A stringer is a longitudinal structural member — running along the ship’s length — typically positioned along the sides of the hull or at deck edges, adding strength and tying transverse frames together.
Stringers vs Girders: Related Longitudinal Members
Stringers and girders are both longitudinal (fore-and-aft) structural members, and the terms are sometimes used loosely — but stringers are commonly associated specifically with side-shell and deck-edge locations, connecting frames together along the hull’s sides, while “girder” more often refers to major longitudinal members at the deck and bottom.
What Stringers Do Structurally
- Connect frames — tying individual transverse frames together along the ship’s length, distributing load between them rather than leaving each frame to act in isolation
- Add longitudinal strength — contributing to the hull’s overall resistance to fore-and-aft bending stress (hogging and sagging)
- Support side shell plating — providing intermediate support to the shell plating between the deck and bottom, particularly important on larger vessels with significant side shell area
Side Stringers in Ballast Tanks
Side stringers are particularly significant in the side ballast tanks common on many vessels (particularly double-hull tankers), where they provide structural support within the tank space while also, practically, affecting how the tank space is accessed and inspected during survey.
Deck Stringers
At the deck edge specifically, the deck stringer plate is a particularly significant structural zone, given the stress concentration where deck plating meets side shell plating — often reinforced or of increased thickness compared to surrounding plating for this reason.
Corrosion and Stringer Condition
Like all structural steel, stringers are subject to corrosion over a vessel’s service life — stringer condition, particularly within ballast tanks where corrosion is often most severe, is a genuine survey and maintenance concern factored into a vessel’s structural integrity assessment.
Exam Relevance
Stringer function, positioning, and their relationship to frames and girders are core Ship Construction topics in deck and engineering officer competency exams.