This study aims to develop an application software to support energy-efficient operation for small boats of less than 20 tons. In order to develop this system, statistical surveys have been conducted on the relationship between ship speed, engine speed, and fuel consumption on a 19-ton small boat for several years. As a result, it was confirmed that fuel consumption does not necessarily increase monotonically with an increase in ship speed. Authors considered that this phenomenon can be utilised for saving fuel consumption in small boats effectively. In order to realise it, it is required to identify fuel consumption trends and compare the trends with the observed data. However, fuel consumption trends are affected by hull fouling, load weight and trim balance. For this reason, fuel consumption trend needs to be determined for each voyage. For the convenience of boat operators, it is desirable that fuel consumption trends are estimated by an easy, simple, and cost-effective method as soon as possible after leaving the port. The method proposed in the previous study was highly accurate, but it was not convenient due to two problems. This study proposes a new method for estimating fuel consumption trends that solves these issues. In order to develop a new estimation method, this study focuses on the hull frictional resistance. It was assumed that the effect of wave-making resistance on energy consumption in small boats saturates at medium to high speeds, and frictional resistance becomes the dominant factor. Thus, the fuel consumption trend of the boat was analysed on the assumption that it follows a fundamental physical law proportional to the cube of the ship's speed. Based on these assumptions, this study developed a new equation model that expresses the fuel consumption trend of small boats sailing in medium to high-speed range. The fuel consumption trend determined with the new model achieved proper performance. In addition, the method of estimating the fuel consumption trend using this model solves the two problems of the method of previous study.
Kondo et al. (Sun,) studied this question.