The author has reanalysed some of the published data of resistance experiments of similar ship models in a form of the so-called residuary resistance coeft. (r_r0) versus Schoenherr's frictional resistance coeft. (r_f0) under constant Froude number.
The r_r0-contours (J=const.) are found out to be not always parallel to the base line. He has explained the causes of these phenomena to be attributable to the form effect on skin friction resistance and the effect of viscosity on wave resistance, and suggests the necessity of the reconsideration of Froude's law of comparison.

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I have expanded the velocity potential of a prolate spheroid submerged in the uniform stream into spheroidal harmonics, and have given its successive approximate solution.
Of a sphere as a limit of it, I have calculated numerically the wave resistance and vertical force. They are analogous to those of the two dimensional circular cylinder, and the accuracy of their known first approximate value is much better than that of the latter case, as we may expect. Geneally speaking, the accurate value is larger in low speed and smaller in high speed than that of the first approximation.

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In measuring ship's resistance in waves, the method of connecting the model to the dynamometer is found to be a difficult matter.
If they were connected rigidly, the dynamometer would be acted by a force over ten times the mean resistance of the model, and if springs were put there as a buffer, the naturo 1 period of the system might become so long as to synchronize with the period of the waves.
The Author thinks the gravity dynamometer method, that has been used at the Hamburg experimental tank, and which was suggested to be used at the Sixth International Conference of Ships Tank Superintendents, is a very clever method, because it allows ship to surge freely, and satisfies the condition of constant thrust.
An experiment was done at the experimental tank of Tokyo Univercity with a model of the S. S. Nisseimaru.
Two devices, one for recording the motion of the model thereby making it possible to measure the mean speed and the surging of the model, and the other for eliminating the effect of accerelation of the weight by reducing the ratio of pulleys, were made at the experiment.

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The differences between a turbulent boundary layer produced by turbulence and that in an undis turbed flow are shown by author's solutions of generalized Navier-Stoke's equations. By this author's opinion experiments with turbulence gitter have no significance but the meaning of effective Reynolds number becomes evident by this calcnlation.

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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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As is only too well known, the quick diving is one of the essential qualities of the present-day submarines.
In this paper, first of all, the authors have made an analytical study on the diving motion of a submarine.
In the next, the question may be solved as to how much degree the trim angle of the vessel does alter, when the vessel submerges with constant speed Vo, along the specified course, into the given depth of immersion D, in the duration of time T, under the regulation by a pair of horizontal rudders with a certain rudder angle.
Fortunate to say, we have still on hand the underwater-performance curves based on the experimental results of the several types of submarine-models, and using them, we obtained numerical values of both the trim and rudder angles of submarine when she performs the diving motion as mentioned above.
In conclusion, it is shown that, if we try to make the time duration needed T, as short as possible, the allowance in inclination of hull matters more, rather than the addition of rudder angle.

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Theoretically and experimentally the author has researched the normal force and the moment of a ship on the turning, and now can calculate them. In this paper the author theoretically deals with the course stability of a ship on the straight course and the steady turning course, and also the steady turning radius. The results are as follows:-
(1) The criterion of the course stability is same to the results which have been researched and now it can be calculated in each ship theoretically. It is more stable when trim by stern than even keel condition and main cause is the large decrease of C_mGα. (C_mGα is the derivative of moment coef. about centre of gravity. C_mG and α is the drift angle.)
(2) The course stability in the steady turning is always stable if stable in the straight course and the increase of stability is very much. So it can become stabe in the steady turning, even if unstable in the straight course.
(3) The turning radius can be calculated by solving the quadratic of ω. (ω=ship length turning radius) Also, Davidson's total less rudder moment can be calculated theoretically and is same to Davidson's experiments qualitatively.

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During the launching of a ship, a large sagging moment nearly equal to the maximum one which will be experienced throughout her life is induced. Availing themselves of this chance, the authors have measured the stress distributions and the stress concentrations induced on the several parts of her hull such as transverse sections, hatch corners, expansion joints, under deck girders and so on.
Genie, Christina, Nikko-maru, Yamazato-maru and Taiyu-maru were chosen as the experimental vessels.
The electric wire resistance strain gauge equipments which were researched and manufactued by the authors have been used in all cases of the experiments.
In this report the results of the measurement and brief considerations on them will be described.

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Recently in relation to slamming in bad weather, the impact of a body on a water-surface has become important. When a falling body has a keel angle, it is not difficult to estimate the impulsive forces, and this problem has been studied by Pabst, Wagner and others. But in the case of flat plate, it is very difficult to calculate or to measure the pressure on a water-surface. The author investigated theoretically and experimentally this phenomena and obtained the following results.
1. If we assume that the mechanism of the impact of a flat body on a water-surface is the rapid compression of the air-layer caught between body and water-surface, the results of experiments are explained sufficiently.
2. The distribution of impulsive pressure on a flat body is uniform and the pressure in each measured point occurs simultaneously.
3. The relation between impulsive pressure and falling height is not constant but the pressure is proportional to the heigher order of falling height as height becomes higher.
4. Effects of falling mass and diameter of plate are complicated as will be seen in the expressions (24), (26) in this paper.

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Recently, in a certain ship (three islander of length 128 metre), some cracks occurred at the corners of the entrance of bridge aft bulkhead, and it seems to be impossible to explain the cause of these damages by the old theories. The author analysed this cause that, the deck girder were pushed up through a pillar by the action of bottom water pressure and as a result of this displacement the plate around the entrance were subjected to the shearing strain and the large stresses occurred at the corners of the entrance. The cause of damages of this kind seems to be cleared by this analysis, because the positions, where the cracks occurred in actual ship, can thereby be understood easily, although this analysis contains some assumptions about the load condition, boundary conditions of the girders, effective breadth of the deck plate, stress concentration factor at the corners of the entrance etc..
The counter-measures of damages of this kind considered as a result of the above analysis are
1) to enlarge the radius of corners of the entrance as large as possible.
2) to change the connections of bridge aft bulkhead from weld to rivet and if possible make some expansion joints in order to prevent the transmission of shearing strain to bulkhead plate.
3) to reinforce the corner parts of the entrance, where the stress concentrates locally.
The author thinks that 1) and 2) are good, especially 2) is available and advisable, because, by the analysis of this paper, the cause of occurrence of cracks is related to strain and the displacement itself is about 1mm, although the stresses of the corners are very large.

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This paper deals with the results of experiments in which the authors have hitherto measured the twisting moment acting upon the rudder-stocks of five vessels during their turning and backing, together with the other related factors. The data thus obtained were compared with the calculating values by the Jossel's, Beaufoy's, and Akazaki's formulae.
The measured twisting moment curves show many newly known phenomena. But the following three features seem to be the most noteworthy.
The first is the difference between the maximum values of the twisting moment in port and starboard turning, in spite of the fact that the speed and helm angle were kept the same for both cases. The second is the large fluctuation of the twisting moment, which appeared in hard port turning only. The third is the alternating twisting moment acting on the rudder-stock during backing trial.
The authors tried to explain these three interesting features, by assuming the velocity distribution against the rudder in the propeller race behind a vessel.

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The author has made a theoretical study on wave propagation along a flat plate which extend to infinity and which forms a boundary wall to a water region of semi-infinite extent. Forced and free vibrations of the plate for following two cases has been treated. (a) elastic plate of infinite radius, (b) elastic plate of finite radius c, the outer part c<r of the plate being a rigid wall.

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The shrinkage distortions in welding are unavoidable trouble in welding procedure, and the complex problem for the welder.
When we build up the welding constructions, it is always interesting problem to intend to decrease these distortions.
If we want to solve this unavoidable, complex problem, we must first know the primary shrinkage distortion in welding. And so in this paper the shrinkage distortions in only one pass welding bead are described.
Distortions in welding are due to both shrinkage transverse and parallel to the direction of the weld. To consider the phenomena simply, we disregarded the effect of the distortion due to shrinkage parallel to the direction of the weld, and measured only the distortion due to the shrinkage transverse to the directiorn of the weld. We experimented two cases. Namely one case was done when the welding speed was constant and the welding current was changed, another case was done when the welding current was constant and the welding speed was changed.

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In the 1st and 2nd report, we have obtaind the formula showing the transition temperature of notched specimen in terms of the ratio of notch radius to thickness of specimen, of notch depth and of notch angle, and the validity of the formula have ascertained by many experiments performed by Bagser, Thomas and Boodberg, etc.
Furthermore, in the 2nd report, we have checkd the theoretical relation by Charpy impact test.
In this paper, using the same steel as in the 2nd report, we have investigated the effect of notch radius, notch depth and thickness of specimen etc. on the transition temperature, and it has been found that the effect of these factors are expressed by the theoretical formula, as in the case of Charpy impact test.
We have also studied the relation between these factors and absorbed energy, at constant temperature, and nominal maximum fibre stress, and we have obtained the facts that absorbed energy drops as increase of notch depth and thickness of specimen, and decrease of notch radius, and the nominal maximum fibre stress drops as increase of notch depth.

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Generally, in the effect of Strong Back to the angular distortion, four factors as below mentioned are to be considerd.
(1) Measure (thickness and size of Strong Back)
(2) Type
(3) Pitch (distance of Strong Back)
(4) Initial constraining force
In this experiment, by defining the measure and type and changing the pitch and initial constraining force systematically, the author investigated how these factors have an effect on the angular distortion principally and also the allowable range of angular distortion on the sense of beauty.
As the result, the matters ascertained are to be enumerated as follows.
(1) The pitch and initial constraining force of Strong Back have the close connection with the angular distorion.
(2) In the removal of Strong Back after perfect cooling, the angular distortion increase almost equally along the welding bead.
(3) The decrease percentage of angular distortion by back welding is that in the first pass is larger than in the second pass.
(4) The allowable range of angular distortion on the sense of beauty for the gauge distance of 100mm is considered to be 0.015 radian in maximum.
(5) If the thickness of base metal, the measure and type of Strong Back and the shape of edge are same as those in this experiment, the result is to be applicable actually.
(6) The load to be added to the Strong Back when welding was ascertained in quantity.

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For the convenience of estimation for the hull steel weights of cargo ships in the early stage of design, it is necessary for us to put the measured datas of actual ships in order, by means of a graphical form which is expressed by a functional relation between the principal dimensions (L, B, D) and the hull steel weight (W).
In order to get the rational relation, the writer calculated the qualitative weights for 41 ships of 3 Islander's type, varying the principal dimensions systematically.
And these results were analized as following sequence.
(1) Relations betweenWandL, BandD
(2) _??_ _??_ W/L(B+D) andL, BandD
(3) _??_ _??_ WandL×B×D
(4) _??_ _??_ Wand block coefficient, length of erection and frame space.
And then it was found that the hull steel weight may be expressed simply in the form :
W=w×L(B+D)
where w is a linear function of L, and the cargo ship's datas were platted graphically in Fig. (10).

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Gas Devourer which is fitted to each oil tanker to suck out gasoline vapour remaining in cargo oil tanks after unloading cargo oils, must be so designed as to have short time required for sucking and small steam consumption because of steam being wasted away completely.
The author has tried the approximate calculation method on characteristic curves of steam ejectors by the same method as tried by Mr. T. Ueda, the Tokyo University, and also some relations between steam consumption and time have been calculated on some typical cases.
The following results have been made clear.
(1) Steam ejectors which have short guide, long parallel throat and large throat area ratio, have large air ratio at low suction vacuum.
(2) It is desirable to use steam of relatively low pressure as driving fluid.
(3) Optimum condition has been found to exist in design of gas devourer.

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The strength of marine cylindrical boilers has been calculated by the Classification Societies rules, which are originated from C. Bach's experiments, but neither theoretical nor experimental certifications are made to confirm these rules.
The authors tested two boilers, one of which is a used cylindrical boiler with dry combustion chamber landed because of the bulging of the rear end plate, and the other a boiler of the same type newly manufactured to replace it.
The stresses of various places of these two boilers were measured by SR-4 gauges, and the rupture test by water pressure was also carried out on the landed boiler.
Investigating the abovementioned tests, the followings are mainly concluded :
1) Shell plates are amply strong at where remoted from openings, which, however, can be the weakest point if they are poorly reinforced, carelessly cut or horizontally neighbored each other.
2) The values of the factor C₁ given in the rules for various supports are adequate as. long as they are not in contact with flame.
3) The allowable stress of the supported flat plates is ascertained to be 17-18kg/mm².
4) Tube holes distributed on end plate give no remarkable influence to the plate strength. It is considered that the permissible supporting distance crossing the tube holes line may be corrected by multiplying the factor : (p-d/2)/p.
5) The current calculating method for the area supported by stay or stay tube gives smaller value when neighboring support is a flanging.
Several points remained unclarified and succeeding test is planned.

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