You are preparing for what promises to be a rough ocean passage. Your 120-foot schooner carries a yard on the foremast, about 50 feet above the water. The yard weighs about 1000 pounds. What will be the consequence if you take the yard down and stow it on deck for the trip?
• Center of gravity (G) and how weight shifts affect it • Relationship between metacentric height (GM) and vessel stability/rolling period • Difference between initial stability (GM) and reserve buoyancy
• Visualize what happens to the ship’s overall center of gravity when you move a 1000-pound weight from 50 feet above the waterline down to deck level. Does G move up or down? • Recall how a larger or smaller GM affects the character of the roll: does a high GM make the ship snap back quickly or roll more gently? • Think about what reserve buoyancy actually means. Does moving weight around change the volume of watertight hull above the waterline?
• Before choosing, decide clearly whether moving the yard up or down will raise or lower the ship’s center of gravity. • Review the rule of thumb: large GM vs. small GM – which one is associated with a quick, stiff roll and which with a slow, easy roll? • Confirm whether reserve buoyancy is affected by weight distribution or by the ship’s hull form and intact spaces above the waterline.
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