The equations of motion of the viscous fluid are not yet solved generally. So they are solved, neglecting inertia terms or terms of small order as in Prandtl's boundary layer equations when the thickness of boundary layer is small. However if we investigate the equations of motion in detail we will find that the variation of the effect of viscosity by the place in case to deduce the viscosity terms are not taken into account. So the author found general equations of motion, taking into account these effects. The flow will change by Reynold's and Mach's number. So the equations of motion are written in the form of zero dimension in order to represent explicitly the effect of Reynold's and Mach's number. When Mach's number is given by some power of the thickness of boundary layer at the trailing edge we can solve the equations of motion, assuming properly the velocity distribution, the variation of viscosity terms and the boundary conditions. In Prandtl's boundary layer theory the velocity at the leading edge is assumed to be zero in spite of that the thickness of boundary layer is zero. So the rate of change of the velocity at the leading edge becomes to be infinity and such is not conceivable. Therefor the author assumed that the velocity at the leading edge is equal to the velocity of the general flow, decreases gradually along a plate and becomes to be zero at a point on a plate. By this assumption the author found that the frictional resistance is created only on this part and is zero on the remaining part.
The formula for correction of the frictional resistance is one of important problems to discuss the resistance of ship. By this solution the author abtained the formulae for the frictional resistance coefficient in which all effects of the pressure, the temperature, the density, the length and the surface condition are taken into account.

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The author proposed a new vorticity transfer theory in the previous paper, and as an application the flow in circular pipe was calculated. The present paper is the second application of the theory for the flow along a flat plate.
Usually the velocity distribution along a plane wall is assumed to be similar to that in a circular pipe, but the author adopted here a different one as follows. “Form of shearing stress distribution is determined by the boundary conditions and is independent on the type of boundary layer, i. e. the laminar or the turbulent ones”.
The calculated results almost coincide with the formula by Prandtl, and moreover, the solution is flexibly adaptable for any condition of flows before the transition point, e.g. for an artificially stimulated flow in the model experiment. The thickness of laminar sublayer is obtained and this showes that the hydrodynamically smooth surface is influenced mainly by the velocity of plate and scarcely by Reynolds number.

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The author has already showed in his other paper that the conception of Prandtl's acceleration potential gave a suitable instrument for the analysis of the wave-system generated by a travelling disturbance.
In this paper he develops the theory in the three dimensional fluid field of wave-system. The wave-system in three dimensions has been sufficiently investigated by many researchers, but the author synthetically analyses it from a different point of view.

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The author has already analysed non-uniform wave-system in two dimensional case generated by a ship moving with constant velocity describing harmonic oscillation in his other paper “1”. In this paper he develops it in three dimensional case.
The process to obtain the velocity potential will be given in the first chapter. In the second, the relation between various kinds of harmonic oscillations of a ship and the fluid field will be mentioned.

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The normal force coef. C_N of normal force acting on a low aspect ratio rectangular plate is
C_N=2π/1+2/kcosα sin a cosα+2 sin²α
where k is aspect ratio, α is angle of attack
The 1st term is the Prandtl's wing theory and the 2nd term is the Newton's resistance law of a plate and the value of C_N when k=0.
The moment coef. C_m about middle point of the plate is
C_m=f(k) sin αcos α
where f(k) is the calculated value.
and some pure moments are added to the moment by Prandtl's wing theory. The former is not neglegible for the latter.
When a ship, k is 0.10.2 and she has breadth. In this case the 1st term in C_N is not changed much, but 2nd term shows the variation by her breadth. In the case of moment about _??_ the effect due to breadth of pure moment is not known, so I start from Munk's formula, multiply this value by some theoretical value and gain the ship's moment. These values agree with the experimental value in the case of the plate and also the ship.

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In connection with the torsional vibration (in water) of marine propeller, it is required to find the effect of surrounding water upon a cascade of flat plates, which vibrates in water.
In this paper the author has estimated the amount of virtual mass for the vibration of a series of flat plates arranged in cascades, assuming the potential flow.
The result of calculation is shown as a chart for coefficient K. Virtual (or added) mass per each blade per unit lehgth is given by the formula
M=ρl²π/4K
where ρ is the density of water, l is the chord length of each blade. In case t/l→∞, that is, for a single blade, we have K=1.
The above value was obtained on the assumption that there is no stream-flow around blades. But, when a marine propeller is working, there are set up a relative stream around each blade. We assume a stream attacking the blades with incidence angle α, and circulating flows around each blades. The amount of circulation is determined in usual manner by condition at trailing edge of blades. Calculating the amount of virtual mass of a cascade of blades which vibrate in the abovementioned stream, we find it to be the same when they vibrate in still water. Thus we see that, at least for a potential flow of ideal fluids, the relative flow does not affect the value of virtual mass which is mentioned above.

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Sometimes it is required to make measurement of water flow using a Petot-tube in a limited duration of time. Making an experiment of water flow by Petot-tube which is mounted on a truck of experimental water tank is an example of such a case. The author has made some theoretical calculation together with model experiment with the object of giving some suggestion regarding the most suitable dimensional proportion of Petot-tube pipe-line to be used for that purpose.
First we estimated the amount of residual velocity of manometer water-column, when the water column has risen to rated value ; the pipe line consisting of (a) pressure hole, (b) leading tube, (c) manometer water column being taken into account. Judging from this estimate, it was thought that, in order that the manometer column may rise quickly, yet no oscillation of appreciable amount does not take place, the value of the ratio D/d should be about equal to 4, in case of ordinary dimensions of tubes etc D is the diameter of large pipe (lead pipe, water column glass-tube etc.), while d is the dia. of small tube (Petot-tube proper) d may be taken to represent the dia. of hole of static or total pressure, in a Petot-tube. When there are n holes, as in some type of Petot-tube, we take √nd instead of d.
In order to confirm experimentally the above-mentioned estimate, we constructed an experimental apparatus consisting of water tank, model representing Petot-tube, pipe-line, manometer water column. Making initially the manometer water column level lower than the level of water tank, and opening suddenly a cock, we observed the rise of water column in a manometer glass-tube. Thus, using (a) manometer glass-tube, (b) petot-tube model of various dimensions, we concluded that the.above mentioned statement may be taken to hold good, at least for practical purposes.

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In this paper, the authors report on a system of indicating shaft-horsepower with a milliwattmeter to which a magneto-striction type torsionmeter and an electric tacho-meter are connected.
The magneto-striction type torsionmeter has been investigated and trially manufactured since 1947, and was tested at the four vessels' sea trials by attaching it to the intermediate shafts.
But the reason was not understood at that time, why the results obtained with this torsionmeter have shown the lower values for the range of low speed and higher values for the high speed than those obtained simultaneously with the torsionmeter of Togino's type and of the Hopkinson-Thring type, and the percentage errors were not negligible at the time of the progressive speed trials of the tested three vessels, while practically successful results had been already obtained in the case of the “Seikan-Maru. No. 11”.
But in this paper, the authors give a solution to this problem after the careful experiments on the “Nichirei-Maru” and the “Gekko-Maru” that the above-mentioned erros were mostly due to the temperature effect on the CuO rectifier in the secondary circuit of the pick-up of the magneto-striction type. This temperature effect can be compensated thoroughly or made smaller enough to be neglected.
The electric tachometer which has shown a superior linearity in its revolution-voltage characteristics, is a D. C. generator with permanent magnets.
For the milli-wattmeter as the shaft-horsepower indicater, two meters have been trially manufactured, one of without core type and another of with core type, and the latter has shown better quality.
Last section of this paper deals with some examples of the results of measurement, obtained with the above-mentioned instruments attached to the intermediate shafts of the “Nichirei-Maru” and the “Gekko-Maru”, at the official speed trials, turning trials and the backing trials.

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Dealing with the strength of ships in bad weather, we must know the external forces acting to ships. Especially the problem of pounding is very important. As the premise of the problem, we had carried out the following experiment.
Fine test pieces made of hard alminium alloy 56 S (2mm thick, 11.3-22. 6cm diameter) were strengthened their rigidity with wood plates (about 2cm thick). They were fixed on the falling part of the testing machine (newly designed), and were fallen upon the water surface from 2.5-20cm height. We had measured the impulsive force using piezo-electromagnetic-oscillograph.
Consequently we had the empirical formula based on the following assumption : The maximum impulsive force of falling flat plate consists of two parts, one which is proportional to√H has the elastic character, and the other which is proportional to H had the hydrodynamical character. That is
P_max=α√2kgMm/M+m√H+βρ gFH
where P_max : The maximum impulsive force
α : Empirical constant 0.7 (non-dimension)
k : Spring constant of falling body
m : Virtual mass of fluid
M : Mass of falling body
g : Acceleration due to gravity
H : Falling height
β : Empirical constant 18 (non-dimension)
ρ : Density of fluid
F : Area of flat bottom

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The stresses in riveted structure and in welded structure show different response under same external force. That difference is mainly due to the slip or deformation of rivet line.
When the rivet line is substained to the action of shearing force parallel to its line or normal force perpendicular to its line, the rivet deforms elastically. In the same time, the elastic deformation is produced in the plate around rivet holes by bearing pressure. Consequently, the slip of rivet line is produced.
The theoretical calculations reported herein show the dimensional consideration on slip factor (displacement coefficient), effect of rivet joint on the effective breadth of stiffened plate and effect of rivet line (or zone) on the stress concentration around a circular hole in plate under-uniform tension etc.
The results showed that, in generally speaking, the welded structures show the better efficiency but also show larger stress concentration than those in the riveted structure.

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In 1935, while the author was on duty in the Naval Technical Research Institute, some warships of Japan met a violent typhoon in their battle practice, and two destroyers were broken in two. By this accident, the necessity of research on the strength of ships running among waves was strongly impressed, and an experiment on the measurement of hull stress in an actual ship was planned.
To obtain the conception, as to what phenomena should appear on ship running among waves, a model experiment in an experimental tank was thought effective as a preliminary test to the actual ship experiment.
An electro-magnetic strain meter was designed to obtain the continuous record. In 1936, a 1.5 m. model having a rectangular section, the most part of which was made of celluloid, was towed in an experimental tank. In this experiment, the hull strain in waves changed with the ship speeds. Vibrational strain was also observed when a heavy blow was delivered to the foreward bottom of the model. The possibility of model experiment was shown.
The project was modified and a new model experiment was designed, because the outbreak of Sino-Japanese hostilities made the actual ship experiment impossible.
In 1939 and afterwards, a series of experiments was tried. The hull strain, pitching and heaving motion of the model and the relative position of the wave and the model were measured.
The experiments demonstrated that model experiments of this kind would permit not only qualitative but quantitative analysis of the dynamical strength of ships. Actual ship experiment is necessary, indeed, to accomplish research concerning with the longitudinal strength of ships among waves. The actual ship experiment, however, has several disadvantages, such as expensiveness, difficulty in bringing ship in desirable experimental condition and difficult reproductivity, etc.
Therefore, the author believes, research should first be made in detail with model, and the actual ship experiment may as well be considered as an experiment confirming the results of the model experiments.

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In the investigation of ship's local vibration, the equilibrium equation is to be got under consideration of rectangular plate, not only with stiffeners but also with various appendics. Among those appendices, it is assumed, masses on the rectangular plate, or elastic pillars can be sufficient factors. In this paper, the author is dealing with the conditions of rectangular plate with these appendices.
As regarding the studying of these problems, Mr. Kanazawa presented “On the Lateral Vibration of Square Plate with any distributed Load”, or “A problem about ship's Local Vibration” in which he deduced the solutions through integral equation. The author for more various boundary conditions, deduced the solutions through the matrix equation. These both methods are two points of view for seizure of physical phnomenon, and it is reasonable that the both are to coincide consquently. But in the easiness of numerical calculation, it is probable that great difference can be between the both methods.

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To prevent or reduce the vibration of ships, it is necessary to know their natural frequencies. Hitherto the various methods of calculating the natural frequency of ship's structure have been published by many researchers ; but some of them are too complicated for preliminary design use, and the others lack in accuracy.
The authors have a plan to carry out a series of vibration tests of many vessels, in order to obtain the accurate method of estimating the natural frequencies of ships for preliminary design use. And they have designed a “Vibration Exciter” for actual ships' experiments. This instrument can give any periodical force acting on an actual vessel by changing the speed of revolution of its eccentric masses.
In this paper the authors report the principle and mechanism of the vibration exciter and the results of their experiments that were made on a 450 tons patrol boat. As the conclusion of these experiments, it may be said as follows;
(1) It is possible to measure the natural frequency and the mode of vibration of an actual ship by making use of this “Vibration Exciter” and vibrographs.
(2) It is possible to make clear the effects of weight distribution, depth of water and position of unbalanced force, the damping factors, the wave making phenomena, and other characters of the vibration of vessels by these systematic experiments.
(3) The natural frequency of the patrol boat measured was 303/min. and 301/min. at respective conditions of experiments and the nodes of vibration were found at Fr. 30 and Fr. 59. The damping factor was about 7%.

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This paper is a part of the research for the causes of breaking of chain cables which recently occurred successively on the newly built small vessels equipped with welded chains operated by electric windlass.
It was concluded by theoretical and experimental investigations that in weighing the anchor, if stopping of windlass were too late to avoid unexpected pull on the chain by force when driving at a high notch or even at a low notch with high speed electric motor, according to its characteristics, the accessive tension should act suddenly on the chain from the inertia force of revolving mass of the motor and the mechanical parts of the windlass. This tension could easily exceed the proof test load of the chain and the repetition of such abnormal pull would be able to cause the chain to break.

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In this paper, the principles of the designing and the building of the welded ships are shown; the numbers of rivets, the length of weldings, and the reduced weight owing to the adoption of welding are calculated from the drawings; comparing above results with the practical field records the methods of estimating the weights of the rivet bars and the electrodes for purchase and the hull weight of the initial design are established ; and the man-hours for the constructions of riveted ships and welded ships are compared to give a reference for the rationalization of the field works.

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An attempt is made in this paper to explain the construction of 12, 000 gross ton welded tanker in which electric arc welding was incorporated to the extent of nearly 90% a feat never attempted in Japan heretofore. The paper deals mainly on the various phases of material preparation and their dimensional accuracy, as well as, on ground prefabrications and subassemblings, erection and welding sequences, and also, on distortions and contractions produced by the welding. In addition, the construction schedule and the labour aspects are also dealt on.
The data contained in this paper has been obtained in actually constructing two vessels of this type, and it is stated in detail, how these findings and actual experience is being applied in the construction of three vessels of the same type now on the shipways under construction.

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“SANT'ANA” was designed to be used at the river of Amazon and was built by the Uraga Shipyard, the Uraga Dock Co. ltd., for Navebras S/A, Rio De Janeiro, Brazil.
This ship is equipped with two sets of diesel engines and twin rudders. The breadth of this ship is very large, compared with the length and the depth. The proportion of L/D (D is measured to the top of expansion trunk) is 16.2, and exceed the limit of the construction rule. The electric welding is adopted as much as possible and welding percentage is 95%.
Principal dimensions & etc. are as follows : -
Length B. P. 75.00 m
Breadth, moulded 14.00_??_
Depth, _??_ 3.15_??_
draught 2.887_??_
Gross Tonnage 1, 354.71 Ton
Dead weight 1, 495.00k. ton
Capacity of cargo oil tanks 2, 000 cub. m
Main engines “Hanshin” diesel engine 460 B. H. P.×2 sets

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A hundred years ago, a train-ferry service across the Firth of Forth in Scotland was born, and fourty years have passed since the Japanese Government Railways inaugurated a car-float service between Shimonoseki and Moji.
On this occasion, it is of interest to look back on the development of this facility in foreign countries and in Japan.
Since the first train-ferry the “Leviathan” crossed the Firth of Forth (1), similar services were inaugurated on the River Rhine (2), the Susquehanna River in the United States and also across the Nile Rever (3) in Egypt.
In this paper, the stages of this development are arranged as undermentioned, and various kinds of landing means are classified as follows :
1. The cradle age of train ferries. -In the first 16 years, the train ferry services were in their infancy, all operating across rivers or firths.
2. The epock making train-ferry. -In 1868, this facility was carried out on the Lake Constance in Switzerland (4), where the crossing was exposed and rough, so that people got an idea on the trustworthiness of the train-ferry service even on an open sea.
All these installations were commenced in the last 17 years, paving the way for the train-ferries of the future.
Kinds of Landing Arrangement of train-ferries : -
(1) Shipway or Slope Type a. Shipway and Travelling Platform.
b. Stepped Slopeways.
(2) Crane or Elevator Type a. Elevator ashore.
b. Elevator aboard.
(3) Elevating or Tidal Deck Type
(4) Movable Bridge Type
3. The development of train-ferry services in Denmark.
4. The development of the train-ferries on Lake Michigan.
5. The technically noteworthy development of the installations of the Warnemunde-Gedser and Sassnity-Tralleborg lines.
6. The popularization and development of train-ferries in twentieth century.
7. Train ferries in Japan.
From the history of train-ferries, the methods of laying tracks on deck are classified as follows : -
1. Through Track Type T
2. Head Terminal Type B (from bow) S (from stern)
3. Isolated Track Type I
4. Athwart Track Type A
The types of tracks on deck are mostly determined by the local conditions of the berths ; some were obliged to select an inferior method due to the original landing arrangement when further improvement was required. This is a point worthy of special consideration when designing ferry boat and landing arrangement in the future.

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