Scantlings
Scantlings are the dimensions of the structural parts of a ship — the thickness of the shell and deck plating, and the size, section and spacing of frames, girders, stiffeners and bulkheads. Together they determine the strength of the hull.
Scantlings are set by the classification society rules for the ship type, size and intended service, with allowances for corrosion over the life of the vessel. A ship built to full rule scantlings has more steel and strength margin; the term also appears as the scantling draught, the deepest draught the structure is approved to load to.
Scantlings are where safety, steel weight and cost meet. Heavier scantlings mean a stronger, longer-lived hull but more steel and less cargo deadweight; lighter scantlings save weight but leave less corrosion margin — which is exactly what thickness measurements at a special survey later check against.
What is scantling draught?
The maximum draught the ship structure is designed and classed to load to — often deeper than the assigned load-line (summer) draught, giving a strength margin.