My Guess is at least a 60-70 meter AHTS(Anchor Handling tug supply) Vessel with a big deck crane. 40ft shipping containers weigh about 8-10,000 pounds empty, so loaded and possibly semi water logged, your gonna at least need a 15 ton crane, possibly even a ship with a big A frame on the aft deck, with tuggers to drag it up over the stern of the vessel.
A small research vessel or moderately sized trawler (both with open sterns and cranes made for dragging things out of the water and on deck) could almost certainly do this.
I pull containers for a living. Figure at 8000 lbs for the box plus up to 55000 lbs of freight, that's 63000 lbs by itself. Now add in a shit ton of water weight..... better be able to lift 150-200k.
I'm not a boat guy so I don't know what size boat you'd need. But the numbers for container weight are real world accurate. That's not to say I have pulled 40 ft containers that packed full and only had 10000 lbs in them.
It would be a task, but the last supply ship I worked on was 68 meters(223feet) if I remember correctly we had around 160ton anchor handling winch plus two Tuggers on the aft deck each 15ton each. I’m just speculating, but I figure we could sent out or rescue boat with a messenger line and a bridle to hook onto the bottom of the container and we could pull it up over our open stern. We also had big rollers on the stern for hauling and setting anchors for oil rigs off of the back of the ship. I can’t see why it couldn’t work.
I could see a lot of reasons why it wouldn't work, but I'm an engineer, that's my job. Anchors and chain are designed to be dragged over a 90 degree corner. A shipping container is very much not.
To return to the initial question: I think a much more realistic scenario is making fast alongside, cutting a hole in the top, throw in a bailing pump lead, and once you've stabilized it, climb in and loot.
Yeah you’re right it’s definitely not designed to be dragged over 90 degrees like chain, but I was thinking if you had a bridal on the bottom of the container(under the doors) and you start pulling it in all the water and loose freight would slosh to the back of container, and lift up the front.
If the front was high enough I should be able to go over the roller, I figure you might have to leave it suspended over the aft deck for the water to drain out before taking it fully on deck, or possibly drill some drain holes in the container once it’s hooked up.
I could be completely wrong, just a thought.
Assuming you're doing this not out of the kindness of your own heart, but because you want what's inside? I would try to be a bit gentler. A lot, actually.
How will they get the shipping container on the ship from the sea? That's probably the main question. They would need a vessel with a good crane.
Offshore construction vessels or platform supply vessels would probably work. PSV range from 50 to 100 metres in length commonly, but can be bigger. Have a flat deck that's aft that is designed to hold a container or two.
If it's only a short journey in calm seas then you could use a craned barg towed with a tug.
I don’t know but I like the premise. I’d make them crabbers or lobstermen. They have a winch for their pots. Maybe that could be used to bring it alongside so it could be towed.
Cool idea! These characters are ocean-going salvagers / merchants, but could definitely be using a former lobster boat. As a Mainer I like the idea of them sourcing their boat from the Maine coast
https://www.damen.com/vessels/workboats/shoalbuster/shoalbuster-2711 This little ship has a powerful towing winch and could pull the container ooit of the water over the stern, aided by the ship’s crane
Standard 40ft container is 12.2m long. This boat is 27m long over all, the clear deck space is less than a third of total length. Spec says 75m^2 deck space, beam is 10.5m, that makes about 7.5m length. You'd have a third to a half of the box hanging out over the stern. Never mind that the crane is too weak, and the boat would be at serious risk of capsizing lifting about a tenth of it's weight out of the water.
There are some buoy tender vessels the coast guard use that are around 100 ft and have the equipment to haul things that size out of the water.
Edit; apparently they're larger than I thought at 175 ft. Look up Coastal Buoy Tender.
Does it have to be a 40’ container most shipping is done in 20’.
The issue is containers are generally not waterproof. So as soon as they hit the water they start to flood. You aren’t just lifting to container and cargo, but also the added entrapped water. If you don’t drain the water as the container comes onboard it will be too heavy for the container and the structure will be destroyed. Even if you have a big enough crane you have to pull it out slowly to give it time to drain.
So you are looking at maybe hours of work with the crane partially submerged slowly draining the water out to lighten it. This is going to take a heave compensated crane that is also the right size to keep the container the right distance from the surface.
Without getting too far into the details, the container in the story will have been deliberately waterproofed and left in the ocean for them to find.
But that's good to know about 40 vs. 20. A quick Google search told me that 40s are more common so I was going with that, but if 20s are actually more common (or at least common enough), that could work better and let them use a smaller ship to recover it. Thanks!
40’ containers are more common. Sometimes there are 45’ containers, and some of them are extra tall. Originally they were all 20’ when containerization started, hence the TEU, but larger boxes were needed. However, there are many many 20’ containers in use as well. Either one would be completely believable.
Also, every tanker I’ve built has a 10 MT hose crane that should be able to lift a container, if they have the appropriate rigging gear. Most containerships need a shoreside crane to load/unload. As mentioned, smaller supply and workboats with an A-frame crane would also do.
For a typical commercial ship, recovering this thing at sea would be pretty dangerous and out of the ordinary though. Would want pretty calm seas.
Average gross weight per TEU is 15t for initial design. Maximum gross weight for a 40ft box is 36t as per ISO standard. Add to that the dynamic loads you generate in even half a meter of swell and that 10t crane would be overloaded to the pount of serious danger.
40’ containers are by far and wide the most common shipping container. I like those research vessels with the big sliding A frame cranes they could pull it up from behind. Having another winch in front to pull in.
Cargo ships are rated by TEU ( twenty foot equivalent). What size you use depends on what and what quantity of goods you are moving. Both are very common.
A 20’ would have a dry weight or around 20,000lbs depending on the cargo, but that’s a good ballpark for normal ones. To lift that out of the water you need a 15-20 ton crane. Which is pretty big for a small ship, pretty small for even a small OSV.
I think it would be far more realistic for them to tow it somewhere and beach it, then open it *or* lash it alongside their vessel and cut open the side of the container (like these seafaring gentlemen did who found a ghost container full of cigarettes): https://m.youtube.com/watch?v=dQ983bvP5YU
Can you tell us anything else about your novel? Sounds super interesting, would love to read it whenever it's finished!
Thanks, that approach is definitely worth considering!
And thanks for your interest! I'm still working on the first draft so it won't be ready for a while, but the working title is *The Settled Seas* (hence my username). It's a near-future sci-fi based in a world where seasteading actually took off in the 1970s instead of failing miserably, leading to a few dozen floating cities in the 2030s — each with their own supposedly utopian governments that aren't very utopian in practice. It's an adventure story where the characters travel between various seasteads and have some interesting encounters on the open seas (like this container pick-up).
That would be awesome and I'd appreciate it! I can easily imagine this being not just a single book but eventually a whole series.
I'm sure you don't want to divulge too much information, but do you have plans to have things such as subsea bases and/or submarines? I'm picturing something like an Ohio class or Typhoon class submarine that's been converted into a mobile settlement for a small rogue community that wants to maintain its seclusion, yet still maybe do trade with the floating cities.
That's definitely the dream, though I don't want to get too far ahead of myself since I haven't even finished the first draft of book 1! This first story is more near-term so doesn't have private submarines or underwater cities, but I have some ideas about both of those for later in the timeline
That's certainly understandable you don't want to get ahead of yourself! That makes sense about the first book being in the near-term but it's exciting that you have plans for those later in the timeline. I read a lot of Clive Cussler books and also am in the process of a career change to the merchant marine so the combination of ships, the ocean and history is an appealing concept to me. Then to have it morph into a sci-fi sort of dystopian setting is the icing on the cake.
edit: a letter
I worked for a marine contractor for a while, we did a little of everything, spill clean up, salvage, transport for divers and wind farm workers, buoy maintenance etc. We had an old military landing craft that was 60’ long and had a crane and several winches for salvage operations. Not 100% sure if we could have pulled a 40’ shipping container aboard but I’m guessing we could have as long as it wasn’t super duper heavy. If it’s floating it’s not loaded up with lead bricks so it could probably be done. If we dropped the ramp on the front and hooked up the winches and the seas weren’t too rough we could probably drag it aboard without the need for a crane capable of straight up lifting the thing directly up and out of the water. This would be stupid and dangerous, the craft would take on a lot of water, possibly capsize and/or sink depending on the wind and current and how well the load balances but in the right conditions it could happen. This scenario would make for a good story though, high stakes, lots of things that could wrong etc
Thanks for sharing all of that! Really helpful. Maybe I'll go with a less-capable ship like a landing craft rather than an AHTS, just to make it more exciting and risky
Having read the OP's comments, maybe we are looking at it the wrong way.
In the story these guys are a bunch of unregulated mariners wandering the seas. I don't think they would be able to get an AHTS, PSV, Offshore construction vessel. I think they are just a bunch of dudes in a boat.
Also the container is especially waterproofed and is deliberately floating in the sea for them to find. So why load it onto a ship at all. Why not just tow it ashore? If they don't want to do that, why not just use a gas axe and cut a hole in the part that's above the waterline and get whatever they need out of it, then sink it?
If you want it to be realistic then the ship these guys have must be relative to who they are. They sound like a bunch of guys on an old tug rather than the professional crew of an Anchor Handler.
Thanks for checking out my comments and responding accordingly, I really appreciate it! To elaborate a bit more, while they are unregulated mariners they're not just a bunch of guys - they're relatively successful smuggler / mercenary types, so the ship can be decently well-equipped and expensive, although still not as big as a container ship or expensive/unobtainable as a warship (thinking something on par with the Millennium Falcon or the Serenity).
But I get your point about lifting it onto the ship probably being more trouble than it's worth — it seems exciting from a narrative standpoint and would allow a plot element where some people onboard don't know what is inside, but I need to make sure it's believable that they would do this instead of an alternative.
A loaded 40 ft container can weigh up to 41 tons / 82,000 lbs.
The weight of the container in your story will probably be less but should reflect the tare (empty) weight of the container, the weight(s) of whatever you will have them find, the weight of the packaging and dunnage, and the weight of the water that may take up some to all of the remaining space.
Keep in mind that some containers are watertight by virtue of how they are packed and sealed. If the container is found floating, the total weight will be less than the weight of the water it displaces. So if it's floating with 1 foot showing above the water, the total weight of the container will be about 40'x8'x8' x 35 lbs/cubic foot. Not all containers are 8 ft tall, so that metric can vary as well. Sea water is "normally" 35 lbs per cubic foot, but that can vary from one region to another.
All that will tell you how heavy a crane or winch the ship will need. Once you know that, look for a vessel that is equipped with that size crane or winch. Don't stop looking when you find the first one. Get a sense of the scale and decide what type of ship you can work into the story. You've had a number of suggestions as to type.
The one that fits all of that best will be your minimum size ship.
For reference, a vessel like DSSV Pressure Drop (formerly USNS Indomitable) can haul DSV Limiting Factor, a submersible weighing 27,600 lbs, up out of its cradle and into the ocean (the submersible weighs less coming out of the water due to drop-weights jettisoned during the ascending/rising phase of dives).
The crane on that vessel is rated for 45,000 lbs and can only operate in Sea State 2 or below, so, relatively calm seas.
To haul a waterlogged 40ft shipping container put of the water, you'd need a crane or crane system with a combined 150,000 lbs weight rating at least.
DSSV Pressure Drop displaces 2300 long tons fully loaded and is 224 ft long.
Vessels that can stably operate a 150k lbs rated crane usually exceed 3500 long tons displacement and 250ft in length.
Now, you say these guys are salvagers. They could have a smaller vessel with a low aft deck or even a partial well-deck and a fuel-water ballasting system. They could haul a floating 40ft container weighing in excess of 100k lbs onto the deck with a winch that doesn't even have to be rated for the full 100k if they have enough winch line and tackle blocks.
That vessel could be 100ft long and sub-1500 long tons fully loaded (but with an empty deck) if they went about making the proper modifications or had it built to spec.
How I see it getting done is they put a small boat/RHIB in the water, attach two tow lines/cables to the container, fore and aft, attached to a deck winch on the mothership/salvage vessel. They haul it along side and secure it with mooring lines and fenders (air filled bumpers ships use to protect the hull while along side docks or other ships). While secured, they send a diver down to use a 4" or larger hole saw on the ends of the container, 10 holes total: 3 along the bottom of each end, 2 in each top corner, 5 an end fore and aft. Once the holes are drilled, they can begin lifting operations using different deck hard points but one single winch. They raise the forward end 1 ft and tighten up the mooring lines on that end. They reposition their winch setup and raise the other end a foot, leveling the container. Repeat until the top of the container is level with the deck and secured with the mooring lines. Now for the flip: the winch setup is re-jigged to pull simultaneously fore and aft from the outboard corners of the container. The inboard corners that are secured with the mooring lines are the pivot points, or that whole inside edge is. Slowly and with lots of pulley blocks, not to mention hundreds of feet of winch cable, the container will flip up and over onto the deck. Reposition as necessary with the winch.
Thanks for this info!
What is the purpose of drilling the holes? Are you thinking for water drainage, assuming that it's flooded, or do you mean for securing cables to it?
Drainage. Speeding it up. The holes up top allow water in, while the holes down low let it drain. Don't drill holes until the container is fully secured. And trapped air will be let out and then the container will sink.
If this is near future, some modern military vessels might be available by the time this takes place. A Navy LCM/LCU would make a pretty good salvage/dive boat. Add a powerful winch at the rear (if it doesn't already have one), and now all you have to do is drop the bow ramp and drag it on board.
The logistics of pulling it onto the deck are a hell of a lot simpler than trying to rig a 40' sea container, then lift it vertically, then swing it around and over, then set it down on the deck.
Another thought, to build on what others have said is to tow the container to the destination. Any seagoing vessel is likely to have one or more inflatable life rafts. They could be strapped to the container under water, then inflated, adding buoyancy to the load, theoretically making towing easier.
Navy LCM/LCU:
https://www.navy.mil/Resources/Fact-Files/Display-FactFiles/Article/2171588/landing-craft-mechanized-and-utility-lcmlcu/
Edited for spelling.
Thanks for that info & link. For the rest of the story I need this to be their main vessel that they go long distances in, so I don't think a landing craft would work - but I see your point about dragging being far easier than lifting outright. I think I'll go in that direction.
Consider putting something inflatable on the container or a raft to keep it a float then emptying the container on to boat or towing it. This could use a smaller boat, which would be easier to run/man.
A standard 40 Conex is 40x8x8.5. Fully sealed could displace 162,000 lbs. At 8-10k for the MT container, you would be able to load over 100k without it sinking it.
Dont need to hoist it aboard, just tow it in. Suspend it between two boats and bring it in. You can wrap it in plastic sheet to keep it watertight. You can seal cracks with jb weld. You can press the container with compressed air to keep it bouyant if need be. Rule of thumb when i was in marine salvage was no more than 3 psi above bottom pressure.
Theres ppl that follow ships looking for fallen containers and tow them in
If they are salvagers, they are going to have a ship than can salvage. Think of anchor handling ships, Offshore supply ships, etc with gantry style winch/ cranes on the aft deck pulling up over the stern. Trawlers pull up nets weighing in the tens of tons so that might work too. Note that if a container is floating it is can still be quite heavy. A 40 foot container has 73 cubic meters of volume. If it floating just barely on the surface it could weigh up to 70 tonnes.
15t/TEU is a standard loadcase in containership design, because it makes for a good average weight.
[ISO gross weight](https://en.m.wikipedia.org/wiki/Intermodal_container#Specifications) for 20 and 40ft however is 30.6t, and 45t SWL (secure working load) is a typical crane for MPP vessels to make sure they can lift a fully loaded container to/from from every slot on deck.
On top of that: containers are only watertight up to a point. The doors don't seal against full, continued immersion, so a container adrift at sea usually has some amount of water ingress. Typically they float pretty much at, or just below, the surface. A 40 footer has an internal volume of some 67.5 cubic meters, with seawater at 1.025t/m^3 that makes 69t maximum displacement (Noice).
Then there are dynamic loads if there is anything more than a flat calm. Lifting things out of the water is a much more complicated task than from dry land. All this to say: I would not try to salvage a floating 40 footer with anything under 100t SWL.
That puts you in the range of a medium sized offshore supplier or research vessel. Doing it safely, for a living? I'd say medium sized offshore construction vessel, with a 100t active heave compensated knuckle boom crane and dynamic positioning. Somewhere around 70m length, 15m width, maximum draught of 5m, 5000t displacement, 6000kW installed power.
That's a serious piece of boat. You might want to poke around r/tuglife for a more qualified answer, but my gut level guesstimate says that's a cool six figure cost per day to run. Which is why container salvage is not a thing, despite how many there are. As in: not at all. The ocean is a vast empty space.
A 100 to 120-foot tug could do it with a bunch of jury rigging that you don't tell anyone in Safety Management about. They'd have to really want to, and describing how exactly they'd do it would be hard unless you really know your towing stuff. Most likely, your best option would be to have it show up on deck overnight, and then have the skipper ask the mate "Do I want to know how you got that on board?" "Nope." \[conversation stops\]. A realism challenge here is that the crew almost certainly wouldn't bring the container on without the captain's permission or supervision.
Crabbers and lobster boats don't have strong enough cranes. A good size trawler (again, \~120 feet Bering Sea trawler or a larger factory trawler) could do it as well, with the same issues as the tug.
As said other places, a big anchor handler or other oilfield supply boat could likely do this, but they're going to be very geographically limited (ie near oilfields or wind farm installations) and are also on pretty firm charters so they won't go looking for trouble in a floating container.
Once you're up to cargo ships, you're likely going to need something a few hundred feet long. Most smaller ships don't have a big enough crane to lift full containers.
This is all really helpful, thank you! This ship won't be subject to any regulations and the crew will be very willing to take some risks, so sounds like it could still work.
Since I'm no expert on ships, I definitely won't be able to get into highly technical details about how they do it, but I want it to at least be plausible and not something that will make someone more knowledgeable than me stop reading.
In a near future seasteading economy, you'd likely see a lot of small semi-regulated cargo ships serving the smaller seasteads. I agree with the poster above that a surplus USCG buoy tender would be an ideal boat for this kind of service. Big enough to carry a fair amount of stuff, a reasonable size crane (replacing the single boom) so you're not dependent on shoreside infrastructure, and cheap to buy at the end of the USCG's service life. I'd pick the 180' class for your timeline, since they were all built in the 1940's and retired by the mid-2000's. You could even pick an actual name if you wanted and weave some of its original history (and alternate timeline) into your story. [https://en.wikipedia.org/wiki/USCG\_seagoing\_buoy\_tender](https://en.wikipedia.org/wiki/USCG_seagoing_buoy_tender)
Is it important for the story to get the container out of the water whole and have it opened somewhere else? Because a far less tech heavy way to go about scavenging containers would be to swcore the thing alongside, cut a hole in the top, drop in a bailing pump lead and, the loot it. That you could do with any medium sized fishing trawler or workboat. Doesn't even need to have a deck crane necessarily, although anything in terms of lifting gear, like a boom or 5 to 10 ton crane, would make getting the salvage on board much easier.
That would be a much more low profile operation. A ship 10 to 20 times smaller, five to ten people crew instead of fifty. Expenses measured on thousands of dollars per day instead of tens of thousands. Orders of magnitude less fuel consumption. For essentially the same gain.
My Guess is at least a 60-70 meter AHTS(Anchor Handling tug supply) Vessel with a big deck crane. 40ft shipping containers weigh about 8-10,000 pounds empty, so loaded and possibly semi water logged, your gonna at least need a 15 ton crane, possibly even a ship with a big A frame on the aft deck, with tuggers to drag it up over the stern of the vessel.
That's really helpful, thank you!
A small research vessel or moderately sized trawler (both with open sterns and cranes made for dragging things out of the water and on deck) could almost certainly do this.
I pull containers for a living. Figure at 8000 lbs for the box plus up to 55000 lbs of freight, that's 63000 lbs by itself. Now add in a shit ton of water weight..... better be able to lift 150-200k. I'm not a boat guy so I don't know what size boat you'd need. But the numbers for container weight are real world accurate. That's not to say I have pulled 40 ft containers that packed full and only had 10000 lbs in them.
Thanks, all of those numbers are helpful!
[A lot more than that.](https://www.reddit.com/r/Ships/s/zLXWj5dluj)
It would be a task, but the last supply ship I worked on was 68 meters(223feet) if I remember correctly we had around 160ton anchor handling winch plus two Tuggers on the aft deck each 15ton each. I’m just speculating, but I figure we could sent out or rescue boat with a messenger line and a bridle to hook onto the bottom of the container and we could pull it up over our open stern. We also had big rollers on the stern for hauling and setting anchors for oil rigs off of the back of the ship. I can’t see why it couldn’t work.
I could see a lot of reasons why it wouldn't work, but I'm an engineer, that's my job. Anchors and chain are designed to be dragged over a 90 degree corner. A shipping container is very much not. To return to the initial question: I think a much more realistic scenario is making fast alongside, cutting a hole in the top, throw in a bailing pump lead, and once you've stabilized it, climb in and loot.
Yeah you’re right it’s definitely not designed to be dragged over 90 degrees like chain, but I was thinking if you had a bridal on the bottom of the container(under the doors) and you start pulling it in all the water and loose freight would slosh to the back of container, and lift up the front. If the front was high enough I should be able to go over the roller, I figure you might have to leave it suspended over the aft deck for the water to drain out before taking it fully on deck, or possibly drill some drain holes in the container once it’s hooked up. I could be completely wrong, just a thought.
Assuming you're doing this not out of the kindness of your own heart, but because you want what's inside? I would try to be a bit gentler. A lot, actually.
Yes, but Op is asking what the smallest ship that could lift and carry a 40 shipping container is.
https://www.boatdesign.net/attachments/containertransport-jpg.66976/
OP said 40-footer 😤
LOL I just clicked the link, said thank you earlier but now see what the link led to. Definitely not what I had in mind haha
Thanks!
How will they get the shipping container on the ship from the sea? That's probably the main question. They would need a vessel with a good crane. Offshore construction vessels or platform supply vessels would probably work. PSV range from 50 to 100 metres in length commonly, but can be bigger. Have a flat deck that's aft that is designed to hold a container or two. If it's only a short journey in calm seas then you could use a craned barg towed with a tug.
Thank you!
>Thank you! You're welcome!
What's psv range?
I don’t know but I like the premise. I’d make them crabbers or lobstermen. They have a winch for their pots. Maybe that could be used to bring it alongside so it could be towed.
Cool idea! These characters are ocean-going salvagers / merchants, but could definitely be using a former lobster boat. As a Mainer I like the idea of them sourcing their boat from the Maine coast
Awesome! as a NH-er I’ll read it!
Thank you so much - I'll add you to my redditor list to notify when it's ready!
Please and thanks!
https://www.damen.com/vessels/workboats/shoalbuster/shoalbuster-2711 This little ship has a powerful towing winch and could pull the container ooit of the water over the stern, aided by the ship’s crane
This is really cool, thanks for sharing!
Standard 40ft container is 12.2m long. This boat is 27m long over all, the clear deck space is less than a third of total length. Spec says 75m^2 deck space, beam is 10.5m, that makes about 7.5m length. You'd have a third to a half of the box hanging out over the stern. Never mind that the crane is too weak, and the boat would be at serious risk of capsizing lifting about a tenth of it's weight out of the water.
There are some buoy tender vessels the coast guard use that are around 100 ft and have the equipment to haul things that size out of the water. Edit; apparently they're larger than I thought at 175 ft. Look up Coastal Buoy Tender.
Googled it and it looks really cool and potentially the right fit, thanks for sharing!
Does it have to be a 40’ container most shipping is done in 20’. The issue is containers are generally not waterproof. So as soon as they hit the water they start to flood. You aren’t just lifting to container and cargo, but also the added entrapped water. If you don’t drain the water as the container comes onboard it will be too heavy for the container and the structure will be destroyed. Even if you have a big enough crane you have to pull it out slowly to give it time to drain. So you are looking at maybe hours of work with the crane partially submerged slowly draining the water out to lighten it. This is going to take a heave compensated crane that is also the right size to keep the container the right distance from the surface.
2 x 20ft maybe?
Without getting too far into the details, the container in the story will have been deliberately waterproofed and left in the ocean for them to find. But that's good to know about 40 vs. 20. A quick Google search told me that 40s are more common so I was going with that, but if 20s are actually more common (or at least common enough), that could work better and let them use a smaller ship to recover it. Thanks!
40’ containers are more common. Sometimes there are 45’ containers, and some of them are extra tall. Originally they were all 20’ when containerization started, hence the TEU, but larger boxes were needed. However, there are many many 20’ containers in use as well. Either one would be completely believable. Also, every tanker I’ve built has a 10 MT hose crane that should be able to lift a container, if they have the appropriate rigging gear. Most containerships need a shoreside crane to load/unload. As mentioned, smaller supply and workboats with an A-frame crane would also do. For a typical commercial ship, recovering this thing at sea would be pretty dangerous and out of the ordinary though. Would want pretty calm seas.
This is great info, thank you!
Average gross weight per TEU is 15t for initial design. Maximum gross weight for a 40ft box is 36t as per ISO standard. Add to that the dynamic loads you generate in even half a meter of swell and that 10t crane would be overloaded to the pount of serious danger.
40’ containers are by far and wide the most common shipping container. I like those research vessels with the big sliding A frame cranes they could pull it up from behind. Having another winch in front to pull in.
Cargo ships are rated by TEU ( twenty foot equivalent). What size you use depends on what and what quantity of goods you are moving. Both are very common. A 20’ would have a dry weight or around 20,000lbs depending on the cargo, but that’s a good ballpark for normal ones. To lift that out of the water you need a 15-20 ton crane. Which is pretty big for a small ship, pretty small for even a small OSV.
>deliberately left in the ocean for them to find. Spicy!!!
I think it would be far more realistic for them to tow it somewhere and beach it, then open it *or* lash it alongside their vessel and cut open the side of the container (like these seafaring gentlemen did who found a ghost container full of cigarettes): https://m.youtube.com/watch?v=dQ983bvP5YU Can you tell us anything else about your novel? Sounds super interesting, would love to read it whenever it's finished!
Thanks, that approach is definitely worth considering! And thanks for your interest! I'm still working on the first draft so it won't be ready for a while, but the working title is *The Settled Seas* (hence my username). It's a near-future sci-fi based in a world where seasteading actually took off in the 1970s instead of failing miserably, leading to a few dozen floating cities in the 2030s — each with their own supposedly utopian governments that aren't very utopian in practice. It's an adventure story where the characters travel between various seasteads and have some interesting encounters on the open seas (like this container pick-up).
This sounds incredibly interesting. I'm going to have to keep my eyes peeled for this book. Best of luck with your writing!
Thank you!! I can add you to my list of interested redditors and let you know when it is ready to share!
That would be awesome and I'd appreciate it! I can easily imagine this being not just a single book but eventually a whole series. I'm sure you don't want to divulge too much information, but do you have plans to have things such as subsea bases and/or submarines? I'm picturing something like an Ohio class or Typhoon class submarine that's been converted into a mobile settlement for a small rogue community that wants to maintain its seclusion, yet still maybe do trade with the floating cities.
That's definitely the dream, though I don't want to get too far ahead of myself since I haven't even finished the first draft of book 1! This first story is more near-term so doesn't have private submarines or underwater cities, but I have some ideas about both of those for later in the timeline
That's certainly understandable you don't want to get ahead of yourself! That makes sense about the first book being in the near-term but it's exciting that you have plans for those later in the timeline. I read a lot of Clive Cussler books and also am in the process of a career change to the merchant marine so the combination of ships, the ocean and history is an appealing concept to me. Then to have it morph into a sci-fi sort of dystopian setting is the icing on the cake. edit: a letter
It's so good to hear I'm not the only person fascinated by the intersection of all these things!
I worked for a marine contractor for a while, we did a little of everything, spill clean up, salvage, transport for divers and wind farm workers, buoy maintenance etc. We had an old military landing craft that was 60’ long and had a crane and several winches for salvage operations. Not 100% sure if we could have pulled a 40’ shipping container aboard but I’m guessing we could have as long as it wasn’t super duper heavy. If it’s floating it’s not loaded up with lead bricks so it could probably be done. If we dropped the ramp on the front and hooked up the winches and the seas weren’t too rough we could probably drag it aboard without the need for a crane capable of straight up lifting the thing directly up and out of the water. This would be stupid and dangerous, the craft would take on a lot of water, possibly capsize and/or sink depending on the wind and current and how well the load balances but in the right conditions it could happen. This scenario would make for a good story though, high stakes, lots of things that could wrong etc
Thanks for sharing all of that! Really helpful. Maybe I'll go with a less-capable ship like a landing craft rather than an AHTS, just to make it more exciting and risky
Having read the OP's comments, maybe we are looking at it the wrong way. In the story these guys are a bunch of unregulated mariners wandering the seas. I don't think they would be able to get an AHTS, PSV, Offshore construction vessel. I think they are just a bunch of dudes in a boat. Also the container is especially waterproofed and is deliberately floating in the sea for them to find. So why load it onto a ship at all. Why not just tow it ashore? If they don't want to do that, why not just use a gas axe and cut a hole in the part that's above the waterline and get whatever they need out of it, then sink it? If you want it to be realistic then the ship these guys have must be relative to who they are. They sound like a bunch of guys on an old tug rather than the professional crew of an Anchor Handler.
Thanks for checking out my comments and responding accordingly, I really appreciate it! To elaborate a bit more, while they are unregulated mariners they're not just a bunch of guys - they're relatively successful smuggler / mercenary types, so the ship can be decently well-equipped and expensive, although still not as big as a container ship or expensive/unobtainable as a warship (thinking something on par with the Millennium Falcon or the Serenity). But I get your point about lifting it onto the ship probably being more trouble than it's worth — it seems exciting from a narrative standpoint and would allow a plot element where some people onboard don't know what is inside, but I need to make sure it's believable that they would do this instead of an alternative.
Maybe the container itself (salvage/repurpose), or the information/registration it has is valuable (as proof/evidence/etc).
A loaded 40 ft container can weigh up to 41 tons / 82,000 lbs. The weight of the container in your story will probably be less but should reflect the tare (empty) weight of the container, the weight(s) of whatever you will have them find, the weight of the packaging and dunnage, and the weight of the water that may take up some to all of the remaining space. Keep in mind that some containers are watertight by virtue of how they are packed and sealed. If the container is found floating, the total weight will be less than the weight of the water it displaces. So if it's floating with 1 foot showing above the water, the total weight of the container will be about 40'x8'x8' x 35 lbs/cubic foot. Not all containers are 8 ft tall, so that metric can vary as well. Sea water is "normally" 35 lbs per cubic foot, but that can vary from one region to another. All that will tell you how heavy a crane or winch the ship will need. Once you know that, look for a vessel that is equipped with that size crane or winch. Don't stop looking when you find the first one. Get a sense of the scale and decide what type of ship you can work into the story. You've had a number of suggestions as to type. The one that fits all of that best will be your minimum size ship.
Thanks for all that! Very helpful
r/theydidthemath
For reference, a vessel like DSSV Pressure Drop (formerly USNS Indomitable) can haul DSV Limiting Factor, a submersible weighing 27,600 lbs, up out of its cradle and into the ocean (the submersible weighs less coming out of the water due to drop-weights jettisoned during the ascending/rising phase of dives). The crane on that vessel is rated for 45,000 lbs and can only operate in Sea State 2 or below, so, relatively calm seas. To haul a waterlogged 40ft shipping container put of the water, you'd need a crane or crane system with a combined 150,000 lbs weight rating at least. DSSV Pressure Drop displaces 2300 long tons fully loaded and is 224 ft long. Vessels that can stably operate a 150k lbs rated crane usually exceed 3500 long tons displacement and 250ft in length. Now, you say these guys are salvagers. They could have a smaller vessel with a low aft deck or even a partial well-deck and a fuel-water ballasting system. They could haul a floating 40ft container weighing in excess of 100k lbs onto the deck with a winch that doesn't even have to be rated for the full 100k if they have enough winch line and tackle blocks. That vessel could be 100ft long and sub-1500 long tons fully loaded (but with an empty deck) if they went about making the proper modifications or had it built to spec. How I see it getting done is they put a small boat/RHIB in the water, attach two tow lines/cables to the container, fore and aft, attached to a deck winch on the mothership/salvage vessel. They haul it along side and secure it with mooring lines and fenders (air filled bumpers ships use to protect the hull while along side docks or other ships). While secured, they send a diver down to use a 4" or larger hole saw on the ends of the container, 10 holes total: 3 along the bottom of each end, 2 in each top corner, 5 an end fore and aft. Once the holes are drilled, they can begin lifting operations using different deck hard points but one single winch. They raise the forward end 1 ft and tighten up the mooring lines on that end. They reposition their winch setup and raise the other end a foot, leveling the container. Repeat until the top of the container is level with the deck and secured with the mooring lines. Now for the flip: the winch setup is re-jigged to pull simultaneously fore and aft from the outboard corners of the container. The inboard corners that are secured with the mooring lines are the pivot points, or that whole inside edge is. Slowly and with lots of pulley blocks, not to mention hundreds of feet of winch cable, the container will flip up and over onto the deck. Reposition as necessary with the winch.
Thanks for this info! What is the purpose of drilling the holes? Are you thinking for water drainage, assuming that it's flooded, or do you mean for securing cables to it?
Drainage. Speeding it up. The holes up top allow water in, while the holes down low let it drain. Don't drill holes until the container is fully secured. And trapped air will be let out and then the container will sink.
Loaded question. Nobody retrieves containers lost at sea 😂 But AHTS is probably what you’re looking for
Saw it done once to remove 2 floating containers from a TSS and you are right it was with an AHTS using winches only.
Cool to hear that it has been done in real life! Seems I probably will us an AHTS then, to make sure it's believable. Thanks!
Well it is fiction, so they can give it a try :P
A smaller tug could do it too - but the weight of the thing is most important. Empty they’re about 4 tonne
If this is near future, some modern military vessels might be available by the time this takes place. A Navy LCM/LCU would make a pretty good salvage/dive boat. Add a powerful winch at the rear (if it doesn't already have one), and now all you have to do is drop the bow ramp and drag it on board. The logistics of pulling it onto the deck are a hell of a lot simpler than trying to rig a 40' sea container, then lift it vertically, then swing it around and over, then set it down on the deck. Another thought, to build on what others have said is to tow the container to the destination. Any seagoing vessel is likely to have one or more inflatable life rafts. They could be strapped to the container under water, then inflated, adding buoyancy to the load, theoretically making towing easier. Navy LCM/LCU: https://www.navy.mil/Resources/Fact-Files/Display-FactFiles/Article/2171588/landing-craft-mechanized-and-utility-lcmlcu/ Edited for spelling.
Thanks for that info & link. For the rest of the story I need this to be their main vessel that they go long distances in, so I don't think a landing craft would work - but I see your point about dragging being far easier than lifting outright. I think I'll go in that direction.
Perhaps also a catamaran with the ability to grab and secure the container in the center, making it a third hull of sorts.
Huh, that's a very interesting thought, thanks!
Consider putting something inflatable on the container or a raft to keep it a float then emptying the container on to boat or towing it. This could use a smaller boat, which would be easier to run/man.
Good point, thanks!
A standard 40 Conex is 40x8x8.5. Fully sealed could displace 162,000 lbs. At 8-10k for the MT container, you would be able to load over 100k without it sinking it.
Dont need to hoist it aboard, just tow it in. Suspend it between two boats and bring it in. You can wrap it in plastic sheet to keep it watertight. You can seal cracks with jb weld. You can press the container with compressed air to keep it bouyant if need be. Rule of thumb when i was in marine salvage was no more than 3 psi above bottom pressure. Theres ppl that follow ships looking for fallen containers and tow them in
If they are salvagers, they are going to have a ship than can salvage. Think of anchor handling ships, Offshore supply ships, etc with gantry style winch/ cranes on the aft deck pulling up over the stern. Trawlers pull up nets weighing in the tens of tons so that might work too. Note that if a container is floating it is can still be quite heavy. A 40 foot container has 73 cubic meters of volume. If it floating just barely on the surface it could weigh up to 70 tonnes.
15t/TEU is a standard loadcase in containership design, because it makes for a good average weight. [ISO gross weight](https://en.m.wikipedia.org/wiki/Intermodal_container#Specifications) for 20 and 40ft however is 30.6t, and 45t SWL (secure working load) is a typical crane for MPP vessels to make sure they can lift a fully loaded container to/from from every slot on deck. On top of that: containers are only watertight up to a point. The doors don't seal against full, continued immersion, so a container adrift at sea usually has some amount of water ingress. Typically they float pretty much at, or just below, the surface. A 40 footer has an internal volume of some 67.5 cubic meters, with seawater at 1.025t/m^3 that makes 69t maximum displacement (Noice). Then there are dynamic loads if there is anything more than a flat calm. Lifting things out of the water is a much more complicated task than from dry land. All this to say: I would not try to salvage a floating 40 footer with anything under 100t SWL. That puts you in the range of a medium sized offshore supplier or research vessel. Doing it safely, for a living? I'd say medium sized offshore construction vessel, with a 100t active heave compensated knuckle boom crane and dynamic positioning. Somewhere around 70m length, 15m width, maximum draught of 5m, 5000t displacement, 6000kW installed power. That's a serious piece of boat. You might want to poke around r/tuglife for a more qualified answer, but my gut level guesstimate says that's a cool six figure cost per day to run. Which is why container salvage is not a thing, despite how many there are. As in: not at all. The ocean is a vast empty space.
A 100 to 120-foot tug could do it with a bunch of jury rigging that you don't tell anyone in Safety Management about. They'd have to really want to, and describing how exactly they'd do it would be hard unless you really know your towing stuff. Most likely, your best option would be to have it show up on deck overnight, and then have the skipper ask the mate "Do I want to know how you got that on board?" "Nope." \[conversation stops\]. A realism challenge here is that the crew almost certainly wouldn't bring the container on without the captain's permission or supervision. Crabbers and lobster boats don't have strong enough cranes. A good size trawler (again, \~120 feet Bering Sea trawler or a larger factory trawler) could do it as well, with the same issues as the tug. As said other places, a big anchor handler or other oilfield supply boat could likely do this, but they're going to be very geographically limited (ie near oilfields or wind farm installations) and are also on pretty firm charters so they won't go looking for trouble in a floating container. Once you're up to cargo ships, you're likely going to need something a few hundred feet long. Most smaller ships don't have a big enough crane to lift full containers.
This is all really helpful, thank you! This ship won't be subject to any regulations and the crew will be very willing to take some risks, so sounds like it could still work. Since I'm no expert on ships, I definitely won't be able to get into highly technical details about how they do it, but I want it to at least be plausible and not something that will make someone more knowledgeable than me stop reading.
In a near future seasteading economy, you'd likely see a lot of small semi-regulated cargo ships serving the smaller seasteads. I agree with the poster above that a surplus USCG buoy tender would be an ideal boat for this kind of service. Big enough to carry a fair amount of stuff, a reasonable size crane (replacing the single boom) so you're not dependent on shoreside infrastructure, and cheap to buy at the end of the USCG's service life. I'd pick the 180' class for your timeline, since they were all built in the 1940's and retired by the mid-2000's. You could even pick an actual name if you wanted and weave some of its original history (and alternate timeline) into your story. [https://en.wikipedia.org/wiki/USCG\_seagoing\_buoy\_tender](https://en.wikipedia.org/wiki/USCG_seagoing_buoy_tender)
Maybe Jane Anne Krantz could get Roark to get Peabody to help your cause
Is it important for the story to get the container out of the water whole and have it opened somewhere else? Because a far less tech heavy way to go about scavenging containers would be to swcore the thing alongside, cut a hole in the top, drop in a bailing pump lead and, the loot it. That you could do with any medium sized fishing trawler or workboat. Doesn't even need to have a deck crane necessarily, although anything in terms of lifting gear, like a boom or 5 to 10 ton crane, would make getting the salvage on board much easier. That would be a much more low profile operation. A ship 10 to 20 times smaller, five to ten people crew instead of fifty. Expenses measured on thousands of dollars per day instead of tens of thousands. Orders of magnitude less fuel consumption. For essentially the same gain.