A merchant ship is likely to be equipped with no less than 200 plans. Usually a full set will be kept on board, and a further set in the Owner’s office. Shipbrokers will need to familiarise themselves with two plans containing much important data, since it may be necessary to obtain data from these particular plans in order to conclude fixtures and/or to prosecute voyages. These plans are known as: the General Arrangement Plan b) the Capacity Plan (including Deadweight Scale). The former plan shows the design of the vessel, the layout of her equipment, cargo spaces, etc. and her dimensions. It should show a profile, a plan and a midship section (a view from forward towards the after part of the vessel, illustrating the shape of the cargo spaces. It should also state the scale to which it has been drawn, and this enables distances between parts of the vessel to be measured and calculated from the plan’s data. Most ship plans are drawn on the scale of 1/200 (that is that one centimetre on the plan equates to 200 centimetres on the ship). But this is not always the case. Smaller ships will have plans drawn, perhaps, 1/150, and large, ‘cape-size’ vessels 1/300. It is therefore essential that the scale is always checked prior
to performing measurement calculations as an error at this stage can cause serious practical difficulties.
The Capacity Plan provides details of capacities of cargo compartments, bunker and water tanks, etc. The plan will include a Deadweight Scale (see alongside) which enable drafts and displacements to be calculated by relating one to another. Draft* can, therefore, be used as an indication of the weight of cargo, stores, bunkers, etc. that the ship has loaded or discharged. The draft of the ship itself can be established by checking the level of the water against the figures painted on the ship’s bows and stern.
(*NB You may encounter the spelling as ‘draught’)
For some bulk cargoes, this is the method used to quantify or check the amount of cargo loaded. When this is the case, it is usually carried out by an independent surveyor and called a ‘draft survey‘.