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View Full Version : Wonder why ships don't tip over?


gonzo1124
April 20th, 2010, 08:58 PM
I do. I remember when ships had heavy, deep keels as ballast. Their draft was so deep they couldn't get into shallow ports, (remember the Cunard France always anchored outside St. Thomas bay?)
It is my understanding that newer ships have more of a flat bottom instead of a pointy keel (and they draft shallower), then huge water holding tanks inside the hull act as ballast. These are controlled by computers to keep the ship level and up.
Anyone knows more about this?

Yo Eleven
April 20th, 2010, 09:00 PM
I do. I remember when ships had heavy, deep keels as ballast. Their draft was so deep they couldn't get into shallow ports, (remember the Cunard France always anchored outside St. Thomas bay?)
It is my understanding that newer ships have more of a flat bottom instead of a pointy keel (and they draft shallower), then huge water holding tanks inside the hull act as ballast. These are controlled by computers to keep the ship level and up.
Anyone knows more about this?
Actually an interesting question, but I don't have an answer.

But I betcha Hank knows the answer? Perhaps ask him. :p

CLICK ME!!!! (http://www.youtube.com/watch?v=zNZczIgVXjg)

:D

dd2355
April 20th, 2010, 09:04 PM
But I betcha Hank knows the answer? Perhaps ask him. :p

CLICK ME!!!! (http://www.youtube.com/watch?v=zNZczIgVXjg)

:D

Marginally better than Cynthia McKinney, but still a state embarrassment.

Props to the Admiral. I couldn't have held it together. (see vid @ 1:30)

Nunu
April 20th, 2010, 09:05 PM
I always assumed they did eventually tip over:confused:

DocF
April 20th, 2010, 09:09 PM
Fixed ballast, very wide beam, high cube design, water ballast, are all elements that combine to give a very stable ship with a draft of less than 26 feet in most cases. The deepest draft ship running until recently was the old Regal Empress which drew at least 32 feet. She was built in 1953, so that makes sense.

The modern cruise ship is flat bottomed and slab sided. This is why they are very stable.

A very good discussion about this aspect of ship design can be found in George W. Hilton's book Eastland: Legacy of the Titanic. The Eastland capsized in the Chicago River in 1915. It is out of print, but should be available at Amazon or ABE Books.

Doc

paper1122
April 20th, 2010, 09:31 PM
http://www.youtube.com/watch?v=deX7R9RbmX0 - Here is a video of very rough seas with a cruise ship.

I also dug up this realic from the past http://boards.cruisecritic.com/showthread.php?t=154578

sarge98
April 20th, 2010, 10:04 PM
I do. I remember when ships had heavy, deep keels as ballast. Their draft was so deep they couldn't get into shallow ports, (remember the Cunard France always anchored outside St. Thomas bay?)
It is my understanding that newer ships have more of a flat bottom instead of a pointy keel (and they draft shallower), then huge water holding tanks inside the hull act as ballast. These are controlled by computers to keep the ship level and up.
Anyone knows more about this?

If I remember right, believe it's called draft, the Valor goes 28' under the water line, 3 floors plus, and the engines are down there, very heavy.. http://boards.cruisecritic.com/images/icons/icon3.gif

MrCo9
April 20th, 2010, 10:07 PM
It's happened as recently as 2007 (http://www.msnbc.msn.com/id/17980169).

2007 (http://www.washingtonpost.com/wp-dyn/content/article/2007/11/23/AR2007112300189.html) was NOT a good year.

If your ship does go down, hopefully the crew (http://www.youtube.com/watch?v=9BFux2AAMso) will be there to help.

gaunerdog
April 20th, 2010, 10:09 PM
I do. I remember when ships had heavy, deep keels as ballast. Their draft was so deep they couldn't get into shallow ports, (remember the Cunard France always anchored outside St. Thomas bay?)
It is my understanding that newer ships have more of a flat bottom instead of a pointy keel (and they draft shallower), then huge water holding tanks inside the hull act as ballast. These are controlled by computers to keep the ship level and up.
Anyone knows more about this?

I think it is probably related to the concern that Congressmn Coleman made in a Congressional hearing a few weeks ago about the possibility of Guam tipping over because it would become too populated if we enlarge our military base there. The cruiseships are not islands so I'm sure they wouldn't tip over.

idlenote
April 20th, 2010, 10:17 PM
This is the real reason, you may wish the question had not been asked:

http://en.wikipedia.org/wiki/Metacentric_height

These ships are built of steel in the bottom, with the engines, fuel and ballast tanks down low to give lots of weight. The superstructures are aluminum and are basically huge empty spaces. Instant stability.

golfadj
April 20th, 2010, 10:20 PM
http://www.youtube.com/watch?v=deX7R9RbmX0 - Here is a video of very rough seas with a cruise ship.

I also dug up this realic from the past http://boards.cruisecritic.com/showthread.php?t=154578

Wholly crap, half the passengers would have died of heart attack myself included.

lillian marie
April 20th, 2010, 10:24 PM
The financial liability would be enormous if modern ships were not built to be stable in even the worst seas. You're safe even in a hurricane as long as you don't get so drunk that you decide to take a nose dive off your balcony.

Suite Travels
April 20th, 2010, 10:36 PM
Crystal always tip's over. LOL:D

Suite Travels
April 20th, 2010, 10:39 PM
We have been through two hurricanes with Crystal and we all survived.:D

Sun R Bunns
April 20th, 2010, 10:58 PM
Marginally better than Cynthia McKinney, but still a state embarrassment.

Props to the Admiral. I couldn't have held it together. (see vid @ 1:30)

I want to deny I even live in Georgia!! What a disgrace for a political leader. And that stupid ass is going to draw retirement and health care plus all the other benefits that a congressman gets for THE REST OF HIS LIFE!! It's a pity one can't resend the appointment.

misguidedangel
April 20th, 2010, 10:58 PM
I suggest that on your next cruise you sign up for the Behind the Fun tour and you can ask the chief engineer that very question!!!!

big_duck
April 20th, 2010, 11:27 PM
The modern cruise ship is flat bottomed and slab sided. This is why they are very stable.

And real beotch to handle at slow speeds in high winds.

jgmpuma
April 21st, 2010, 08:53 AM
I mostly worry about my wife tipping over after all those DOD's.

kzguns
April 21st, 2010, 08:59 AM
Fixed ballast, very wide beam, high cube design, water ballast, are all elements that combine to give a very stable ship with a draft of less than 26 feet in most cases. The deepest draft ship running until recently was the old Regal Empress which drew at least 32 feet. She was built in 1953, so that makes sense.

The modern cruise ship is flat bottomed and slab sided. This is why they are very stable.

A very good discussion about this aspect of ship design can be found in George W. Hilton's book Eastland: Legacy of the Titanic. The Eastland capsized in the Chicago River in 1915. It is out of print, but should be available at Amazon or ABE Books.

Doc
My first cruise was on the regal empress when she was the caribe I back in 1989.
Anyway like most have said here these ships have huge heavy keels google for some pics of some of these ships in dry dock you'll see.

KZ

elcuchio24
April 21st, 2010, 09:31 AM
It is exactly that wide, shallow hull that makes it more stable then deep keeled ships with shorter beams.

WayTooCool
April 21st, 2010, 09:33 AM
I want to deny I even live in Georgia!! What a disgrace for a political leader. And that stupid ass is going to draw retirement and health care plus all the other benefits that a congressman gets for THE REST OF HIS LIFE!! It's a pity one can't resend the appointment.
Sun-R-Buns will be speaking for me today -- not only is THIS doofus getting all the bennies, but think of what Cynthia McKinney is getting as well -- for LIFE! and for what? For regularly embarrasing the very people she was supposed to represent . . . that's the list.

MrPete
April 21st, 2010, 09:42 AM
None of these formulas help me remembering being in a ship in the Pacific ocean, heading toward Hawaii, beginning to tip so bad the beds started sliding toward the door, as well as ALL THINGS LOOSE, emptying out pools, trashing the gift shops and liquor stores, as well as breaking a LOT of tableware dishes.

But I'm here, so obviously, the ship eventually righted itself. :)

dprg644
April 21st, 2010, 10:10 AM
http://www.youtube.com/watch?v=deX7R9RbmX0 - Here is a video of very rough seas with a cruise ship.



Oh my God:eek: Made me sick just watching that.

DanJ
April 21st, 2010, 12:15 PM
http://www.youtube.com/watch?v=deX7R9RbmX0 - Here is a video of very rough seas with a cruise ship.



That ship did actually sink. It had 35 or so crew members on board, and they were rescued by the coast guard off Virginia or thereabouts. The ship had been taking on water and lost it's engines. It was one of Premier Cruises ships when they went out of business 7 or 8 years ago.

I remember watching one of those ship tour videos on the cabin TV and they said that everything you see of the ship sitting there next to the pier comprises something like 20%
or so of the weight of the ship, with the rest being below the waterline.

MrPete
April 21st, 2010, 12:22 PM
That ship did actually sink. It had 35 or so crew members on board, and they were rescued by the coast guard off Virginia or thereabouts. The ship had been taking on water and lost it's engines. It was one of Premier Cruises ships when they went out of business 7 or 8 years ago.


You're thinking of the SS Seabreeze, of the Dolphin Line. It sunk 10 years ago.

That video is not the Seabreeze.

JohnsPrincess
April 21st, 2010, 01:17 PM
This is a total fear of mine. Our last cruise was this past Christmas with Disney and I could feel the ship rocking side to side and I was Freaked out. My husband told me all the above and tried to calm my fears but all I could picture was it rocking more...and more...and more and eventually just turning right over!!! Lol. Of course, we're booked on the Legend in Aug so I obviously know somewhere in my brain that we'll be fine.

mboatman
April 21st, 2010, 01:32 PM
I do. I remember when ships had heavy, deep keels as ballast. Their draft was so deep they couldn't get into shallow ports, (remember the Cunard France always anchored outside St. Thomas bay?)
It is my understanding that newer ships have more of a flat bottom instead of a pointy keel (and they draft shallower), then huge water holding tanks inside the hull act as ballast. These are controlled by computers to keep the ship level and up.
Anyone knows more about this?
Same reason weebles wobble!!

dan40
April 21st, 2010, 01:43 PM
I do. I remember when ships had heavy, deep keels as ballast. Their draft was so deep they couldn't get into shallow ports, (remember the Cunard France always anchored outside St. Thomas bay?)
It is my understanding that newer ships have more of a flat bottom instead of a pointy keel (and they draft shallower), then huge water holding tanks inside the hull act as ballast. These are controlled by computers to keep the ship level and up.
Anyone knows more about this?


Your question contains the answer, BALLAST. The deep hulls of ocean liners were for riding the oceans rough waters, not for ballast. They had to carry tons of ballast the same as cruise ships do. The shallow draft flat bottoms are so ships can use unimproved shallow harbors of tourist destinations.
Remember a ship with 90,000GRT or 220,000GRT has NOTHING to do with its weight. Each will weigh millions of pounds, much of it ballast.

Brewzz
April 21st, 2010, 02:05 PM
I've sailed through lots of very rough seas, and left a lot of footprints on the bulkheads, but never worried about tipping over. As a few others have said, modern ship are designed so that only a small percentage of the ship's weight is above the waterline.

LHP
April 21st, 2010, 07:27 PM
I think it is probably related to the concern that Congressmn Coleman made in a Congressional hearing a few weeks ago about the possibility of Guam tipping over because it would become too populated if we enlarge our military base there. The cruiseships are not islands so I'm sure they wouldn't tip over.

That was going to be my answer....

because they are not Guam... :D

glrounds
April 21st, 2010, 09:13 PM
I do. I remember when ships had heavy, deep keels as ballast. Their draft was so deep they couldn't get into shallow ports, (remember the Cunard France always anchored outside St. Thomas bay?)
It is my understanding that newer ships have more of a flat bottom instead of a pointy keel (and they draft shallower), then huge water holding tanks inside the hull act as ballast. These are controlled by computers to keep the ship level and up.
Anyone knows more about this?

Fixed ballast, very wide beam, high cube design, water ballast, are all elements that combine to give a very stable ship with a draft of less than 26 feet in most cases. The deepest draft ship running until recently was the old Regal Empress which drew at least 32 feet. She was built in 1953, so that makes sense.

Although any water stowed onboard is obviously kept in the lower sections of the ship, but even better the incredible amount of steel, all the diesel engines, electric motors, pumps, compressors for the refrigeration, air conditioning, lighting and for air pressure, food storage, etc. which is much more dense than water would be the main "ballast" giving the ship its stability. All this is kept at the absolute lowest point possible on a cruise ship. Cabins and public areas above the waterline are also made of much lighter materials. Additionally, stabilizers are used to keep the ship from pitching from side to side.They are hydraulically operated to quickly send out an "uplifting wing" under water whenever the ship starts to pitch to one side.They're fast and, for the most part, while at speed, very effective. All this lowers the center of gravity which is at or near the waterline.

As another poster has stated, the real problem with these ships is when they are in port with limited speed and manuverability and are struck by high winds as one of the videos showed. The high slab sides of these modern day ships makes an excellent sail ! ! :) I think most recently high winds while in port were responsible for several Carnival collisions (low speed of course) and a couple years ago caused a Princess ship in open seas to heel over for quite some time. These ships are incredibly safe from capsizing. It would take a super high wind or a freak sea wave to capsize them.:)

Try to keep in mind, the Poseidon was a movie ! :D

oncruisecontrol
April 21st, 2010, 10:21 PM
http://www.youtube.com/watch?v=deX7R9RbmX0 - Here is a video of very rough seas with a cruise ship.

I also dug up this realic from the past http://boards.cruisecritic.com/showthread.php?t=154578


A harrowing experience for the passengers, I'm sure. But, the ship in the video appears to be drifting (as in engines not running): A different situation than what occurred today on Carnival Ecstasy.

noblepa
April 22nd, 2010, 10:52 AM
As others have mentioned, all the really heavy stuff, like the engines, water tanks, fuel tanks, etc. are in the bottom of the ship, below the water line.

Although it does seem counterintuitive that a ship with perhaps 30 feet below the waterline and 100 feet above would not be top-heavy, they aren't.

In order for a ship to capsize, the center of gravity must cross the waterline. Because of all the weight below the water line, the center of gravity is only a few feet above the water line. A ship would have to list well over 45 degrees to capsize. Even the worst case of listing that have been reported are usually only 15-20 degrees. I'm sure it feels like the ship is going over, but it really isn't.

As a result, its almost impossible for an undamaged ship to capsize. Now, if the hull is breached or too much water is taken aboard, due to heavy seas, the geometry of the ship changes and all bets are off.

What I've always wondered about is if the ship IS damaged and begins to list even a moderate amount, say 15 degrees, that may be enough to make it impossible to launch the lifeboats on the "uphill" side, effectively cutting the number of lifeboats in half. Now you're in a Titanic-type situation, in which you don't have lifeboat seats for everyone on board.

Paul

waiting4acruise
April 22nd, 2010, 10:57 AM
What the reason I think those on the Ecstasy yesterday were glad it did not capsize when it did a manuver to avoid a bouy.