Tonnage

After washing cargo spaces, dirty water is drained away from the hold bottoms into ‘bilges‘ through ‘strum-boxes‘ which act as filters and prevent solid matter from blocking bilge pipes and damaging pumps. Prior to loading bulk commodities, these bilge openings might be intentionally covered over for the same reasons. A term that might be encountered – especially in the short-sea market sector – is ‘shelter-decker‘. The ‘shelter’ refers to a design specifically adapted to overcome stringent tonnage regulations, by which vessels could maximise cargo capacity and intake (and thus maximise earnings potential) yet restrict the registered tonnage assessed against the vessels and thus reduce those expenses and liabilities which are based on the ship’s registered tonnage (e.g. port costs and certain liabilities as to crew numbers). The tonnage regulations creating these innovative designs have long been altered and there is now no need for clever naval architecture to overcome this legislation. Nevertheless, the term lingers on in certain market sectors, and where the term ‘shelter-decker’ is used today it should be taken to mean ‘tweendecker’. The most obvious exterior cargo fitting on a general-cargo ship is her ‘gear‘ – her derricks or cranesDerricks may be old in design, but they remain important equipment; their use (and dangers) being readily understood throughout the world, relatively simple, as they are, to rig and to maintain, and being reasonably inexpensive. There are basically three parts to a derrick (see Appendix 1:2): A vertical supporting pillar – a ‘samson post‘ – sunk into the ship’s weatherdeck, to the base of which is attached: The boom, and Rigging (e.g. wire ropes, blocks and tackle).