Floatplane is a type of airplane that can take-off and land on the surface of the water, for that it is equipped with a float that is installed under the fuselage to serve the buoyancy force. An important phenomenon that often occurs and should be avoided during a take-off operation is porpoising because it causes longitudinal instability of the float which has an impact on passenger safety and comfort. This paper describes the porpoising mechanism and the variables that can influence the occurrence of this phenomenon. The most dominant variables include the location of the longitudinal center of gravity (LCG) and the deadrise angle which are optimized by considering the take-off speed. A numerical arrangement based on computational fluid dynamics (CFD) techniques is proposed to simulate a three-dimensional fluid flow around a free-floating float in calm water. The accuracy of the simulation results shows a good fit compared to the previously published experimental and numerical results.

In the operation of floatplanes, porpoising must be avoided, but it is a common occurrence during takeoff, as it induces longitudinal instability and compromises the safety and comfort of passengers. The mechanism of porpoising and the factors or variables that influence the occurrence of this phenomenon are explored in this study. Based on a review of the literature, the position of the longitudinal center of gravity (LCG) and the deadrise angle were found to be the two most significant variables affecting the porpoising phenomenon. The mechanism of porpoising was simulated using a numerical model based on computational fluid dynamics (CFD). The simulation findings were then compared to the results of a related model's towing tank experiment. With five velocity differences, a validated computational model was used to analyze the impact of LCG ordinates and deadrise angles on the frequency of porpoising. Compared to the LCG 50% length overall (LOA) configuration, the floater with an LCG 53% LOA configuration caused a higher heave porpoising amplitude by 4% for the floater with a 10° deadrise angle and 1% for the floater with a 20° deadrise angle at all speed variations. However, the pitch porpoising amplitude produced by the floater with an LCG 53% LOA configuration was found to be 4% higher than the LCG 50% LOA configuration for the floater with a 10° deadrise angle and -1% higher than the LCG 50% LOA configuration for the floater with a 20° deadrise angle. The results showed that the higher heave and pitch porpoising amplitude was generated by a low deadrise angle and a shift in the floater's center of gravity toward the bow.

Energy efficiency and environmental sustainability are important aspects in ship design and operation. Hull-shape optimization, hull cleaning and coating, and the use of appendages are, among others, well-known efforts to reduce ship fuel consumption. Regarding energy efficiency and environmental sustainability, it is possible to effectively reduce the resistance of an existing catamaran by retrofitting a foil system to it. In this study, a foil system is designed and retrofitted to a catamaran to reduce its total resistance. Reynolds-averaged Navier-Stokes simulations, utilizing k-w SST turbulence model, were performed to study the effects of the foil system on the vessel’s total resistance. Free surface effects were modelled, i.e., the generation of waves due to the vessel’s movement on the water surface. The foil system affects the wetted surface area, running sinkage and trim, and the wave pattern generated by the vessel, which ultimately affect the vessel’s total resistance. At relatively low speeds (Fr < 0.7), an increase of the total resistance, reaching a value of approximately 11%, was observed due to the foil system. However, at higher speeds (Fr > 0.7), the foil system decreases the total resistance, reaching a value of approximately 32% at the service speed (Fr = 1.24). The 32% resistance reduction at the service speed is promising in view of the intended purpose of the foil system as an energy saving device.

Considering recent global temperature increase and observed climate change, efforts have been made towards energy efficiency and reduction of green-house gas emission. A foil system is proposed in this study and retrofitted to an existing catamaran to reduce the energy use and to improve the vessel’s seakeeping characteristics. The objective of this study is to investigate the effects of the application of the foil system on the seakeeping performance of the vessel. CFD simulations based on a panel method were carried out to obtain the seakeeping characteristics of the catamaran with and without foil system. Simulation results show that the foil system reduced the vessel motions in a seaway: the heave-, pitch- and roll significant amplitudes were reduced 4.41, 9.97 and 3.30 percent, respectively, due to the application of the foil system. In addition, the vertical accelerations at the fore perpendicular (FP) and at deck were reduced 3.66 and 9.70 percent, respectively. A check against the NORDFORSK criteria for fast small crafts shows that the vessel can operate safely up to sea state 2.

Fishing has been one of the main sources of livelihood in Indonesia, to the point that it gives birth to numerous fishing culture preserved by the locals in the country. However, the development of Indonesia’s fishing tourism is quite slow, despite its identity as an archipelagic state. In attempt to boost the fishing tourism sector, this study proposes a design of a fishing boat with a touch of Pasuruan cultural heritage, a region in East Java. The design is hoped to attract the tourists’ attention by presenting them a local heritage fishing experience. Laminated bamboo is utilised as the boat’s material so it can be recycled as furniture when no longer in use. The boat’s main dimensions are obtained by means of intuitive design method. Technical calculations including the boat’s resistance and propulsion, required power and stability are carried out subsequently. The main dimensions for this boat are: LoA = 8.2 m; B = 1.1 m; H = 0.6 m; and T = 0.42 m. The service speed is set to be 7.5 knots. While the required power to move this boat is around 7.481 kW to power an electrical motor with 25 HP.