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How do they not capsize?
Posted by: DP
Date: December 02, 2021 06:37AM
I'm seeing images of these container ships waiting to unload their goods and, while my brain knows the reason, my eyes just can't understand how these ships don't roll right over!





The pile of containers-heavy even when not loaded-is higher than the height of the hull from the deck to the waterline! And they're loaded with goods.

Plus, it looks like the ships are riding very high in the water...





A little break from the grief...






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Re: How do they not capsize?
Posted by: Sarcany
Date: December 02, 2021 06:53AM
For some ships, there's more ship under water. Like icebergs. That tiny line at the waterline is the halfway-mark up the hull.

But many are built like long flat sleds.

They float because they're hollow. So long as the average density of the ship is less than the density of a similar volume of water, they float. And salt water is pretty dense.

But you're missing another problem.

See those gaps at the top-edges?

That's probably where the containers rolled off into the sea.

...And they do sometimes roll over when they aren't balanced. They usually have pumps to balance the ship by taking on water on one side or the other.









Edited 1 time(s). Last edit at 12/02/2021 06:54AM by Sarcany.
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Re: How do they not capsize?
Posted by: macphanatic
Date: December 02, 2021 07:01AM
It's amazing how many containers are lost overboard every year. The last couple years have been really bad for shipping losses.
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Re: How do they not capsize?
Posted by: rgG
Date: December 02, 2021 07:26AM
They have just finally removed the last of the big ship that rolled over and sank in Savannah a few years ago. It was loaded with cars, so I don’t remember if it had any containers on the top or not, but it was a HUGE mess.

So, they do roll over and sink, sometimes.





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Re: How do they not capsize?
Posted by: DP
Date: December 02, 2021 07:44AM
That image you posted, Doc, makes me wonder how the other containers aren't over the side! That's quite a list to starboard...





A little break from the grief...






Disclaimer: This post is checked for correct spelling, punctuation, and grammar. Any attempts at humor are solely the responsibility of the author and bear no claim that any and all readers will approve or appreciate said attempt at humor.
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Re: How do they not capsize?
Posted by: Speedy
Date: December 02, 2021 09:24AM
Quote
DP
That image you posted, Doc, makes me wonder how the other containers aren't over the side! That's quite a list to starboard...

Each container has pins in the bottom corners and pin holes in the top corners. They can then be kept in place with keepers through those pins. This is what they do on trailers to keep them in place and also on trains where they are usually double stacked.



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Re: How do they not capsize?
Posted by: mrbigstuff
Date: December 02, 2021 10:53AM
I agree it looks bizarre. And it probably has a lot to do with the country from where they disembark (ex., not strict regulations). But, since it does work, the cargo shippers have figured it out, apparently.
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Re: How do they not capsize?
Posted by: Paul F.
Date: December 02, 2021 11:56AM
Those stacks go below the "deck" you can see, too... so, not all the weight is up high. They also know the weight of each container as it's loaded, and the containers of machine tool parts go on the bottom, and the containers of plush toys go on top.
Well, that' the way it's supposed to work... sometimes things don't work out at the port, and they get loaded a bit more slapdash.
But, not all the weight is those containers way on top.



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Re: How do they not capsize?
Posted by: Filliam H. Muffman
Date: December 02, 2021 11:59AM
Cruise ships confuse me a little in the same way. They look so top heavy. The vast majority of containers are not full. Most will float like corks if lost at sea.

About six weeks ago the container ship ZimKingston lost between 40 and 100 containers off of Vancouver Island, BC and burned for several days. This was due to a bomb cyclone on October 21, 2021.



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Re: How do they not capsize?
Posted by: MrNoBody
Date: December 02, 2021 12:11PM
makes you wonder...



USS Gerald R. Ford, CVN-78 departing Newport News Shipbuilding



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Re: How do they not capsize?
Posted by: RAMd®d
Date: December 02, 2021 03:31PM
Ballast.

But as noted in the pic above, it doesn't always work.




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Re: How do they not capsize?
Posted by: Diana
Date: December 02, 2021 04:36PM
A ship’s stability is dependent on several things, including it’s center of buoyancy (COB). An empty cargo ship will have a very low COB relative to other types of ships, as additional weight shifts the COB upward, particularly if the added weight is above the COB. As it rises, the ship becomes more unstable. Any force that causes the ship to move will also cause the ship’s COB to shift—for instance, a wave hits the side of the ship and causes it to heel over, and the COB shifts laterally; wider ships are more stable than narrow ones because the COB is less likely to shift outside the boundaries of the ship as it heels over.

Heavy stuff is placed in the ship’s hold and lighter stuff on top. Anything on board that shifts can alter the COB and so containers are latched down, chained down, or otherwise fastened so they can’t move. Adding water is sometimes done to lower it’s center of mass and thus it’s COB; however if it isn’t done properly it results in a mass that sloshes around (known as a slack tank) and will cause a ship to go down if not promptly attended to.

Any ship that appears narrow and small at the waterline is deceptive in its appearance. They’re much bigger than they look. The less it presents to the water, the faster it can go but there are limits. Hydrofoils get around that limitation as much as they can.

The Coast Guard has been researching into ships that self-right, and there is some rather impressive footage out on the webs of boats that do so.



Edited 1 time(s). Last edit at 12/02/2021 04:38PM by Diana.
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Re: How do they not capsize?
Posted by: N-OS X-tasy!
Date: December 02, 2021 05:30PM
Quote
Diana
A ship’s stability is dependent on several things, including it’s center of buoyancy (COB). An empty cargo ship will have a very low COB relative to other types of ships, as additional weight shifts the COB upward, particularly if the added weight is above the COB. As it rises, the ship becomes more unstable. Any force that causes the ship to move will also cause the ship’s COB to shift—for instance, a wave hits the side of the ship and causes it to heel over, and the COB shifts laterally; wider ships are more stable than narrow ones because the COB is less likely to shift outside the boundaries of the ship as it heels over.

Heavy stuff is placed in the ship’s hold and lighter stuff on top. Anything on board that shifts can alter the COB and so containers are latched down, chained down, or otherwise fastened so they can’t move. Adding water is sometimes done to lower it’s center of mass and thus it’s COB; however if it isn’t done properly it results in a mass that sloshes around (known as a slack tank) and will cause a ship to go down if not promptly attended to.

Any ship that appears narrow and small at the waterline is deceptive in its appearance. They’re much bigger than they look. The less it presents to the water, the faster it can go but there are limits. Hydrofoils get around that limitation as much as they can.

The Coast Guard has been researching into ships that self-right, and there is some rather impressive footage out on the webs of boats that do so.

An excellent explanation, Diana.

Sometimes you remind me of Charlie, a former forum member who was also very knowledgeable and intelligent.



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Re: How do they not capsize?
Posted by: MrNoBody
Date: December 02, 2021 09:42PM
The Coast Guard has been researching into ships that self-right, and
there is some rather impressive footage out on the webs of boats that do so.


Late '60s-70s USCG had some self-righting rescue boats. They were
designed & made by the now defunct Winner Boat Co. of Tenn.
No wood was used, they utilized a fiberglass 'skeleton' with inner and
outer fiberglass hulls pumped full of foam. iirc, they had twin sterndrives
fueled from bladder tanks and were around 42ft long.

Like this:




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Edited 1 time(s). Last edit at 12/02/2021 09:42PM by MrNoBody.
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Re: How do they not capsize?
Posted by: freeradical
Date: December 03, 2021 02:29PM
The SS Petersburg...



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Re: How do they not capsize?
Posted by: Thrift Store Scott
Date: December 03, 2021 10:59PM
Quote
freeradical
The SS Petersburg...




What is that it's launching, some kind of dredging or excavation platform?



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