There is a vessel which shall not impede the passage of any other vessel in the COLREGS 1972. But the issue was raised that the words of "not to impede" were vague. Therefore, IMO adopted new paragraph (f) to be added to Rule 8 that a vessel which is required not to impede the passage of another vessel is not relieved of this obligation if approaching the vessel so as to involve risk of collision. It means that the ship which is obliged not to impede should contributes to avoid collision and to the safe passage of the other vessel. Also it results that the application of Collision Rules should be changed. But until now, it seems that the mariners are not familiar with this subject. This paper, therefore, aims to define the meaning of "not to impede" and clarify it's legal concept so as to adequate application of the Collision Rules for the collision avoidance at sea.on avoidance at sea.

The effect of the submerged high speed vessel on the ocean wave is made clear in the point of hydrodynamics view. In connection to the design of high speed ship, the flow analysis is carried out to predict the pressure distribution for drag and lift. The purpose of the research is to help the preliminary design of the economic hull form advancing under the ocean wave by estimating the resistance performance and the wave behaviour. In the present study, more efficient numerical approaches are investigated for the viscous flow analysis around a submerged NACA0012 hydrofoil with the laminar and incompressible fluid. Through the numerical simulation, it is found that the new numerical method becomes more efficient primarily due to the fact that the wave elevation is reasonably developed.

According to careful study on the COLREGS, 1972, we can easily find out a main point that is to eliminate risk of collision at sea through exercising due regard to all danger of navigation and collision and to any special circumstances including the limitation of the vessels involved, or precaution which may be required by the ordinary practice of seamen. This paper, therefore, aims to clarify legal concept concerning the risk of collision so as to easier assimilate and understand by all mariner before being presented with a situation of danger in realty. After such a forethought and understanding the mariner will be in a position timely to implement the due regard or precaution to avoid collision by himself. For the purpose of good guidance, comprehensive legal practices of collision avoidance are adequately summarized by foreign and domestic cases.

항만 설계에 영향을 미치는 네가지 중요요인인 선박요인, 인간요인, 환경요인 및 항로표지요인들이 실제 항만 및 수로의 설계에 미치는 구체적인 영향들을 각 요인별로 분석하였다. 아울러 항만 및 수로 설계요소인 수심, 항로의 폭, 항로의 배치, 선회수역의 크기 및 부두의 배치 문제에 대한 분석을 기하였다. 그리고, 항만 및 수로의 설계 문제에 관한 최근의 연구결과들과 각국의 설계 Guideline들을 수집하여 특히, 항로의 폭, 항로의 배치 그리고 선회수역의 크기에 대해 그 내용을 비교하고 분석하였다. 이들 연구 결과들과 항만 설계기준들은 연구 방법과 설계 기준을 마련한 기구들에 따라 그 내용의 차이가 있음이 확인되었다. 따라서 이들 기준들은 항만 설계를 위한 1차 계획 수립시에만 활용되고 세부적인 설계는 1차 설계 후 항만 설계 시뮬레이션 기법을 통한 검정을 거쳐야만 안전한 항만의 설계 및 개발이 이루어질 수 있다는 것이 확인되었다.

This paper aims to investigated the reasonable objectiveness of trading areas on the Korea Ship Safety Act and to make a regulated proposal of trading areas. To achieve the above mentioned object, we analyzed the existing rules and other related circumstances of maritime fields. On the basis of this viewpoint, this paper was focused on three topics of concern : (1) the relationship between the ship Safety Act and other Maritime Acts. (2) the legislative examples of foreign countries, (3) the reasonable revised reasons of trading areas. In this paper, we proposed following four matters such as (1) the modification of ship's length and speed which are the designative basis of trading areas, (2) the extension of the smooth sea area to limit of territorial seas (3) the extension of the near-coastal area to the coasts of the P.R.C., Japan, the U.S.S.R and the R.O.C ., and rename of its area into the near & greater coastal area, (4) the annulment of greater-coastal area.

It is of great importance for any vessel under way, especially in rough sea, to be maneuvered safely with proper seakeeping performance. In this paper, the author aims to develope a navigational safety evaluation system in rough sea by analyzing ship's with the theory of wave spectrum using random process analysis and the theory of evaluating the seakeeping performance. The scope and the method of this study are as follows ; (1) Modelized typhoon mathematically to represent the sea condition in rough sea. (2) Estimated sea conditions by getting wave spectrum, supposing that the wave by typhoon is fully developed short crest irregular wave. (3) Defined evaluation factor of vessel's seakeeping performance and obtained response amplitude operators thereby. (4) Obtained the response spectrum of factors on seakeeping performance. (5) Defined and obtained evaluation index, dangerousness, relative and maximum dangerousness of factors on seakeeping performance. (6) Analyzed the calculated dangerousness of evaluation index and picked the vertical acceleration out of 7 factors as the presentative factor on seakeeping performance. (7) Carrid out the judgement of danger by obtaining dangerousness value according to steaming hour, course alteration and speed change. By synthesizing the above items, the authors suggests a computer model of navigational safety evaluation system and examined the validity of the model by computer simulation.

Recently, there is a tendency to design the large full ships with lower-powered engine as the means for energy saving in ship's navigation at seas. Such a lower-powered ship is anticipated to show the different propulsive performance in rough seas, because the fluctuation of main engine load of lower powered ship is relatively large as compared with higher-powered ship is relatively large as compared with higher-powered ship. The fluctuation of propeller load is nonlinear at racing condition in waves. It is due to the variation of inflow velocity into propeller, the propeller immersion and the characteristics of engine governor. In this paper, the theoretical calculation of the nominal speed loss and the numerical simulation for the nonlinear load fluctuation of a model ship in rough seas are carried out. From the results of calculation, the following are discussed. (1) The ratio of nominal speed loss to the speed in still water. (2) The manoeuvring ability of ship and the operational ability of main engine in a seaway. (3) A method of the evaluation for the fluctuation of propeller torque and revolution on the engine characteristics plane. (4) The effect of engine governor characteristics on the propeller load fluctuation.

Nowadays, the transportation of almost all cargoes depends on sea routes in international trade. In the transaction of trade, cargo transportation must be completed on the base of two contrary objectives, one of which is to protect the vessel, cargoes and crew aborad her safely through every step of the transportation and the other is to pursue profits from the transaction of the trade. In spite of the great development of the modern techniques in shipbuilding today, many sea disaters of big merchant vessels have been occurring successively in winter seasons every year on the sea routes of the North Pacific Ocean. Whenever the accident of losing a vessel in rough sea occurred , many experts of the country to which the vessel belonged had tried to take out the reason of the missing without manifesting the exact cause of the unhappy occurrence. In this paper, we calculated ocean wave status along the route of the North Pacific Ocean theoretically concluded by us as optimum on the basis of weather and sea conditions. In the calculation, we used ITTC wave spectrum formula and meteorological data of "Winds '||'&'||' Waves of the north Pacific Ocean" edited by Ship Research Institute of Japan on the basic data assembled by World Meterological Organization through past 10 years. We selected three sample vessels of most common size in the North Pacific Ocean Routes, a container, a log carrier and a bulk carrier and applied tree sample vessels to the calculated sea conditions for getting the rolling angles of the vessels and stress exerting on the hulls. Examining the calculated results, we concluded as follows; 1. Under the condition of these status7 by beaufort scale, "heave to" maneuvering is the best and safest way to steer every vessel. 2. The most dangerous part of sea area along the west bound optimum route of the North Pacific Ocean in winter season, is the southern sea area of the Kamchatka peninsula.a peninsula.

For the purpose of estimation of navigational method and ability about fishing raft, we have practical navigation of her from Chujado on Oct, 7 to Maryang-ri , Kangjin-kun, Jeonranman-do on Oct.10. The results obtained are as follow : 1. Ancient navigation of her is thought to over to an isolated island in the vicinity with a good informations and experiences. 2. Speed of her in outward voyage is 1.34 knots, but is varied with structure and shape of her and ability of fishing raftman. 3. The lee way(U) of her with sail of hight 2.5m and breadth about 1.2m according to windspeed(W) is U=0.038×W 4. We could estimate to take only three days to go over from Chujado to Maryang-ri, Kangjin-kun. Jeonranam-do by her with sail, and make a voyage total 55 miles for thirty-four hours and ten minutes i, e, mean speed is 1.6knots resulty.

A vessel encountered heavy weather is face to two kinds of danger ; the danger of upset due to the lack of stability and the lack of the longitudinal strength. Generally a small vessel is face to the former and the large vessel to the latter. Most of people do not consider the danger of upset by the latter but the former. But many ships missed at sea, the exact causes being not known. This pper investigated and analyzed the causes of accidents. The result was that the lohgitudinal strength of the hull is not enough to cope with heavy weather, and the particular cautions are needed to handle a ship in heavy weather.