Page 161 - Practical Design Ships and Floating Structures

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form and position, the total resistance could be the same or even smaller in comparison with the
equivalent catamaran or monohull.
In this work the results of towing tank trimaran resistance tests performed at University of Naples are
presented. The first part of the research programme has dealt with the modification of transverse and
longitudinal position of outriggers in order to minimise the total hydrodynamic resistance through
favourable wave interference among the hulls and favourable effect of the lift. The influence of the
side hull form on the total resistance has been considered testing two different outrigger forms. Special
attention has been focused on model ship correlation; resistance data of two trimaran geosim models
have been analysed through the ITTC-57 and ITTC-78 correlation procedure.

TABLE 1
PRINCIPAL CHARACTERISTICS OF THE TRIMARAN IN FULL SCALE

2 THE TRIMARAN MODEL CONFIGURATION
The resistance model tests were carried out on trimaran ship design whose main characteristics are
reported in Table 1. A round bilge transom stem displacement hull with high length to beam ratio was
selected from series 64 as the main hull. Two different side hull forms were selected: one was the well
known Wigley mathematical form and the second one was derived by geometrical affinity from the
series 64. Each outrigger hullform had length equal to one half of the main hull length and
displacement equal to 4 % of the main hull. The trimaran hulls body plan is shown in Fig. 1.
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Figure 1 : Trimaran hulls body plan