According to Wartsila “A ship with one or more decks, having ability to carry a variety of commodities in different forms such as boxed, palletized, refrigerated, and with the possibility to accommodate bulk materials such as grain.”
A general cargo ship is extremely adaptable and can be used to transport virtually every form of dry non-bulk cargo, from railway lines to agricultural machinery.
A distinct feature of general cargo ships is that they normally have their own gear, which means that these versatile ships can trade to smaller ports and terminals that do not have shoreside loading and unloading equipment. And while these ships are often employed with abnormal loads that other ships could not accommodate, in lean times general cargo ships can easily turn their hand to carrying containers, bulk or bagged cargo.
Size of Hold
For general cargo ship, the required hold size is roughly constant in proportion to underdeck volume. For container and Ro-ro ships, reducing CB increases the ‘noxious spaces’ and more hold volume is required.
Usually the underdeck volume ∇D=L · B · D · CBD is kept constant. Any differences due to camber and sheer are either disregarded or taken as constant over the range of variation. CBD can be determined with reasonable accuracy by empirical equations:
with c=0.3 for U-shaped sections and c=0.4 for V-shaped sections. See also Section 220.127.116.11.
With the initial assumption of constant underdeck volume, the change in the required engine room size, and any consequent variations in the unusable spaces at the ship’s ends and the volume of the double bottom are all initially disregarded. A change in engine room size can result from changes in propulsion power and in the structure of the inner bottom accommodating the engine seatings.
In a general cargo ship the transverse framing will consist of main and hold frames with brackets top and bottom, and lighter tween deck frames with brackets at the tops only. A typical miship section for a general cargo ship is given below
Inner bottom plating
The inner bottom plating may, in a general cargo ship, be sloped at the side to form a bilge for drainage purposes. It is not uncommon, however, for it to be extended to the ship’s side, and individual bilge wells are then provided for drainage purposes. In vessels requiring a passenger certificate it is a statutory requirement for the tank top to extend to the ship’s side. This provides a greater degree of safety, since there is a substantial area of bilge that may be damaged without flooding spaces above the inner bottom.
At the center line of the ship the middle strake of the inner bottom may be considered as the upper flange of the center line docking girder, formed by the center girder and keel plate. It may therefore be heavier than the other strakes of inner bottom plating. Normally, a wood ceiling is provided under a hatchway in a general cargo ship, but the inner bottom plating thickness can be increased and the ceiling omitted. If grabs are used for discharging from general cargo ships the plate thickness is further increased, or a double ceiling is fitted. Source: Wikipedia, Sciencedirect