Hydrodynamics Factors Correspond to the Weather Criterion Applied to an Indonesian Ro-Ro Ferry with Different Weight Distributions

Abstract

The effect of weight distribution on hydrodynamics factors in the weather criterion was investigated. Two types of weight distribution were examined. With the first type of distribution, the weight was concentrated near the centerline of the model. With the second, the weight was positioned farther from the centerline in order to obtain a natural roll period corresponding to that provided by the standard formula in the weather criterion of the International Maritime Organization (IMO). The three-step procedure recommended by the IMO was applied. A roll decay test and a roll test in a regular beam wave were conducted to obtain the natural roll period, the damping factors corresponding to the breadth-to-draught ratio and the bilge keels, and the effective wave slope coefficient. The damping factor corresponding to the breadth-to-draught ratio for the ship with a larger radius of gyration was larger than that for the ship with a smaller radius of gyration. The ship with a smaller radius of gyration had a larger damping factor due to bilge keels compared to the ship with a larger radius of gyration. The effective wave slope coefficient of the ship with the larger radius of gyration was larger than that for the ship with the smaller radius of gyration. The effect of bilge keels on the effective wave slope coefficient for the ship with a radius of gyration equal to that obtained by the weather criterion formula was not significant. The effect of weight distribution on the weather criterion was significant for the ship without bilge keels. A significant effect of bilge keels on the weather criterion occurred for the ship with a weight distribution corresponding to a radius of gyration coefficient closer to that obtained by the formula in the weather criterion.

Vulnerability of Ship with a Large Breadth to Draught Ratio Against Excessive Acceleration Criteria

“…On the other hand, the damping coefficient, for the vulnerability criteria level 1 called as non-dimensional logarithmic decrement of roll decay could be underestimate. Some researches corresponding to the effect of bilge keels on the damping moment of a ship with large breadth found a significant effect mainly if the ship has a large vertical centre of gravity [12], [13]. A ship with large lateral acceleration should pay attention on the handling of pay load to avoid shifting which can significantly affect the ship stability.…”

“…𝜎 𝐿𝐴𝑖 is the standard deviation of lateral acceleration corresponding to wave characteristics follow the scatter wave data used to determine the short-term environmental wave condition. This standard deviation is calculated by using the equation (13).…”

Alternative Method for Stability Assessment of Indonesian Traditional Wooden Boats

“…where 𝑘 is the damping factor due to the bilge keels, 𝑋 1 designates the damping factor corresponds to the breadth-to-draught ratio and 𝑋 2 designates the damping factor corresponding to the block The damping factors corresponding to the breadth-to-draught ratio and the bilge kees are determined by using the procedure proposed by Paroka, et al [7], [9]. The damping factor due to the block coefficient, the effective wave slope coefficient, and the wave steepness is determined following the values given in the vulnerability criteria level 1 [5].…”