By questionnaire investigations, we have attempted to examine the above subject from 1,233 navigators of vessels over DW 5,000 tons. We obtained the following results: 1. Mental strain of navigators does not depend upon the human factors (for example their respective position on duty and career) and the vessel's factors (for example the magnitude of vessel), but upon their preoccupation concerning with natural factors of water way. The most important of the last was existed in traffic convergency. 2. The most difficult area to pass through was Kurushima Kaikyo with Kanmon Kaikyo. 3. A large number of captains said that under meeting condition they should have 2, 000 meters water way in width, in passing it through without anxiety or tensity.

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Some results of a questionnarie investigations for captains of the large vessels, which have D.W. 40,000 tons and over or draft 10 meters and over, are as follows: Most of captains consider that they can pass without so much as having mental strain through water way, which are deeper than one and a half times draft or wider than ten times length of vessel. Then this shows a limit of Critical Water Way. Anxiety and tensity of captains are caused mainly more by width than depth of water.

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Static electricity generated during marine operations has caused several explosions in oil tanks. So it is necessary to study the static electrifications of oil to determine electrostatic ignition problems and to establish necessary preventive measures. In the study, various phenomena of static electricity must be investigated. This paper reports an accumulation of free electrostatic charge on an insulated conductor and a spark discharge in the vapor space that possibly causes an explosion.

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Recently, bulk carrier vessels of heavy tonnage, which are called the manmoth ships, has rapidly increased in their number, because of their economical excelence and remarkable technical development in shipbilding. Those ships are offering various difficult problems in every respect, especially in maneuvering ship in port. This paper is to report the noticeable gap between the inertia forces of ship's movement and the power of means to control them. (1) Comparison the value of manmoth ships with 20,000 DWT oil tanker, in displacement, out put of main engine, weight of anchor and etc, based on the length between perpendiculars. (2) Head reach in case of maneuvering crash astern. (3) Impact load of berthing ship against the dolphine and etc. (4) Difficulties in turnning ship.

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Nowadays we use natural fibre and artificial fibre (chemical fibre) tarpaulin for hatch way cover. We pick up four typical articles and examine following test for finding their characters and properties. (1) Weather test (2) Water proof test (3) Friction test (4) Medicines test

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The final diameter of a turning circle is calculable by the following non-dimensional equation: D'=1.03kV_0/m' where D'=D/L diameter length ratio V'_0=V 0/√<L> initial speed length ratio k=V_1/V_0 speed decreasing ratio m'=m√<L> m: angular velocity The factors k and m' in the equation are expressed by the following relations that were shown in our previous paper: k=1-0.8C_b・A/Ld・α+4.5(t/L) m'=(0.46V'_0-0.36)sinα+0.11 For easy estimation of the final diameter basing on the equation proposed here, the nomogram using the following five factors is shown in this paper…rudder area ratio A/Ld, block coefficient C_b, trim ratio t/L, initial speed V_0 and helm angle α.

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It is a well-known fact that variable pitch propeller improves the performance of the maneuverability of ship such as the propulsive efficiency, the control of speed either going ahead or stern, etc. In the variable pitch propeller, there are two controllable factors by which it is possible to make the ship go at a given speed ; namely, the number of revolution is defined by the pitch angle or vice versa. The author conducted a series of field experiments using a fishing boat, in an attempt to clarify the relation between the pitch angle and the maneuverability of the ship going at a given speed. Among many factors of maneuverability of the ship, the turning ability was analyzed in this report, and the following results were obtained: 1. The reduction in speed of ship during stationary turning towards starboard was larger than that towards port. And the speed reduction was out of relation to the pitch angle of propeller. 2. The better results in turning ability was brought by the smaller pitch angle, i.e. by the faster revolution. 3. The turning circle towards starboard was smaller than that towards port when the rudder angle was the same, but larger when the slip ratio of propeller was the same. 4. The larger slip ratio brought the better result in turning ability at small rudder angle.

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In general, the effect of steering on the motion of the ship is of complexity when she goes either ahead by her inertia or astern by the propeller thrust. From navigator's standpoint, the author conducted a series of field experiments on the motion of the ship equipped with the variable pitch propeller, in an attempt to clarify the effect of the pitch angle on the transfer/advance ratio and some other performance of the ship in such a state as mentioned above. And the following tendencies were found out: 1. The turning ability of the ship going ahead by her inertia depended on the pitch angle of the propeller regardless of the turning direction or of the rudder angle: The ability is the better when the pitch angle is the larger. 2. The ship going ahead by her inertia represented at 8 to 30 percent decrease from that by propeller thrust, in respect of the ratio, T/A, at 45°to 90°of turning. 3. When the ship goes ahead by her inertia, the propeller of the smaller pitch angle acted the more efficiently as the brake on the distance of advance of the ship along her track. 4. It should be paid special attention to the fact that the ship with variable pitch propeller showed the inverse relation to that with fixed pitch one when they go astern by propeller thrust, in respect of the difficulty in turning due to the difference in the direction: namely, by the starboard steering, it is easy to make her head turning leftside along the same track regardless of the rudder angle. On the other hand, it was possible to make her head turning rightside when the inertia before steering or external forces were favorable to make her so ; otherwise, however large the rudder angle may be, it ended in scarecely no effect.

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This paper discusses the effect of ultrasonic wave energy for the protection of attaching lives to the steel plate. The continuous ultrasonic waves of 28kc were radiated against the Artemia salina just hatched in the vessel where the transducer was set. The pulse wave of 28kc and 50kc and the continuous waves of 50kc were continuously transmitted from the transducers attached to the steel plates covered with various kinds of paints which were suspended below the sea surface. The effect of ultrasonic waves against the barnacle and such lives were observed during winter and summer. The results show the effect of ultrasound which is evident, but it seems that the effect is not so perfect when the growth of the lives is active. The study is now going on to the selection of intensity, frequency and method of setting the transducer to the hull.

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We made researches on the clearance distance from the dangerous objects by using the working ship for bowling the sea bottom anchored in the vicinity of the recommended route, East of Akashi Kaikyo. The results are as follows: (1) The clearance distance to the dangerous objects around the route will affect the vessels underway is about up to 300 meters. On D/L (D…clearance distance, L…length of a ship) it has become to 2. (2) If the clearance distance from the dangerous objects around the route indicated by D/L is within 0.56 to 2. The average is 1.57, viz., about 1.5 times the length of a ship.

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The writer informed the results of the calculation of the optimum (minimal time) ship routes on some wave field models using the electronic digital computer. Moreover, he intended to establish new navigational technique in application of the results…he called it pattern navigation…for analyzing the essentials of navigation.

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Measurements of tidal currents by means of present current-meters at such a deep and rapid one as the Akashi straits are often in failing or inaccuracy owing to the difficulty of anchor-hold. So, for the survey of tidal currents in the Akashi straits, we attempted the two ways by utilizing of techniques and the implements about the aero-photogrammetry. One way is the vector-method of pursuing many drifting buoys, another way is the parallax-method by applying the Cameron's effects. As the results of adopting of two photogrammetric methods, we could show the simultaneous distributions of detailed currents, more 9 knots, at outer sea-area of narrowest part of the straits.

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The Loran-ground-wave over the sea-fronts between Kagoshima and Manila was measured and exmined seasonally, with the following results obtained and summarized: -1) In each sea-front were obtained errors charged generally with the value of+and bigger than those expected by the author ; which are perhaps caused by the differences in the speed of the electric-wave transmitted from the master and slave stations ; namely they depend upon whether the speed is a little faster or a little slower than the other. 2) The difference in the speed of the electric-wave may perhaps be caused by the following factors ; namely, the abnormal meteorological conditions in the transmission route ; the presence of the intercepting islets, and besides these, the influence of the tide-current might be taken into consideration, but as to the last factor, further studies might be necessary before it is fixed. 3) Although no excessive errors which would obstruct navigation were ascertained, the presence of the error, by itself, might be worth noting.

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Succeeding to the 1st and the 2nd reports, the results obtained from the investigations in the central part of Kagosima-bay and in the sea-fronts touching the sea shore both on Satsuma and Osumi Peninsulas were summarized here as the 3rd report: -1. In the central part of the bay almost all the errors are fixed to be western ; maximum 4°W local attraction measured. 2. In the southern coast of Satsuma-peninsula, almost all of them are western; maximum 3.5°W local attraction measured. 3. In the eastern coast of Osumi-peninsula the errors are supposed chiefly to be western ; the figures being not only generally small, compared with those in Satsuma peninsula, definite but too complicated and obscure to draw any conclusion from them. 4. As to the magnetism-color of the land around the Kagoshima bay, on Satsuma peninsula side it is blue, and on Osumi peninsula side, red ; the former being supposed to be stronger ; the cause of which might reasonably be attributed to the distribution of the iron-sand and the mineral-deposits.

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Navigators may obtain four or more position lines by star sights at night or twilight. Then they can determine the most probable position through calculation based on the least square method. The writer gives formulas for position fixing and division of errors into a correction term and accidental errors. Position fixing by calculation is rigorous and free from personal prejudice, but the calculation is rather complicated, and does not suit navigators' routine work. The writer explains a geometrical method for determining approximately the most probable position and a simple computation for correction term and estimation of standard deviation. Navigators can find their own observation errors from their sights at sea.

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It seems that there is no definite view about how to interpret the relation between the navigation rules about "route" in Port Regulation Law Article 14 Paragraph 1, 3, and 4 and the navigation rule about "miscellaneous vessel" in Port Regulation Law Article 18 Paragraph 1. From a navigator's point of view, the author interprets that Port Regulation Law Article 18 Paragraph 1 should have priority to Port Regulation Law Article 14 Paragraph 1, 3, and 4.

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In the previous paper we reported that, as the way of keeping fresh water suitable at the value of pH for drinking use in ships, the method of changing water in ships' tanks which were coated with wash-cement was not so much effective. Then, we had some model-tank-tests by using dry ice as the 2nd study of the problem. And, the purpose of this paper is chiefly to report the results of tests with some discussions and proposals.

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It is urgently necessary to establish the fundamental means preventing the maritime disress of the tuna fishing boats. Out of the proximate causes of the distress, about 70 per cent is due to the mental or social origin, 20 per cent to the inadequecy in ships' structures and their maintainance, and 10 per cent to the act of God and etc. This paper emphasizes the remote causes of the mental or social origin. Contents are as follows. (1) The sources of rapid increase of the tuna fishing fleet. (2) The Critical situation of the tuna fisheries at present. (3) The details according to the statistics on the maritime distress by the Maritime Safety Agency. (4) The remote causes of the mental or social origin of the maritime distress. (5) The necessary countermeasures to improve the present situation in the tuna fisheries.

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The magnetized state of the ship's body by block system differs from that by the system heretofore in use (riveted structure), despite of the magnetic compass deviation depending on it. This report dealt with the magnetism of the ship's body of "Tenyo-maru" built by block system in relation to her structure or to the direction of her head during construction. And the results obtained are summarized as follows : (1) The magnetic force of the ship's body was weaker on the compass bridge deck than on other deck. (2) The components of the magnetic field of the ship's body could be arranged as follows according to the intensity : vertical field, horizontal permanent field, induced field by athwartships horizontal soft iron, and that by fore-and-aft one. (3) The ship's body was more strongly magnetized on building berth than on fitting-out basin, but the direction of permanent magnetic field of the ship's body did not always depend on the building direction. (4) There was great magnetic force at the stations near the transceiver of marine radar. And the effect of local magnetic field due to nearby transceiver of radar, in some case, could not be compensated for by the ordinary correctors. (5) Vertical magnetic field by the ship's structure was directed downwards on the compass bridge deck and upwards on the navigation bridge deck.

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The author has already reported about the result of the same iuquiries in "The Journal of VOL. 32, Jan. 1965, " and treated "The Problems of the Radar Images which were Experienced by Actual Ships in Japan." This is a paper which is continued to that report, and treated the opinions of navigators about the following problems-"The advantages of using Loran on the sea." "The failures which are experienced by the reasons of the errors of Radar equipments, " "What types of Radar-charts are required" and "What kind of troubles were happened." The author analyzed those problems and advised to the makers that, what kind of problems are being required by users, and what kind of considerations must be offered by the makers. The paper has many relations with the one of the same subject which were reported in "Electronic Navigation Review" JACRAN.6.-1964, by the same author and his group.

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