How long could a modern ship remain afloat without maintenance?

Factual Questions
1

Let’s say you’ve got an Evil Genius who has a typical Island Lair somewhere. Since supplies for the henchmen and champagne and caviar for “guests” don’t grow on trees (even Super-Science, regardless of how Evil you are, has its limits!), they have to be imported. Since the Island isn’t big enough for an airfield that could operate a C-130 (or anything bigger than a Gulfstream or a Learjet, for that matter) said Evil Genius has to operate at least one cargo ship that can carry things in and off the Island Lair.

Assume, for the purposes of this hypothetical, that said cargo ship is reasonably new, has a hull made of whatever metals hulls are made of these days, and is of medium size, say about the same size and overall specifications as the RMS St. Helena.

Now, further, let us assume that in the course of said Evil Genius’ attempts to Evil-Do, a Super Spy from one of the “Good” countries arrives on the Island and… you’ve all seen Bond films, you know how it goes. The Evil Genius is defeated, the Super Spy gets the girl, and the henchmen and minions are either all dead, captured, or fleeing in the Learjet.

As a result, the island is abandoned, completely and utterly. It’s not on any maps, the surviving minions couldn’t find the place again even if they wanted to, and for the Super Spy Agencies of the world, Evil Genius Island Lairs are ten cents a kilo, so they pay no more attention to it.

Anyway, the supply ship is still moored at the private dock on the now abandoned Evil Genius Island. The water is tidal saltwater and the harbour is protected from the elements, and there are no cranes, trees, or buildings nearby to collapse onto the ship.

Roughly how long will the ship remain afloat without being careened, cleaned, or otherwise maintained in any way?

2

Depends. Do I get to design it? With a right mix of corrosive-resistant metals, it c ould last basically until the slgiht thermal damage and ever-so-slow wearing from waves finally makes enough holes in enough compartments to sink her. I’m not evern sure we can adequately calculate how long this will take.

3

A standard river barge, left to rust, will last aaaaabouuuut 15 years, floating, with nothing more than complete neglect. I know this because that’s what happened to the floating breakwater at the local yacht club. Sank about two years ago, and now it’s a stationary breakwater.

Note that this is on the Hudson River, which has tides, and is salty enough where the barge was. It also was hit by a number of just-shy-of-hurricane storms, and I think at least one actual hurricane.

4

resistance to corrosion is tested extensively using jets of hot salt water, this is intended to simulate many years of exposure to salt.

It’s possible to simulate several years in a matter of a few days.

Other corrosion prevention measures include sacrificial anodes.

The main enemy is likely to be marine fauna which will attach itself to paint and damage it.

You’d get a few years, but I doubt we would be looking at decades.

5

Ships require water to be pumped off, seawater can enter through the driveshafts and any hole in the hull, I believe these can’t be totally sealed off, and the seals will deteriorate over time. Also rain/snow will eventually make it’s way in as well, eventually the ship will sink unless the water is pumped out. So it would be how well the ship is sealed below the water line and how well is it sealed against rainwater.

6

It will depend on the condition of the ship and how often the bilges had to be pumped when the ship was operating. If there are no leaks below the water line then it is still open.
One opening would be the stern tube. If the packing is in good condition and properly adjusted it should not leak with the shaft not turning. But it would be possable to have water dripping into the shaft alley, but this area is not normally open to the engine room.

 If circulating pumps were poorly maitained it would be possable the packing could be leaking, or if they were in good condition and not running they could hold.

Some rain water may work in an open door. The scupper drains will direct most of the water overboard.

 I would expect the zincs on the hull to last at least a year. So the hull probably would not begin to rust below the water line for a year.

My guess would be from a year to maybe 10.

7

The packing on a stern tube can last for years with little or no maintenance.

8

On Life After Humans they had an episode talking about various types of ships. IIRC, the warships (especially the battleships) were the ones that lasted longest (several hundred years), gradually becoming islands. They didn’t stay afloat though, but gradually sank after a few decades, and then slowly were covered with plants and such.

The ships that were at sea could, in theory, float around for quite a while (according to my memories of the show), but eventually they would crash into something hard enough to sink them.

If you weren’t worried about the ship sinking though, just about it being preserved, you could drop it in the Black Sea…even the crew might last for a few centuries, and the ship could last for thousands of years as long as the conditions didn’t change. There was a show on NatGeo (Ghosts of the Black Sea I think) where they were looking at wrecks from the early Byzantine era that were perfectly preserved. Still had their masts on them, even the ropes and rigging were still there. I have no doubt that after they really start exploring the area in detail they are going to find some amazing things…perhaps even the completely preserved bodies of some of the crews.

-XT

9

There are modern ships all over the world sailing with little to no maintenance. I’ve been on foreign ships that have holes in their freeboard.

In the US, there are a fair amount of ex-USN warships as museums. They get a lot less maintance than you’d think.

I think the answer to the OPs question is decades.

10

I wouldnt doubt they would take two hundred years or more. I always found it interesting to watch the last of the old schooners slowly deteriorate as I drove up Rt. 1 in Maine. I remember in the late 90’s noticing it was gone all but a pile of wood, the masts went last. The navy retired the ship in 1930 and it took almost 60 years for the wooden boat to be swallowed up by nature.

Here are some pics-

http://www.hazegray.org/features/schooners/

11

It’s interesting there’s such a diverse range of answers here. Personally, I thought maybe 20-25 years at most, maybe longer for a military ship…

12

Well, there’s ‘deteriorate till gone’ and there’s ‘deteroriate till sunken’. Now, that barge I was talking about, the one with no care at all, moored not far off shore as a breakwater, designed to take as much abuse from the river and storm as possible. sunk in 15 years. However, it’s not gone. It’ll probably be around for quite a while, yet.

In the 40s and 50s, a lot of 18th Century ships were just stuffed along the shoreline and abandoned, as they were work freighters and no longer useful. Worn to death. They lasted till the 90s before they were just completely gone.

However, if there is an active crew on a ship, it’ll last a while longer than one that’s just abandoned.

13

I have to lean towards a lot less time than many people are suggesting. I’m not thinking so much about rust or seals breaking down. But I do think that a lot of bilge water could build up over time. Especially on a ship that has just been abandoned, as in the Op.

This article talks about bilge water buildup and includes rainwater as one of the sources. It seems to me that an abandoned ship could gradually fill up with water even through just one or two open hatches. This could easily lead to a list which could accentuate the problem.

In fact, this article about the US Navy reserve fleet notes that bilge pumps are operated continuously on these ships. And these are ships that are prepared for long term storage.

I can’t find anything on what rate water typically accumulates in the bilge. But my guess is that within as little as a few years, and maybe much less, gradual accumulation of bilge water would be enough to sink an abandoned ship.

14

An open hatch is one thing figure 15 inches a year. Figure The cross section of the hatch is maybe 1/5 cross section of the hold. That should about 3 inches a year. a hold maybe 20 to 40 feet in depth. It will take a few years to fill.

The bilge pump on a operating ship do not run continuousy, I would doube they would need to on a ship that has been laid up. They are probably monitores continuously.

On a operating ship the bilges in the cargo areas are seldom pumped, like not even once a week or month. In an operating engine room maybe once a watch and most or the water will be from leaks of operating equipment. But on a cold iron plant they would not be leaking.

15

Though it’s not so much a question of filling as stability, particularly with free surface water. Serious stability problems occur with surprisingly little water, particularly if it’s a little water across many holds, maximising free surface.

16

But if the ship is just sitting tied up to a dock then stability is really not going to be an issue. It only becomes and issue if the ship is under weigh.

-XT

17

Incorrect. A vessel is normally loaded or ballasted to be inherently stable ie any reasonably expected upsetting force will be resisted by righting forces and the vessel will remain upright. However the pernicious thing about free surface water is that *virtually any *list causes the water to flow to the side of the list, thus potentially worsening the list, however imperceptibly. In theory, this won’t occur if the vessel is balanced absolutely perfectly upright in absolutely still conditions, in rather the same way a pin stood perfectly upright on its point won’t fall over. Needless to say, in the real world these conditions don’t exist and the vessel is always listing or rolling slightly. Consequently, whether the vessel is at a berth or at sea, free surface effect instability is a potential problem.

Just to fill in more background, this doesn’t usually matter because vessels are built to have, and operated so that they maintain, righting forces that increase as the vessel starts to list. As the list increases, the righting forces increase at a rate faster than the listing force caused by the flowing water, so that a balance point is reached and the vessel remains upright.

However, increasing amounts of free surface water will overcome righting forces, and suprisingly small amounts can have drastic effects.

An industry acquaintance of mine was flown into I think Pakistan to advise on fighting a smouldering cargo fire on a ship alongside (I think it was a grain cargo). Land based firefighters kept pumping water in, and he kept saying “you are going to turn this thing over. Stop, fer Og’s sake: a fire is not as bad as an capsized ship!”. He could not get them to understand how the relatively small amounts of water they were pumping in could affect such a seemingly big and stable vessel. He knew that Pakistan had recently thrown a foreign expert into jail as a scapegoat in similar circumstances so he just got in a taxi, went back to the hotel, grabbed his bag, went to the airport and got on the first plane out. As he was boarding he got the message that the vessel was on the harbour bottom on its side.

18

I am a Pakistani lawyer, I do a lot of work in shipping and I can not remember that happening.

There was a ship which ran aground was an oil tanker. It caught fire.
Lots of Moolah for many lawyers.

19

The Baychimo lasted at least 38 years.

20

From your “Ask the…” thread I recall you have been practicing in Pakistan for only a few years and that probably doesn’t take you back far enough. This casualty would probably have been in the late nineties or maybe earlier. I am really struggling to remember the name of the vessel in question. It may come to me.