Author Topic: Stability of the HUGE cruiseships  (Read 5420 times)

Offline csaba

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Stability of the HUGE cruiseships
« on: May 17, 2016, 04:15:21 AM »
Gentlemen, could somebody please explain to me the stability technology of those new HUGE cruise ships? It has been many decades since I studied it and the technology must have changed. Relatively shallow draft compared to their height, very long ships etc. What is underwater that we can't see, inside and outside the hull? How are the high parts built compered to the low parts of the ship/ What about the many pools, how do they affect the stability?
Could somebody could answer this in a nutshell?
Many thanks...

Offline Bob Scott

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Re: Stability of the HUGE cruiseships
« Reply #1 on: May 17, 2016, 06:43:48 AM »
Centre of gravity kept low by engines and heavy machinery way down low. Stability aided by wide beam and lighter materials (eg aluminium) used extensively in the upper works. Weight of water in pools no significant problem and anyway pools will normally be emptied in exceptionally rough weather (to prevent sloshing).

Offline PHa

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Re: Stability of the HUGE cruiseships
« Reply #2 on: May 17, 2016, 11:21:22 AM »
For some different answers to your question, pls see as follows:

http://www.cruiselawnews.com/2012/03/articles/sinking/are-cruise-ships-dangerously-top-heavy/

Regards Peter

Offline Allan RO

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Re: Stability of the HUGE cruiseships
« Reply #3 on: May 17, 2016, 12:47:22 PM »
well I know which answers I believe....those from someone who has been involved in the industry for along time, not a media friendly blogger !   

Allan

Offline Bob Scott

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Re: Stability of the HUGE cruiseships
« Reply #4 on: May 17, 2016, 01:00:08 PM »
Peter:
That link you gave us contains the biggest load of ballcocks I've read in a long time. Mr Walker says he is a lawyer so I would have thought he would have sought his evidence from someone who knows at least something about naval architecture - not from a load of talking-through-their-posterior tweeters
« Last Edit: May 17, 2016, 01:12:18 PM by Bob Scott »

Offline Malim Sahib

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Re: Stability of the HUGE cruiseships
« Reply #5 on: May 17, 2016, 01:22:36 PM »
Aside from machinery and bunker fuel etc, modern cruise ships have a number of enormous fresh and grey/black water (aka sewage) tanks low down in the hull (as might be expected for the thousands they have onboard). These help to keep the centre of gravity low.
All the same, it is those tanks which present the usual stability issues found in cruise ships, principally with regard to longitudinal forces and stresses on the hull.
Another stability issue which plays a part are angles of heel caused by the wind. Due to their slab sided nature (many thousands of square metres) even moderate winds will exert forces which will heel a cruise ship over a number of degrees. Naturally this is not ideal for old ladies with dodgy hips and in those (many) ships where internal furniture and fittings are not routinely adequately secured.
These angles of heel are corrected regularly when underway, sometimes using dedicated heeling ballast tanks but also by juggling around the aforementioned fresh/grey/black water in the double bottoms.
« Last Edit: May 17, 2016, 01:24:24 PM by Malim Sahib »

Offline smithy166

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Re: Stability of the HUGE cruiseships
« Reply #6 on: May 17, 2016, 01:32:00 PM »
Cruise ships are just as stable as any other vessel of their size - And meet the minimum stability criteria set out in SOLAS/class regs.

Most of the machinery (bar AC stations, lifts and the likes) is usually contained within the first 3 decks above the keel, so it's mostly underwater.

The weight of the pools is only a minor issue in the grand scheme of things. That said, the FSM the pools create is often a bigger problem, which is why they're drained during "heavy" weather if possible - Or, at the very least, emptied into a holding tank much lower down.
Enough torque to restart a dead planet! OOW with an unlimited CoC looking for work. :)

Offline Captain Ted

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Re: Stability of the HUGE cruiseships
« Reply #7 on: May 17, 2016, 03:53:16 PM »
I would today worry much more on how to evacuate 1000,s of peoples in a real emergency during bad weather.

stability is really not the problem for such big vessels as it is surely calculated and controlled extensively pre and during construction and the ships builded with light materials in the upper decks and everything what is heavy is integrated in the lower decks.
What I personally noticed on container ships (2500 TEU)is that the listing easy went to 3-5 degrees
when the wind from the side is higher than 25 kn, special when MT,s are carried to 5-6 high stowed or more. 
I believe the wind factor was never really good incorperated into the stability issues, one can only hope that now,, 8-10 years later they are more advanced to do so.
NOW!!!,,,if we could get rid of the sailors,,how safe shipping would be !!!!!!!!

 

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