Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGBulkheads consist of plating and reinforcingbeams. The reinforcing beams are known asbulkhead stiffeners . Two types of bulkhead stiffenersare shown in figure 2-21, Bulkheadstiffeners are usually placed in the verticalplane and aligned with deck longitudinals; thestiffeners are secured at top and bottom to anyintermediate deck by brackets attached to deckplating. The size of the stiffeners dependsupon their spacing, the height of the bulkhead,and the hydrostatic pressure which the bulkheadis designed to withstand.Bulkheads and bulkhead stiffeners must bestrong enough to resist excessive bending orbulging in case of flooding in the compartmentswhich they bound. If too much deflection takesplace, some of the seams might fail.In order to form watertight boundaries,structural bulkheads must be joined to alldecks, shellplating, bulkheads, and other structuralmembers with which they come in contact.Main transverse bulkheads extend continuouslythrough the watertight volume of the ship, fromthe keel to the main deck, and serve as floodingboundaries in the event of damage below thewaterline.In general, naval ships are divided into asmany watertight compartments, both above andbelow the waterline, as are compatible with themissions and functions of the ships. The compartmentationprovided by transverse and longitudinalbulkheads is illustrated in the bow sectionshown in figure 2-22.T-BAR'ANGLE'11.30(147)CFigure 2-21.— Bulkhead stiffeners.SHIP COMPARTMENTATIONEvery space in a naval ship (except forminor spaces such as peacoat lockers, linenlockers, cleaning gear lockers, etc.) is consideredas a compartment and is assigned an identifyingletter-number symbol. This symbol ismarked on a label plate secured to the door,hatch, or bulkhead of the compartment.There are two systems of numbering compartments,one for ships built prior to March1949 and the other for ships built after March1949. In both of these systems, compartmentson the port side end in an even number and thoseon the starboard side end in an odd number. Inboth systems, a zero precedes the deck numberfor all levels above the main deck.Figure 2-23 illustrates both systems ofnumbering decks. The older system identifiesdecks by the numbers 100, 200, 300, etc., withthe number 900 always being used for the double147.24Figure 2-22.— Compartmentation provided bytransverse and longitudinal bulkheads.bottoms. In the newer system, decks are identifiedas 1, 2, 3, 4, etc., and the double bottomsare given whatever number falls to them.26