page_title: Parbuckle salvage
section_title: Mechanical advantage and difficulties
hierarchical_section_title: Parbuckle salvage / Mechanical advantage and difficulties
caption_attribution_description: English: A parbuckle is a method of using line or cable which passes around an object, to gain mechanical advantage in lifting or moving the object.
context_page_description: Parbuckle salvage, or parbuckling, is the righting of a sunken vessel using rotational leverage. A common operation with smaller watercraft, parbuckling is also employed to right large vessels. In 1943, the USS Oklahoma was rotated nearly 180 degrees to upright after being sunk in the attack on Pearl Harbor, and the Italian cruise ship Costa Concordia was successfully parbuckled off the west coast of Italy in September 2013, the largest salvage operation of that kind to date.
context_section_description: While the mechanical advantage used by a laborer to parbuckle a cask up an incline is 2:1, parbuckling salvage is not so limited.  Each of the 21 winches used to roll the Oklahoma used cables that passed through two 17-part tackle assemblies (17:1 advantage).  Eight 28-inch (710 mm) diameter sheaves, eight 24-inch (610 mm) diameter sheaves, and one 20-inch (510 mm) diameter sheave comprised just half the mechanical effort.
  A major concern during salvage is preventing rotational torque from becoming a transverse force moving the ship sideways.  USS Utah, lost like the Oklahoma in the Pearl Harbor attack, was meant to be recovered by a similar rotation after the Oklahoma.  As the Utah was rotated, however, its hull did not catch on the harbor bottom, and the vessel slid towards Ford Island.  The Utah recovery effort was abandoned.
caption: Parbuckling a cask up an incline
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