13.11.1 Hull

A hull is the watertight body of a ship, consisting of shell plating, framing, decks, and bulkheads. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline. The structure of the hull varies depending on the vessel type.

13.11.2 Shell plating

Modern ships have flush, fully welded shell plating which forms the watertight skin of the ship. Shell plating has to be able to withstand the static and dynamic loads created by the sea. The shell plating contributes a great deal to the longitudinal stresses caused by hogging and sagging.

Shell plating is broadly divided into side shell plating and bottom shell plating. Side shell plating is the shell plating above the upper turn of bilge, and bottom shell plating is the shell plating below it.

Shell plates are sometimes called by different terms depending on their locations, e.g., keel plates, sheer strake, bilge strake, forward bottom plating.

• Keel plate: The keel is a thick plate laid throughout the length of the bottom of a ship along the centerline of the hull.

• Sheer Strake: The strake of side shell plating immediately below the strength deck.

• Bilge strake: The turn of bilge at the bottom of a ship, to which a bilge keel is fitted, is called a bilge strake or bilge plate.

• Side shell plating: Is the shell plating above the upper turn of bilge.

• Bottom shell plating: Is the shell plating below the turn of bilge.

Shell plates are joined together in the rolling direction of steel plates, aligned with the longitudinal direction of a ship.

13.11.3 Shell expansion drawing

A shell expansion is a two-dimensional drawing showing the arrangement of the shell plates, stiffening members, all butts, seams, fillet welds, etc. The drawing shows the various plate strakes and their identification number.

Each shell plate is numbered, and the integral arrangement of numbered shell plates is shown on a shell expansion plan.

Shell plates are counted from the one next to the keel plate, and are named ‘A’ strake, ‘B’ strake, and so on. Shell plates in each strake are numbered from the aft. For example, plate "C—5" is the fifth plate in C strake counted from the aft. Generally, to avoid confusion, letters I and O are not used.

A shell expansion drawing is used for checking dimensioning, topology, material, and structural integrity of the shell plates.

• A strake: In modern ship construction, 'strake' refers to the longitudinal run of plating covering the hull, deck, and bulkhead structure. Certain specific strakes are uniquely identified.

  

13.11.4 Deck beam, knee, brackets, Side longitudinals

Deck beams, knees, brackets, and Side longitudinals are the supporting members of the hull structure, which increase the strength of the vessel as well.

Deck Beams and Knees

Deck beams are fitted across the width of the ship and are joined to the side frames by brackets known as beam knees.

Brackets

A general term that identifies any part used to connect two members.

Tank Side Brackets

The lower end of the frame may be connected to the tank top by means of a flanged or edge-stiffened tank side bracket.

Side longitudinal

The longitudinal frames at the sides which fit into notches cut into the transverse frames.