cruise ships

[Stan Carter]

today, while reading the daily mail, there was a photo of the "anthem of the sea's", owned by royal Caribbean line. there' a lot of super structure above the deck level which got me thinking, how stable are these ships, they look top heavy. a question for our senior navigation members, would their stability be in question in a bad north atlantic storm, or for that matter in any storm of gale force or above, in any of the notable oceans of the world. as the other half said to intimidating. regards, stan.

[Doc Vernon]

The design of cruise ships has changed dramatically during the past decades. One of the biggest changes has been moving the passenger cabins from inside the hull to the superstructure and adding individual balconies both due to customer demand and because, from a business standpoint, the cruise line can charge passengers much more than for inside staterooms. This has considerably increased the overall height of the ships, making them more susceptible to side wind and waves. As a result, there have been concerns about the stability of modern passenger ships especially in heavy weather. Because there is much more ship above the surface than beneath it, modern cruise ships may appear top-heavy to some.[

Despite the large superstructure, the center of mass of modern cruise ships is relatively low. This is due to large open spaces and the extensive use of aluminium, high-strength steel and other lightweight materials in the upper parts, and the fact that the heaviest components — engines, propellers, fuel tanks and such — are located in the lower parts of the ship. Thus, even though modern cruise ships may appear top-heavy, proper weight distribution ensures they are not. Furthermore, large cruise ships also tend to be very wide, which considerably increases their initial stability by increasing the metacentric height.

Although most passenger ships utilize stabilizers to reduce rolling in heavy weather, they are only used for crew and passenger comfort and do not contribute to the overall intact stability of the vessel. The ships must fulfill all stability requirements even with the stabilizer fins retracted

Cheers

[Doc Vernon]

This is not a passenger Ship but it is a pretty rough ride !
Cheers

https://www.youtube.com/watch?v=fX2Augg8Zk8

And here is the QE2 in a bit of rough weather!

https://www.youtube.com/watch?v=XS-KZXiV8DQ

[Peter F Chard]

As Vernon points out, the modern cruise ships are very wide, the breadth allows the draught to be kept low which allows the ship to enter quite shallow places with ease. We did a cruise on the "Diamond Princess " earlier this year, she drew 8.5m only. The Load Line was about another metre above the waterline. Regards Peter in NZ.

[happy daze john in oz]

Though many cruise ships are very large they resemble a shuttlecock, weight at the base and open in the middle. Some have been designed for use only in certain waters, though the smaller ones, up to 95,000 tons can usually manage all waters. Most have only about 25 foot below the waterline whilst the part above water can be as much as 140 feet.

[Captain Kong]

The biggesr problem is the wind surface area.
A ship over 1,000 feet plus, in length, and the height above the sea, around 150 plus, That is One BIG Sail.

Entering or leaving a port with a narrow channel the ship with the wind on the beam will set down quite fast onto the reef or bank. This happened to a famous liner in 2006.
In a narrow channel wind on the starboard beam, setting down , alter the ships head to starboard for example to try to keep away from the reef the stern will swing to port and hit the reef.
With a 1,200 foot long ship, the turning point amidships, that is 600 feet of ship down aft swinging towards the port side of the channel. Crunch!!!
.
Also large cruise ships are designed for Blue Water. Not so long ago a P&O cruise ship was crossing the Atlantic in a Storm of great proportions. Cabin windows were smashed and cabins flooded up to the deck head and one couple almost went through the windows as the water poured out.
Most cruise ships follow the sun. in winter cruise the West Indies and then cross over to the Med in summertime and then go back to the Indies in winter after the Hurricane season.
Cheers
Brian.

[Ivan Cloherty]

As Kong points out most of these very large Cruising Vessels are designed basically for blue water trade and rarely see the North Atlantic or North Pacific and can be very uncomfortable in what we seamen would consider moderate weather conditions, which is why there are numerous cheap offers on voyages from the UK to the West Indies in November and December when these vessels are being switched from their Medi routes to Island routes. Whilst I am sure that Naval Architects have taken every eventuality into their design both passenger and stability wise 'on paper' or by 'mathematical modelling' we seamen know that very few Naval Architects have any actual sea experience, and many of us have uttered the words 'I wish the barsteward who designed this bloody ship could be on her now he would revise its seakeeping qualities'. Naval architects always stated that rogue waves were a figment of a seaman's imagination and their mathematical modelling had shown that these waves could not possibly exist and so never took them into account when calculating the hull form and stability criteria when designing the finished product; the advent of satellites have of course proved them wrong in their assumptions with a study sometime ago showing that at least 100 rogue waves were active in any one day around the globe. I personally feel that even today, judging by the number of mishaps happening to cruise ships, that the disregard for the rogue wave element still prevails in the design criteria, to take it into account would mean heavier scantlings both in hull form for'd and forward accommodation, this would entail greater cost and make the revenue earning part of the ship less profitable as perhaps up to twenty cabins (or more) would have to be sacrificed so that correct stability could be maintained within the displacement criteria. Even the 'Queens' which are designed as 'Liners' and not 'Cruise' ships are susceptible to the effects of rogue waves and they are built with scantlings for the North Atlantic and North Pacific trades and with a hull form that allows them to maintain schedules, where they do not have the luxury of cutting out a port if falling behind in schedule.

[Captain Kong]

There is only one ship specially designed for the North Atlantic winter and that is QM2, I have sailed on her a few times including the Maiden Voyage Trans At, and around Cape Horn etc.and she is magnificent. the Architect was on her as well. a Mr Paine. The other Queens that I have sailed on are Blue Water ships.
The old QE2 was also built and designed for the Winter North Atlantic, In 1995, think on a vioyage to New York in October, Hurricane season, She hit the 100 foot wave at around 2 am,. Captain RW Warwick described it as hitting the white cliffs of Dover.
He went around to have an inspection after to see if there was any damage and people were still dancing in the Yacht Club
Most passengers never knew until they got a Certificate under their doors saying they had survived the 100 foot wave.
The only damage was to the fore deck which was crushed down by around two feet into the mooring deck below by the many thousands of tons of water crashing on it. I joined her two days later in New York and saw it,
Another ship would not have survived.
Cheers
Brian

[Keith Tindell]

Another huge cruise ship entered Southampton water yesterday, maiden voyage, another left a couple of weeks ago maiden voyage, they cant produce them fast enough certainly a growing industry. Where these things are so high above the waterline, they have to be built of aluminium or light materials sooner or later there has to be a serious fire, and you only have to look at what happened to HMS Sheffield down in the Falklands, aluminium on fire producing its own oxygen, goes like the clappers, but we will see, KT

[Graham Payne]

There is only one ship specially designed for the North Atlantic --100 foot wave.
.
Cheers
Brian

Hi captain kong
Mr Graham Payne the Architect of the QM2 lives just a few hundred yards from me in Marvels Lane London SE12. also has the same name and spelling as myself ( My only claim to fame ) oh dear how sad never mind.