CHAPTER 3

SHIP COMPARTMENTATION AND WATERTIGHT INTEGRITY

A ship's ability to resist sinking after sustaining damage depends largely on the ship's compartmentation and watertight integrity. When these features are maintained properly, fires and flooding can be isolated within a limited area. Without compartmentation or watertight integrity, a ship faces almost certain doom if it is severely damaged and the emergency damage control (DC) teams are not properly trained or equipped.

In this chapter, you will be introduced to compartmentation, material conditions of readiness, watertight integrity, and how they relate to each other. You will also learn about compartment checkoff lists, the DC closure log, the proper care of access closures and fittings, compartment inspections, the ship's draft, and the sounding and security patrol watch. You will need to know the information in this chapter to complete your PQS for general damage control.

COMPARTMENTATION

The compartmentation of a ship is a major feature in its watertight integrity. Compartmentation divides the interior area of the ship's hull into smaller spaces by the use of structural members. Refer to figure 3-1 while reviewing the following information on structural members.

Figure 3-1.-Hull structure of a cruiser. 3-1

The keel is the backbone of the ship. On steel ships the keel does not extend below the ship's bottom. Its usual shape is that of an I-beam. All other members used in constructing the hull are attached, either directly or indirectly, to the keel.

The athwartship structure consists of transverse frames and floors. The floors run outboard from the keel to the turn of the bilge (where the bottom turns upward). This is where they are attached to the transverse frames that extend upward to the main deck.

Frames running parallel with the keel are known as longitudinal frames. From the turn of the bilge up the sides they are called stringers. The network of floors and longitudinal resembles a honeycomb and is known as cellular construction, which greatly strengthens the bottom. When the honeycomb is covered by plating, double bottoms are formed. The space between the inner and outer bottoms (known as tanks) is used for liquid stowage. Planks laid upon the tank tops are called ceilings. The forward end of the keel is extended upward in the stem. The after end has a similar extension called the sternpost. The part of the stem above water is the prow; the forward edge of the-stem is the cutwater.

The interior of a ship is divided into compartments by vertical walls, called bulkheads, which run both transversely and longitudinally. Most bulkheads are merely partitions, but transverse watertight bulkheads are spaced at appropriate intervals. These structural bulkheads extend from the keel to the main deck and from side to side. They provide extra transverse stiffening, and partition the hull into independent watertight sections. Largeships have a series of longitudinal side bulkheads and tanks that provide protection against torpedoes. The outer tanks usually are filled with oil or water. The inner tanks, which are called voids, are empty. The innermost bulkhead is called a holding bulkhead. When a torpedo hits, the outer tanks, although ruptured, absorb enough energy from the explosion that the holding bulkhead will remain intact. This helps to prevent flooding of the vital spaces.

The hull plating is fastened to the framework in longitudinal rows called strakes. The keel forms the center strake. The strakes are lettered, beginning with the A-strake on either side of the keel, and extending up to the main deck. Some of the strakes also have names. The A-strake is called the garboard strake; the strake along the turn of the bilge is the bilge strake; the uppermost strake is the sheer strake. A projecting keel running along the bottom near the turn of the bilge is called a bilge keel. Its purpose is to reduce rolling of the ship. (A ship rolls from side to side; it pitches when it goes up and down fore and aft; it yaws when the bow swings to port and starboard because of wave action.)

The upper edges of the sides where the sheer strakes join the main deck are called the gunwales (rhymes with funnels). The foremost part of the ship, where the gunwales join the stem, is known as the eyes of the ship. Where the gunwales curve inward to the sternpost are the port and starboard quarters.

The water level along the hull of a ship afloat is the waterline. The vertical distance from the keel to the waterline is the ship's draft. Freeboard is the distance from the waterline to the main deck.

Figure 3-2.-Hull terms. 3-2

Figure 3-3.-Weather decks.

Figures 3-2 and 3-3 illustrate some hull and deck terms.

The floors of a ship are called decks. They divide the ship into layers and provide additional hull strength and protection for internal spaces. The lower surface of each deck forms the overhead (never the ceiling) of the compartment below. Compartments are the spaces within a ship.

A steel deck is made of strakes running fore and aft. The outboard strake in the deck plating is composed of stringer plates, which are welded or riveted to the side plates and are, therefore, important strength members. Decks are supported by transverse frames (deck beams) and by longitudinals (deck girders). Further deck support is provided throughout the ship by vertical steel pillars called stanchions. These are mounted one above the other or one above a strength bulkhead. (The short posts used as lifeline supports also are called stanchions.) Decks usually are arched from the gunwale to the centerline to provide for drainage of water and to strengthen the deck.

A deck or part of a deck exposed to the weather is called a weather deck (fig. 3-3). Bulwarks are a sort of solid fence along the gunwale of the main (weather) deck. It is fitted with freeing ports (scuppers) to allow the water to run off during heavy weather.

A deck that extends from side to side and stem to stern is a complete deck. In aircraft carriers the uppermost complete deck is the flight deck, from which aircraft take off and land. In all ships (except for aircraft carriers) the uppermost complete deck is the main deck. In aircraft carriers the hangar deck is the main deck. The hangar deck is the deck on which aircraft are stowed and serviced when not on the flight deck.

The first complete deck below the main deck is the second deck (fig. 3-4), the next the third, the next the fourth, and so on.

Figure 3-4.-Deck numbering system. 3-3

3.95

A strength deck is a complete deck (usually the main deck) designed to carry not only deck loads on it but also the hull stresses. The damage control deck is the lowest deck having access through the main transverse bulkheads, from forward to aft. The main repair equipment and the principal facilities for the control of flooding, sprinkling, and pumping under conditions of damage are located on this damage control deck. The DC deck is either the second or third deck on most ships.

Following are definitions of the decks in modern ships. The location of each deck is also given.

Forecastle deck (pronounced fohk'sel): The deck is above the main deck at the bow. Ships that do not have raised forecastles are called flushdeckers. In them the part of the main deck from the stem to just abaft the anchor windlass is the forecastle.

Half deck: Any partial deck between complete decks.

Platforms: Partial decks below the lowest complete deck. They are usually broken to admit machinery or other spaces and are called platform decks or just platforms. They are numbered downward, as first platform, second platform, and so on.

Flats: Plating or gratings installed only to provide working or walking surfaces above bilges.

Levels: Level is a general term used to designate deck heights above the main deck. The first level above the main deck is the 01 (pronounced oh-one) level, the second the 02 level, and so on. Different decks at a particular level, however, carry different names. For example, both a poop deck and a boat deck (usually) are on the 01 level.

Upper deck: A partial deck extending from side to side above the main deck amidships. It is part of the superstructure, which is the part of a ship's structure above the main deck, exclusive of masts, yards, stacks, and related parts. The side plating extends upward to the upper deck.

Superstructure deck: A partial deck above the main, upper, or forecastle deck that does not extend to the sides of the ship; or if it does, it does not have the side plating carried up to it.

Poop deck: A partial deck above the main deck located all the way aft. A flush decker does not have a poop deck, so the stern area of the main deck on a flushdecker is called the main deck aft or the fantail.

Well deck: (Forward) part of the main deck between upper deck and forecastle, and (after) between the upper deck and the poop deck.

Gallery deck: First deck or platform below the flight deck.

Quarterdeck: The quarterdeck is not an actual deck, but an area designated by the commanding officer for the conduct of official functions. It is the station of the officer of the deck in port, and usually is on the main deck at the starboard gangway.

Companionways (ladders) lead from one deck level to another; they mayor may not be covered by hatches.

The number of compartments into which these decks and bulkheads subdivide the ship's interior area will depend upon how many the ship's mission will allow. These compartments are both above and below the waterline. When the degree of compartmentation on a ship is increased, that ship's resistance to sinking is also increased. Compartmentation serves the following functions. l Allows for more effective control of fires and floods.

. Strengthens the ship's structure. 

. Helps defend against a chemical , biological, and radiological (CBR) attack. 

. Segregates various ongoing activities.

. Provides underwater protection by the use of tanks and voids to help control the ship's buoyancy and stability.

Most large combatant ships have an armor belt to protect the vital machinery spaces. Armor plating may reduce the ship's speed or have an adverse effect on the operation of the ship. Aircraft carriers are a prime example where excessive armor plating would interfere with the ship's operation by reducing the ship's speed. Therefore, armor plating on aircraft carriers is reduced, while compartmentation is increased to compensate for the reduction of armor.