Experimental study of hydrodynamic effect of loading and longitudinal variations of the center of gravity on the performance of a single-step craft in calm water

Performance of stepped planing vessels is notably influenced by loading and longitudinal position of the center of gravity. These factors directly affect trim angle, rise, total resistance due to motion, and overall hydrodynamic efficiency. This study experimentally investigates a 2.5 m Fridsma series model with 20° deadrise angle, length-to-width ratio of 5, step distance of 28% of the overall length from the transom, and step height of 4% of the model's width. It involves testing the model with two different weights: 63 and 76.6 kg, corresponding to load coefficients of CΔ=0.5 and CΔ=0.61. Center of gravity is placed at 0.8 m (32%), 0.85 m (34%), and 0.9 m (36%) from the transom. Experiments are conducted at speeds of 1, 2, 3, 4, 5, 6.5, and 8 m/s, which correspond to beam Froude numbers of 0.45, 0.9, 1.35, 1.8, 2.26, 2.9, and 3.6, respectively. The results indicate that increasing the load from 63 to 76.6 kg leads to approximately 12% increase in static trim across all center of gravity positions. The final trim is shown to increase by around 15% at all tested speeds. Additionally, load variations result in 20% rise in the rise up and total resistance. The model achieves optimal performance with load coefficient CΔ=0.61 and center of gravity at 36% of the overall length from the transom, showing the lowest resistance to weight ratio. Overall, the findings reveal that optimizing internal load distribution and LCG placement can enhance the boat's hydrodynamic efficiency, resulting in improved speed, stability, and fuel economy under different operational conditions.