Trim by the Stern

Trim by the stern is the condition where the aft draught of a vessel exceeds the forward draught, meaning the ship is deeper at the stern than the bow. This is the preferred trim condition for most cargo vessels during sea passage because it improves propulsive efficiency by ensuring the propeller is well immersed, enhances steering response due to greater rudder immersion, reduces the risk of slamming in head seas, and is generally more comfortable for the crew. The magnitude of the preferred trim by the stern varies by ship type and is specified in the vessel's trim and stability manual; typical values range from half a metre to over a metre for large bulk carriers. The chief mate aims to achieve the specified trim by the stern at the completion of loading by adjusting the fore-and-aft distribution of cargo and ballast. As fuel and fresh water are consumed during the voyage, the trim changes because the consumption usually occurs from tanks whose centres of gravity are not coincident with the ship's centre of flotation; the chief mate or OOW must monitor this change and transfer ballast as necessary. On arrival at the discharging port, the ship's trim affects quay accessibility—some berths impose maximum aft trim restrictions—and the chief mate calculates the required trim adjustments well before arrival.