Okay, now this is just getting silly!
hmr170...
Have you even read the requirements for damaged stability for a tanker?! There are very specific requirements they have to meet! And class specifications doesn't mean anything here, because they have to, at least, meet the IMO criteria and are usually set higher (since a ship can't enter 98% of territorial waters unless it meets IMO requirements making sea travel very hard).
As to the accidents mentioned: Erika broke up due to heavy corrosion in the tanks... Not ballasting. The exact same thing happened to the Prestige which was known to have several severe structural deficiencies prior to the final voyage and had not undergone proper inspection and vetting (read an accident investigation report)! It had a huge gaping hole caused by an external force (rough weather and high seas). Both were single hulled and both had servere structural damage. Ballast was only applied after the structural damage had occured and was done as a meassure of stabilizing the ships so they could be towed to calmer waters. Had the ships been in good condition (the Erika was thought to be, but actually wasn't), a flooded ballast tank wouldn't have been that big a deal (again, read the requirements for damaged stability). A flooded cargo tank however will have a HUGE influence on the stability and structural integrity of the ship due to the size of the tank and the higher density of water.
But we are not talking about a ship with serious structural damages here. We are talking about a double hulled ship which developed a leak that allowed water to fill a ballast tank in minutes not hours or days! If you have ever sailed on a ship with computerized control (ICS) you will know that it is very easy to detect such a leak since the system will give an alarm as soon as it detects a considerably different water level than the preset one!
I do not know what the cause of the leak was, but a leak of this size can, and did, occur causing the ship to veer off course, that is an indisputeable fact... It is pretty obvious that we are not talking about a corrosion related fracture here (it can however very well be stress related, since stress related fractures can be many things). If you don't believe that this can happen, well, that is your problem, I know and have seen it happen (never tried it myself fortunately, but I've seen ships where similar things have happened)... Again, if you really don't think that a flooding of a tank can't alter the course of a ship, you need to read up on your seamanship!
And still, I have yet to see an example where a tanker have broken up due to a flooded ballast tank! If that was all it takes, we would have broken up oil tankers lying all over the ocean floor! If a hull plating is compromised by a crack, it's strength is greatly reduced, and a direct hit by a wave could make it buckle giving direct and virtually unrestricted access to the tank behind it (I haven't eer seen a cracked hull plating myself, even after a close encounter with a tug boat in Jeddah, but I guess it does occur). I don't even need to have experienced a crack to know that, that is all physics...
Ohh... And as to the sheer force and bending moments... The notion that sheer forces and bending moment isn't that big a deal onboard container ships couldn't be more wrong! Just look at the MSC Napoli! I've sailed on ccontainer ships, and one of our biggest concerns during loading, is to reduce sheer force and bending moment to a minimum because of the weightdifferences of individual containers (stability is usually not an issue)! Because unlike an oil tanker, we can't just move some cargo from one tank to another to alter the moments. If you are ever onboard a M