Page 71 - Practical Ship Design

42 Chapter 2

2.5.4 Research vessels - hydrographic, oceanographic and fishery

These are fairly small ships but often have to go to remote waters where help, if
needed, will not come quickly. Some of their voyages will take them to the more
stormy regions of the world. Good sea-keeping and good reliability must therefore
come high in their requirements. Whilst a need for good sea-keeping is based on
safety considerations, another almost as important consideration is the need for
these ships to have limited motions to facilitate the work of their scientists who
may have to carry out delicate tasks and are frequently unused to working in a
violently mobile environment.
Some aspects of scientific work require a minimum of noise and vibration and
limits should be set for these in consultation with the scientists who should,
however, be given a clear idea of the costs that may be associated with meeting low
signatures to dissuade them from over-specification.
An ability to operate at low speeds is usually required as is an ability to handle
boats and scientific equipment over-side, over the stern or via an internal moon
pool.

2.5.5 Fishing vessels

The main requirements that need to be set for fishing vessels relate to the type or
types of fishing for which they are intended: bottom trawling for demersal species
or mid water trawling for pelagic species, long lining, etc. The next most important
requirements are the time that has to be spent at the fishing ground and its distance
from the port at which the catch is to be landed. As most fishing vessels are small
and they go to sea in all but the most stormy conditions, another requirement is
very good seaworthiness.

2.5.6 Fish factory ships

Where the distance to the fishing grounds involves a lengthy voyage, it may be
necessary to process the fish on board so that the product remains in good condition
until it is landed. Once the decision to process on board is taken, the corollary can
clearly be a much longer stay on the fishing grounds, a bigger catch per trip and a
much larger ship. There are several different types of processing to suit different
types of fish and different markets and it is necessary to specify the one required.

2.5.7 Oil production vessels
There is a wide range of vessels involved in oil production: exploratioddrilling
rigs, supply boats, safety vessels, oil storage and tanker loading vessels, and
floating oil production vessels.