Last night, I went to the Science Museum in St. Paul (currently hosting the Titanic exhibit) and listened to ex-U of M professor Dr. Bill Gerberich's lecture on the causes of the Titanic's sinking. His conclusions: the steel plates used in the Titanic were OK and not especially notch sensitive. He talked about the "silly putty" effect of the steel -- that it stretches and deforms under moderate stress and pressure, which is the kind that the hull plates took on during the Titanic's encounter with the iceberg. Survivors, he noted, said that the ship shuddered and rumbled as it slid along the berg and that a fireman below watched the seams open up under that pressure. It was not a big hit but a series of glancing pressures on the hull. The steel deformed and stretched, but did not crack, as many believe. Instead, the rivits gave way and "unzipped" the hull in five places. The rivits had been purchased from hundreds of suppliers, many of whom had no experience in forging the iron ones, and had large contents of slag, which forms weak spots. Also the shipbuilder, under deadline pressure from the White Star Line, had to hire thousands of inexperienced workers to hand-rivit the hull (they had only two hydraulic riviters) in what is considered a high skill job. The result: the hull glanced along the iceberg, the plates bent but not that much, and the pressures snapped off the rivit heads -- unzipping the hull. The size all the openings? Bigger square footage than a truck? According to one source, it was just the size of a human body. Interesting, eh?