T. H. Havelock and H. Maruo dealt with the problem of the mean wave pressure, or so-called steady drifting force, acting on fixed bodies amongst regular waves. There lies, however, great analytical difficulties, and in general the first approximation gives no fair result.
Meanwhile, this problem is greatly simplified under the restriction that the body has wallsided infinite draft, for the local disturbance cancels out and the diverging wave only is left, and the problem becomes two dimensional.
The author has solved numerically the integral equation, which is the boundary condition on the body surface, firstly in the case of a circular cylinder as a trial of the method to be used here, and secondly in cases of three wall-sided parabolic waterline ships with infinite draft. (B/L =0.10, 0.15, 0.20)
The results have shown that the first approximation is wrongly fitted to the calculated source distribution, and to give the steady drifting force by its approximation is hopeless.
The steady drifting force obtained is nearly proportional to the square of the beam in the range λ/L=16, and has maximum value between λ/L=23. (see Fig.4)

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The present report deals with the reading-out apparatus of the towing carriage speed of the experimental tank, using Dekatron that is a kind of the cold counting tube of glow discharge type. The apparatus consists of five parts ; the pick up of electromagnetic type, the counting adjustor, the timer, the counting indicator and the power source. The counting adjustor is composed of a gate circuit, an amplifier, a reset circuit and a reserving circuit of the counting indicator and the timer is a combimation of a standard oscillator of 1, 000 cycles and a counting unit. The measurement of the speed during one second and the indication of it during 0.8 second are repeated alternately. If we desire to keep the indication unchangeable, it can be done by the reserving circuit. Thses operations being worked out electrically, there is no room for entering of individual error, time lag and etc., As to error there may be considered three causes, the unavoidable miscount of ± 1, drift of standard frequency and a characteristic in construction of the pick up. At usual speed, however, the error remains within 0. 300. 15 %.
Besides, the counting indicator for measuring propeller revolution is attached to the apparatus.

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In this paper the optimum distribution of circulation is examined and from which a designing method of the submerged hydrofoil is proposed.
In § 2 a calculating method for obtaining the distribution of chord length and attack angle over the span of the submerged hydrofoil with a prescribed distribution of circulation is considered in detail.
In § 3 the expression is introduced for the resistance of arbitrary distribution of circulation and the relation between both resistance, induced and wave-making, is discussed in the extremely high Froude number.
In § 4 applying the variational method, it is verified that the optimum distribution of circulation can be obtained in such case that the induced velocity is constant over the span under the effect of free surface. At the same time a practical method for calculating the optimum distribution of circulation is shown.
In § 5 the wave motion is examined and it is shown that the surface disturbance peculiar to the submerged hydrofoil of finite span exists in the vicinity of the hydrofoil and is caused by both vortex motions, free and bound.
In § 6 the numerical examples are shown of optimum distribution of circulation, distribution of chord length and attack angle over the span of the designed hydrofoil and surface disturbance for two Froude numbers.

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When a ship goes in regular waves, the torque, the thrust and the r. p. s. of the propeller fluctuate about some mean values. These fluctuations, the motion of ship and the characteristics of the driving machine interact each other. The author studied these interactions and the following results were obtained.
In the self-propulsion test in waves the motion of ship is fed back into itself through the propeller and the driving machine. For the ship of ordinary type, these feed backs are so little that the motion of ship is not affected by the characteristics of the driving machine. Then there are no differences between the motion of the model in the self-propulsion test and that in the resistance test with the gravity dynamometer. However, the patterns of the fluctuations of the torque and etc. are altered by the characteristics of the driving machine. Therefore, in the self-propulsion test in waves the characteristics of the driving machine are not important matters, when the self-propulsion factors are not affected by the patterns of the fluctuations. When the effects of patterns are not negligible it is necessary to reconsider the self-propulsion test together with the driving machine.
The considerations of the actual engine give the fact that the driving machine of the ship is less in firmness and heaviness in comparison with the electric motor used for the self-propulsion model at the Mejiro Basin of the T. T. R. I. (Table 1 & Fig. 4).

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The author proposes a method of computation of the additional resistance of a ship going in a regular seaway. Numerical results are shown, indicating the general trend of the resistance increase.

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The wave-making characteristics of after hull bodies are more or less affected by the viscosity of water, to which the most important cause of the discordance between the theory and the experiment may be attributed.
The authors attempt to find by the photographic method to what extent the mentioned effect of viscosity might be changed according to Froude number as well as to the fineness of the run.
The results are that the observed position of the stern wave separation varies with Froude number and the fineness quite in a similar manner with the shifting factor δ, which has been obtained from the comparison between the measured and the calculated wave-making resistance.

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The effect of breadth on the frictional resistance of a flat plate can be explained by the boundary layer around edges of the plate. As the first approximation this may be obtained without considering an athwart flow induced by non-uniform thickness of the layer. To solve this problem, the authors showed that when the coordinate system is properly chosen the equations of motion can be reduced to a single equation in the direction of main flow, and that the elliptic coordinates are almost satisfactory to this condition. Thus the equation to be solved is simplified as eq. (4. 1) in this paper.
The velocity distribution is obtained by the momentum transfer theory with some modifications corresponding to thd elliptic coordinates. Putting this velocity in the momentum equation, the frictional resistance of the plate is calculated as a function of its Reynolds number and aspect ratio.
The results are shown in figs. 3, 4 and 5. Fig. 3 is the distribution of shearing stress in the athwart direction, Fig. 4 the experiments by several authorities, and Fig. 5 the percentage increase of the resistance.

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This paper follows the preceding paper of the authors in 1956. Now it may be concluded that ;
(1) Steering quality of a ship may be described by a transfer function of the form K (1+T₃p) / (1+T₁p) (1+T₂p) or a set of the steering quality indices K, T₁, T₂ and T₃. These indices are functions of hull form, rudder size and other particulars of a ship. Analytically, they are composed of coefficients of governing equations of motion.
(2) In a more practical sense, steering motions of ships are described substantially by a first-order equation of motion T dθ/dt+θ=Kδ. Accordingly steering quality may be described in brief by two fundamental indices K and T.
(3) Use of the transient response test and frequency response test of a free self-propelled model is an effective means of providing a full description of steering quality in terms of K, T₁, T₂ and T₃, through a procedure not so lengthy as the usual approach of resistance derivatives.
(4) Kempf's zig-zag test followed by an analysis employing the first-order equation of motion provides a figure of merit for steering qualities of actual ships in terms of K and T. The zig-zag test would bring out many things about steering quality if it were carried out for many ships.
(5) Refering the values of K and T for a number of actual ships, it may be said that (a) improvement of turning ability (increase of K) brings necessarily some reduction of quick-responsibility and stability in steering (increase of T), if the relative rudder size remains constant, (b) rudder size, cut-up of dead-wood and other similar arrangement have fair effects for steering quality, while main hull form has much smaller effects for it.
(6) It may be expected that the present expression of steering quality would provide a reasonable basis for design work relating to steering and turning. In this connection, consideration of a feed-back system composed of a ship, a steering gear and a helmsman or anautopilot may be an important aid.

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Assuming that the centre of gravity of a ship advances horizontally with a uniform velocity, the equations of general motions of the ship in oblique sine waves are obtained. From the solution of the equations, we have found that the effect of the exciting moment and accordingly the angles of oscillations vary complicatedly with respect to the angle of encounter when the wave length is short or comparable with the length of the ship.
It is also revealed that the interactions of rolling, pitching and yawing are small.
Making use of the results as to the motions in regular waves, the author has worked out an illustrative calculation of pitching and rolling angles in irregular seas and obtained some re markable results which are, however, ordinarily experienced on board.

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The author who stated the outline of the theory of free-running screw propellers in his previous paper (the Journal of the Society of Naval Architects of Japan.No. 100, p. 15) calculated the characteristics of the practical propellers and proved that the theoretical values agree nearly with the experimental results, and suggested a method of design of optimum propellers. Finally the following results were obtained :
1. The characteristics of 3- and 4-bladed propellers are mainly due to the breadth and contour of blades, and the cascade effects are negligible.
2. Skews of ordinary type propellers have little influences on the characteristics.
3. Weissinger's method on the single wing is applicable to calculate the characteristics of screw propellers.
4. The values of k₁ (ξ') can be calculated by the author's method, but can not be forecasted immediately. If this values are initially known, the characteristics of propellers can be calculated very simply and very easily by the strip method.
5. Modern propellers analogizing from one of B₃-50 type (Transportation Technical Research Institute, Japan) have nearly an optimum efficiency in open water.

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To investigate the effects of the rudder area, its location and its number, upon the ship's turning characteristics, the authors carried out the turning experiment of 112 cases with a selfpropelled twin screw model ship, 2.5m in length. All apparatus on board the ship for propulsion, steering, photographing & etc were prepared to work automatically.
In this paper test results obtained from these experiments are described.

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The statistical distribution of the heights of sea waves is various and complicated for sea state and weather conditions. This is generally expressed empirically
φ(γ)=e^-(γ√γ)n, γⁿ=1/NNΣi=1 γiⁿ
where, φ (γ) is the chance that the value of wave height exceeds γ ; N is the number of waves, γ or γ_i denotes wave amplitude; n is the parameter which expresses the sea state.
Usually n=2 ; and for seas n<2, for swells n> 2. When wind velocity increases, the value of n decreases, and waves all vanisch away. Even if wind velocity may be large, for prevailing wind n becomes large.
So that expected rolling angle is different for each value of n. Analytical results indicate that in the centre of storm, perfect resonances occur rarely, but when it is calm weather, every rolling is almost in resonance state, but the value is usually diminished by 1/21/3.

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There are many sides on the rolling resistance by the bilge keel, but the authors have divided it into the fin resistance and the surface resistance after G. H. Bryan and Prof. Sasajima line.
The present paper is the first report of these works in which the systematic experimental results about the fin resistance and the total resistance by the bilge keel of the two dimensional model ships are shown, and an approximate calculating method about the surface resistance of the two dimensional ship is stated.

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Typhoon “Marie” capsized five ferry-boats including Toya Maru at Hakodate Harbour in the night of September 26, 1954. The disaster was so great that it invited a serious public attention.
In accordance with the request of the Marine Disaster Inquiry Agency, the authors conducted experiments in order to investigate its technical causes. In the experiments two specific cases of Toya Maru (passenger boat) and Tokachi Maru (freighter) were dealt with as representatives of the wrecked ferry-boats.
The main interest of this experiment was focused on the following items.
(1) To study the mechanism and to measure the amount of water poured in through the stern opening of the wagon deck, while the ship anchoring, heaving-to or advancing in waves.
(2) To study the effect of water stagnant on the wagon deck or flooded in the engine and boiler rooms on the stability of a ship
(3) To study the effect of bottom contact on the stability of a ship, in case of Toya Maru.
From these investigations, a number of problems have been clarified or could be presumed with a good confidence, which may be outlined as follows.
1. Flooding on the wagon deck at the time of anchoring was caused by the dipping-up of the water due to pitching of the ship. Such flooding is the heaviest when the wave length is approximately equal to the length of the ship, and the deck would not be flooded unless the ship is in full loaded condition and the wave height is more than 5 metres.
2. It is presumed that the wave at the time of disaster was such that the length was approximately equal to the length of the ship, that is, 100 metres or thereabout, and the height was about 6 metres.
3. In case of freighters (Tokachi Maru type), there is a certain danger that, when the wave height is more than 6 metres and the wave period is about 9 seconds, the ship overturns merely due to the flooding of sea water onto the wagon deck through the stern opening. It is considered that this is the reason why all of 4 freighters capsized and sank as they dropped anchors at the offing and stood facing with wind and waves.
On the contrary, in case of passenger ferrys (Toya Maru type), the breadth of the wagon space is so narrow that they do not result in capsize merely due to the flooding of the waves. The reason why Toya Maru did not overturned until she had drifted to the shore and then contacted the bottom would be this as well as the fact that the accomodation spaces were located at the both sides of the wagon deck, which contributed to the stability of the ship.
4. It is generally thought that, when the ship encounters with wind storm, it is the safest way that the ship stands facing with the wind and waves. However, this would aggravate the danger in case of ships having stern openings.
5. According to the statements of survivors of Tokachi Maru, GM was presumed to have been negative before capsizing due to the stagnation of water on the wagon deck and the flooding in engine and boiler rooms.
6. In case of Toya Maru there is little probability that wind and waves then would cause her capsize merely due to the flooding, just before her bottom contact, of the assumed amount of about 200 tons in engine and boiler rooms and about 300 tons on the wagon deck. The vital cause is assumed to be the loss of stability affected by the bottom contact.

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Using the same steels as in the previous report on the impact tension test of mild steel, we performed slow tension tests of round bars with circumferential notch, and studied the effects of notch radius etc. on the brittle fracture of mild steel.
The validity of the theoretical relation between the transition temperature and notch radius which were based on the theory proposed in the previous paper was verified by the experimental results as in the impact tension test.

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In order to explore the behaviour of continuous panel such as transversely constructed bottom shell plating of ship, series of tests were carried out by these specimens with various amount of initial deflection and the ratio of frame space to thickness of plate. Some theoretical considerations on the continuous panel were performed simultaneously.
After analysing the results of these tests with reference to the theoretical calculations, critical stresses for buckling and corrugation were obtained, and the allowable limit of initial deflection of bottom plate was discussed over large and small ships.

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A thin elastic shell in form of a circular cylinder is assumed to has small initial deformation. The shell is assumed to suffer the following loads : -(a) At a state of static equilibrium, it is under the action of a normal pressure q₁, together with an axial thrust P. (b) During the period o<t<t₀, the shell is suddenly acted on by an additional normal pressure q₂. (c) At time t₀<t onwards, the pressure q₂ ceases to act, and the static pressure q₁ only acts upon the shell.
The Author has made a theoretical study on the vibratory motion of the shell, which is set up by the above loading condition, and has given expressions for deformations of the shell at three periods (a), (b) and (c) as mentioned above.
Keeping in mind the case of a pressure-hull of a submarine, which is subjected to an action of impulsive pressure, the effect of virtual mass of surrounding water upon the deformation of shell is also taken into account. The present report (Part I) gives only the theoretical formulae. The discussion about numerical values is expected to appear as Part II of the present Report.

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The purpose of this paper is to consider the influence of ship forms and ship drafts upon the slamming and the strength of ships going in waves. The self propulsion tests were performed in the experimental tank on two model ships, the U and V-form ship. Ship motion, acceleration, pressures, and stress were measured at various ship speeds and drafts. Tne comparative merits on the effect of ship forms are discussed from the experimental results.

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This paper presents the results of a theoretical investigation of the motion and the bending moment of a ship among waves. Expressions are obtained for the bending moment taking into account the dynamical pressure of the fluid disturbed by the moving ship.

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An analysis into the factor β in Todd's formula for estimation of the two-node natural frequencies of the flexural hull vibrations are carried out by the calculations of the characteristic values. of the flexural vibration of a beam with such distributions of mass as both cases of light and full load conditions of modern tankers and cargo ships in the vertical and the horizontal transverse vibrations.
For estimation of the natural frequencies of the two-node flexural vibrations of tankers and cargo ships by the use of Todd's formula in early stage of hull design, the ratios of the factor β in full load condition to that, in the light condition are presented with various displacement ratios. The normal modes of the vibrations in various cases mentioned above are also presented in the last paragraph of the present paper.

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In the first report, the author studied the “Effectiveness of Panting Stringers and Web Frames of A Ship”, and showed that the stringers with web frames whose sizes were determined by the Rules of Classification Societies are not strong enough to support side frames.
Recently, however, strong stringers with web frames are often adopted, which is known as “Web and Stringer System”. This paper gives the result of an analysis made to the structure of panting zone of a 8, 750 G. T. cargo ship which has been strengthened in such a way as stated above and shows that the effectiveness of “Web and Stringer System” is practically sufficient in this case.

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In the first report, the authors presented a bending theory of the superstructure with consideration of shear lag effects, and the calculated values by the theory were compared with the experimental results obtained by the bending test of the box-typed ship models with a good agreement, even in the case of comparatively shorter deckhouse.
This theory can be easily applied to the simple structure which has constant cross section and constant stiffness factor of the upper deck, but it is difficult to apply it to the actual ship structure whose cross section and stiffness factor of the deck vary irregularly along the length, therefore, to find the method which can be easily applied to the actual ship, we determined the effective cross sectional area and the effective moment of inertia of the simple superstructure, and using these values, we introduced an approximate method for the bending calculation of the superstructure and its numerical values were compared with the experimental results.

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we know numerous methods of developing shell plating, which are used at many shipyards in the world and are founded on the principle that the straight line squaring to the chord line of a frame line on the body plan is at right angles to the chord line of the frame line on the developed plan.
But the author has discovered that the above principle is not right. Specially on the shell plate of the said title the error due to this wrong principle is excessive.
Then the author intends to explain the reason why this principle is wrong, and the practical know-how in future.

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In our third report we studied ventilation with the cargo holds filled with bale cargo.
As a result of the studies covered in our first, second and this third report, we have reached the following conclusions :
(1) In the event that the holds are filled with grain cargo, the stream lines and stream velocities in the upper air space may be obtained by hydrodynamical calculations.
(2) In the event that the hold is empty or filled with bale cargo, the inlet current becomes a jet flow. By utilizing this jet flow efficiently the ventilation efficiency is increased.
(3) By leading the inlet current by ducts into the air spaces between the, bale cargo, the ventilation efficiency can be increased.
(4) By alternating inlets and outlets at regular intervals large changes can be obtained in the stational flow, and as dead space can thereby be eliminated, the ventilation efficiency is increased enormously.
(5) By experiments with actual ships it has been possible to confirm that the model experiments are useful in determining the characteristic properties of ventilation efficiency.

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The exact application of the theory of queues to ships' congestion at port is, if not impossible, very difficult, and may be too complicated to use. More practical way of approach may be an approximate expansion of that theory in limited accuracy.
Wellknown result of Fig. 1 may be approximately corrected by the correction factors C₁ & C₂ given in Fig. 2 & 3. The effect of control of arrival time interval at port and service time at quay can be discussed by these factors. In sec. 5, 6 & 7, actual data of several Japanese ports are analised.
So called the “Monte Carlo” Method can be benefitially applied to this problem. In sec. 8 examples of application are shown and used to cheque the accuracy of the above approximate method.

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It has been burning questions among the dock yards that on the new ships, the paint film of hull top side was peeled off after short voyage and the priming coat showed its red or orange color among the top coat. This fact gives not only bad impression for appearance of new ships but also gives bad influence for the protection of hull because of succeeding to rust. These defects are considered mainly coursed by following facts :
1. By the progress in the practice of ship construction and the preparation of painting, the procedure of painting had made so much differ from former process and intervals between coatings were very much prolonged, therefore the primer films are exposed for long time before next coating.
2. According to the progressive improvement of high polymer chemistry, we have adapted the phthalic resin as the vehicle of paints, however, the characteristics of this resin are, not perfectly scrutinized.
The question of adhesion of paint film on hull top side, we consider, should be solved completely by clarifying of following three factors :
A. The composition of vehicle and pigments in the paint.
B. The resolubility of primer films by the next coat.
C. The permeability and swelling rate of paint film.
In order to settle above factors, we made careful tests in our laboratory by means of our own creative testing installation in which we reproduced co-incident influence of water in sea going, we succeeded at last in obtaining suitable paints for severe services on hull top side and we found out excellent combination of primer and finish paint using the phthalic resin modified by linseed oil fatty acid and the phenolic resin varnishes.
By adapting this combination of varnish and keeping its P. V. C. (Pigment Volume Concentration) 20 to 40, we succeeded to prevent peeling of hull top side paint.

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