As an aside, if crack initiation did begin in the double hull, the strength deck is the corresponding member and might have actually held long enough to pull the stern into a more 'dramatic' trim condition as the entire bow was sinking. The geometry of that actually works out neatly. I've read the arguments for the crack starting in the keel, though, and I have to say I remain conflicted -- you can't separate any part of the hull structural girder, it was functioning as designed as a girder, until the bitter end the rest of the hull including the strength decks should have been distributing load and working as a system to resist much greater strength. At some point, the materials failed... Almost certainly at an identifiable weakness. Materials fabrication was not good enough to prevent variations in the period, something was weaker than the rest of the hull (this is why factors of safety were so high then, to guarantee you had a reasonable margin for the uncertainty of the means of production).