Handling performance of a vessel is greatly related with her steering characteristics which consist of two kinds of motion characteristics ; namely course stability and turning ability. The correct prediction of the qualities, especially the steering characteristics is as much important in ship handling as in ship design. It is the purpose of this paper to provide ships handlers better understanding of steering characteristics and then to help them in safe controlling and maneuvering of vessels presenting distinct inherent steering characteristic difference that lies between a fine-form vessel and full-form vessel. The authors calculated dynamic course stabilities of two kinds of ideal models, one of which represents a fine-form ship and the other a full-form ship, based on hydrodynamic data of forces and moments obtained by model tests in maneuvering tanks. The result of calculations indicated that a ship of full-form configuration has inhernet course instability. Though significant nonlinearties affect ship montions in maneuvers, application of linear theory is sufficient for prediction of the maneuvering characteristics of vessels on calm waters for handling reference.

The Navigational System is the Fundamental System of Port Transportation System and comprises 3 Subsystems, say, the Waterway System, the Shiphandling System and the Support System. The Waterway System of Navigational System is the important and fundamental System for Traffic Safety inside the Port like a Car Road System on Land. This study aims to make a Guideline for the Optimal Waterway System of Port Development and Safety. The Conclusion of this Paper are drawn : 1) The complicated Shiphandling Operations should be avoided for the period of Physical night Time for eliminating the Human Errors. 2) For the Maneuverability and all-weather Combined Piloting the Inside Turn Point Buoy and Begin the-turn Buoy should be mounted with Racon(T) and Radar Reflector for foggy and bad weathers. 3) The Seabuoy located in the Approaching Area for Pilot Station and making Landfall should be mounted with Racon(G) and Morese A Light for giving a Hint of Pilot Station to the Captain on the Bridge, and these Equipments of Racon and Light should be operated normally and effectively even in a Heavy and stormy weathers. 4) A Basic Practical Expression, 1/2 L sin D, for calculating the Extra Width of Cutoff Turn Regions was derived Originally from the Viewpoint of Turn Maneuvers and Maneuverability of the Ship.

Marine casualities in the high sea are mainly classified into the breakage of hull and capsize , of which the latter occurs frequently to a small craft and container vessels by extreme rolling. The aim of this study is to develop shiphandling techniques for the prevention of ship's large rolling by way of evaluating dangerous degree of rolling in heavy weather. In this study, rolling motion is analized by using statistical method as follow : (1) 8 sample ships is presented for calculation. (2) Analized sea state are Beaufort scale 7 and 10 (wind velocity 30kts and 50kts respectively) and significant wave height is put as 5.2m and 11.2m. (3) The formula recommended by International Towing Tank Conference (ITTC) is used to calculated the wave spectrum. The results of this study are as follow : The results of this study are as follow : (1) Most of the vessels with beam of 20 meters or less was found to be capized in the waves abeam under the sea condition of Bearfort scale7(30kts). (2) For the vessels range 20m to 30m was found safe under the sea conditions of Bearfort scale 7(30kts) and imminent danger under the sea condition of Beaufort scale 11(50kts). (3) It is proved that any vessel could be capsized by heavy rolling regardless of vessel's size whenever the motion is synchronized with waves abeam. This study concludes that the navigator, especially at night , must anticipate the exact wave direction, referring to the wether report and coastaline, not to lay the vessel in the serial wave abeam.

The transportations of most of cargoes in world trade have been fulfilled through sea lanes and it seems this trend will not change in near future. Nowadays, inview of the technical aspects of merchant vessels, they are continuously enlarged in hull size and greatly specialized in structure for the cargo spaces and dramatically automatized in navigating, piloting, cargo operating and various other operations, which unavoidably require high technicals in operating the modern merchant vessels. On the contrary to the trend of requiring of operating high technicals, the capabilities of crew on board have been gradually declining in technical competence and their morale for accomplishing their duties on board vessels has greatly falled won compared with that of old days. The above result inevitably brings many problems in operating modern vessels and causes accidents which are avoidable through good competence and high morale of the crew. We intend to analyze the causes of several great sea accident with which it seems some human errors are connected more or less directly or indirectly. We hope that this study could suggest some measures which help to prevent the recurrence of similar accidents by Korean ship's crews.