Cargo intake: deadweight, cube and draft
How much cargo a ship can actually load: the deadweight, volumetric and draft limits that compete, and which one binds for a given commodity and port.
Cargo intake is the smallest of three competing limits, and which one binds decides both the freight earned and the ship chosen for a fixture. The deadweight limit is the summer deadweight less bunkers on board, fresh water, stores and the ship’s constants. The volumetric limit is the cargo’s stowage factor against the grain or bale capacity. The draft limit is set by a port sill, a river passage or the seasonal load line zone the voyage crosses.
A dense cargo such as iron ore is deadweight-limited and leaves hold volume unused; a light cargo such as woodchips cubes out well before the ship is down to her marks. A draft restriction can bind before either, which is why a ship can be turned away from a full cargo at one berth and load it at another.
The full article will work each limit through with its arithmetic, cover constants and their estimation, the broken stowage allowance in a bulk hold, the deadweight scale and the effect of water density on the summer draft, and the charterparty consequence when the charterer fails to supply the agreed minimum. See voyage estimation and deadfreight .