Costa Concordia is almost a carbon copy of Titanic. Similar damage, between 4-6 compartments open to the sea, no hope of surviving. As with all "Two Compartment Damage Stability" ships, both vessels had the capacity for more adjacent compartments flooding, until the weight of the ship overcame the weight of displaced water, when Archimedes takes over. Costa started to sink on an even keel, and if she'd stayed in open water would have just about gone down the same way. However when a ship sinks, towards the end it's difficult to say what will happen, and most move away from upright somewhere along the line. As the two vessels were both built with transverse WT bulkheads, they would most likely emulate each other. However, if one side touches an underwater object then the ship's natural buoyancy in staying upright (heavy weather would also affect it) is compromised, the water cannot equalise and so rushes over to the unsupported side, and this is in fact what happened to Costa. A shame she didn't sink in deep water actually as it would probably have saved everyone's lives and a lot of money in salvage!In most I agree with you Scott, the only issue I'm having a problem wrapping my mind around is once Titanic began listing to port wouldn't she have kept that same list or more likely continued to list to port?
What would make her shift the list from port to starboard or vise versa? The only thing I can imagine causing it to shift is if the hull had a breach from the stress of the list. For example if she had an 8 degree list to port then the starboard hull might have had enough stress to partially buckle the hull.
If that had happened could that explain the two "explosions" heard by some of the survivors? It was said those two explosions were about 10 to 20 minutes apart. Possibly starboard hull buckling and then shortly after the port hull?
Back to Titanic and Britannic - the double side fitted in Britannic and retrofitted in Olympic didn't save the ship, and I reckon Wilding didn't think it would either. Naval architects don't like outboard WT compartments, and both Lusitania and Britannic - possibly - showed he was right. Some later ships did have them, but not many, and the likes of Canberra and the current cruise ships don't have them either.
So what caused Britannic to list? Undoubtedly because she was holed on the starboard side, but even though the inner skin was called "double sided" it was in fact very narrow, only around 3' if I remember rightly without checking it in the plethora of stuff I have on the ship. This wouldn't have caused a capsize, only a list, and from the "sinking in real time" it seems that was the case - she went down in calm water with a slight list. To me, the speed that she went suggests that the WT doors throughout the ship were open, and that the ones up forward into BR6 definitely were because one of them is shown open in the underwater filming (just past an abandoned wheelbarrow). Britannic did have her bulkheads going up to the weather deck, so the open portholes would have hastened the end, but as we don't know how many were open, it's not really quantifiable. The closed decks, even though not watertight, would have restricted this water from down-flooding in to the bottom of the ship anyway, and I rather think it would have just risen with the waterline - the ship was lost anyway.
Back to Lusitania which went even faster, some deja vu from the report into the sinking by modern computer methods from RINA and H&W which I attended and which Sam references in his flooding article, there is a section where Peskett of Cunard and Wilding were discussing the subdivision of M&L v the Olympic class. Peskett was reticent on this as he was more or less subservient to Admiralty and had to mind his P's and Q's, but it was generally agreed that with coal firing, it was impossible to ensure the closing of the longitudinal bunker doors in the Cunarders, and that flooding would occur to such an extent - plus possible capsize - that M&L would have foundered in the same way as Titanic did with similar damage - as Lusitania tragically did a few years later. With oil firing this would not have been the case, and if L had managed to shut all her doors, would maybe have survived or at least lasted longer and with the capability possibly of correcting the list by counter-flooding. Interesting food for thought, but of course as in all these cases, pure conjecture!
Being a marine engineer of some 50 years working life, having sailed on all types of ship for 18 years and done a lot of naval architecture in my time, I find it to be a good thing to revisit in retirement to keep my mind awake and think things like this through...
If you haven't read it, the Costa report is quite good, though the translation from Italian is a bit awry at times. If anyone wants a link or attachment I can supply one. It's probably too big for this portal though.