Trans RINA, Vol 157, Part C1, Intl J Marine Design, Jan - Dec 2015


opportunity was taken to incorporate novel features as the


(TriSWACH) hullform.


Trimaran Small Waterplane Central Figure 6 shows


s such Hull


the overall


configuration of the illustrative design and Table 4 gives the principal particulars.


L ike all small waterplane requires ballast tanks


to


hullforms, t maintain th


he TriSWACH e


draft within


acceptable limits for seakeeping. For a small craft like a WFSV, there is ample volume in the submerged bulb to accommodate ballast tanks, a


as shown in Figure 8. As this


virtually doubles the volume required for fuel tankage, the impact on the design can become significant as range increases.


Figure 6: Illustrative WFSV design showing hullform and upperdeck equipment


Table 4: Principal partic ulars for the UCL WFSV design Displacement (maximum)


Length Ove erall


Length Waterline (centre) Beam Water


rline (centre)


Bulb Diameter (Horizontal) Draught Overall


Clearance Under Box Length Waterline (side) Beam Water Draught (side) Accommodation Endurance


rline (side)


Propulsion Power Maximum Speed Generating Power


4.3


159te 24.5m 23m 1.5m 3.5m 2.6m


3.15m fwd / 1.65m aft 16m


0.75m 2m


12 technicians & 6 crew 24 hours @ full speed 1600kW 22.5knots 72kW


HULLFORM AND “FLOAT” FUNCTIONAL GROUP


Figure 7 illustrates the TriSWACH hullform and lo of the aziimuthing propulsors. The TriSWACH is a variant on the trimaran hullform, featuring a central hull consisting of a submerged bulb and a narrow surface piercing strut. Stability is provided by the long side hulls. Proposed by Dubrovsky [20] this hul lform has a greater surface area than an equivalent displacement trimaran, but the very


ocation y small waterplane area significantly reduces


both wavemaking resistance and motions. The latter aspect is of particular interest for a WFSV as the reduced pitch and heave will increase the ability to transfer personnel to turbines, and provide greater flexibility in selection and location of the turbine access equipment to be fitted.


Figure 7: Bowview of the UCL WFSV showing the TriSWACH hullform and location of the azimuthing pr


ropulsors between the hulls.


Figure 8: UCL WFSV design showing the “FLOAT” Functional Group, including ballast tanks in the hull


UCL has examined the application of the TriSWACH hull to a range of warships, including OPVs [21], destroyers [22] and small aircraft carriers [16]. A variant of this concept has been developed by Austal and used in the 27m turbine access vessel Cable Bay [23].


4.4 “MOVE” FUNCTIONAL GROUP


Figure 9 shows the MOVE Functional Group, primarily consisting of the propulsion machinery but including motion control (stabiliser machinery) and the cockpit.


The narrow strut makes installation of machinery in the lower hull difficult, unless delta shaped waterlines are used as in the Austal design. However, the large de ck in multihulls allows an upperde ck


area available machinery space to be incorporated. This has potential © 2015: The Royal Institution of Naval Architects C-141


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