SHELL PLATING

1. Why is shell plating one of the most important constructive members?

2. What is the relation between length and depth of the vessel?

3. The strake of the bottom shell plating at the center line is a horizontal keel, isn't it?

4. What are butts and seams?

The ship's shell plating is one of the most important members of the hull. Its functions are:

1) to shut out the sea water;

2) to take up the stresses resulting from the water pressure perpendicular to the shell plating;

3) to take up the bending stresses caused in a sea way.

The ship's hull may be regarded as a box girder being bent upwards and downwards alternately. The relation between length and depth of the vessel plays an important part, as with an increase of length the thickness of the shell, particularly the top and the bottom plating, being the most heavily loaded, will have to be proportionally increased. The strake at the center line of the vessel is called flat keel plate and that in way of the strength deck the sheer strake. The stakes of plating are connected together by means of seams, the connection between the plates of a strake is effected by butts (or butt welds).

DECKS

1. What is the duty of a deck?

2. What kinds of decks are known?

3. What are the functions of the camber and the sheer of the deck?

A vessel has one or more decks not only to make her top watertight but also to protect her cargo and accommodation of passengers and crew. Moreover, a deck adds to the longitudinal and partly also to the transverse strength of a ship. Decks should be watertight and are considered to be among the most important scantlings.

The topmost continuous deck of a full-scantling vessel is called the main deck, and in a complete-superstructure vessel the upper deck. Below these strength decks may be various other decks such as the upper tweendeck, the tweendeck and the orlop deck. The lower decks are not always continuous, but may be interrupted in way of the engine room and the boiler space. Most decks have a transverse camber, i.e. lowering of the deck to the sides, the degree of camber is called height of camber. The longitudinal run of the deck line is also a curve with a rise towards bow and stern. This line is called the sheer (-line).

The function of sheer and camber is to increase the strength of a deck and to enable sea water swept on board to flow away through the washports and scupper pipes. In addition, the sheer improves a vessel's outward appearance and increases her reserve of buoyancy and the safety during floating. The lower decks generally have the same amount of camber and sheer as the uppermost deck.

Date: 2014-12-28; view: 1838