Written by Kerryn Caulfield, Executive Director, Composites Australia Inc.
Central to this transformation has been the strategic integration of composite materials in workboats and ferries, responding to a clarion call for reduced fuel consumption and minimised greenhouse gas emissions. At the forefront of this innovation is the southern hemisphere’s first fully electric high-speed passenger ferry, Ika Rere, introduced by East by West Ferries and constructed by the Wellington Electric Boat Building Company (WEBBCo) in New Zealand.
Demonstrating the leap to electrification and efficiency, the 19-metre catamaran operates across Wellington Harbour, showing the viability of high-speed electric ferries in commercial settings.
The vessel, capable of transporting 132 passengers at speeds of up to 20 knots, features an extensive energy storage system that charges overnight using a 300 kW shore-based charger, and is equipped to accommodate future infrastructural developments for rapid 1 MW charging.
This project’s success stemmed from a synergy of maritime experts focusing on various aspects such as hydrodynamics, energy propulsion, and infrastructural support, all geared towards optimising operational efficiency and achieving a sustainable return on investment—coupled with the significant advantage of zero operational emissions.
The operational cost of ferries, mainly driven by energy consumption and maintenance, can dwarf the initial purchase price. Transitioning to electric propulsion presents a promising avenue for cost Systems (ESS) bring a significant weight penalty, which paradoxically can hike energy demands. Addressing this, the focus turned to reducing the structural weight without compromising the energy storage capability.
Gurit’s approach involved energy modelling and cost analysis to determine the best construction materials, balancing displacement, energy efficiency and durability. The selection of carbon fibre—despite its higher cost per kilogram compared to aluminium or fibreglass—proved crucial. It provided a structure that was not only strong but significantly lighter, enabling considerable energy storage without the added burden. As a result, Ika Rere enjoys a remarkable 75 per cent reduction in energy costs per trip compared to diesel counterparts.
Weight management extended to every corner of the vessel, employing techniques like using heavy multiaxial fabrics for toughness while simplifying the build process. The design also integrated structural seating to further diminish the need for additional support structures.
Gurit applied principles from high-performance yacht construction, known for its pursuit of speed, into a commercial context. Comprehensive 3D modelling served as the groundwork to streamline the assembly process of the vessel modules in parallel with reducing material waste.
To maintain structural integrity while minimising weight, Gurit created large format structural panels, each 9 metres by 2 metres, which could be assembled swiftly and with minimal excess weight from connections. These were vacuum-infused, a technique ensuring optimal resin content, reinforcing the lightweighting initiative.
A critical component of the design was fire protection in the battery space. An A30-rated fire boundary and a resilient composite structure with integrated intumescent materials were crafted to safeguard the ferry’s structural integrity. Additional safety features included fireproof sealing and thermally protected hatch fasteners to prevent heat and smoke transfer to passenger areas.
Ika Rere’s successful launch and subsequent operation have proven its design’s merits. In its first year, the ferry saved an estimated 220,000kg in carbon emissions and decreased East by West Ferries’ total fuel consumption by 40 per cent. The cost of energy for a round trip on Ika Rere is a mere quarter of that required for a similar diesel-powered journey.
In conclusion, the Ika Rere is a model of how technical innovation, environmental consciousness, and economic pragmatism can be harmonised. The success of this vessel showcases the potential for such technologies to revolutionise maritime transport, offering a blueprint for future endeavours in the sector.
CONSTRUCTION INNOVATIONS OF THE IRA KERE
Modular Innovation meets Commercial Maritime
In the competitive sailing world, an extreme lightweighting approach is crucial for performance. Gurit has successfully transferred this high-performance methodology into the commercial maritime sector with Ika Rere. The key was developing a modular construction process that relied heavily on digital manufacturing and the proprietary use of Gurit Hi-Panels.
Digital Precision in Design and Fabrication
The vessel’s design and construction capitalized on comprehensive 3D modeling. Every aspect, from the overarching vessel geometry to the intricate onboard systems, tooling, and jigs, was digitally rendered to ensure millimetre-accurate precision. This meticulous attention to detail provided by a unified digital model guaranteed a seamless fit during assembly, reducing the risk of errors that can occur with traditional construction methods.
Innovative Use of Carbon Fibre and Corecell™
Gurit’s Hi-Panels, crafted from carbon fibre and Corecell™, were essential in achieving the desired weight reduction without sacrificing strength. These components were pre-laminated, CNC cut to exact specifications, and then delivered to WEBBCo for efficient on-site assembly. By shipping these pre-fabricated sections, the construction process became more akin to an assembly line, enhancing speed and reducing overall build time.
Large Format Panels for Efficiency
The production of large format panels, measuring 9 metres by 2 metres, further enhanced the efficiency of assembly. These oversized panels facilitated quicker construction, as fewer pieces needed to be joined together, significantly decreasing the ‘parasitic weight’—the excess weight that typically comes from bonding smaller panels together. Additionally, the vacuum infusion process for these panels ensured precise resin-to-fibre ratios, avoiding the addition of unnecessary weight and optimizing the panel’s strength-to-weight ratio.
Advanced Techniques for Complex Shapes
Female moulds and thermoformed foam cores were utilized for the curved areas of the hull. The thermoforming process shaped the Corecell™ material to the exact curves of the hull, minimizing resin usage and further contributing to the weightsaving objectives. This technique not only reduced the hull’s weight but also maintained the integrity and hydrodynamic efficiency necessary for the vessel’s high-speed operations.