Cruise Ship designs

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Sailfree

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One other feature that may come out of this accident is how vunerable cruise ships are to water ingress.

With their sole reliance on electrical generation for both pumps and propulsion there may be a case for a back up generator either at a higher level or in a inner water tight compartment.

I would not speculate as to what difference it would have made in this case but the inabilty to steer, propel or pump the ship must be a further problem after any incident.

My understanding is that diesel engines work submerged providing the exhaust and air inlet are above water and uncontaminated fuel but the gas turbine generators (QM2) and the diesel generators in the Concordia I believe are all vunerable in the event of water ingress.

Happy for others more knowledgable to correct me or pass an opinion.
 
As I understand the sudden power loss was due to the high power cables shorting in water and the breakers activating, in which case the engine running would not make a difference.
In fact power was restored, but eventually the circuits gave up again for the same reason.

What i found shocking is:

1) the proportion between wet hull and the height and number of decks above water.
2) the absolutely flat bottom, no wonder why it drifted sideways forever during the emergency turn.
 
Not many vessels would be able to stay afloat with a rip down the side the size of the recent sinking, pump or no pump. My guess is that if it hadn't tipped over that more people would have been able to get off safely.
I do hope that any new ship isn't built in that fashion, I wonder what can be done about existing vessels ?
 
there must be loads of qualified naval architects, near Canary Wharf as a wild example, who must be asking similar questions. Except that the commercial crowd management and control people will always have the final word: they are after all, the customer, and the customer is always right...
 
haydude said:
As I understand the sudden power loss was due to the high power cables shorting in water and the breakers activating, in which case the engine running would not make a difference.
In fact power was restored, but eventually the circuits gave up again for the same reason.

What i found shocking is:

1) the proportion between wet hull and the height and number of decks above water.
2) the absolutely flat bottom, no wonder why it drifted sideways forever during the emergency turn.
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Those proprtions and a predominatly flat bottom and sharpish chinesare inevitable features in a large ship, where COG is above its COB. It could admittedly have a shallow fin keel (like a rowing boat has), but little more without compromising their draft. the captain surely knew that aspect of her handling, but never expected to have to U turn like that with no tugs to help.

Only in yachts with deep keels is COG below COB.
 
sarabande said:
if COG is above COB isn't there a de-coupling effect at any angle of heel ?
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No.
Read the recent thread on "big ship stability".http://www.ybw.com/forums/showthread.php?t=300573
It explains how these things stay upright normally, which is quite contrary to the way yachts stay upright.

As a ship heels , its COG moves laterally, but the COB also moves even further, as the rectangular shape of the displaced water becomes more triangular , whose CofB is substantially shifted outside the COfG

The upthrust from the CofB then pushes the ship back towards its upright position.
 
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Sailfree said:
Thats a reason to do nothing!

Surely there are shorcomings in this need for electical power that any water ingress leaves it powerless.

Imagine a hole half that size!
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I'm sure ship engineers are not idiots. Ships are largely safe nowadays if you keep their hulls intact.

The stability of the ship is improved by keeping the heaviest bits down low, so that's where they are, so they can be compromised if flooded in extremis. They could be put higher up, but then make it less stable for most of its operational life. Canberra had steel lower decks and Aluminium upper decks to keep the CofG low.

A compromise has to be struck, like a double skinned hull to protect the mechanics, but how far apart should the skins be to prevent an inner rupture by a 50 ton rock at 15kts?
 
chewi said:
A compromise has to be struck, like a double skinned hull to protect the mechanics, but how far apart should the skins be to prevent an inner rupture by a 50 ton rock at 15kts?
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I suggest that one internal back up generator room with pumps should be in a waterproof enclosure vented only at upper deck level would be better than complete failure of everything immediately there is a hull breech and a flood.

I appreciate there is a cost but there was when they introduced double skinned oil tankers.
 
Sailfree said:
I suggest that one internal back up generator room with pumps should be in a waterproof enclosure vented only at upper deck level would be better than complete failure of everything immediately there is a hull breech and a flood.

I appreciate there is a cost but there was when they introduced double skinned oil tankers.
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Just having a back up genset doesn't solve the problem if your power distribution system is damaged. Equally back up pump capacity is all well and good but it has to be connected to a working ballast control network to have any real value. Real time damage control in cases of flooding needs both pumping out and flooding in under control to manage stability and list.

Double skinning of tankers took a lot of time to get accepted. Before jumping down any new design path I would rather see the report on just what happened after she was holed before looking for a band wagon to jump on.
 
Sailfree said:
With their sole reliance on electrical generation for both pumps and propulsion there may be a case for a back up generator either at a higher level or in a inner water tight compartment.
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And do you imagine you're the first one to think of this?

Standby generators well away from the engine room are a completely standard part of ship design. I'm no expert on the subject, but even on little Stavros and William the emergency generator room is under the focsle head, so the opposite end of the ship from the engine room and as high as it can get (above deck level) and still be under cover. There is also an emergency battery box on the open bridge (highest place on board without putting it up the mast) that powers the radios and essential nav kit. The backup telephone system (connecting bridge, engine room, and steering flat for in-extremis operation of the ship) is self-powered, using a hand crank to ring and the energy in the sound waves to transmit voice, hence needing no external electrics at all.

Concordia will have had a far more sophisticated system of backup power.

Pete
 
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Sailfree said:
I suggest that one internal back up generator room with pumps should be in a waterproof enclosure vented only at upper deck level would be better than complete failure of everything immediately there is a hull breech and a flood.

I appreciate there is a cost but there was when they introduced double skinned oil tankers.
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Er, yes,its such a good idea that we have in fact had emergency generator(s) and emergency fire pump(s) - on all ships for a long time now!

Which is why there wasnt a complete failure of everything immediately!

And if the emergency generator(s) fail the emergency battery takes over for navigation comms and escape lighting
 
Minn said:
Er, yes,its such a good idea that we have in fact had emergency generator(s) and emergency fire pump(s) - on all ships for a long time now!

Which is why there wasnt a complete failure of everything immediately!

And if the emergency generator(s) fail the emergency battery takes over for navigation comms and escape lighting
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Sorry I was confused by reports that after the impact it lost the ability to steer , propel or pump obviously media hype.
 
I am a very out of date Naval Architect, but I am pretty sure than any ship is at risk of sinking. No matter how many generators, pumps, engines, compartments, it will sink if you try hard enough. I suspect that modern maritime accidents mirror modern aviation incidents: it is the organic matter in the front that is the cause of most of them. In aviation we put as much emphasis on the human factors as we do the mechanical ones. I don't think it is the design of the ships that needs addressing, so much as the behaviour of the people operating them (and I am not pointing a finger at any single person involved with the Concordia - this is a more of a cultural thing).
 
I've no doubt whatsoever that the Concordia was fully compliant with all the relevant build standards, which would have included provision for emergency power and pumping, but these standards are intended to mitigate against theoretical and credible risks which did not include the damage incurred by what appears to be the sheer imbecilic stupidity of the Captain and his complete disregard of the safety of thousands of passengers whose safety was his responsibilty.
Of course she would have been built and operated as cost-effectively (edit: cheaply :end edit) as possible...:(
 
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boomerangben said:
I am a very out of date Naval Architect, but I am pretty sure than any ship is at risk of sinking. No matter how many generators, pumps, engines, compartments, it will sink if you try hard enough. I suspect that modern maritime accidents mirror modern aviation incidents: it is the organic matter in the front that is the cause of most of them. In aviation we put as much emphasis on the human factors as we do the mechanical ones. I don't think it is the design of the ships that needs addressing, so much as the behaviour of the people operating them (and I am not pointing a finger at any single person involved with the Concordia - this is a more of a cultural thing).
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We are rapidly following suit in shipping. (Next meeting of the MCA Human Element Advisory Group January 30th at Warsash...I wonder what one of the topics may be...)
 
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