Leading classification society ClassNK and Nakashima Propeller Co., Ltd have announced the world’s first installation of a carbon fiber reinforced plastic (CFRP) propeller on the main propulsion system of a merchant vessel. The CFRP propeller was installed on the Taiko Maru, a domestic 499 GT chemical tanker owned by Sowa Kaiun YK by Marugame-based Koa industry Co., Ltd. in May 2014. The CFRP propeller installed on the vessel was developed and produced by Nakashima Propeller Co., Ltd. with support from ClassNK, which granted approval for the design and manufacturing process of the CFRP propeller, as well as provided research and funding support for the project as part of the ClassNK Joint R&D for Industry Program.
Research and development on the use CFRP propellers for merchant vessels in Japan was supported by the Nippon Foundation and the Japan Ship Machinery & Equipment Association (JSMEA) from 2007 to 2011. From 2012, this research continued as a joint research project carried out by Nakashima Propeller Co., Ltd, the University of Tokyo School of Engineering, Japan’s National Maritime Research Institute (NMRI), NYK Line, MTI Co., Ltd., Imabari Shipbuilding Co., Ltd, and ClassNK as part of ClassNK’s Joint R&D for Industry program.
Despite its ultra-lightweight composition, CFRP exhibits the same, if not superior strength, to the aluminum-bronze composite materials used in conventional propellers. Due to the light weight of the propeller, however, propeller shafts can be manufactured with smaller diameters, contributing to a significant reduction in weight and fuel costs.
The sturdy yet thin blades of the CFRP designed by Nakashima Propeller Co. Ltd. have been designed with an increased diameter similar to the wings of a Boeing 787 aircraft. This should allow CFRP propellers to achieve even greater efficiency when employed for maritime use and the potential for further performance improvements continues to be explored via testing model tank testing.
The Taiko Maru had already previously installed CFRP propellers in its side thrusters in September 2012. Based on their successful performance, Sowa Kaiun YK made the decision to extend use of the CFRP propeller technology to its main propulsion system, making the vessel the first in the world to use a CFRP for its main propulsion system.
During sea trials the CFRP required 9% less horsepower to operate compared to conventional aluminum-bronze propellers, and expansion of their use on merchant vessels is expected to contribute to better fuel economy and greater efficiency in operations.
As part of its contribution to the project, ClassNK carried out rigorous fatigue testing and material testing to assess the basic mechanical properties of the propeller, as well as conducted static load testing on full-scale propeller blades to determine the adaptability of the propeller for marine-use prior to approving the CFRP propeller for use as part of the merchant vessel’s main propulsion system,
ClassNK also carefully evaluated the manufacturing process and quality control systems for the 2.12m diameter CFRP, and expert ClassNK surveyors further assessed mechanical properties and results of stress analysis tests for each component during the vessel’s construction, as well as verified the installation of the system during construction.