3.5 Uncertainties

  3.5.1.1 The model may turn out to be more stable than the ship due to scale effects. This problem seems to be less serious when employing a large model. Consequently, to reduce this effect model scale ratios comparable to that considered acceptable for resistance and self-propulsion tests should be specified for manoeuvring tests that use a free-running model. Captive model tests can achieve satisfactory results with smaller scale models.

  3.5.1.2 While the correlation data currently available are insufficient to give reliable values for the accuracy of manoeuvring model test results, it is the intent of the Standards to promote the collection of adequate correlation data.

  3.5.2.1 The mathematical model that can be used for the prediction of the manoeuvring performance depends on the type and amount of prepared data.

  3.5.2.2 If there is no available data, under assumptions that resistance and self-propulsion factors are known, a set of approximate formulae for estimation of the derivatives and coefficients in the mathematical model will become necessary to predict the ship’s manoeuvrability.

  3.5.2.3 If there is enough experimental and accumulated data, it is desirable to use a detailed mathematical model based on this data. In most cases, the available data is not sufficient and a mathematical model can be obtained by a proper combination of different parts derived from experimental data and those obtained by the estimated formulae.

Figure 1 The equilibrium yaw rate/rudder angle relation

Figure 2 Definitions used on turning circle test

Figure 3 Zig-zag 10°/10° test

Figure 4 Definitions used in stopping test