SHELL AND DECK PLATING

General: Seams, or ‘Edge Laps’, are joints which run fore and aft; that is, along the longer edges of the plates.

Butts, or ‘End Laps’, are joints which run athwartships, or vertically; that is, along the shorter edges of the plates.

Strakes are continuous, fore and aft, lines of plates.

Garboard strakes are the strakes of shell plating next to the keel on either side (i.e. the ‘A Strake’).

Sheerstrakes are the upper strakes of shell plating on either side, next to the upper deck. (The ‘J strake’ in the sketch opposite.)

The Deck Stringer is the outboard strake of deck plating, which is connected to the sheerstrake. (Strake ‘E’ on the deck plan, opposite.)

Stresses on Plating: The obvious purpose of plating is to keep out water and to tie together the ship’s framework. It also plays an important part in resisting longitudinal bending stresses, so it needs to be stronger amidships than at the ends, particularly at the deck and bottom. In long ships, it may

also be necessary to strengthen the shell plating against shearing stresses at about the half-depth of the ship, in the region of about one-quarter of the ship’s length from either end.

Shell Expansion and Deck Plans: These are plans which show all the plates in the hull, drawn to scale. They also show many other details, including frames, floors, deck edges, stringers, etc. The partial plans shown in the plate, opposite, are simplified and are merely intended to illustrate the fitting of shell and deck plating.

Identifying Plating: Strakes of shell plating are distinguished by letters from the keel outwards, the garboard strake being strake ‘A’. The plates in each strake are usually numbered from aft to forward. For example, plate D5 would be the fifth plate from aft in the fourth strake from the keel.

Strakes of deck plating are lettered from the centre line, outboard; whilst deck plates are numbered from aft to forward.

Stealer Plates: The girth of the ship decreases toward the ends and so the width of plates must be decreased in these parts. To save making the plates too narrow at the ends of the ship, it is usual to run a number of pairs of adjacent strakes into one. This is done by means of a stealer plate.

This can be seen in the upper shell expansion plan, given here; in which Plate B4 is a stealer, since it runs the B and C strakes into each other. Note how the stealer and the plates beyond it, always take the name of the lower of the strakes which are run together.