Ocean liner vs Cruise ship

[Mauretania1907]

May I join this discussion. I am certainly no engineer, and I am not a fan of the boxy-looking new cruise ships. It makes no sense to me to build a mega-cruise-ship at enormous expense and skimp on materials, thickness of plating, spacing of frames etc. However, I wonder if they have the same sea-keeping qualities as ships such as QE2 and other older ships.
6mm plating is about as thick as this IIIII (at least on my screen) and I bet Voyager's steel is much thicker. 28mm is more like this thick                         IIIIIIIIIIIIIIIIIIIIIIII
which makes sense for any ship, no matter how ugly she might be. As for sea-keeping qualities, all ships must pass a classification of some sort (and I realise there are other classification societies besides Lloyds).
therefore I agree with Magic Pipe that Maxtome-Graham"s text could be read to say that Voyager's steel was 6mm throughout, which for a ship her size would be tempting fate, and would violate any classification .

[Jem]

Enjoying this topic! As far as I'm concerned QM2 and QE2 are liners as they rarely reduce much speed in foul weather. A cruise ship reduces speed as she'll get damaged otherwise.!

[matdark]

I can hardly believe we're even discussing this...

[Matt]

Enjoying this topic! As far as I'm concerned QM2 and QE2 are liners as they rarely reduce much speed in foul weather. A cruise ship reduces speed as she'll get damaged otherwise.!

This is what i agree with. In the rough weather, cruise ships slow down significantly, whilst the 'liners' can power through it.

[Clydebuilt1971]

Good discussion here.

To me the main differences are

(1) Speed - the reserve required to maintain a timetable whatever the weather.
(2) Hull Form - entry is critical here ie a stem design capable of cutting through waves.
(3) Hull Form - Wave dispersion ie the ability to push the waves away rather than taking them over the bow.
(4) Hull Strength - The ability to endure heavy seas without damage
(5) Superstructure position - On cruise ships the superstructure tends to be closer to the bow to maximise space - this is fine until the ship buries herself into a big wave. QE2 & QM2 have their superstructures starting further back on the hull to allow the wave energy to be reduced before it reaches the superstructure (assuming it gets there in the 1st place!!)

With regards to the position of machinery within the hull it would appear that almost midships would be ideal although the tanker style machinery aft location seemed to suit ss Canberra just fine!!

Gav

[Rob Lightbody]

I've got a copy of 'Genesis of a Queen' from Chantiers d'Atlantique which includes various technical information... it goes into great detail, much of which i don't understand, about how QM2 was one of a kind.  she was built to withstand 40 years of being hammered by the Atlantic at speed.  No ship had been built to do this since QE2, they make this absolutely clear. 

QV is by all accounts a truly wonderful cruise ship, and her passengers thorooughly enjoy her, and they've managed to create a lovely on board ambience not dissimilar to QE2 BUT if they constantly drove her back and forth across the Atlantic she wouldn't last long, its not what she's designed for.

[Magic Pipe]

I really enjoy discussions like this.  But to be fair, there were some transatlantic liners of the past that had truly horrendous seakeeping ability such as the SS France of 1912 and the Imperator.  Back then, hull designs were simply not put through the scrutiny that they were in later years.  There are some cruise ships today that were put through a seakeeping analysis every bit as rigorous as the Queen Mary 2 went through.  Granted, not all cruise ships have outstanding seakeeping, but there are some that do.  And a cruise ship built today is designed for a fatigue life of 40 years, the same as the Queen Mary 2.  With the cost of steel being such a small component of the ship's total cost, it make sense to do this.

[Clydebuilt1971]

Hi Magic Pipe,

Apart from Car Ferries and Paddle Steamers ie small vessels the only large passenger vessel I've ever been on is QM2. I see a lot of cruise vessels when they call at my home port of Greenock. Can you say which cruise vessel design is better than others?

Ta!

Gav

[Rob Lightbody]

Cruise ships have >TUG< written at specific points on the side of them, to show where the Tugs may apply pressure without damaging them.

QE2 & QM2 have no such markings, the tugs can push anywhere they like, because the hull is strong enough everywhere.

[Rob Lightbody]

Got this from someone rather knowledgable, who works on QM2.

it is correct in saying that any ship classed for deep sea can cross the Atlantic. However, if you sent a cruise ship on the QM2's or QE2's schedule they would suffer structural damage and never be able to keep to the arrival times.... QM2's hull is built of thicker steel, the framing is thicker and closer together, the full form is specifically designed for bad weather and the supertructure is stonger, further back and better protected than that of a cruise ship.

[Magic Pipe]

Clydebuilt, among the best cruise ships when it comes to seakeeping would probably be NCL's Star/Jewel class ships. 

Rob, the purpose of having >TUG< or >NO TUG< on the side of the ship is to prevent the tug operator from pushing on the shell doors and tender platforms.  If you look at the QM2, her tender platforms have >NO TUG< written on them.  Some ships take this a step further by having saying >TUG<, >TUG AREA<, >TUG PUSH HERE< or the equivalent marked some distance away from the tender platform, the intended purpose being that the tug operator will not but his tug between the >NO TUG< marking and the >TUG<, but not all ships have this additional marking.  The QE2 does not have a need for these markings, as she does not have any tender platforms.

And on your second point, lets forget about passenger ships for the time being and look at a container ship that crosses the North Atlantic on a frequent schedule, 12 months a year, year after year.  Is that container ship built to a different standard than one that never goes into the Atlantic at all?  No, it's not.  It is expected that any ship, no matter where it operates, must be able to weather any storm it will come across.  The Atlantic by no means has a monopoly on bad weather.

[highlander0108]

And on your second point, lets forget about passenger ships for the time being and look at a container ship that crosses the North Atlantic on a frequent schedule, 12 months a year, year after year.  Is that container ship built to a different standard than one that never goes into the Atlantic at all?  No, it's not.  It is expected that any ship, no matter where it operates, must be able to weather any storm it will come across.  The Atlantic by no means has a monopoly on bad weather.

Don't container ships and other cargo ships like tankers have stress monitors and programs to monitor the hull that guide the operators in slowing the ship down in heavy seas so that the stresses are minimized and that the ship does not break up?  Don't they have to slow way down or risk major damage?  A true liner might slow for passenger comfort or have the speed to divert its course to avoid bad weather.  I swear I read somewhere that QM2 had one of these systems added and QV and the new QE are getting the stress monitoring system as well.  Perhaps these newer ships are jsut not overbuilt as QE2 was, which did not have the benefit of major structural analysis programs available now.

[skilly56]

OK,

The link below is to a 300 metre long container ship, suffering from a bad case of the 'Bends'! Keep watching until you see the companionway flexing.

Can anyone ever recall seeing a 'properly built' passenger liner doing this?

Cheers
Skilly

[Jem]

Cruise Ship VS Liner Enough Said

[Magic Pipe]

Some container ships have strain gauges affixed to their structure, and some do not.  Container ships tend to have very good seakeeping ability.  I imagine the Emma Maersk could teach the QE2 or QM2 a few things about weathering a storm.  And the ships that are most to immune to heavy seas without slowing down are large tankers and bulk carriers.  Their mass combined with their low speed to begin with allows them to plow through a storm without the need to reduce speed.  And all ships bend similar to that container ship in the video.  That's just a fact of life that there is no such thing as a completely rigid structure.  There are stories that the original Queen Mary would bend in rough seas like a dog wagging its tail.