To study the effects of the longitudinal position of centre of buoyancy and area and shape of midship section of intermediate liner forms upon the resistance, sixteen models were tested at Teishinsho Experiment Tank, and the results obtained are compared herewith.

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It is known that the transverse metacentric height of a ship, when trimmed or on the wave crest, is reduced, sometimes even becoming negative. Therefore when she is pitching on the wave, she will become unstable instantaneously if the angle of pitch is large. In this paper, the dynamical properties of this transve se instability are treated According to the calculation, the reduction of a metacentric height can only in very small measure be attributed to the reduction of the trimmed water plane area contrary to the general belief, and also the effect of the wave form is not so large for an ordinarily formed ship, assuming the standard wave adopted for strength calculation, but the reduction should be considered to be mainly owing to the rise of the centre of gravity of the ship due to trim. Therefore the reduction is large as the longitudinal metacentric height is large and the angle of trim increases. The rolling motion of such a ship is called the “quasi-harmonic oscillation”, and has the critical ranges of periods for which the instability of motion occurs, compared with the only one critical value of period for the simple harmonic oscillation. The problem for such a motion can be generally solved by the Hill's method.
In consequence of the executed calculation, the dynamical transverse instability occurs not only when the angle of pitch is so large as the instantaneous negative GM appears, but even when the pitching angle is small, although in less magnitude.
The critical range of instability increases as the angle of pitch increases, and also as the longitudinal metacentric height gets more. This tendency is not much altered, if the effect of the change of water plane area due to the trim and wave form is rejected. The multiplication factor of the amplitude during a single swing is adopted for the difinition of the grade of instability which occurs in the critical period. This grade of instability depends mainly on the ratio of the longitudinal metacentric height to the transverse one. For the ordinary value of this ratio, approximately 200, the grade of instability is nearly two, assuming the max, pitching angle 5° This value may be taken as the standard of the ratio of the two kinds of metacentric height, and if the ratio is less than this standard, the ship will be more stable; if greater, more unstable and the manoeuvering will be more difficult. When a ship rolls, lying transversely on the wave, the motion is less as the metacentric height is less, while, when lying longitudinally on the wave, the motion is more stable as the metacentric height is greater, -this fact may be noteworthy. As the result of the analysis, the lower limit of the transverse metacentric height, from the point of view of the transverse instability due to pitch, is obtained as follows:
M₀_??_C.φ/12C_b•(L/100)²/d
where M₀: transverse metacentric height. C_b: block coef.
L: length of ship, d: draught of ship.
φ: function of water plane coef. C_w and φ=C_ω/3-2C_ω
C: const.{4 for merchant ships, 3 _??_ warships.

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Comparison is made between two designs of coasting cargo steamers of about 3, 700 ton deadweight and 9 1/2 knot sea speed. Design “T” represents a steamer designed in the last years of Taisho era and completed in the beginning of Showa, namely the year 1927. Design “X” has been prepared for the purpose of illustrating the rapid progress, made within recent few years, in the mercantile steamer designs, and it involves every improvement undertaken by the Uraga Dock Co., since the completion of the first named steamer. It is described that “X” will burn about half the quantity of coal as that of “T”, for an equal load of cargo and equal speed of 9 1/2 knots, and further details are given as to how such highly economicol results are to be arrived at.

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When ships are subdivided in compliance with the “Rules for the Safety at Sea”, a certain difficulty is encountered in the arrangement of cargo handling gears of vessels of smaller sizes owing to the shortness of hold lengths in comparison with those of larger sizes.
This is the result of the smallness of the freeboard ratio which effects mostly upon the floodable length.
In order to mollify such difficulty, it is necessary to give a suitable sheer-ratio together with a greater freeboard-ratio to the ship at a definite draught, i.e. to increase the depth of the ship, maintaining the equivalent strength & necessary stability of the ship.

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The Nagoya works of Mitsubishi Aircraft Co. have a wind tunnel of 2 metres in diameter.
This report describes the details of construction and the method of measurement of the apparatus for testing air propellers in the wind tunnel and is supplemented with some measured results of testing by using this apparatus.
The measured results can be summarized as follows:
1) Propeller efficiency and number of blades.
Metal propellers of 2 and 3 blades and wooden propellers of 2 and 4 blades with the same blade from in each group were tested. The results of measurements show that in the metal propellers the difference of the efficiencies between the two and three bladed propellers is small, but in the wooden propellers the difference of the efficiencies between the two and four bladed propellers is noticeable. The efficiency of the four bladed wooden propeller is inferior by about 5% to that of the two bladed propeller.
2) Propeller characteristics in yaw.
Two bladed metal propeller acting in the inclined wind was tested. The inclination of the wind against the propeller axis was up to 25°. The result of measurements shows that the effect of the inclination of the propeller axis against wind is small and can practically be neglected; that is, if we take the component velocity of the wind along the propeller axis as the advanced: velocity of the propeller we always get about the same characteristics for that propeller.

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This engine is of two-cycle airless-injection type and has been developed by Mitsubishi Zosen Kaisha after about five years of experiments and studies.
The first four sets of the engine were adopted by Osaka Shosen Kaisha for their M. Ss. “NANKAI MARU” and “HOKKAI MARU” and the actual service records have now been obtained.
This paper deals with some special features of the engine, such as the scavenging, combustion, mechanical efficiency and construction.

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Now-a-days, small turbines are widely used for driving pumps and fans in naval vessels. These small turbines, having sometimes a capacity of less than 10h p., naturally offer difficulties to the designer to obtain the specified characteristics unless his design is based on accurate experimental data.
In this paper some of the reuslts obtained from experiments on a number of such small turbines are described and the author proposes the most suitable type to give better efficiency and less weight and space.
Some notes on design are also stated

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An approximate formula for the deflection of a triangle plate, clamped at boundaries and loaded uniformly is worked out to the practical use by the present author on the strain energy method as follows:-
w=C(x-K)²(y-Mx)²(y+Nx)²
where
C=15/4(1-σ²)p₀Q/(Eh³K²P), P=M⁹+N⁹+M⁷+N⁷+M⁵+N⁵+7MN(M⁷+N⁷)+23M²N²(M⁵+N⁵)+47M³N³(M³+N³)+66M⁴N⁴(M+N)+5MN(M⁵+N⁵)+11M²N²(M³+N³)+15M³N³(M+N)+5MN(M³+N³)+10M²N²(M+N)
Q=M⁵+N⁵+5MN(M³+N³)+10M²N²(M+N)
M=m/k, N=n/k, K=3k=height of a triangle, 3(m+n)=length of a base side. See Fig. 1. p₀=uniform pressure, h=thickness, E=modulus of elasticity, σ=Poisson ratio.
We easily get the corresponding formulae by putting M=N for an isosceles triangle plate, N=0 for a right-angled one, M=1 and N=0 for the latter with two equal sides and further M=N=3 ^1/2 for a regular equilateral one in tie above expression.

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From the nature of hydrostatic curves of ships was first obtained the new formulae for the following items, viz;
1. The variation of the coefficient of water-plane area due to the change of draught.
2. The variation of the block coefflcient due to the change of draught.
3. The height of the centre of buoyancy KB at any draught.
4. The moment of inertia of any water plane.
5. The height of transverse metacentre KM at any draught.
These formulae were checked on 30 ships, and the errors were found to be negligible for practical purposes.

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