Explain what is meant by longitudinal and transverse framing, and which ship types use each method with reasons?
Short answer
| Ship type | Framing system | Typical location | Reason |
|---|---|---|---|
| Bulk carrier | Longitudinal | Topside, double-bottom tanks | Continuous strength against longitudinal bending from distributed cargo |
| Bulk carrier | Transverse | Cargo hold side shell | Resist transverse cargo pressure |
| Single hull tanker | Longitudinal | Deck, side shell, bottom plating | Primary strength for large continuous structures |
| Double hull tanker | Longitudinal | Double bottom, double sides, single deck | Main structural integrity under liquid cargo loads |
| Double hull tanker | Transverse | Deck transverses | Prevent buckling of cross deck strips under axial transverse forces |
| General cargo / Container | Transverse | Cross deck members | IMO A.866(20) §6.1.4: transverse system preferred to avoid buckling |
- Longitudinal framing: members run fore-and-aft; named deck/side/bottom longitudinals
- Transverse framing: members run athwartships; named hold/side/main/shell frames
- Bulk carriers: longitudinal in topside and double-bottom tanks, transverse at cargo hold side shell
- Single hull tankers: longitudinal for deck/side/bottom, transverse bulkheads and web frames
- Double hull tankers: longitudinal stiffeners for double bottom/sides/deck, plus deck transverses
- General cargo/container: transverse for cross deck members to prevent buckling
- Key reason: longitudinal resists longitudinal bending; transverse resists transverse loads and prevents buckling
- IMO: A.866(20) Annex 1 §4.7, §6.1.4; MSC.371(93) Annex 3 §1, §15
- IACS: UR I2 §I2.5.2
- UK: MGN 107 Annex 3 §4.7; MIN 208 Annex 2 §12.9, Annex 6 §9.9; MSIS38 Part B Chapter 11 §11.3.2, §11.3.9
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the MEO Class IV section of the Marine One forum, open to members enrolled for the MEO Class IV exam.