The Center of Buoyancy B - Where Does it Come From The center
of buoyancy Bis the centroid, i.e. geometric center, of the submerged watertight volume of the vessel calculated at the given heel angle.
In addition to the hull, this volume may also include the watertight superstructure or deckhouses on the vessel. The left diagram shows how the location of atypical fishing vessel’s center of buoyancy shifts outboard as it heels over. Note how the outboard shift reduces when the freeboard deck edge becomes submerged and eventually reverses direction as the vessel heels further.
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Why a Fishing Vessel Remains Upright The Shifting of B Buoyancy To understand how a fishing vessel stays upright, imagine the rocking of a baby cradle shown in the figure. The fishing vessel (weight) is the cradle. Its center of gravity G is the near the center of the cradle. The buoyant force supporting the cradle is the rocker resting on the floor. The center of buoyancy Bis the point where rocker contacts the floor.
As with a fishing vessel, the cradle’s (vessels) center of gravity G is above its rocker, the center buoyancy B. The slightest disturbance (wind, waves, or the movement of weight on the deck) causes the cradle (vessel) to roll heel) to one side. As the cradle (vessel)
rolls to one side, the point where the rocker touches the floor (the center of buoyancy B) shifts outboard. To keep the cradle (vessel) upright, the point where the rocker touches the floor (the center buoyancy B) must shift faster outboard than the cradle’s (vessels) center of gravity G. It is this shifting of the center buoyancy B that allows a fishing vessel to stay upright after being heeled by the wind, waves, or the movement of weight on the deck.
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