Page 73 - Practical Ship Design

44 Chapter 2

2.5.12 Oil production vessels

Most of the requirements stated for the storage vessel apply, with one major differ-
ence being that a production vessel will generally have a moon pool surmounted by
the production derrick with a pipeline dropping directly to the sea bottom and the oil
well beneath. This requires a definitive statement of the permissible movement of
the ship about this fixed point, together with a specification of the worst wind and
sea conditions in which production should be able to continue. As the oil reaching
the ship is raw crude, it is necessary to specify what type of oil is envisaged and in
particular the anticipated gadoil ratio.

2.6 STAFF REQUIREMENTS FOR WARSHIPS AND NAVAL AUXILIARY
VESSELS

2.6.1 Stafs requirements - general

Setting the staff requirements for warships or naval auxiliary vessels is a very
difficult task which may have to start with a political assessment of possible
enemies and allies and an estimate of the naval assets each of these may have at
some time in the future.
With “a week being a long time in politics” it is essential to consider a large
number of alternative scenarios. Only after pondering these very carefully is it
possible to move to consideration of the requirements for a particular ship or class
of ships - noting that these will not enter service for several years and will then
remain in service for a lengthy period.

2.6.2 Frigates and corvettes

One of the more significant differences between setting the requirements for a
warship and those for a merchant ship, including service and offshore working
ships, is that the requirements of all these can usually be set on an individual ship
basis, whereas those of a warship may have to consider scenarios both for the ship
operating on its own and with other vessels, either getting support from or giving
support to these.
This greatly complicates the task of setting the requirements for a new ship, as
does the related and continually debated question of whether a limited budget
should be devoted to a small number of highly capable ships or be spread more
thinly over a larger number of cheaper but less effective vessels.
The argument for spending money on minimising signatures, for example, goes
thus: if the enemy can detect your ship, he is a long way towards sinking or