships also flex in waves (hogging or sagging) and it can be a serious problem for them.
There’s no consequence to the curvature of the planet, other than the fact that you’d design the ship to fit it. Large suspension bridges are already designed to fit this curvature.
Now, the fact that the curvature changes could be an issue. For example, on the equator, a ship oriented north-south would have to curve more than the same ship oriented east-west. But it’s a pretty tiny distance and I doubt you’d need more flexibility than any ship would already have to account for it.
Yes, but bridges stay in one place. The curvature of the planet is different NS vs SW (and everywhere in between, and there are local differences). There probably is a range of sizes where a good approximation to the curvature would keep the bow and stern in the water and the middle above, and it wouldn’t matter significantly if you were sailing west or north. And also any ship made of currently available materials might be flexible enough, at those scales, to accommodate the differences.
In engineering terms, a ship is essentially a beam. When you build a long bridge (also a beam) you can stop it from sagging in the middle by suspending it from above or supporting it from below.
A ship on the sea will be constantly flexed up and down by swell. At one extreme it will be supported at both ends, and at the other, the centre. To make the beam strong enough it has to be made thicker and stronger.
No doubt a marine architect could definitively say at what point adding length and height becomes impractical. I suspect that today’s supercarriers may well be near that limit.
Tankers and bulk ore carriers are largely underwater when fully laden which goes a long way to relieve the stresses. Maybe it would be possible to build a very long submarine?
Diamonds are extremely hard. They are pretty much at the top of the hardness scale. Scratch pretty much anything against a diamond and the diamond always wins.
Diamonds are not tough. They shatter easily. They also have poor ductility. If you tried to build a ship out of diamond it would fracture under its own weight. The diamond wouldn’t flex, it would sheer.
You do have a valid point that a lot of things that we consider to be solid and inflexible are in fact quite flexible at extremely long lengths.
I’m not sure how one distinguishes a “ship” vs “series of floating platforms”.
The USS Ford is the largest aircraft carrier ever built (around 1000 ft long). The longest container ships are regularly over 1300 feet long, the longest being the Seawise Giant at 1500 sq feet. The one thing I noticed is that large cargo ships do tend to become wider and more “platform like” the bigger they get. Cruise ships OTOH can get away with being very tall as they are mostly full of air and passengers.
From an structural standpoint, I don’t think there is an actual limit. The limits seemed to be more based on practicality of docking facilities and canals, propulsion, and the economics of actually needing a ship that big.
If you make ships long and thin, you end up with torsion issues and the ship will tend to want to twist itself apart.
Cargo ships also can’t be too tall or the weight of the upper containers will crush the containers on the bottom. A ship that is too tall would hit bottom in many ports and also would have issues with cranes not being able to reach the top of the container stacks.
The only practical way to make a cargo ship bigger is to make it more “platform like”.
