HB-68 "TRIM AND BALLAST"
Two systems, one principle. Fill to descend, blow to ascend, and trim until the boat sits exactly where you wanted her.
Main ballast tanks took the boat down and up. Trim tanks moved water fore and aft to keep her level. A good chief of the watch held the boat steady at periscope depth with a few pounds of correction at a time. A bad one let the bubble run, broached the boat, and broke the attack. The technique was the most delicate piece of seamanship in the submarine. It was also the one most pressing on the success of every approach.
For those who understand that depth control is mostly about not allowing small errors to grow into large ones.
Harborborne. Built to Endure.
Original maritime artwork; Created in-house
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