Section 5 Single and double bottom structure

5.1.1 For dry cargo ships exceeding 120 m in length, and for all ships which are strengthened for heavy cargoes, longitudinal framing is, in general, to be adopted, see also Pt 4, Ch 9, 1.3 Class notation and applicable Rules for CSR Double Hull Oil Tankers.

5.1.2 For ships having the notation `strengthened for heavy cargoes', the requirements of Pt 4, Ch 7, 8 Double bottom structure are also to be complied with, as applicable.

5.1.3 For ships intended to load or unload while aground, see Pt 3, Ch 9, 7 Bottom strengthening for loading and unloading aground.

5.1.4 Provision is to be made for the free passage of water and/or air from all parts of single or double bottoms to the bilge or tank suctions, account being taken of the pumping rates required.

5.1.5 For passenger ships, see Pt 4, Ch 2, 6 Double bottom.

5.2.1 In after peak spaces, floors are to be arranged at every frame. For details and scantlings, see Pt 3, Ch 6, 6.1 Bottom structure.

5.2.2 In way of dry cargo spaces aft, the arrangement and scantlings of transversely framed single bottoms are to be generally as required in the midship region, as given in Pt 4, Ch 1, 7 Single bottom structure, except that the thickness of the centreline girder may be tapered from the midship thickness at 0,3L from the A.P. to mm or 6 mm, whichever is the greater, at 0,075L from the A.P. In ships having considerable rise of floor towards the aft end, the depth of the floors may be required to be increased.

5.2.3 Where the shape of the after sections is such that there are large flat areas of shell plating, additional stiffening and/or increased shell plate thickness may be required, see Pt 3, Ch 6, 3.3 Bottom shell and bilge. The extent of this stiffening will be specially considered.

5.3.1 The scantlings and arrangement of longitudinally framed single bottoms in way of dry cargo spaces will be specially considered.

5.4.1 The minimum depth of centre girder aft is generally to be the same as that required in the midship region by Pt 4 Ship Structures (Ship Types) for the particular type of ship concerned, but in ships with considerable rise of floor a greater depth may be required at the aft end to provide adequate access throughout the double bottom tank.

5.4.2 Where the height of the double bottom varies, this variation is generally to be made gradual by sloping the inner bottom over an adequate longitudinal extent. Knuckles in the plating are to be arranged close to plate floors. Otherwise, suitable scarfing arrangements are to be made.

5.4.3 For dry cargo ships, the arrangement and scantlings of girders, floors, inner bottom plating and inner bottom stiffening in the aft end region are to be determined from Pt 4, Ch 1, 8 Double bottom structure.

5.4.4 For double bottom construction in way of the cargo tanks of oil tankers or ore carriers, see also Pt 4, Ch 9 Double Hull Oil Tankers, Pt 4, Ch 10 Single Hull Oil Tankers or Pt 4, Ch 11 Ore Carriers, as appropriate.