In recent days the Electric Arc Welding are getting adopted very widely in the hull construction of ships. Owing to the heat generation due to the Electric Arc, we must take care so seriously about the deformation of plates, when we apply the Electric Arc Welding to the hull coustruction.
Mr. T. Fukuda, Member, read his valuable paper at the last spring meeting of this Society, in the title of “How to minimize the Deformation due to the Electric Arc Welding, ” which introduced us useful methods in minimizing the deformation of the plates.
In this paper, auther describes how widely Electric Arc Welding are used and what deform minimising methods are adopted practically in the hull construction of the H. M. S. “Yaeyama, ” a mine layer.

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The government of Formosa has completed at Mitsubishi Dock Yard, a large fishing boat, equipped with two direct reversible four cycle Diesel engines, each developing 340 B. H. P. at 275 r. p. m. for main propulsion.
She is accommodated with many up-to-date fishing and sailing apparatus, among which most remarkable one is the auxiliary Diesel electric propulsion. In case of the tunny fishing with line-hauler, it is most desirable to propel the boat at a very slow speed nearly same as winding of line-hauler. Such a slowest speed of propeller as 11 r. p. m. is easily obtained by the Diesel electric propulsion.
There is another remarkable merit. Captain himseff can manoeuver the engine by remote control from the bridge, while inspecting the condition of the line-slack or tight-which is most important for this special fishing practice.
The electric propulsion is of Leonard system, where electric power is supplied from auxiliary Diesel generator of variable voltage type, to the variable speed 75 B. H. P. D. C. motor which is connected to the shaft through reduction gears and a clutch. There are two clutches provided for one propeller shaft, one of which is engaged to the main engine and the other to the auxiliary propelling motor through reduction gearing. When one of the clutches is engaged, another is disengaged by the same operating handle so as to avoid the mishandling.

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Assuming a very simple form of expression for the lift distribution along the span of a rectangular aerofoil, formulas for the transformation of aspect ratio and the wind tunnel boundary correction have been obtained which agree quite satisfactorily with experiments

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In this paper the results of model experiments on a special sectional form of a submarine hull under external pressure as well as on an ordinary circular form are given.
The author points out : -1. The deflection of the special form is greater than that of the circular form. 2. The buckling pressure of the shell plate of the special form is somewhat lowered by the excess compressive stress due to bending. 3. The position where the excess compressive stress should occur could be found by means of the strength calculation. 4. If the special sectional form is to be adopted it is recommended that the length of the special sectional part should be kept as short as possible and if practicable main bulkheads should be placed so as to stiffen that part.

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This paper treats the rolling of a ship of a moderate size relative to the wave by a similar method as Prof. Kriloff did, but it is endeavoured to get a more accuracy for approximation, and several new results are obtained. At first, the general equations of motion are deduced retaining the terms of order γ₀/R compared to unit, but as these are too complicated for practical use, gentle waves are taken as a first approximation for analysis. Moreover, a simple ship form is taken instead of real one for the convenience of the deduction of practical formulae, i. e., the cylindrical form with the section of the load water plane, but the draft being modified so as to give the probable results.
Important results are those :
1. Equations of motion of centre of gravity of a ship are written;
V₀/gd²X_g/dt²=_??_wAwh' A sin ωt-_??_wAwMθ cos ωt.
V₀/g d²y_g/dt²+Awyg'=γ₀Aw [B-h'/RA] cos ωt-_??_wAwMθ sin ωt …… (1)
where
A_??_e^3γ [1-αβ/2-β²/6A₃/A₁] B_??_1-β²/6A₃/A₁
M=bβ [A₃/3A₁-α²/2], A₁=1-1/n+1, A₃=1-3/n+1+3/2n+1-1/3n+1.
If θ is small, the 2nd terms of the right-hand sides can be neglected, and x_g and y_q are obtained as
x_g=-γ₀A sin ωt.
yg=a+γ₀ [σ_d²B-ω²A] /σd²-ω²cos ωt=a+r₀B-h'/RA/1-h'/Rcos ωt.
these show that the path of C. G. of the ship is elliptic, major axis being vertical, and the motion is less as the C. G. lies higher. The draft is much more influential than breadth for this motion.
2. When the rolling is considerable such as in a synchronous one, 2nd terms of thé right-hand sides of (1) are not negligible, and, by inserting θ=θ_o sin (tω-δ), approximate solutions can be got. By these substitutions, a constant term _??__wA_w/2γ₀θ₀ sin δ appears in both equations, positive in the first and negative in the second.
The positive constant term in the first means a drifting force in the direction of wave propagation, though, in the second, the constant term only changes the origin of the vertical oscillation. This drifting force was shown by Dr. Suyehiro's experiment, though owed to the quite different cause. By inspecting M, it will be seen that the drifting force is positive for a broad and shallow ship, and is negative for a narrow and deep one, which phenomena can be simply tested in the experimental tank.
3. By rejecting the terms of order γ₀/R, the equation for rolling is;
Id²θ/dl²+Wmθ=_??_wρgKsin ωt+_??_wρgθ· Q cos ωt…… (2)
where K=2R∫^l₀dε∫^ξ₀-ξ₀ξsin ξ/Rdξ-∫∫∫_v0e^-η/R (ξsinξ/R+ηcosξ/R) dv

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The object of this paper is to obtain the solution of the problem of the vibration and its stability fo a rectangular plate clamped at its four edges and subjected to edge thrusts. The solution of the problem is deduced from the differential equation :
D₁ (∂⁴w/∂x⁴+2∂⁴w/∂x²∂y²+∂⁴w/∂x⁴)+P₁∂²w/∂x²+P₂∂²w/∂y²+ph∂²w/∂l²=0,
in which D₁=1/12 Eh³/ (1-σ²);
E is Young's modulus; σ, Poisson's ratio; ρ, the density; w, the deflection of the plate; x, y are Cartesian coordinates parallel to edges; and P₁, P₂ the thrusts acting parallel to x and y axes respectively.
It is seen from the calculation that the following sets of P₁ and n are the values of the thrust and the numbers of the half wave length in the case, in which P₂=0 and the vibration becomes unstable.
In this table, a is the length of the plate; and b, its breadth.
The number of vibration p/2π, when P₁=P₂=0 and a=b, is tabulated below.

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In the manual arc welding, the skill of welder plays one of the important factors; the author treats the subjects on the training of welders, necessary equipments in welding practice and the qualification of welders.
During three months in the welding school, the trainees should be supplied with ample quantity of steel scrap, oxyacetylene cutting sets, breaking instruments of welded joints, etc., in order to assure the promotion of their own ability by producing great number of welded joints and breaking them to inspect the fractured surfaces of welds. Another three months, they will be helpers to the welders in the shop.
The easy posture of welders, good welding equipments and accessories, good electrodes and ingenious design of the joints will produce the good welding products. He prefers the AC-DC welding sets to AC transformers, and helmets to hand shields; and makes some remarks on the nature of electrodes and the design of the joints to be welded.
As fillet weld test specimens will include all the defects of welding procedure, if any, and as bending test will show the ductility of the welds, he asserts that both tests must be done along with the butt weld test in the qualification of welders.

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This paper has been written with a view to examining whether or not it is possible to fix a general standard of the transverse strength of the hull-structure of steel ships. Here not only the transverse members such as floor, side frame. beam and pillar, but the longitudinal members such as shell plate, deck plate and inner bottom plate, which form a transverse belt, are also taken into account.
The author's investigations are based on the “Principle of Continuity”.
In Section 1, the outline of the “Principle of Continuity” is described briefly. As is well known, this principle developed by Prof. Hovgaard is equal in effect to the “Principle of Least Work” developed by Castigliano and suggested by Dr. Bruhn as a method of solutions of the transverse strength of steel ships. General equations of solution and the formulae for internal stress are given in the same Section.
In Section 2, the strengths of standard frame rings are dealt with. The standard frame rings are one frame space in length and are assumed to represent cross sections under various conditions, of a steel ship of particular principal dimensions and draft.
The ship is assumed to vary in type, i. e., to be of flush deck type having one or two decks in certain cases, and of one deck type with one tier erection. The number of rows of pillar is assumed to be one or two, and three in two special cases. The results of calculations are shown in tables.
In Section 3, the transverse strength of steel ships is considered. The conclusions reached are :
1. The transverse strength of the hull should be considered in association with the stiffening effect of the transverse bulkheads as well as the co-operative action of the longitudinal members which serves to maintain the effect.
2. It is not possible at present to fix a general standard of the transverse strength of the hull structure.
3. The transverse deflection at the points of support of the transverse members can practically be disregarded when ships having sufficient longitudinal strength are subdivided by suitable number of efficient transverse bulkheads. When the value of the modulus of resistance of the cross section of the hull is not less than that calculated in accordance with the requirement of the Ship Load Line Regulation, the longitudinal strength of the ship is considered sufficient.
4. The present method of determining the scantling of transverse members separately on the bases of lateral or axial load or both combined, is considered to be practically most preferable, if not perfectly correct.

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Experiments of air resistance with models of above-water portion of 4 typical warships were carried out in the Wind tunnel of the Naval Research Institute and the following are the formulae deduced.
For battle ship, battle cruiser and destroyer :
R_a=.0332 A V.²
For aeroplane carrier : -
R_a=.024 AV, ²
in which R_a=air resistance in kg.,
A= transverse projected area of ship above water line in m².,
V=relative velocity between wind and ship in m./sec.
Secondly, in view of obtaining the formula for calculating the air resistance of aeroplane carrier advancing obliquely to the direction of the wind, one model of this type tested in the same tunnel, and from the results of experiment next formula deduced : -
R_a=C'_R (Acos²θ+Bsin²θ) V, ²
where R_a air resistance in kg.,
C'_R=coefficient of air resistance,
A=transverse projected area of ship above water line in m².,
B=longitudinal projected area of ship above water line in m².,
θ=direction of relative wind to middle line of ship measured from the bow in degrees.
Some remarks on the tendency of variation of the coefficient C'_R in the above formula influenced by other elements, etc. are described; in addition tables and curves of the result of experiments are appended.

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The auther discusses on the causes and the natures of various kinds of cavitation in the marine screw propeller, and then describes his own method how to deal with the effect of cavitation in propeller design. Moreover, the principle of the “Thrust Indicator, ” which is the most convenient apparatus for the study of cavitation problem, is explained.
Some results of experiment on cavitation are reported in appendix I, II & III.

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Several experiments with model rudders were carried out at the Naval Technical Research Institute to investigate the effects of the aspect ratio, the forms of section and periphery, and also the stream at the ship's stern on the behavious of the rudder. The author tested a series of rudder models in the water-circulating tank by measuring the horizontal and vertical forces acted on and the twisting moments on the rudder stock against the varying water velocities and helm angles, and calculated the amount of the normal pressure and the position of the centre of pressure from the quantities so measured.
Besides the open experiments, the author made the turning trial in the test basin by using the self-propelled model ship fitted with some of the model rudders and investigated how the items above referred to affect the turning circle of a ship.
The chief conclusions drawn are : (1) Systematic experiments of several series of model rudders with varying aspect ratios, forms of section and periphery are needed to obtain the normal pressure. (2) The position of the centre of pressure calculated from the Jossel formula is fairly accurate. (3) The effect of the stream at the ship's stern on the twisting moment must be taken into account owing to the experimental fact that there exists a great difference between the twisting moments measured in open water and those measured behind the ship. Diagrams showing clearly the results of the experiments are appended at the end of the paper.

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Ever increasing demand of motor ships in these days resulted remarkable improvement of the marine Diesel engines both in types and constructions.
Air injection principle has been widely applied now, for all types and sizes with a great success and also demand for the engines of larger output made number of leading makers turned their step to start building of double acting two stroke engines. Range of application of double acting two stroke engines has been increased both in 'larger and smaller sizes as these engines have several superior characters. The first double acting two stroke airless injection engine was installed to the Japanese Motor Ship “KWANTO MARU.” During first one year's service, several difficulties experienced, but all probable cause investigated through and now completely eliminated.
Thus M. A. N. double acting two stroke airless injection marine Diesel engines are proved as one of the most ideal engines.

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