Wind patterns, and piracy would be big concerns.

There are some unmanned sailing yacht designs, but they’re not cheap, and I don’t know what their real long-term and extreme-situation capabilities are. I expect that if/when there’s damage or maintenance needed, they go to port.

I also don’t know that there are any large-scale designs, nor how practical those could be made, but it’s an interesting concept. I expect the technology to make such a ship practical even for very-slow-boat traffic is far far in the future.

The main thing that comes to mind is the slow speed, and the effects that would have on trading if the markets remained all about megacorporate profits, which have a lot to do with predicting prices and fast delivery. Some goods also suffer in various ways from delays, such as “NEW” products, and of course perishables.

From a sailing perspective, handling of maintenance, repairs, unforeseen situations, and emergencies would be a much greater problem with no human crew. So would judgement calls in various situations. And sailing a ship under wind power faces different/greater challenges from weather, both becalming and high seas.

Also, I think the crew costs compared to ship costs and profits from shipping a huge container ship, are very small. A modern large freighter might have a crew of about 22. .

@Zaku I’m no engineer but I’m pretty sure it’s impractical/impossible to build a sail that could power a large modern freighter. The result is you’d need a fleet of smaller vessels to move an equivalent cargo, and each one would be on the water longer. Consequently, the crew costs per ton would be much higher I’d wager. A few other benefits of autonomy is that all of the weight/cost/space allocated to the crew and their living would be eliminated. On a massive freighter, as an overall percent, it’s probably pretty small (as you rightly point out), but on lots of smaller sailing freighters, all of those facilities start to take up significant room. Also I believe piracy predominantly focuses on ransoming the crew members rather than the cargo itself. If you’re shipping cargo containers of laptops a smash/grab of the highest value stuff sounds possible in theory, but I’d imagine most cargo would be things like thousands of metric tons of raw coal—valuable, but not the kind of thing you can haul off to your pirate base. Then again, I know next-to-nothing about modern-day piracy…

You definitely raise some great points though. I think the supply chain timing could be extremely problematic—as you point out. Also I don’t know how emergencies could or should be handled? If there was a fleet of these things though, they could all talk to each other and help find the safest/fastest routes. I guess it’s a fun mental exercise to think through at the least.

Here’s something to think about.
Container vessels are huge = 1,200 feet long
I sail Hobie Cat sail boats that are 16 feet long that have a mast length of 26 feet long
A container vessel that is 1,200 feet long would require a mast length of 19,500 feet. Or several masts with a total hight of 19,500 feet.
Also you still need a diesel powered engine to maneuver the container vessel safely as it gets closer to port as well as a fleet of diesel powered tug boats to maneuver cargo vessels.

Larger, nuclear powered vessels are the way to go here.

First, the concept of autonomous vessels the size of the Empire State Building is ridiculous. Too many moving parts, too many mechanical things that can go wrong and would need fixing by humans.

Second, navigation and handling ocean currents, ocean weather, etc. – both of those require years of training and familiarity with the high seas. Those are learned skills, not machine-based ones. Look at all of the cargo ships that have sunk all over the world in recent years.

Third, as others have noted, sail power isn’t enough to push a ship of the size we’re talking about. You would need huge sails and huge masts, and those would themselves make the ship harder to maneuver and far far heavier. And to some degree, top heavy as well, make it prone to sink.

And you would need humans, at least to some degree, to handle raising sails and turning them to catch the wind.

All in all, a cute idea but not really practical.

Very impractical for all the above reasons. Great question however!

@gondwanalon “A container vessel that is 1,200 feet long would require a mast length of 19,500 feet. Or several masts with a total hight of 19,500 feet.”

I did some extremely crude calculations that are probably way off, but it would take about 44 Preussen-type ships https://en.wikipedia.org/wiki/Preussen_(ship) to equal the capacity of one Colombo Express. If we further calculate the time it takes to move an equivalent tonnage from A to B in a fixed period of time, then you’d need even more to make up for the reduced speed.

I’d imagine modern ship design and building techniques could make it a more fair fight and for autonomy purposes, you’d likely want fewer/larger sails instead of lots of square sails, but I’m not sure it’s entirely beyond crazy to think about. If we could close it from 44:1 to something more like 10:1 I think it could be feasible in the future. Maybe I’m nuts though.

Another option would be massive airships.

Totally doable from an engineering prospective. Sails can be configured to be
very effective. All ships need a ‘pilot’ and tugs to pull into port. Sails can dramatically
mitigate the use of fossil fuel. There is a logistical problem… TIME!

Getting cargo to be on time has simply become the most important rule for transport.
When the Suez canal closed operators spent up to 250k in added fuels costs to go around
Africa! I’m with @Blackwater_Park nuclear power is the way to go! Right Now!

Finally to your last point yes, you are nuts!

No. Winds are fickle and can come and go without any indication, and blow it the wrong directions.
And, just for the heck of it here, many Diesel powered ships can also burn waste oil, like what comes out of your car during a oil change.

Remember the Ever Given

^^ I remember the ‘Ever taketh away’

I like the thought but I think we are working against physics here.
If we just scale up a good sailing vessel design, the area will go up with the square of the length while the volume and hence the displacement will go up with the cube. A ship triple in size would have a sail area 9 times the original size while the tonnage would be 27 times. That is a lot of friction. The ship would travel slowly indeed. But ideally it would be at low cost. I’m not sure it is worth the trouble.
Also to be successful the fleet would need internet tracking capability and weather information. That can be done but it would be signalling to the bad guys where it is. Even a load of coal on a freighter would be a target for the unscrupulous looking for easy pickings.

If the craft were armed with autonomous Phalanx guns that fired on any uninvited vessel that approached within 500 meters it might have a chance of successfully reaching port.

@LuckyGuy The weapon systems wouldn’t have to be autonomous. In theory, they could be remotely controlled by a centralized command center via satellite uplink.

What do you think the upper limit would be on the number of shipping containers that could reasonably be transported on a purpose-built ship powered by sails using modern technology?

“Even a load of coal on a freighter would be a target for the unscrupulous looking for easy pickings.”

I’m just trying to picture how they could effectively transfer tons of coal at sea. The examples I have seen of modern pirates are piloting pretty tiny vessels that can evade detection from the world’s navies. Maybe they would disable the ship and tow it to their pirate base somehow? I’m having a hard time seeing how that would work.

They take the whole ship and hold it and the crew for ransom .
Here is a recent list:
Ships attacked by Somali pirates

Here is an article about the number of containers a ship holds.

I was on one of those ships (Maersk) loading cars from Japan going to the US. They put over 3000 cars on one vessel below deck. The drivers were extremely skillful. They worked in groups of 6. One transport vehicle driver and 5 drivers. They’d drive in at ridiculous speeds and place the cars within inches of each other and climb out the windows. Another crew would be fastening them to the ground. The transport vehicle driver would pick up the 5 man crew and drive them back off the ship to the next vehicles in line.
There was lots of tire screeching!

In the future almost everything will be 3-D printed. 3-D printing will drastically reduce the need for shipping worldwide.

Edited
Yes, autonomous cargo transport vessels with sails would be useful for that that can’t be 3-D printed, and would be a solution to global trade.

@RedDeerGuy1 no way. Small stuff may be 3-D printed. But a 1200 foot ocean liner? Get real.

@elbanditoroso I edited my answer. A 1200 foot ocean liner would be shipped.

Here is how the Navy Seals rescued the pilot held at gunpoint by Somali pirates in 2009.

I bumped into this interesting related video on YouTube last night:
Why Don’t Sails Work On Ships?

@Zaku Awesome video. Thanks for sharing!

One thing it got me thinking about was how the lifetime of a ship is determined. If a ship travels 3x as fast but had the same lifespan, then the hull cost would be depreciated over 3x as many miles. That’s a huge win in terms of cost savings and something I hadn’t considered. Now if the hulls of big ships wear out faster than several smaller ones, that could negate or even reverse that savings. I really don’t know how the end of life is determined for cargo vessels.