How Ships Survive Flooding: Calculating the Minimum Number of Watertight Bulkheads

How is the minimum number of watertight bulkheads on a merchant ship calculated? In this video, we break down the classification society rules (such as IACS, Lloyd's Register, DNV, IRS) and statutory regulations governing transverse watertight bulkheads. We look into why collision bulkheads, machinery space bulkheads, and aft peak bulkheads are strictly mandated, and how vessel length determines the total number of intermediate cargo hold bulkheads required. Whether you are preparing for your Competency Examinations (Mates / Masters / Marine Engineers) or looking to sharpen your naval architecture and ship construction fundamentals, this guide walks through the exact criteria step by step. ⚓ Key Takeaways: Minimum mandatory 4 bulkheads for vessels with machinery amidships (Collision, Fore Machinery, Aft Machinery, Aft Peak). Minimum mandatory 3 bulkheads for vessels with machinery aft (Collision, Forward Machinery/Cargo boundary, Aft Peak). Additional transverse bulkheads scaled according to rule length ($L$) under classification society tables. 👍 If you found this breakdown useful, make sure to like, subscribe, and share it with your fellow mariners! Drop any questions or exam-specific doubts in the comments below. #ShipConstruction #NavalArchitecture #MaritimeStudies #MerchantNavy #ChiefMate #SecondMate #SOLAS #Bulkheads