A longitudinal bulkhead is a structural dividing wall running fore-and-aft (bow to stern) through a vessel, dividing the ship’s width rather than its length.
Longitudinal vs Transverse Bulkheads
- Longitudinal bulkheads — run bow-to-stern, dividing the ship’s width
- Transverse bulkheads — run side-to-side, dividing the ship’s length into sections (forepeak, cargo holds, engine room, aft peak)
Most vessels use transverse bulkheads as their primary watertight subdivision; longitudinal bulkheads are an additional structural feature, particularly common in specific vessel types.
Where Longitudinal Bulkheads Are Most Common
Tankers typically use longitudinal bulkheads extensively — dividing the cargo tank space into port, center, and starboard tank sections along the vessel’s length. This serves multiple purposes: limiting the free surface effect of liquid cargo within any single tank, allowing segregated carriage of different cargo grades simultaneously, and contributing structural strength.
Structural Role
Beyond cargo segregation, longitudinal bulkheads contribute meaningfully to a ship’s overall longitudinal strength — helping resist the bending stresses (hogging and sagging) a vessel experiences moving through waves, working alongside girders and stringers as part of the ship’s longitudinal strength members.
Longitudinal Bulkheads and Stability
On tankers, dividing tanks with longitudinal bulkheads specifically reduces free surface effect compared to one large, undivided tank of the same total capacity — a real, practical stability benefit, not just a cargo-segregation feature.
Exam Relevance
Longitudinal bulkhead function, particularly its role in tanker design and free surface effect reduction, is a core Ship Construction and Ship Stability topic in deck officer competency exams.