NEW DELIVERIES


Ship safety award presented T


HE 2006 RINA-Lloyd’s Register Ship Safety Award has been presented to a


team from Southampton University, Ecocats Ltd, and the Port of London Authority for its innovative study ‘Wash reduction for vessels operating in shallow water and subsequent development of a wash-optimised design for river patrol craft’. The authors of this study, PA Wilson and AF


Molland from the ship science department at the University of Southampton; H Mayhew and A Fox from Ecocats Ltd; and RA Cartwright from Port of London Authority, picked up this award at the Institution's Annual Dinner at the Royal Lancaster Hotel, in London on 25 April 2007. This research, development, and design


project has added substantially to the potential for improved safety in inland waterway and inshore patrol and rescue craft, while also providing benefits to both the riverbank, atmospheric, and water environments. The initiative establishes a new level of


constructional and environmental ‘best practice’, now available to the benefit of other UK and overseas ports, inland water and rescue authorities, and the general public which they serve.


The winning idea The Port of London Authority and many other inland waters’ navigational and rescue authorities provide marine patrols for safety and assistance to other river users, including those in commercial pleasure craft, and members of the public enjoying their leisure afloat. Traditional designs of patrol and safety/


rescue craft, whether of semi-displacement or planing hull form, including rigid inflatable boats, create substantial wash when required to move at high speed, for example when responding to an emergency. Indeed, it is not unknown for rowers and


others in small vessels to be caused substantial distress by a rescue craft necessarily passing at high speed to another’s emergency. Furthermore, the large wash created at speed may be damaging to the riverbank environment and the high resistance created by the wash causes increased fuel consumption, with subsequent depletion of fuel resources and creates unnecessarily high atmospheric emissions. The characteristics of wash at high vessel


speed have been the subject of much research in recent years, particularly following accidents involving high-speed ferries operating at sea. However, the additional effects created by the shallowness of water, where under- keel clearance may be as little as or less than vessel draught, have until now not been widely understood. The Port of London Authority’s marine


engineer and harbour master recognised the importance of providing river patrols in vessels that caused the least wash at the range of normal and emergency patrol speeds. The winning submission describes the operational


4


Chelsea is the result of the study ‘Wash reduction for vessels operating in shallow water and subsequent development of a wash-optimised design for river patrol craft’, and recently won the RINA-LR Ship Safety Award.


driving forces for change, the processes that have been undertaken in the scientific study of wash characteristics of different hull forms operating at high speed in shallow river conditions, and the processes involved in the subsequent design and build of two new patrol launches for the PLA's Upper District. The theoretical studies and practical trials


were commissioned by the PLA to optimise the design for a replacement class of safety patrol launch, where the operational environment has constraints that limit the wave wake developed by the craft. The current design, a Nelson 35 semi-


displacement monohull, has been in service for many years and has proved a reliable and dependable craft but, at higher speeds, does create a substantial wave wake. To assess the potential contending designs -


of semi-displacement and planing catamaran hull forms - a series of computational and model tests were undertaken by the school of engineering sciences, University of Southampton, to determine wash characteristics not only for optimisation of the potential new designs but also, for confidence in the theory, the conditions created by the existing craft. This work demonstrated that existing theories


can be used to model the wave wake, in shallow water conditions, and that model tests at a scale appropriate for tank tests, and at ‘near full- size’ in the real operating environment, are in broad agreement. Subsequent to the research and trials


programme, the form and dimensions of the best-performing hull were fine-tuned, by the boatbuilder’s consultant naval architect, to achieve the buoyancy and performance characteristics required for operational deployment. Material selection, hull lay-up, and the


processes for construction (described in the submission) were focussed on achieving minimum weight commensurate with appropriate standards for commercial vessel design and MCA certification, while achieving minimum impact upon the environment by choice of ‘least depletion’ high-strength composites, and minimisation of waste. Traditional boat-building skills have been


readily adapted to these novel materials and techniques. The close involvement of the workforce, in developing the detailed vessel design and constructional processes, has provided further opportunity for weight- saving. The hull resistance data from the model


tank tests were used to calculate the power required to achieve the ‘emergency speed’, for operational service of the full-sized launches, at predicted displacement. Machinery selection is constrained by fuel type availability, within the operational area, and fineness of hull to achieve lowest wash. There is no marine petrol available on the


tidal Thames and commercially-available inboard engines would not fit, with room for ready servicing, within the intended fine hull dimensions. A diesel outboard machinery configuration


therefore became necessary. Within a very limited availability of suitable motors, Yanmar D36, 36hp diesel outboard engines were selected and built to special order. Calculations indicated that these engines should give an ‘emergency speed’ of 18knots, which exceeds that available from the existing launches. Throughout the design and build, the


combination of optimised low-wash/vessel displacement and performance in design; and careful attention to materials selection and processes in construction, should provide


SHIP & BOAT INTERNATIONAL MAY/JUNE 2007


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