Optimising Storage Space

When considering production costs for a vessel, the most cost influencing parameter is the length of the ship. Assuming certain practical limitations on breadth and draft, it is important to achieve the accommodation of the longest possible cargo space within a given ship length. When considering a vessel of a bulk carrier / container type, the goal is to create a prismatic cargo space. With regard to the bow, the lines define the loss in "pay-length" at this end. These can be optimized in various ways including the introduction of bulbs or 'bulbous bows', which is a common feature today.

The stern end including the machinery space, steering gear platform, aft peak, rudder and propeller shaft boss is an area where one can see a number of solutions to minimize the distance from the transom to the forward machinery bulkhead.

When considering conventional propulsion machinery, the length of the engine plus reduction gear (where applicable) is the most dominant factor for determining the above-mentioned distance. The selection of a suitable engine type and gearbox configuration is therefore important. The length occupied by the tail-shaft, propeller and rudder can be marginally influenced. Necessary auxiliary machinery is positioned on platforms, above and on the sides of main machinery. To achieve full breadth in the aft end, a barge-type stem should be considered.

The design of the stern end around conventional optimized main machinery will finally have a limitation when it comes to the possibility of minimizing the length of the machinery space, i.e. the station where the forward machinery bulkhead can be located and thus how long the prismatic load box will be. In the modern bulk / container vessel design of today, it may be assumed that one has considered most of the possibilities with regard to optimizing the stern when utilizing a conventional machinery concept.

Layout and General Features

For any normal self-propelled ship the following functions are essential:

A Propulsion System

This provides the necessary thrust to give the vessel in question a specified speed (in some cases the static thrust or bollard pull is also of importance). The normal answer to this function is a conventional marine propeller with a shaft line, stern tube with seals, and line shaft bearing and reduction gearbox (in the case of medium or high-speed diesels). Remote control of the machinery from the bridge is normally incorporated as well (Refer Figure 17.1).

A Steering System

This provides for control of the ship's steering and course keeping at ship speeds, at which the rudder is efficient. The standard solution is of course a conventional rudder with a rudderpost, bearings and steering gear with auxiliaries. In the wheelhouse, a means for rudder control is available (a wheel, lever or a similar device) with a control link to the steering gear system. An interface for an autopilot system is normally arranged.

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