3.1.1 To be able to assess the manoeuvring performance
of a new ship at the design stage, it is necessary to predict the
ship manoeuvring behaviour on the basis of main dimensions, lines
drawings and other relevant information available at the design stage.
3.1.2 A variety of methods for prediction of manoeuvring
behaviour at the design stage exists, varying in the accuracy of the
predicted manoeuvres and the cost of performing the prediction. In
practice most of the predictions at the design stage have been based
on three methods.
3.1.3 The first and simplest method is to base
the prediction on experience and existing data, assuming that the
manoeuvring characteristics of the new ship will be close to those
of similar existing ships.
3.1.4 The second method is to base the prediction
on results from model tests. At the time these notes were written,
model tests must be considered the most reliable prediction method.
However, it may be said that traditionally the requirements with regard
to accuracy have been somewhat more lenient in this area than in other
areas of ship model testing. The reason for this has simply been the
absence of manoeuvring standards. The feedback of full-scale trial
results has generally been less regular in this area than in the case
of speed trials. Consequently the correlation basis for manoeuvrability
is therefore of a somewhat lower standard, particularly for hull forms
that may present a problem with regard to steering and manoeuvring
characteristics. It is expected that this situation will improve very
rapidly when it becomes generally known that a standard for ship manoeuvrability
is going to be introduced. Model tests are described in section 3.2.
3.1.5 The third method is to base the prediction
on results from calculation/simulation using a mathematical model.
Mathematical models are described in section 3.3.