Ship Construction, Stability and Cargo Operations
What the exam tests
This domain tests how hull structure, watertight integrity, load line and intact stability interact with safe cargo loading, lashing and sequential ballast operations.
Core rules
- Hull structure includes keel, frames, longitudinals, transverse and longitudinal bulkheads, double bottom and watertight subdivision.
- The load line and freeboard are assigned under the Load Lines Convention; overloading reduces reserve buoyancy.
- Intact stability is assessed using KG, KM, GM and GZ curves; the 2008 Intact Stability Code sets minimum criteria.
- Free surface effect reduces effective GM and must be included as free surface correction, not ignored.
- Cargo must be secured under the Cargo Securing Manual; grain has additional stability requirements; dangerous goods follow IMDG segregation.
Worked example
A ship displaces 8,000 t, KM is 7.40 m and KG is 6.20 m. Solid GM = KM - KG = 1.20 m. The total free surface moment is 400 t·m, so FSC = 400 / 8,000 = 0.05 m. Fluid GM = 1.20 - 0.05 = 1.15 m. Reason: the free surface correction must be deducted because slack tanks reduce the righting lever. If the result falls below the applicable IS Code minimum, the loading plan must be changed before sailing.
Traps
Using solid GM without free surface correction; confusing list with trim; accepting a cargo plan without checking lashings and segregation; ignoring ballast sequence effects on shear force and bending moment.