Stability of Cruise Ships

[Dave Gittins]

Captain Wood, I wonder if you would like to comment on the stability of the modern cruise ships. (No names, no pack drill!)

I spent much of Thursday pottering about under motor, taking photos of SuperStar Virgo. She's currently cruising Australian waters because of the SARS panic. Looking at her from dead ahead, I was struck by how high she is, compared with her beam. I'm a rotten judge of height, but I think I can safely say that here highest deck is about 90 to 100 feet above the waterline. There are other structures even higher.

All this is on a beam of 105 feet and a draft of 26 feet. That's a lot of windage and not much draft.

Any comments?

 

[David G. Brown]

Dave --

Captain Wood is here in Toledo, away from his computer and the ET Forum. We talked about this last night and he has some interesting observations about both stability and the problems of all that "non-reefing" sail area. He will be back home probably on Monday.

-- David G. Brown

 

[Martin Owen Cahill]

How about the new QM2?
I have seen photos of her before and after being floated out at St Nazaire and she has a draught of 10 metres yet she stands very high out of the water. [taller than the original QM]

Martin

 

[Erik Wood]

I actually have several comments. Before I get to deep into my thoughts, I must post the following caveat:

I am under the influence of medications to cure a current infection so things might come out garbled.

First cruise ships today have a much larger and much lighter super structure then there earlier counterparts. The newer 1000 footers put out by Carnival and several other companies lend to several manvering problems in tight quarters.

Although these ships have the latest in bow thrusters and other fancy manvering devices when the wind wants to take you it will take you. Sometime ago in some other thread I mentioned the port of Gulfport. Wind in this area can be very hard to judge, while it generally moves west to east the layout and geography of the bay lend it to "bowling" or sending sudden bursts of wind from the north east going west.

A carnival ship recently had a bad encounter with such a wind burst. You will further notice that these lighter newer ships avoid bad weather like the plague. High winds (over around 50 knots) can make the vessel almost impossible to handle in a rough sea and the wind pushs the lighter sail like superstructure in what ever direction it wishes to.

These newer ships have for the most part a light draft and are built for comfort. In today's ecomony you make money based off the luxury of your accomdations, the newest addition is balconies. Most ships make up most of there money by having lots and lots of these (2nd class cabins as they are called) balconied cabins.

What happened in Gulfport not that long ago will happen again and eventually will have some kind of nasty results. In my opinion today's ship builders are running off the same thoughts as 1912 ship builders. They are pushing the envolpe of techonolgy. Just because you can build bigger, doesn't mean that bigger is better or safer.

 

[Jesse D O'Neill]

cruise ships are built terribly too high these days, if one of those ships was rammed today by another ship and had its stabilizers knocked out it would capsize and sink.

 

[Dave Gittins]

Jesse, stabilisers don't enter into it. They only stop the ship rolling badly when she is underway. They are for comfort, not stability. Once the ship stops, they do nothing, except get in the way of lifeboats. If possible, they should be retracted before abandoning ship.

Captain Wood actually commands large cruise ships, so his comments are always valued. We read them and learn.

Personally, I fear that one day one of these ships will be rammed amidships. A container ship smack in the atrium would be deadly.

 

[Jake Angus]

How do stabilisers work to keep a ship from rolling? And what is their evolution?

 

[Dave Gittins]

They work rather like ailerons on a plane. As the ship rolls, they change their angle of attack to produce an opposing force. That's why they don't help if the ship stops. In 1912 they tried to stop rolling by fitting long keels along the bilges. These helped a bit but they were only passive devices. Some small ships used sails for the same purpose and some still do. Fishing boats use what some call birds, which are metal plates that are dragged through the water on the end of long booms. None of these things are much use on big ships.

Somebody who knows history better then I do could tell you when true stabilisers first appeared. My guess is the 1950s. There is a Titanic connection. Quartermaster George Rowe was awarded the British Empire Medal for services to marine engineering after he helped fit stabilisers to Queen Mary and Queen Elizabeth.

 

[Jesse D O'Neill]

I Think Keels were fitted to the bilges of ships earlier than 1912, though im not quite sure. as for mechanical devices for stabilizing ships, the first attepts were mostly w/ river boats and other ships sailing in closed relatively calm water. the first attempt w/ an ocean liner i believe would be the Imperator, though they didnt help her much as she was the most unstable ship on the atlantic 1913 - 1938. the next major attepmt was the Rex's Running Mate the Conte Di Sovai (i think i spelled it right) which was a marginal success. the first ocean liner to be fitted to stabilizer fins i think was a cunarder on the canadian run.

 

[Dave Gittins]

The earliest stabiliser-equipped liner that I can find is Cunard's Media. She was given hers in 1953. This may have been the ship on the Canadian run that Jesse is thinking of.

I didn't express myself clearly. I meant to take 1912 as a period, not as when bilge keels were first tried.

Conte di Savoia was the name. (Count of Savoy).

 

[Noel F. Jones]

Bilge keels, running approximately one-third of the vessel's length amidships, date from at least the 1860s. Although a static device, they do not depend upon forward motion to dampen rolling.

Gyroscopic stabilisers were patented by Dr E.O.Schlick in 1903. Schlick stabilisers were experimentally installed in the British steamer "Lochiel" in 1906

Sperry inboard gyroscopic stabilizers were in service by 1917.

The Italian liner "Conte di Savoia" of 1931 was the first transatlantic liner to be fitted with Sperry gyrostabilisers. These were made by Vickers-Armstrongs Ltd at Barrow-in-Furness.

The P & O "Chusan" of 1949 was the first ocean liner to be fitted with Denny-Brown stabilisers.

Noel

 

[Martin Owen Cahill]

On the subject of stabilizers has anyone out there heard of the FLUME system. This involves a tank across the beam of the vessel just below the waterline which contains baffles to obstruct waterflow. The water in the tank rolls when the ship does but the baffles interrupt the period and the synchronicity is so interrupted that the water ends up at the high side of the roll thus damping in down by transferred tonnage.

One of our ships, the WAHINE had one and it was very effective. it's just a shame it wasn't being used on the morning she got into trouble in heavy weather. Maybe she would have been kept of the reef. (more about her elsewhere in the OTHER SHIPS section)

Martin

 

[Philip Bowler]

Hello people,

In no particular order.

The old BI (British India) passenger ship Uganda had that or a similar system. It was a complete pile of pants. Never worked (1982) and I saw some "big ship" Captains looking pretty green at times.

Stabilisers as known today were 1st invented to keep the "gun platform" of a battleship steady. The ship with stabilisers had the edge over the one that didn't. Sometime around the 1st world war I think but couldn't be sure.

Stabilisers don't necessarily get in the way of lifeboats during abandonment. They are usually sufficiently below the waterline to be out of the way. (see the end of my next paragraph)

Modern cruise ships are easier to keep stable than those of 20 - 30 years ago. Do not confuse stability with motion due to weather. They are designed with damage control stability in mind. It will take something very, very extreme to make them sink, and if they do, design features are in place to ensure that they sink in an upright condition.

They do not handle weather extremes as well as the older ships, hence the prudent Captain studies the weather continuously. Cruise ships are usually scheduled to be clear of usual/known hostile weather.

Regardng manoeuvring. 2-3 bow thrusters, 2-3 stern thrusters, twin high lift independent rudders, twin screw controllable pitch propellers (cpp)and you can move that large ship sideways in most weathers, spin it round on the spot (can't do that in a car!). The newer ones control all of that lot with one joy stick. It seems that the waste of life playing on the playstation is justified!