In the first section of this paper, the Author describes the state of shipbuilding in recent several years in this country concerning the general outline and tendency of new ships built during the period, the development of Home made propelling and auxiliary Diesel machineries and various deck machineries; he points out building of Naval auxiliary vessels at Private yards protected this industry from pronounced depression, and ship and engine repairing business has exerted a great influence on the business of leading firms, he also explains outlook of the modern problem of rationalisation of shipbuilding industry in Japan.
In the latter section of the paper, the Author proposes a reform measure of mercantile fleet replacing the old aged ships with new and economical ones, he also recommends the stabilization of the building schemes of new vessels in order to keep up the least annual capacity of shipbuilding in this country in future; he draws attention ta building of ships under special service so far necessary as developing the other auxiliary important industries. He gives a warning to whom concerned with the shipbuilding industry to get out the crisis and warns of the influence of the latest progress of engineering in both theoretical and practical sides.
In the last, there gives a short description about the development of air craft.

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Ocean waves are not regular, as are assumed in the ordinary theory of rolling, and accordingy the max angle of roll deduced therefrom is not directly applicable in practical case. In this paper, the waves are not assumed to be regular, but only one wave, which passes the ship in one swing, is considered as sine form, and the limiting angle of swing possible in that ease is found. The angle of swing is generally given by
θ=K-∞Σn=1θn cos nkt.
But a large swing can safely be represented by
θ=K-θ₀cos κt…(1)
This fact, valid both for apparent and absolute rollings, can be mathematically proved in both cases(Appendix)and also is observed from the record of actual rolling on sea as Fig.1
Assuming the form(1), only the swing, whose final amplitude is not less than the initial one, need to be taken into consideration for the present problem, then this condition gives the relation that σ must be less than unity. The final amplitude of swing θ_f is given by
θ_f = [2eσ⁸+a_e(1-σ²)] sinσπ/2/e√4σ²(e²σ²-1)²+a_e²e²(1-σ²)²tan²σπ/2…(2)
The maximum value of θ_f for various σ is the desired limiting angle, which occurs, practically σ= 1/e. Consequently θ_fmax occurs at σ=1 for e>1, and at σ= 1/e for e>1, the results being as follows,
θ_fmax=1/√(e²-1)² +(2a_ee/π)² for e<1 or T_w<T_s
T=T_w.
θ_fmax=2+a_e(e²-1)/a_ee²(e²-1)cosπ/2e for e>1 or T_w>T_s
T=T_s
θ_fmax=π/2a_e for e=1 or T_w=T_s
T=T_w=T_s.…(3)
The effective extinction coef. a_e in these expression is to be determined by the following equations
a_e=a+√2b_γΘw/e [(1-e²)²+(2a_ee/π)²] for e<1.
a_e=a+2b_γΘw/a_ee²(e²-1)cosπ/2e for e>1.
a_e=a+b_γΘw/2a_eπ for e=1.…(4)
For the absolute rolling, the limiting angles are given by multiplying e² to the results (3), and the a_e, by taking e²γΘw instead of γΘHw in (4).
These results are calculated and given, in Fig. 2.
The same method can also be applied for the swing on waves affectedby wind, in which the, new. variable θ=θ-φ is to be used instead of θ and the_fmax is given by(3), then the limitting angle is equal to θ_fmax plus φ.
These treatment is based on the assumption of isochronous stability curve, but the above results can also be applied to the non-isochronous case. The approximate θ'_fmax for non-isochronous ship can be got by taking the same area below the stability curve in both cases.

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Effect of a Quadrate Hole on the Stress Distribution in a Beam under Uniform Bending Moment, By D. Sadahide Ogawa, Member. In the structure such as aeroplanes, ships, steel cars which are regarded to receive bending action, the quadrate holes are frequently perforated for the purpose of saving of weight, side ports, windows etc. So far as the author is aware, however, this practical problem has not yet been solved theoretically, though the effect of circular hole was attempted mathematically and experimentally by Z. Tuzi.⁽¹⁾ Therefore I have given theoretically the stresses in a deep beam having a quadrate hole of various roundness of corners or a crack of star shaped with its center on the neutral axis and subjected to uniform bending moment in the plane of beam.
The results obtained by author will be applied well to a beam, the depth of which is great enough compared with the size of hole.
First, the stresses due to the quadrate hole with its four corners on the neutral and vertical axes of beam have been examined. The quadrate boundary of hole is given by α=αi of the series of curves, which are introduced by the relation
x= a (3e^α cos β+re^-3α cos 3β),
y =a (3e^α sin β-re^-3α sin 3β),
x and y axes being the neutral and vertical axes of beam. The stress-components αα, ββ, and αβ in the orthogonal-curvilinear co-ordinates α and β are determined by the equations (11), (12), (13) and (16), (17).
Then, the case of the quadrate hole with its centers of sides on the neutral and vertical axes of beam has been deduced by substituting r = -r and β=β-π/4 (=β' say) in the foregoing results.
In these results,
α varies from 0 to ∞.

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The Imperial Japanese Lifeboat Institution has been annually attaining about the same result for the rescue at sea as that of the Royal National Lifeboat Institution, notwithstanding the.former's far inferior equipments and less efficient lifeboats.
The authors point out in this paper the contradictory fact that such handicap has been compulsorily compensated by the selfannihilating endevour of men engaging, at the risk of their lives, in the gallant task of rescue at sea, and emphasize the necessity of building a number of exclusively designed motor lifeboats in future in order to diminish the danger of rescuing men as well as to augment the efficiency of this noble work. For this, a building scheme for motorlifeboats in Japan is hereby propitiated.
As a standard type for this purpose, the “No. 1 Motor Lifeboat” of 15 metres long was designed by the authors under such conditions as not to conflict with the Goverment Regulations for the Ship's Survey and the Law of Seamen.
The most suitable ship's form was determined by model tests in the miniature experimental tank owned by one of the authors. The course and details of the design and calculation are apprehensively explained. Further, the details of design of a 60 b. h. p. watertight Diesel engine which rendered the most effective influence to the complete design of the boat, and also the trial results for the acceptance after completion are fully published. Various bibliographical references as to motor lifeboats are appended.

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I tried to investigate some tentative relations which could be applied with much confidence and accuracy to the form coefficients of warship and merchant vessel, and partly published, some years ago, on Zassan Nos. 56 & 65 of The Society of Naval Architects of Japan
As this continuation, this paper deals with some other relations between initial metacentric height KMand ship form., and also with a simple but reliable method of computing this KMfor any given types, forms, etc. of ships.

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To study the effects of fore-body form, longitudinal distribution of parallel middle body and breadth of cargo ships upon the resistance and mean annular wakes at the position of screw propeller, seventeen models are tested at Teishinsho Experiment Tank, and the results obtained are compared.

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In the present-day practice, an aeroplane is designed with assurance, as to performance, strength, and stability, depending upon theoretical analysis. Control surfaces, however, are designed with risks, relying upon the experience of designers and the judgement of test pilots
The angular velocity with which an aeroplane rotates corresponding to the maximum rudder angle when it flies with the minimum velocity is calculated for recent aeroplanes, and it is shown that the control surfaces are to be so designed that the angular velocity is greater than the mean value for the category to which the aeroplane belongs.

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彎曲管の撓性に關しては過去約20年間に多くの實験的及理論的研究が發表せられて居る。理論的研究の糸課は普通の梁理論で計算したものに對してpipe factorλ (=tR/r²) なるparameterの函数で修正せねばならぬことには皆一致して居るが、其の修正因子Kの値は各研究者の定めた假定に依つて可なり相違して居る。從つて系統的な精確な且つ廣汎な實験的研究に依つてのみ最も實際に近いKの値を確むべきであるが、實験的研究には色々と難しい状態が伴ふ爲に、各研究者に依つて得られた結果は區々である。然し現在では一般に普通のλの範圍では、換言せばt/rの値が普通である管をR/rが普通の値になる様に彎曲したものに對しては、KármánのKの値が最も實際に近いと認められて居る様である。
茲に発表するものは近年横須賀海軍工廠造機部で行はれた種々な彎曲鋼管に就ての實験の結果の一部であるが、此の實験の目的は誰の理論が最も實際に近いかを確あると云ふことよりも、與へられた圖面で製造した實物のKの値がKármánのKの値を標準とした場合如何なる程度に狂ふかを見當つけるに在つたのである。
茲に發表しない實験の結果、殊に彎曲波型鋼管の撓性に就ては、若し機會を與へらるゝならば更に發表する豫定である。

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The coefficient of mechanical viscosity in a turbulent motion of fluid is put proportional to the product of the distance from the boundary and the mean velocity of the fluid over it. The velocity distribution in the turbulent boundary layer and the coefficient of the frictional drag of a smooth flat plate have been obtained.

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The paper shows that the profile resistance of the propeller blade elements has a large influence on the determination of the maximum efficiency propeller and two simplest cases of constant angle of incidence and constant pitch propeller are investigated.

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The object of this investigation was to study mathematically the effect of the deck band on the natural frequency of turbine blades in a group which are mounted on the rim of a turbine wheel rotating with a constant speed.
For the purpose of obtaining the result the method of combination of two kinds of frequencies, one of which is that for an elastic body without rotation and the other is that for the same body when the effect of the flexural rigidity is neglected, was employed. The section of each blade was assumed to be uniform throughout its length in order to avoid the complexity of the problem. The series of blades in a group was considered as endless. The deflection vibrations of blades in one group are mainly in the direction of the least moment of inertia of the blade section.
When the density, Young's modulus and the effective breadth of the deck band are respectively equal to those of the blades, the values of (ρ1P'²/E₁K₁²) ^4/1l₁, where the effect of the rotation is neglected, are shown in the table below.
a₁/a₂ 1/10 1/2 1 2 4 6 9
l₁/l₂=10 5 1.72 - 2.13 1.98 2.226 2.10 2.22 2.19 2.09 1.97 1.97 1.90 1.90 -
In this a₁, and a₂, are effective areas of blade and deck band, l₁, and l₂ their respective efective lengths, and ρ₁, E₁, K₁ are the density, Young's modulus, the effective radius of gyration of the section of a blade, while p'/2π is the natural frequency under the assumed condition of the problem.
When the conditions concerning densities, Young's moduli and breadths are similar to those of the preceding case and the effect of the flexural rigidity is neglected, the values of l₁/R corresponding to different p''²/ω² and l₂a₂/l₁a₁ are shown in the following table.
p''²/ω² 3 6 10 15 21
l₂a₂/l₁a₁=0 1/40 1/20 1/10 1/5 1.736.719.698.678.617.410.291.285.280.263.250.151.1615.160.153.149.136.082.104.102.009.097.090.052.073.071.069.968.061.038
In this table ω is the angular velocity of the wheel in radian and p''/2π is the natural frequency of blade under the assumed condition.
The effectiveness of the deck band on the, stiffness of turbine blades, excepting the prevention of the mutual impact of blades, was discussed from theoretical point of view and the method of application of the present result to practical problems was shown by the introduction of the formula indicating the actual natural frequency of the blade, namely
p/2π=1/2π√p'²+p''².

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The problem of the bending of a rectangular plate 2a×2b×2h clamped at its four edges (or clamped at the two opposite edges and supported at the other) and loaded with a uniformly distributed pressure is solved from the differential equation, assuming the deflection to be
w=∞Σm=1∞Σn=1Amncosmπx/2acosnπy/2b+ (1-x²/a²) ∞Σn=1Bncosnπy/2b+ (1-y²/b²) ∞Σm=1C_mcosmπx/2a,
where m and n are positive odd integers. The bending moments at several points and the deflection at the centre are calculated for rectangular plates with various ratios of b/a by the second approximation, taking the first double series and the first two terms of each of the single series, in which a high degree of perfection in clamping, especially on the middle half length, is attained.
The solution for the transverse vibration of the same plate is also obtained to satisfy the differential equation, using a similar form for the normal function as in the case of bending.Frequencies for different values ofb/aare calculated and compared with those obtained by other methods.

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The author introduced a convenient arrangement of recording apparatus by combining those of the speed, the engine revolution, etc. with his modified track table, the detailed description of which was reported in the previous paper. [Jour. Jap. Soc. Nav. Arch, XLVII (1931), 185-194] In this arrangement, the speed, the engine revolution, the turning angle of the steering wheel, the helm angle, and the change of the ship's course are simultaneously transmitted to their respective recording pens by means of the electric transmitters from the S. A. L. log, the main shaft, the steering wheel, the rudder head, and the gyro-compass except in the case of the heeling angle, where the lever from the pendulum of the clinometer is used. Thus the systematic recording of the various elements in the turning trial can be obtained.
The results of the experiments carried out on board two warships in their turning trials and a motor-launch in the large test basin at the Naval Technical Research Laboratory, Tokyo, are fully explained. The latter showed that the turning circles described by the author's apparatus agreed very well with those obtained by the “camera” method. The author is of the opinion that the recording system deviced by him may be useful for standardizing the results of the turning trial.

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Double acting Diesel engines have rapidly increased in number and output in late years in this country, owing to the idea of applying Diesel engines as only means of economical power production of large units for marine propulsion. Few reports of theoretical or experimental analysis about the piston rod of the double acting Diesel engine have been published, which would be of great value for designers and engineers. The author reports the analysis of the causes of the damage on the piston rod of the main engine of the motor ship “Kohwa Maru”, the first double acting two cycle Diesel engine adopted for ship propulsion in this country.

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The marine casualties in Japan are said to have the largest percentage in the world. And the loss of many human lives is reported to be caused chiefly by the lack of proper arrangement of boat lowering gears on board ships.
I hereby desire very practical and efficient boat davits to be invented by ship-builders in this country, although there are many types of foreign made davits.
The following is strongly recommended to their consideration : -
(1) Davits shall be simply constructed so as to enable anybody to control them.
(2) Davits shall be fitted with gears of sufficient power to ensure the boats to be lowered under any circumstances.
(3) Boats shall be stowed on the uppermost deck if possible, as it is a natural tendency with any and every body to go up to higher places when the ship is sinking.
(4) Boats shall be safely lowered with a full complement of persons and equipment, and also controlled by persons in the boats.
(5) The cost of davits shall be reasonable.
The designer of davits must consider the conditions of ships in peril and the state of the sea, and understand the difficulties attendant upon the operation of lowering boats.

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