Costa Concordia, 80 deg list, really scary !!

Discussion in 'Stability' started by smartbight, Jan 15, 2012.

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  1. Starbuck1
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    Starbuck1 Junior Member

    A ship close to land is not uncommon. These flybys are not uncommon. This one was badly done by the captain and bridge crew. At 15 knots a ship advances 1500 feet/500 meters per minute. The basic error was holding course toward the island 30-60 seconds too long in the dark and not catching the error until too late. All the rest is just looking at the results of a simple error in handling a big ship. Plenty of time now for regrets by all involved. For this forum, lets keep looking at how the ship lost stability and died after massive accidental damage.
     
  2. smartbight
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    smartbight Naval Architect

    Latest revision Rev. 3

    Revised damage from 4 to 5 compartments.
    Moved propulsion motors.

    With help from the forum we will get it right.
     

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  3. CliffordK
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    CliffordK Junior Member

    Ok,
    Sorry for heading off the stability topic earlier. I now see the 3 different Costa topics here, each related, but each with a slightly different purpose

    Anyway, I found it interesting to see port side damage, and starboard sinking.

    The ship apparently had poor transverse compartmentalization, so you could think of it as a big sloppy tank.

    The advantage of no transverse compartmentalization is that a hole in the Port side should cause the ship to sink vertically, rather than severely listing to the Port.

    However, a much greater area of the ship is exposed to sea water, and thus more ingress of sea water (including flooding of all the primary generators, and perhaps also flooding both primary propulsion motors), as well as more weight of water entering the ship. As a side, if one distributed the generators along the keel, they could be better protected, and one could still consolidate the exhaust to a central location if desired.

    Once flooded across the 35m ship's width, it becomes much more difficult to compensate for the list.

    Consider a hole on the Port side, and a Port side list.

    The response would be to transfer ballast from the port to starboard side. And, that might be ok as long as the ship is not brought back to vertical. Once at vertical, with the sloppy tank covering the ballast tanks, and ballast transfer, it would have to continue to shift towards the starboard side, and you end up with the Cougar Ace. In fact, it may be impossible to manage the ship's stability with water ballast transfers and the "sloppy tank" flooding. At least the ballast tanks that are covered with water would be ineffective. The ballast tanks that are not covered with water would still be of some use unless they are later flooded.


    I did a little study of ballast tanks.

    [​IMG]

    If the water level covers the ballast tanks, and the water and ballast are of equal density, then the tanks become ineffective as the area of maximum density would be independent of the ballast tanks.

    If, on the other hand, one used steel or lead ballast, the center of gravity is maintained low and in the center, and the ship remains upright.

    There are reasons to have dynamic water ballast tanks on a cargo ship that has severe weight fluctuations. But, assuming the cruise ship's weight remains fairly constant, then the majority of the ballast should be a higher density static ballast (steel, lead, thick steel armor plating on bottom, rocks, whatever). One could build a mechanism to move lead ballast if desired, but perhaps provide 90% of the ballast with lead & steel, and the remaining 10% being movable water tanks.

    It may in fact be true that the cruise ships are reasonably stable with heavy ballast down low, and a towering light superstructure, as long as their water ballast tanks remain uncovered. Once the tanks are covered, they loose all vertical stability.
     

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  4. Heiwa
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    Heiwa Naval architect

    Before any ship sinks it must lose buoyancy by up-flooding of watertight hull compartments, progressive flooding of watertight hull compartments and/or down-flooding of watertight hull compartments until the available buoyancy is less than the weight of the ship. The stability of the vessel may change during the flooding of watertight hull compartments.

    An example by an Accident Investigation Commission, AIC, is given at http://heiwaco.tripod.com/impossiblesinking.htm where also the statements of the AIC are analyzed.

    Hopefully the Costa Concordia AIC will learn from above. :p:rolleyes::p
     
  5. Starbuck1
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    Starbuck1 Junior Member

    Ballast?

    Clifford,

    Check the photos in some of the other and earlier parts of these discussions. The cross section of the ship is very much a box, with a little rounding at the corners, not round bottomed.

    I doubt if these ships use much ballast other than some water for minor trim purposes and to compensate for the reduction in fuel and stores weight as they are used up. Certainly not expensive stuff like steel or lead. Hauling non-productive weight like lead or steel around is fuelishly expensive.

    The designers concentrate all of the heavy items in the ship in the bottom 25-30 feet: engines, fuel tanks, waste water tanks, fresh water tanks, stores, etc., to accomplish the desired concentration of weight down low and along with large stabilizing fins, manage the roll characteristics for the comfort of the passengers.

    Thankfully, the double bottom tanks are no longer used for fuel storage, which is why CC didn't create an immediate oil spill. They would have been empty or filled with sea water for ballast.
     
  6. CliffordK
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    CliffordK Junior Member

    Square or round bottom.
    The point is that you loose stability if you have no crosswise compartmentalization. You can simulate it easily enough with a flat bottom bread pan in your sink filled with a couple inches of water.

    I'm seeing reports of the Costa Concordia having 8000 to 9100 tons of water ballast capacity, plus 3500 tons of fuel and oil.

    It doesn't indicate how much of the tanks are kept full. Obviously fuel is consumed during the voyage. But, the weight of ballast and fuel could be close to 10% of the weight of the ship.

    A 9000 cubic meter tank would be 30 meters wide, 300 meters long, and 1 meter deep.

    The ballast is what keeps essentially a floating skyscraper upright, and gives it better than expected stability under "normal" conditions.

    While it is nice to have control of liquid ballast, i believe the stability of a flooded ship would be improved by using a dense ballast, or thicker lower hull plating.

    While relatively low density, even the concrete used in the WWII Liberty ships might be better than water ballast.

    As far as decks, it should have been possible to seal off the lower decks. Deck 4 (lifeboat deck) being the first deck that potentially might have been open to top-down flooding. However, somehow decks that were not damaged from the impact, or resting on the seabed became flooded.

    Perhaps had the Capatain treated the impact as a critical emergency, then the lower decks would have been evacuated and all watertight doors would have been closed. That is assuming the ship was designed to keep successive decks from flooding.
     
  7. IEWinkle
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    IEWinkle Retired Naval Architect

    Revision of Post 58 Simulating Costa Concordia – a Scenario for Progressive flooding

    Analysis of the profile photograph and cabin arrangements (see PDF file) – particularly of Deck 1 (Olanda) suggests that the structure of the ship is made up of a series of equal bays of length 2.9 m (one overall cabin spacing) which corresponds to the spacing between the large transverse web frames supporting the longitudinal frames running throughout the lower structure, implying a transverse frame spacing of 725 mm through the double bottom (in the zone of damage). Multiples of these bays (4, 5 & 6) allow the position of pillars between lifeboats to be established giving the possibility to reference the damage location fairly accurately in terms of web and frame locations. This allows an estimate of the location of the major damage (of the soft side shell) on the port side as running from 37.7m forward of the AP to 74.4m forward of the AP. The AP appears to be 10 m forward of the transom at the Load Waterline, in line with the twin rudder stocks. The damage to the bilge area only appears to run forward to about 92.8 m forward of the AP. Careful analysis of the arrangement in 'profileCCONCORDIA9 Rev3.pdf' together with the photos of the early stage fabrication of the vessel, suggest that the deck heights can be deduced as:
    Deck 1 – 14.18 m (given as vessel’s depth)
    Deck 0 – 11.28 m + 4 longitudinal spaces of 725 mm = 2.9 m
    Deck A – 8.38 m + 4 longitudinal spaces of 725 mm = 2.9 m
    Deck B – 5.48 m + 4 longitudinal spaces of 725 mm = 2.9 m
    Tank Top - 2.03 m + 6 longitudinal spaces of 575 mm = 3.45 m
    The significant change here from my earlier scenario (post 58 – Simulating Costa Concordia) is the height of Deck A which modifies the analysis below.

    Overlaying this information on 'profileCCONCORDIA9 Rev3.pdf' identifies at least four (from a bulkhead around 31.85 m forward of AP to one at 89.125 m forward) and possibly five compartments along the length (up to 101.45 m forward) that will have been compromised. The ‘definitely flooded’ compartments would include Compartments 4 to 7, the two main diesel generator rooms and the motor room aft - the after generator and motor rooms subject to immediate inundation, with the forward generator room flooding more slowly (hence the blackout after 10 mins). Overall damage length therefore varies from 57.275 m (min) to 69.6 m and will include a substantial length of double bottom port wing tanks of some 14 sq m cross-section which were probably empty in this condition (no obvious oil leakage and no significant ballast). If we assume about 60 m of these tanks were flooded together with a rock of some 70 tonne (immersed weight) there would be a port listing moment of some 880 tonne at about 14.25 m from the centreline which would displace the vessel’s centroid by about 0.244 m. This would produce an initial list of about 7 degrees to port if the GM is assumed as 2 m.

    Analysis of the night photo as the vessel approaches the shore heeling to starboard shows a trim by the stern of 4.95 m between perpendiculars giving draft aft of 12.05 m and draft forward of 7.10 m (see post 57 Simulating Costa Concordia). Heel would appear to be about 13.2 degrees to starboard putting the bulkhead deck about 3 m underwater at its starboard after corner. The estimated inflow of water (lost buoyancy or added weight) for this condition based on an estimated WPA of 8339 sq m with an LCF 15.89 m aft of amidships would be about 14470 to 15325 tonne depending on the initial draft which probably ranges from the maximum load draft of 8.2 m down to 8.1 m (estimated from photos of the bow draft marks on 2 separate photos). If we deduct the 880 tonne loss of buoyancy in the double bottom to port, discussed above, that leaves 13590 to 14445 tonne to fill the compartments above the double bottom at an assumed permeability of 85%.

    Noting the presence of B deck at 8.38 m above base and assuming all water was contained by this, then the flooded length would be from 68.86 to 73.20 m. If this deck is assumed to only run for 25% of the breadth each side outboard of a machinery casing running from 56.5 m to 78.25 m forward of the AP which is flooded to an average depth of 8.687 m (mean local draft 10.687 m), the casing would contain about 776 tonne of floodwater and the flooded length would then be from 64.94 to 69.27 m. The latter figure almost exactly matches the assumed maximum 5 compartment length and provides the basis for a stable near upright condition which could be maintained as long as there is no progressive flooding into any of the wing areas of Decks A or 0. To provide the necessary extra floodwater to cause the starboard list it might be assumed that the flooding was contained by B deck in Compartment 8 as all damage in this area is only to the bilge corner. This would allow up to 1100 tonne of ‘spare’ flood water to permeate the starboard spaces to counteract the lost double bottom buoyancy and rock to port to give the condition seen in the night-time photo.

    Exactly how this happened has yet to be determined, but in evacuating the machinery spaces, one or more doors giving access to the starboard wing spaces may have been left open onto A deck (possibly around the engine control room which seems to be at the aft end of compartment 6) which allowed progressive flooding to establish itself in the 30 minutes or so before the vessel grounded, resulting eventually in the 13.2 degree list to starboard deduced from the photo. Continued acceleration of this progressive flooding would have resulted in the vessel’s increasing list to starboard experienced as the starboard lifeboats were launched which eventually immersed the passenger decks and led to complete capsize onto the rocky shelf. If this progressive flooding had been prevented the vessel could have probably survived, near upright, close to the final centreline draft deduced above despite her 5 compartment damage case – although this would not have been considered a SOLAS 90 survival case in the normal course of events.
     
  8. CliffordK
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    CliffordK Junior Member

    As far as watertight doors, perhaps I'm not clear of the distinctions, but I do see several doors on the ship with multiple heavy latches.

    Here are a few screen shots from the Channel 4 special:
    Terror at Sea, the Sinking of the Concordia.

    I can't say exactly where things were. I'm assuming from the Crew Quarters.

    On this door, "No Entry" is marked in pen. Howver, the door is clearly open during normal operations. Heavy latches. Should there be any rubber seals?

    [​IMG]

    This one was apparently taken at the time of the impact. Door swings closed, apparently swinging freely.

    [​IMG]

    Timing is unclear. It was shown in the film after 10:42, over an hour after the impact, and after the "General Emergency" is called. Rotating emergency red/white lights are clearly visible when this next photo was taken. Two successive watertight doors are shown fully open.

    [​IMG]

    Ahhh, that was the "No Entry" door, still open.
    [​IMG]

    Perhaps there are different types of watertight, and heavy doors and compartmentalization of the ship. However, the film doesn't show an effort to shut the doors and enforce compartmentalization.

    I suppose ultimately the reality would be seen by the divers. Of course, they would be opening as many compartments as possible now, but they should have an idea of what is open and what is closed.
     

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  9. IEWinkle
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    IEWinkle Retired Naval Architect

    Thanks for the screen shots. They bear out my contention of general crew panic and lack of discipline over WT doors. They are all typical of what I would expect in 0 and A deck crew areas and would appear to cover the corridors running from the forward to the after stair & lift wells. Only fire doors would be found in the passenger spaces from 1 Deck upwards.

    I hadn't realised the Channel 4 Doc had reached the States yet - I'm waiting to see what National Geographic and Discovery made of it - no sign of these in the UK yet!
     
  10. Heiwa
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    Heiwa Naval architect

    I doubt very much the 'screen shots' are from Costa Concordia. Ships are not built with hinged w/t doors as shown in the hull or in the superstructure. Just study the SOLAS rules! :)
    So I wonder ... where are the doors from? :rolleyes:
     
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  11. IEWinkle
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    IEWinkle Retired Naval Architect

    Addendum to Post 307 above – a Scenario for Progressive flooding

    The sketch attempts to show the waterline W3L3 (in red) relating to the 13.2 degree heel as seen in the photo discussed as it intersects the Engine Casing lying between the two main generator rooms. At this point substantial flooding has occurred into the Starboard side of Decks A and possibly 0 thorough a point somewhere just above Deck A as shown.

    To make some sense of the sequence of flooding I have proposed 2 intermediate waterlines W1L1 and W2L2, the first of which represents the condition after initial stabilisation of flooding at which overtopping of an opening to starboard probably started. In this condition the vessel would still have a small list to port to support the extra weight of flooded double bottom + rock on the port side. As the flooding continued the list would slowly move to starboard (W2L2) as the extra floodwater counterbalanced the excentric port load and from here progressive flooding would begin to accelerate. Much beyond W3L3 and the loss of the stabilising influence of the port side of deck A would lead to significantly reduced stability - again accelerating the final capsize.

    In the initial phase of flooding it is probable that for a minute or so the floodwater would pile up to port as suggested by the 'Intermediate Flooding in Engine Rooms?' line as it attempted to rush across the ship past the fixed plant and equipment. During this initial phase it is likely that the ship rolled to about 10 degrees to port (as a continuation of the roll as it picked up the rock) and this would have slowly corrected itself as the water flooded up to waterline W1L1. During this period the loss of waterplane inertia would have been significant enough to knock about 4.25 m off the BMt and the ship would have been technically unstable (in a state of loll) which would have quickly been recovered as A deck hit the water. Once A Deck to port left the water, after W3L3, that instability would have been re-established through the massive free surface running across the machinery space further accelerating the capsize.
     

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  12. Heiwa
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    Heiwa Naval architect

    It is quite simple. A vessel will survive multiple compartments up-flooding as long as the bulkhead deck is above water, buoyancy/stability remains positive and no down-flooding occurs.
    If, due to unforeseen listing/heeling bulkhead deck comes below water and down-flooding occurs ... vessel slowly heels more and sinks.
    On the other hand ... if progressive flooding takes place and GZ suddenly becomes <0, then vessel capsizes and heels 180° ... unless stopped by, e.g. a rocky shore.
     
  13. jehardiman
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    jehardiman Senior Member

    Yep, that is a manualy operated Type 1 (weathertight) door. They are not permitted for flood control below the bulkhead deck, so any structure that door is attached to is within the flooding boundary. Below the bulkhead deck the only flood control doors permitted are sliding operated by a manual gear (Type 2), or sliding operated by manual and remote gear (Type 3). On a passanger ship, crew passageway (i.e. below the bulkhead deck) WT doors are permitted to be "Normally open" with remote closure, all others are to be "Normally shut" and required to be logged open by permission from the OOD.

    As for the screen shots, why would the writing be in english? No Italian flag vessel I've been on had placards in english...it was even "Vietato Fumare" and you had to know what it meant without asking the crewman smoking under the sign.
     
  14. Starbuck1
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    Starbuck1 Junior Member

    I think you are referring to longitudinal bulkheads to create compartments across the width of the ship. They are very hazardous if not done well because with damage on one side they can produce severe instability and a rapid capsize of the ship or at a minimum, overtopping of bulkheads at the edges. A full width compartment promotes even settling. Smaller wingtanks are very useful in containing damage to the sides, especially around the engine rooms. "Double hull" ships rather than just double bottoms. Costa Concordia didn't have these while many other ships do. One of these comments by others has two photos that compare the CC bottom section during construction with another ship's that is much better built, with such wing tanks.
     

  15. Starbuck1
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    Starbuck1 Junior Member

    Crew training

    In addition to the obvious need for better passenger and crew abandon ship training, the notes above make the need for at a minimum basic damage control training for all crew really obvious. Evacuate the people and close the flipping WT doors!

    Thanks IEWinkle, Heiwa, Smartbight and Clifford for the great notes, calculations, drawings and pictures!
     
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