Hull Design and Strength
Polar Sea has sufficient hull strength to absorb the high-powered ice ramming common to her operations. The shell plating and associated internal support structure are fabricated from steel with superior low-temperature strength. The portion of the hull designed to ram ice is 1¾ inches thick (44 mm) in the bow and stern sections, and 1¼ inches thick (32 mm) amidships. The hull strength is produced almost entirely from a sophisticate internal support structure that features canted ribs for approximately the forward two-thirds of the ship's frame. Polar Sea's hull shape is designed to maximize icebreaking by efficiently combining the forces of the ship's forward motion, the downward pull of gravity on the bow, and the upward push of the inherent buoyancy of the stern. The curved bow and heavy weight allows Polar Sea to force ice edges to break off downward as cusps. Contrary to some myths, this design does not use sharp edges or hammer-like blows to cut or break the ice, as the round bow and massive weight are sufficient. With high power to back it up, the 13,000-ton (13,200-metric ton) Polar Sea is able to continuously progress through 6 feet (1.8 m) of new hard ice at 3 knots (6 km/h) and break up to 21 feet when using back-and-ram methods.
Read more about this topic: USCGC Polar Sea (WAGB-11)
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