The latest fruition of Ecocat’s award winning company philosophy is two new technology catamarans designed and built specifically for the Port of London Authority by Ecocats. The new Ecocats E31 design for use as harbour/river patrol boats on the upper reaches of the River Thames replaces the PLA’s two Nelson 35 monohull craft. The first of these catamaran launches, ‘Chelsea’, has just gone into service after acceptance trials and crew familiarisation training. The second, ‘Richmond’ is scheduled for delivery in January 2007.

There were two factors behind the PLA’s decision to move to Ecocats. Alan Cartwright, chief marine engineer, explained that a prime concern on the tidal Thames is the wash made by powerboats. ‘Our patrols invariably meet rowers, from single sculls to racing eights, as they patrol the river. With a freeboard of only a few inches these are very vulnerable to wash. The new Ecocat catamaran launches create only one third of the wash caused by our old launches. Although we still slow down for rowers and other boats we can now respond to urgent calls without putting them at risk from our wash.’

The riverbank benefits too. Wash from boats creates erosion and subsequent silting as the mud and sand falls to the river bottom. It disturbs wildlife habitats, especially nesting and feeding birds, and has even been known to ruin a peaceful picnic! Less wash means less disturbance, less erosion, less silting.

The other environmental concern tackled by the provision of the new Ecocat launches is emissions. The old monohull launches retired from PLA service by the new Ecocats, were powered by 240hp diesel engines, giving a maximum service speed of 16 knots. The new Ecocats are achieving the same performance with twin Yanmar 36hp diesel outboards. Fuel consumption is 67% less than previously. Alan Cartwright commented, ‘For each Ecocat launch we’ll save 3,660 litres of fuel a year. With a litre of diesel producing 2.7kg of carbon dioxide, that represents almost 10 tonnes of CO2 per launch per year. Over the anticipated 15 year life of these two launches, we’re looking at a total saving of around 300 tonnes of CO2.’

Henry Mayhew, MD of Ecocats, anticipates environmental concerns beginning to influence all forms of vessel choice around the globe. ‘The PLA is leading other ports and harbour authorities in looking at green solutions. The ability to replace thirsty monohull launches with more economical and functionally equivalent Ecocats will enhance port and river authorities’ environmental credentials as well as their bottom lines.’

Captain Ray Blair, deputy harbour master for the Upper District, cites other advantages. ‘The new Chelsea and Richmond launches have been built specifically to meet our requirements. We involved the crews of the existing launches fully in their specification, with the objective of giving them a better working platform. The 10m Ecocat provides just that. It’s more stable and has a much bigger and more secure deck area. It has low freeboard, and with entry doors almost on the waterline recovery of casualties and debris from the water is much easier than previously. The boats turn in their own length, and at half the draught of the monohulls, can operate closer to banks and shoals, which is very important at low water.’

Both the old monohull launches have now been disposed of, leaving one Ecocat to cover both patrol zones for the next two months until the second vessel comes into service. ‘Because the low-wash speed of the new launch is so much greater, its effective range is much longer than that of the old boats, added Captain Blair. ‘An Ecocat can transit from the Tower of London to Richmond in a couple of hours, against the tide. With the older boats, limited to six knots because of wash considerations, the trip could have taken double that. With all the advantages of the Ecocat, we are very pleased that the first one is in service, with another to follow shortly. The new design of launch does exactly what it says on the tin, and as we helped write what’s on the tin, that’s gratifying.’

Indeed, the PLA has been closely involved with the new Ecocats E31 design ever since the Harbour Master was a guest on board an earlier E28 model which was working as a camera boat during the Oxford – Cambridge boat race. Favourable impressions led to a scientific study of the wash characteristics of different hull forms operating at high sped in shallow river conditions. Theoretical studies and practical trials involving the Nelson 35, the E28, and another catamaran were commissioned by the PLA to optimise the design for replacement patrol boats.

A series of computational and model tests were undertaken by the School of Engineering Sciences at the University of Southampton to determine wash characteristics and demonstrated that the Ecocats design produced wave wakes between a third and half those of the Nelson 35.

Subsequent to the research and trials programme, the form and dimensions of the Ecocats hull were fine tuned by the boat builder’s consultant naval architect to achieve the buoyancy carrying a 3.8 ton load and the performance characteristics required for operational deployment.

Material selection, hull lay-up and the processes for construction focused on achieving minimum weight commensurate with appropriate design standards and MCA certification while also achieving minimal impact on the environment by the choice of minimum depletion high strength composite materials.

Traditional boat building skills were readily adapted to the novel materials and techniques by the Ecocats boatyard at Torpoint in Cornwall UK. Technical director Andy Fox is experienced in the application of advanced foam sandwich mouldings and other systems for lightness and strength. Close involvement of the Ecocats workforce, many of whose background is in advanced aviation lamination rather than boatbuilding, was enlisted in developing the detailed vessel design and construction processes and provided further opportunities for weight saving. These highly skilled composite technicians built up the understanding of the local staff, thus adding to the strength of a re-emerging boat building industry in East Cornwall.

In the production of the Ecocats E31, maximum use of the foam sandwich was used in areas such the upper topsides and deck where the weight saving advantage could be taken. To obtain he necessary combination of impact resistance, panel strength and light weight, the hulls below deck level were constructed from a monolithic Kevlar matrix. Vinyl ester resins, which are most resistant to osmosis and consequent weight gain in later life, were drawn into the Kevlar matrix by vacuum bagging to provide the highest structural integrity and the least specific mass.

The transverse beams and all other structural members of the hull were moulded separately, again using vacuum bagging, and then bonded into the hull. This process ensured that material use could be tightly controlled, keeping weight 30% less than the traditional lay-up technique required for strength by the naval architect.

The vessel’s hull and component mould units have been designed such that resin infusion can be readily adopted for larger vessel builds. To the PLA boats’ river patrol and support duties could be added a list of other potential Ecocats applications, including diving support, escort duties, facilities inspection and maintenance, SAR and passenger ferrying.

Although the launches will operate on the relatively sheltered Thames, the vessels are coded MCA Category 3 (up to 20 miles offshore)

suitable for use in significant wave heights and wind strengths. ‘Chelsea’ was delivered from Plymouth to the Thames under its own steam, by sea, through typical Northern European autumn weather.

Ecocats managing director Henry Mayhew explains the thinking behind the design, saying, ‘Almost all patrol craft have their roots in military thinking, where power and speed were paramount. But that formula is not really applicable to many of today’s patrol operations, which have a major environmental agenda. What is needed today is craft that offer the same performance using much less power and making much less wash. Our objective is to provide users with craft which do everything they demand of their current fleet, sustainably.’

The Ecocats E31 is the result of inspired joint initiative by the client, the builder/designer and academia. It has established a new level of constructional and environmental best practice for small commercial vessel design which is now available to benefit a wide range of commercial and leisure users both in the UK and abroad.

A PLA Ecocats E31 will be on the floating pontoon at Seawork 2007, where Ecocats will also sponsor of the Divework component of the show.

MJ Information No: 22521