In the Iguana view, most workboat design innovation over recent years has aimed primarily at increasing vessel speed. In the current political and economic climate, the issue of vessel speed and subsequent fuel consumption/ cost intersects with pressure on vessel operators to embrace new environmental imperatives. Craft should be as economical and environmentally friendly as possible with regard to fuel efficiency, emissions, shoreline impact, and integration with other forms of transport.

Iguana sees the tide of environmental pressure rising to demand standards of compliance exceeding the requirements of marine legislation such as MARPOL Annex VI. Repercussions in vessel operations will first hit workboats and ferries operating in close proximity to populated areas.

The Iguana envisioned accommodation of conflicting interests sees vessels fuelled by compressed or liquefied natural gas, a clean and abundant energy source favoured by the UK Government. A long-standing reduced duty on natural gas provides a cost advantage of approximately 10% over marine diesel for vessel operators.

The crystallisation of Iguana Seacraft's natural gas marine propulsion vision is the Eco Ferry catamaran design (see www. ecoferry. iguanas. org). The vessel's carefully designed hull form combines a low resistance and low wash underbody with a powerful topside section for enhanced seakeeping in estuarial chop. The aluminium construction is based on a longitudinally framed system for DNV classification. The 25m craft is to be powered by two natural gas fuelled engines of 900kW each, coupled to conventional shaft and propeller drivetrains for a speed of 25 knots at 85% MCR.

Benefits of such a vessel would be appreciable fuel cost savings, longer service intervals, reduced noise and low exhaust emissions, the latter aspect carrying the potential to attract public funding.

Natural gas fuelled vessels are already operating in the Norwegian offshore industry and the USA is studying a natural gas programme, with the possibility of breakthrough natural gas powered ferries operating in San Francisco Bay.

MJ Information No: 16832