tom

Tomming is the practice of creating and filling a void space directly below the hatch coaming of a bulk carrier to improve vessel stability and trim. When a bulker loads cargo that settles unevenly or leaves gaps between the cargo surface and the underside of the hatch cover, crews will dig down into the cargo mass, excavate a pocket, and pack it with additional material, usually the same cargo, denser stone, steel scrap, or water ballast depending on what the vessel needs. This shifts weight to where it is most needed for stability.

The term arises from the deliberate creation of a temporary depression or hole (a "tom") in the cargo pile. In older shipyard and stevedoring vocabulary, tomming crews would use shovels and manual labour to carve out these pockets before mechanical grabs and spreaders became standard. The practice persists because bulk cargo, iron ore, coal, grain, bauxite, does not always stack uniformly, and the empty space above it represents both a stability problem and wasted deadweight capacity.

Modern tomming happens most often in iron ore and heavy bulk trades where density variation is high. A carrier might load cargo with a free surface (a liquid-like behaviour in partially filled holds) that threatens the ship's metacentric height. Digging and packing below the hatch creates weight in a high position relative to the ship's centre of gravity, lowering the centre of gravity and increasing the righting moment. The operation must be done before hatch closure and usually before departure from the loading berth.

Safety hazards are real. Crews working inside the hold with mechanical excavation equipment, or shovelling by hand in confined spaces with poor ventilation, face crushing risk if cargo shifts and entrapment risk in dust or flowing fines. Some cargoes, sulphide ores, concentrates, can self-heat or generate toxic gas. Modern practice increasingly favours ballasting solutions, stability calculators, and revised loading plans over manual tomming, though the technique remains in use in ports where equipment or expertise is limited.

Tomming sits at the intersection of cargo handling and naval architecture. It is a practical response to the gap between theoretical loading plans and the physical reality of how loose cargo behaves in transit. A well-tommed hold can mean the difference between a safe passage and excessive list or trim; poor tomming, or tomming with the wrong material, can introduce unexpected weight in the wrong place and create stability problems rather than solving them. Surveyors and captains must approve tomming work before hatch closure.