Kentledge

Kentledge is permanent fixed ballast, usually cast-iron pigs, concrete, or scrap steel, placed low in a vessel’s bottom or double-bottom tanks to lower the center of gravity and correct trim without occupying cargo or water-ballast capacity. Unlike water ballast, which is taken on and discharged for each voyage, kentledge stays aboard for the ship’s life. Naval architects specify its mass and longitudinal position from the stability and trim calculation; it also serves as test weight during inclining experiments to find the lightship vertical center of gravity (KG).