Rolls-Royce is targeting the workboat sector with its new A5 Series line of Kamewa waterjets. Officially unveiled at the Workboat event in New Orleans, US in late November 2018, the A5 has been developed as a compact option for boats of approximately 10-25m in length, albeit with superior thrust to what might be typically expected from a smaller unit.
Fredrik Appel, Rolls-Royce general manager, product – waterjets, says: “We have listened to our customers asking for a smaller inboard footprint and adapted the design to meet this by reducing the space by 20%. However, we have also maintained an inlet waterway to accommodate the propulsion improvements.” Effectively, the A5 Series will gradually replace Rolls-Royce’s FF-branded jets. Shival Sapre, the group’s general manager for sales in the Americas, adds: “The A5 Series offers the best price per performance for vessels operating at speeds between 25-40knots…[including] workboats, motor yachts, smaller passenger vessels, patrol boats and other high-speed, shallow-draught vessels."
The A5 Series is manufactured from high-grade marine aluminium and, although comprising a “completely new product”, has been “developed on the same design principles as our steel series,” Appel explains. The new series comes in seven sizes, with power outputs spanning 100kW to 1,230kW, to cover a broad range of applications.
The launch has been preceded by intensive CFD analysis and model scale testing, which was carried out at the manufacturer’s Kristinehamn hydrodynamic research facility in Sweden, plus a round of sea trials aboard the group’s own demonstration craft in Finland. Consequently, in comparison to the FF-Series, the A5 is claimed to offer potential improvements of: 13% in bollard pull; 8% in steering and reversing efficiency; and 3% in pump efficiency.