SciTech Tuesday: Sinking of the SS Samuel Dexter

Seventy years ago today, the SS Samuel Dexter sank in the North Atlantic. The ill-fated Liberty ship, built in New Orleans by Delta Shipbuilding Company, broke apart due to hull fracture. While no lives were lost aboard the SS Samuel Dexter, her sinking was one of approximately 127 major hull fractures during the war.

Liberty ships were cargo vessels produced quickly and inexpensively to meet wartime shipping demands. Designated as an emergency cargo vessel, design modifications using prefabricated components allowed the ships to be produced at a rapid rate. In fact from 1939 to 1945, 5,777 merchant ships were produced by US shipyards, an over 8000% increase of the previous seven years!

Changes in ship design and building material contributed to the phenomenon of Liberty ship hull failure. First, the seams in the steel hull were welded closed rather than fastened with traditional rivets. Defective welds often contained tiny cracks and flaws. Second, hatch openings, vents and other interruptions in the hull surface producing a weak point where fractures often began. Third, wartime steel, high in sulfur and phosphorus content, became brittle in the cold temperatures of the Atlantic. Additionally, rough seas and frequent overloading ships beyond their 10,000 pound maximum likely contributed to the failure of Liberty ship hulls.

The launching of SS Samuel Dexter. Gift of Earl and Elaine Buras, 1999.060.016

Post by Annie Tête, STEM Education Coordinator.