Page 177 - Practical Design Ships and Floating Structures

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The present work is to develop a 2,500ton class trimaran and to quantify the powering performance of
it. A series of resistance tests and numerical calculations were carried out to investigate the influences
of side-hull form and the location of side-hull on the resistance characteristics of trimaran. Also, the
propulsion test was conducted to investigate the propulsion efficiency of the trimaran, and the
powering performance of it was compared with that of the similar mono-hull ships in full scale.

2 PRINCIPAL DIMENSIONS AND HULL FORM DESIGN
2.1 Principal Dimensions

Hull form should be designed to satisfy the whole hydrodynamic performance at design spced, where
the resistance performance is very important. In particular the main hull and side-hull should be
optimized at the same time to ensure the excellent resistance performance for the trimaran. The key
parameters for trimaran design are main hull length to beam ratios, side hull length and location etc.
The principal particulars of the 2,500ton class trimaran are shown in table 1, which are decided from
the concept design refemng to the design requirement and the ‘RV Triton’.

TABLE 1
PRINCIPAL PARTICULARS OF THE 2,500TON CLASS TRIMARAN
Item (unit) Main Hull Side-Hull Trimaran
Displacement (ton) 2,324 176 2,500
Length between perpendiculars (m) 120.0 45.0 120.0
Breadth (m) 9.0 1.8 30.0
Depth (m) 12.0 12.0
Draft (m) 4.2 2.5 4.2
Block coefficient 0.50 0.423
Water-plane area coefficient 0.7745 0.9
Mid-ship section area coefficient 0.8468 0.5
Longitudinal center of buoyancy -2,48 0.0
(%)
Cruising speed 18 knots (Fn=0.27)
Maximum speed 30 knots (Fn=0.45)
Propulsion Twin propellers, diameter = 3.h

2.2 Hull Form Design

The wave resistance of the main hull affects dominantly on the resistance performance of the trimaran.
Therefore, it is very important to find out the hull form with excellent resistance performance for the
design of main hull form at initial design stage. A displacement type hull, which was recently
developed as a high-speed hull in KRISO, was selected as a parent ship of the main hull. Three kinds
of side-hulls (inboard, symmetry and outboard type) with a wedge shape were designed refemng to
Ackers.(1997). Figures 1 & 2 show the graphic model of the trimaran and the definition of the
side-hull location at each. Figure 3 shows drawings of main hull and three kinds of side-hull.

3 MODEL TEST AND NEMERICAL METHOD

The numerical and experimental studies were conducted to figure out the influences of side-hull form
and location on the resistance characteristics of the trimaran. And the propulsion test was also
conducted to investigate the propulsion efficiency of the trimaran.