Although the ship-building in our country has made a remarkable progress in these thirty years, it is regretful that we yet find many points of dissatisfaction, as we consider the present situation of our ship-building industry as it occupies a part in the industry of recent times. For, though we are now being recognized in the world by the vast capacity of ship-building or the excellent design of warships, the ship-building industry, as a whole, has come to be left under a unstable and pitiful condition on the account that the consideration as to the management and administration as the means of production has been almost neglected.
And it is believed that we can, and must, make great contribution to the national prospects, if we continue our efforts with additional care to relieve from these defects.
To relieve from these defects, it depends much upon the protection and encouragement from the national policy, and is equally necessary to have suitable administration of each establishment, but it is also believed to be one of the important and effective ways to make up the shift of improvement on shop management, taking in the idea of scientific management and rationalization of industry which is the amulet of recent industry.
This paper is the report of the author's investigation and experience - be it of so short a period - together with his opinion, and he will be so much contented if he can give any hint upon the problem of rationalization of our ship-building industry.

View full abstract

When a ship is inclined to the upright, the shearing stress in the ship's structure cannot be found at once. The shearing force should be resolved into two components parallel to the principal axes of the cross-section. The shearing stress at any point on the cross-section can then be found by taking the algebraic sum of the effects produced by the component shearing forces. One of the components acts on the ship as when she is upright, and the other as when inclined to 90°. The shearing stress at the up rightcondition can be found by the usual method, but, when inclined to 90°, the cross-section of the ship is not symmetrical about the principal axis parallel to the component shearing force, and we are not accustomed to compute the shearing stress on such section. In this paper, the distributions of the shearing stress on some simple cross-sections of vessels when inclined to 90° are found from the approximate theory of thin sections deduced from Saint-Venant's theory of flexure. Observing these results some reasonable assumptions are made for computing the shearing stress on the more complicated cross-section as a ship's section when she is inclined to 90°. Thus the distribution of shearing stress on the cross-section of a ship when inclined is found.
The result of the calculation on an ordinary two decked steamer shows that, when the angle of inclination is 30° to 45°, the shearing stresses at the side of deck plating and inner bottom plating are more than 10% greater than those when upright, and, when inclined, though the neutral axis passes through bilge plating, the shearing stress at this part is not much greater than that when upright. It is also observed that, at the centre of deck plating, bottom plating, and inner bottom plating, the shearing stresses are nearly equal to those at the sides, but, as these are only for the angle of inclination near 90°, an actual ship will not be subjected to such stresses. Therefore, roughly speaking, for ordinary merchant ships, the calculations of shearing stresses when inclined are not necessary if they are made for the upright condition. However, the method of calculation suggested in this paper may be helpful when computing the shearing stress in some cases dealing with ships of special type.

View full abstract

The longitudinal strength calculations of ships are very important for designing ships; but there being many unknown factors, accurate numerical results cannot be easily got theoritically.
The author describes on this paper the results of actual researches and theoritical investigations taking the interesting example occurred recently-the buckling of deck platings of oil tanker “Erimo” and her sister ship “Shiriya.”
He especially wanted to investigte the relations between buckling stress, elastic limit and stability of deck platings, and moreover wanted to eliminate some unknown factors of longitudinal strength calculations.

View full abstract

A new calculator was deviced, which admit of rapid calculation of the air-ratio n, the rate of producing soot S and the percentage heat-loss φ, due to incomplete combustion and excess air, from the results of Orsat's gas analysis, i.e, volume percentage of carbon di-oxide, mono-oxide and oxygen in the exhaust gas, say p, r and q. The rate of producing carbon mono-oxide is converted into equivalent soot with respect to heat efficiency and it is included in the rate of producing soot S. Thus it can be immediately determined wbat an amount of air ratio is most economical for particular boiler and particular rate of fuel consumption, and also we can decide the quality of the combustion system by the amount of minimum heat loss. The ground of the theory is very simple. If we assume, as it is very probable in most cases, that all the constituents of the fuel make complete. combustion, except some parts of the carbon, say Cy and Cz, which produce carbon mono-oxide and soot respectively, then the compositions of the exhaust gas, p, q and r, must be certain functions of the three variables Cy, Cz and n. Consequently we can solve Cy, Cz and n as the functions of p, q and r, provided that the chemical composition of the fuel is known. Finally some examples of application are shown.

View full abstract

The formation of deep water waves, when some disturbances act on a point in the interior of the water, has been studied. The compressional disturbances of the simple-harmonic type being propagated radially from the origin, a succession of gravity waves is gradually developed by the surface conditions of the water.
The method of analysis employed in this is, in the first place, to apply on the primary waves the mathematical results due to H. Lamb, i.e.
H⁽²⁾₀(hR)=i/π∫^∞_-∞e^-aye^_??_ifx/αdf, [R²=x²+y²]
and
e^-ihR/R=∫^∞₀e^-az/αJ₀(fr)fdf, [R²=x²+y²+z²]
where α=√<f²-h²>ori√<h²-f²>,
according as f²_??_h². Some modified formulae have also been employed. In the second step, gravity waves, which are to be superposed on the primary waves, have been formulated to satisfy the boundary conditions.
It must be acknowledged that the conception of the “small motion” in the sense concerning the slope or the gradient of the displacements has been introduced. Again, in all cases of contour integration the “principal values” due to Cauchy has been taken.
The paper consists of six sections: the beginning three sections deal with the cases in which lithe origin is either a singlet, a doublet oscillating horizontally or a doublet moving vertically all in two dimensions, while the remaining three treat of the similar cases in three dimensions.
The principal results obtained by this investigation are enumerated as follows:
1. In spite of very small displacements of the compressional waves in the neighbourhood of the origin in the interior of the water, the excited surface waves have relatively large amplitudes.
2. The generated surface waves are chiefly the ordinary gravity waves having the same frequency as that of the origin together with their wave length proper to the period.
3. The distribution of the wave motion on the surface of water always conspires with the modes of oscillation at the origin.
4. This fails in a three-dimensional case where a doublet oscillates horizontally. In this, notwithstanding the maintenance of the natures of the vertical and the horizontal components of displacement in wave x profile and in azimulthal distribution, the azimuthal component of displacement quickly disappears as the distance from the disturbed portion is increased.

View full abstract

The ordinary diving equipments, which has hitherto been used in every country, being incomplete, it has long been thought exceedingly difficult to work in the water at the depth of more than twenty five fathoms.
The author has carefully investigated the cause of difficulties, and by some devices to take them off, he has come to make it possible to stay and work several minutes at fifty fathoms.
Now he is going to summarize the points of the improvement.

View full abstract