Ship Construction
Structure and watertight integrity
This domain tests hull structure, bulkheads, double bottoms, hatch covers and the survey and maintenance standards that keep water out.
- The keel, floors, frames and longitudinals form the primary hull strength; corrosion at frames and tank boundaries is a survey item.
- The collision bulkhead is a watertight boundary near the stem; it must not be pierced by doors or openings.
- Double-bottom tanks provide grounding protection and ballast capacity; sounding and air pipes must be functional.
- Hatch covers rely on coaming, gaskets, cleats and drainage channels; a failed gasket can flood a hold.
- Watertight doors must be tested and recorded; doors required to be closed at sea must be kept closed.
Worked example
A ship has length L = 150 m. The collision bulkhead must be not less than 0.05L or 3 m from the forward perpendicular, whichever is lesser: 0.05L = 7.5 m, so the minimum is 3 m. It must be not more than 0.08L or 0.05L + 3 m, whichever is greater: 0.08L = 12 m; 0.05L + 3 = 10.5 m; so the maximum is 12 m. The bulkhead must therefore lie between 3 m and 12 m from the forward perpendicular.
Traps
Assuming a collision bulkhead may have an access door. Confusing the forward perpendicular with the stem. Accepting a watertight door held open at sea because it is convenient. Ignoring hatch cover drain channels blocked by cargo debris.