This paper consists of two parts. In the first part, prediction methods of the roll damping of a ship proposed by one of the present authors are experimentally examined to confirm the applicability of them to a barge The experimental results are compared with the results by the prediction methods. The comparisons demonstrate that the prediction method is valid only when the roll amplitude is smaller than five degree and that at large roll amplitude the methods gives overestimated results. In the second part, the effect of a new antirolling device using vertically oscillating fins on roll motion reduction of a barge in waves is experimentally investigated. Since the system is effective even if the barge has no forward speed, it can reduce the ship motion when the barge operates installation works in ocean at zero forward speed.
Barge type ships are used to transport large offshore structures like jack-up rigs, jackets and semisubmersible rigs, and crane barges are used to install various offshore structures in offshore and ocean. For such a barge ship, the knowledge of the seakeeping quality of it is very important to secure the cargoes from severe damage or to operate the installation safely and efficiently. Ship-motion theories have been developed for these thirty years as well known. Now the seakeeping quality of a ship like a conventional cargo ship can be estimated by using these theories in enough accuracy for practical purpose, if the non-linear roll damping due to vortex shedding phenomena is obtained by experiments or by some prediction methods. Ikeda (1976,1977a,1977b,1978a), one of the authors, proposed a practical method to predict the viscous roll damping moment acting on a conventional cargo ship on the bases of experimental results and theoretical calculations.
