The manoeuverability of a tunny fishing boat under the strong wind was investigated for her three different conditions of trim, and the effects of the spanker and the bonito fishing platform on her manoeuverability were also studied separately. And the ranges of manoeuverabihity, or the limiting values of the direction and the velocity of the wind under which she can barely keep up her manoeuverability, were shown for these conditions. In the first half part of this report, there are given the results of a series of the wind-tunnel experiments with the image models of the above-water and the under-water portions of a tunny fishing boat carried out for the purpose of the above-mentioned investigation. And the distinctive features of the above-water portion of the fishing boat were made clear. In the latter half, the motion of the fishing boat under the strong wind with three different conditions of trim, or without aspanker, or with the bonito fishing platform, was solved using the experimental data obtained in the first half. In conclusion, the authors shew that the condition of even keel was the most fovourable for a fishing boat of this type to keep up her manoeuverability and safety, and that the excessive trim by the stern as well as by the bow was unfavourable, and they were convinaced quantitatively of the fact that the spanker played its part perfectly effectively under the oblique head wind and that the bonito fishing platform had almost no effect on the manoeuverability under the strong wind.

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In the railway ferry-boat for the Aomori-Hakodate route, especially the “Seikan-maru” No 5 and other ships of the wartime type which followed it, serious damage has been caused to the hull part near the fender which is liable to strike against the quay-wall.
So that, the investigations are need for obtaining data for the theoretical designing of the ship structure near the fender by clarifying the impact force between the ship and quay-wall.
In this paper, the author gives a result of theoretical study on the pressure between the ship and quay-wall in contact, according to the Hertz's theory of impact.
In the hull part which is liable to strike against the quaywall, the equation of motion becomes as follows,
where η+αηⁿ=0 η is displacement of this part. α equals to C/Me. c is constant, or the rigidity of the hull structure, Me is effective mass of ship.
From the theory of contact, n equals to 1.35, then, solving this equation, he obtains the impact pressure between the ship and quay-wall as follows.
F_max=1.097 C^0.4255•(M_eη0²)^0.5745

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Previous reports of this series of article concern the impact force of a ship receives from the quay-wall when the ship contacts it. This paper discuss the stress and deflection in outside plate of ships subjected to the impact force.
Various possible conditions of contact between quay-wall and a ship are considered. A model experiment is given. Numerical results presented in the form of graphs showing the maximum speed not induced the damage in the ship.

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Recently the superstructures of train ferries are made gradually larger, consequently the manoeuvering becomes difficult or sometimes even impossible in Aomori-Hakodate line, where the strong winds blow in winter. The train ferries need regular arrival and deperture in order to perform their service, so they are required the high manoeuverability. To satisfy this requirement, we must make clear the effects of wind on the manoeuverability of train ferries and find the measures for reducing or preventing that harmful effects.
Many able researchers have studied on the directional stability and the turning motion of vessels, and it seems that some of them have attempted to obtain the relation between the directional stability and the turning motion but none has been successful in his attempt. Notwithstanding the fact that the nature of directional stability or turning motion has been made clear to some extent, we have not been able to consider the problem of manoeuverability for practical cases. For instance, it has been said that the manoeuvering of trawlers and drifters is difficult under strong winds, but this subject has not been analysed and has not been able to discuss in detail.
The author supposed that a vessel will take a stable course and advances on this course after a long time, and that she may be said to be manoeuvered when she is possible to turn to both sides. Then the author considered the steady motions of a vessel and investigated their stability; by this study the relation between the directional stability and the turning motion was made clear, and it became possible to discuss the effects of wind on the motion and manoeuverability of vessels. In this paper, applying these results, the author discussed this subject on the case of train ferries.
The results obtained from this study are as follows.
(1) The train ferries has the tendency to turn windward except in the case when the strong adverse wind blows diagonally. This tendency agrees with the actual experiences in Aonzori-Hakodate line.
(2) The manoeuvering is possible at high speed and becomes impossible at low speed as compared with wind velocity. Namely a train ferry will be in the following ranges according to the value of wind velocity/ship speed:
(i) When the wind blows diagonally from behind,
(a) the range where she is manoeuverable,
(b) the range where she turns windward.
(ii) When the adverse wind blows diagonally,
(a) the range where she is manoeuverable,
(b) the range where she turns windward,
(c) the range where she is manoeuverable,
(d) the range where she turn leeward.
(3) To widen the range where the manoeuvering is possible, the following are effective:
(a) To make smaller the force by the wind and the moment by the wind blown diagonally from behind.
(b) To make larger the moment by the adverse wind blown diagonally.
(c) To enlarge the effectiveness of the rudder.
(d) To make directionally stable, namely to trim by the stern and to attach dead wood to the stern.
The above results were obtained for train ferries. Some kinds of vessels may have the opposite tendency.
Still there are many unknown factors, so this subject must depend upon the further experimental studies.

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According to the records of actual ship experiment on S. S. Nisseimaru in the North Pacific Ocean last, year steering angle in automatic steering condition often exceeds 20 degrees in heavy storm, and the loss of amount of horsepower due to this excessive steering cannot be overlooked.
The steering angle in the above condition exceeds the amount necessary to hold the ship's course straight, and even causes the ship to yaw beyond the natural yawing by waves.
The author investigates in this paper into the relationship between steering angle and her condition, and finds, there is relationship between excessive steering angle and relative wind direction, and notes that the phase lag in steering due to“weather adjust”is one of the important causes of excessive steering and yawing.

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A ship, which is directionally unstable on straight course, can turn against the rudder in a certain range of rather small rudder angle. This singular phenomenon was first pointed out by P. Contensou.
The present writer discusses this phenomenon mathematically by assuming that the resistance derivatives are linear functions of the curvature of ship's path. He assumes, for simplicity, that C_Yβ=C_Yβ₀ (1+kΩ), and descrives the motion of ship by nonlinear differential equations. Then the stability of the steady turning of an unstable ship can be tested topologically on a phase plane.

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The upsetting accidents on small vessels caused by the wind and wave have happend of ten times in recent years in our country.
When we are to certify the safety of small vessels, the heeling moment due to the wind pressure is one of the most important factors.
This paper deals with the results of wind-tunnel experiments in which the author has measured the heeling moment as well as the force due to wind pressure on three typical small vessels with the dynamometers of the magneto-striction type.
The meassured values of heeling moment are larger than those which were hitherto estimated generally from calculation.

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In this paper the authors represent the principle, the mechanism, data of design and the results of calibrations of a newly designed torsionmeter which applied the “torsional magnets-striction effect” under an alternating magnetic field, and the results obtained on various kinds of sea trials with the new torsionmeters attached to the intermediate shafts of some twin-screw turbine steamers. This newly designed torsionmeter has the merits as follows:-
(1) It can record accurately the working torsion and numbers of revolution of each intermediate shaft continuously for a long time in the view of the operator
(2) No usages of special amplifier,
(3) It can record torsional vibration of each shaft.
(4) It works without regard to the direction of revolution and of the torsion of each shaft,
(5) It can make clear the time correlation between the changes of the torsion and the speed of revolution and the motion of the vessel or the handling of the main engines.
Attaching the torsionmeters of the new type to the intermediate shafts of three train ferry boats-twin screw turbine steamers-between Aomori and Hakodate, the authors and collaborators made various kinds of sea trials and obtained the following results in short.
(1) Continuous records of the torsion, numbers of revolution and the speed through the water not only on the measured mile course but also before and after of it, were obtained and it was made clear how they were changed during that period.
(2) The changes of the torsion, the speed of revolution of each shaft etc, during the turning trial were made clear.
(3) The changes of the torsion, the speed of revolution of each shaft, the ship speed, the steam-pressure in the high pressure turbine etc. during a backing trial were made clear. And the presumption made by Kinoshita and Nakajima in the previous paper read at the spring meeting of 1947 was verified that three maxima would appear in the working torsion (and thrust) of a shaft during the transition period of the change from going ahead to going astern or vice versa.
(4) Torsional vibration of each shaft were recorded.
(5) The shaft bearing and the sterntube losses ware measured and percentages of these losses to the power output were obtained.
From the the above mentioned results we can learn many new experimental facts. For instance, we can determine how long a ship must run in order to settle on a constant revolution, a constant torsion and a constant speed before she enters a measured mile course.

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There are many sorts of apparatus for measuring the oscillations of ships around and in the direction of the three axes. The ordinary type of apparatus measures directly the displacement itself, but it is very difficult to get any sort of pendulum that has a period sufficiently long enough to measure the displacement of a body that is oscillating slowly, such as a ship at the period of 45 seconds to about 20 seconds. Moreover here are some cases in studying the motion of ships, when knowledge of the velocity or acceleration of oscillations is necessary.
So, utilizing the operating circuit of electronic analogue computers, we succeeded in setting up a system of measuring capable of getting displacement, velocities and accelerations at once. By integrating or differentiating once or twice the easiest of these three measurements to obtain, the remaining two measurements will automatically be obtained.
We made a set of integrators, differentiatars and multipliers by the circuit of ana-com., and by using an angular velocity meter of a rate gyroscope unit as a pick up, we established a measuring system of angular oscillations of ships.
We used this set on the voyage of a certain ship, and because we received excellent results, we want to report our method and conclusions in the following paper.

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It has been believed that when a ship is steered, it will at first drift outward considerably, and then drawing the Figure of an“S”, cut the original course and will turn gradually inward as is shown in Fig.5 A.1.
In fact, according to results of turning trials of actual ships, some of them drift outward as much as one-third of their length, and a majority of them seem to drift outward to a considerable amount.
On the other hand, accoring to records of the“Turning course recorder”or results of model experiments, it will be noticed, that there is no“drifting out”or such slight“drfting out”that ships seem to deviate tangentially from their original courses.
The Author has investigated into the difference between the results of turning trials of actual ships and that of model ships both theoretically and experimentally, and describes in this paper that the amount of“drifting out”is so small that it does not exceed one per-cent of the ship's length, and he mentions that the present method of measuring the ship's turning path on the turning trial is not sufficiently accurate.
The Author also proposes a method of obtainig more accurate turning path of actual ships.

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On Aomori-Hakodate sea line wind is very strong in winter and train ferries often suffer from unfavourable effect of wind on their manoeuvering. To investigate the wind effect on ferries contributing to putting out plans for the reconstruction or for the new design of them, wind-tunnel experiments were carried out on some typical types of them. Changing the direction of wind relative to ship-model in whole range, wind forces and moments acting on ship body above water line were measured. The results of experiments are somewhat different from what are believed generally.

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It has been considered that the purpose of the automatic steering system of ships is to maintain ships' course as far as possible.
However, the author would like to point out that this definition is not proper, because, there might be reasonable limitation to the rudder angle in relation to the speed loss, that is : if an excessive rudder angle was taken to maintain the ship course too much strictly, it will induce considerable power loss.
The real purpose of applying the automatic steering to a ship in a seaway is to bring her from one side to the other end of a route as fast as possible within a limited cost. Therefore, the author prefers to define the purpose of an automatic steering to be “to minimize the increase of resistance in a wide sense under the disturbance of wind or waves in the ocean.”
Making the use of this definition, the author obtained the performance function of the automatic steering system of ships at sea, namely :
J=θ²+λδ²
where
θ² : mean square of course error.
δ² : mean square of rudder angle.
λ : a constant which shows the weight of above two values.
A full scale measurement of yawing motion is also carried out on a cargo ship, “M. S. Florida-Mar” in Pacific Ocean to obtain the spectrum of angular rate which is affected by disturbance caused by wind or waves.
Applying these results, some suggestions are obtained to improve the automatic steering system of ;ships, for example,
1) The rudder angle ratio has to be chosen not too large.
2) The weather adjustment of conventional system is injurious and cannot keep the rudder angle small, because it necessarily requires rather deep rate control.
3) First of all, we should pay attention not to make the rudder too much sensitive to each wave.
and so on.

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