Tweendeckers

With the introduction of containers and of ‘parcel‘ tankers, there is nowadays less demand for small quantities of liquid cargoes to be carried in the ‘deep-tanks‘ of cargo-liners, but there is increased demand for vessels with holds and decks capable of carrying several tiers of containers. Thus, the internal as well as the external designs of general-cargo/multi-purpose vessels have altered in recent years and these changes can perhaps best be explained by studying various aspects applicable and, in some cases, peculiar to these vessels. Modern general-cargo ships are nearly always constructed with two (very occasionally three) decks and can thus be termed ‘tweendeckers‘ the upper deck being the ‘main‘ or ‘weather-deck‘, and the lower deck the ‘tweendeck‘. Most tweendeckers have just one ‘tweendeck’ located somewhat closer to the weatherdeck overhead than to the bottom of the cargo hold beneath – about two-thirds up the height of the holds (See NB:1 below). The cargo area enclosed between the tweendeck and the weatherdeck is, logically, referred to as the ‘tweendeck space‘, and the area beneath the tweendeck down to the bottom of the cargo area, the ‘hold-space‘. These vessels are ideal for the carriage of bagged, baled and drummed commodities, the support of the tweendeck meaning that a high tier stowage of these goods can be safely accommodated, whereas the same number of tiers in a bulkcarrier, for example, might well lead to splitting of lower stowed bags or crumpling of drums due to the sheer weight pressing down from above. It is true to say, however, that this is less of a factor than was previously the case, given the improvement in the quality of the cargo bags and the subsequent tendency to larger sized bags (e.g. one tonne ‘jumbo’ cargo bags, although these can equally be a problem when they require stowing in the wings or ends of holds).