Applying the elliptic-hypotrochoidal co-ordinates recently introduced by Prof. Y. Watanabe, the author investigated the stress distribution in a plate, or in a deep beam h wing an elliptic-hypotrochoidal hole (representing such as hatchway, deck-opening, cargo-port etc.), small enough in comparison with the size of the plate or the beam, under (1) uniform tension, (2) simple shear and (3) simple bending, respectively.
Although the decisive conclusion should be retained owing to the lack of experimental verifications, the author states the augumentation of the stresses in the following degree in the presence of the hole in a plate or a beam.
For a plate or a beam having a rectangular hole with moderately rounded corners, and with the ratio of the breadth to the length of the hole being 20.4.
a) When it is subjected to a uniform tension T parallel to one side of the hole, the max. pull stress occurs i a the neighbourhood of corners and amounts to 3.53 times the mean pull stress at the vicinity clear of the hole. The values of pull stresses at the mid-point of the sides parallel to the pull direction, are about 2.31.2T. Whatever the form of corner-rounding may be, the more the hole lengthens in the pull direction, the more the stress will diminish.
b) When it is subjected to a shearing stress S, parallel to one side of the hole, the max. tension or the max. compression occurs at the vicinity of corners of the plate, as in the case (a), and is of the value of 8 S thereabout. The more the hole tends to a square shape rather than a rectangular one, the more the max. stress will diminish.
c) When a deep beam having such a hole in the web, as its edges being parallel to the axis of beam, is subjected to a uniform bending, the stress at the mid-point of the edge of the hole amounts to 11.5 ββ₀, where ββ₀ is the bending stress at the same point of the intact beam, and as the hole lengthens in the direction of the neutral axis of beam, the stress will diminish.
When the edge of a hole is inclined and its centre lies out of the neutral axis of a beam, the calculation may be somewhat complicated, but it can be carried out in a similar manner. It is also observed that the general expressions (7), after slight modifications, may be applied to the cylindrical or anticastic bending of a plate having especially a circular hole or an elliptic one.

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Assuming the fluid perfect, the general expressions ((6) and (9) in the text) are obtained for the forces and moments, which act on the body immersed in the fluid, when the motion is not steady. Applying these formulae in two dimensional cases, the forces on one circular cylinder are approximately calculated by the image method, when there exist two circular cylinders, which may be moving with any velocity in any direction respectively.
The forces consist in two parts, the one (P ₍₁₎ ) due to the instantaneous stream line condition, the other (P ₍₂₎ ) due to the unsteady condition of flow, that is, to the rate o change of velocity potential on the surface of the cylinder.
The forces on one cylinder (I) are as follows, x-axis being taken so as to coincide with the direction of velocity of circle (I), and the origin fixed at the centre of that circle. (See Fig. A, page 7)
P_x(1)=4πρa₁U₁² φ² {-ψσ³cos (3γ₀-η) + (1+ψ²φ²) σ⁵cosη₀}
P_y(1)=4πρa₁U₁²φ²{-ψσ³sin (3γ₀-η) + (1+ψ²φ²) σ⁵sinγ₀}
P_x(2)=2πρa₁U₁² φ² {-2ψ [ψcos (3γ₀-2η) -cos (3γ₀-η)] +3σ⁵ [ψcos (γ₀-η) -cosγ₀]}
P_y(2)=2πρa₁U₁² φ² -2ψ.σ³ [ψsin (3γ₀-2η) -sin (3γ₀-η)].
Where ψ=U₂/U₁, φ=a₂/a₁, ρ : density of fluid, σ=a₁/d. These expressions are valid only for moderate φ, and for the case of large a₂ compared with a₁, the other formulae are obtained.
From these results, several simple cases are considered and the forces are evaluated.
The further development from this study is to cover the calculation of the interacting forces and moments between two stream line bodies.

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For the precise comparison between ship and model performances, it is necessary at an experimental tank to have a torsionmeter by which shaft horse power can be accurately measured on board. Such a torsionmeter, torque being not uniform in one shaft revolution, should be one which can record continuously its variation. The author devised an optical torsionmeter which not only satisfies this requirement, but also has many merits, in actual torque measurements. The present report describes the construction of his torsionmeter and compares shaft horse powers measured by this instrument at the sea trial of the “Shinshu Maru” with those predicted from model tests at the Teishinsho Experimental Tank.

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In the practical strength calculations of stiffeners, beams, frames, etc. fitted to plates, we usually take into consideration some so-called “effective breadths, ” in order to make up the unsuitable assumptions in the ordinary beam theory and to meet the actual behaviors of the plates. So far, the full nature of the effective breadths, however, has not been brought into light, and necessarily some empirical and hypothetical rules have hitherto been employed.
The author gives a theoretical method to determine the effective breadths, referring, as an example, to the plate of infinite breadth with a flat-bar stiffener carrying any given load, and also gives some notes connected thereto. In the method, every panel in the structure under consideration is to be treated separately, as domains of the systems of “stresses due to bending” and “stresses in plane, ” having special boundary conditions by which all the systems are united to form the whole stress system of the structure. The boundary conditions are derived in a reasonable manner and their validities are exemplified by some experiments.
The applications of the method to the cases of usual plates with parallel stiffeners are remained to be dealt with in detail in the subsequent section of the anther's papar.

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The method of calculation regarding the elements of a screw propeller was published by Dr. Helmbold and simplified by Dr. Lerbs according to Betz-Prandtl's vortex theory, and Dr. Shigemitsu also gave descriptions on similer lines. These methods require complex calculations notwithstanding the insufficient accuracy of results, and are considered not to be fully adaptable to the phenomena on marine propellers. This paper deals with the method of the first named author modified to suit application to the marine propellers in a more simplified process, and suplemented with some studies made by the writer.
In such cases as when the sizes of the propeller hub of the built-up type are considerably large as not to be neglected, the correction factors are shown in fig. 6 for the thrust coefficient and fig. 8 for the torque coefficient. Fig. 9 is drawn to determine easily λ and b₀ when C_sh and k_dh are given, and Cag. t found by use of figs. 12 and 13 and an equation, Cag. t=K.r.M. With regard to the effect of the centrifugal force, figs. 10 and 11 and a simple equation, b''=b (1+^A_B) will be applicable.
The wake variation within the region of the propeller disc can be reasonably treated with the centrifugal force by employing the equations, tan β_r''=v_r-v/γω+b'' and Ca·t=cosβ_r''/cosβ·Cag·t/Ka, where Ka is known by Numachi's curve. Finally, the pitch angle of each blade section is the algebraic sum of β_r'' and incidence angle.
The calculation curves and simple equations above-mentioned may be very convenient and useful for practical engineers to design marine propellers.

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In this paper, the author has tried to introduce an independent practical method for obtaining the “Floodable length” at any point of the length of a ship, as defined in the International Convention for the Safety of Life at Sea, 1929.
The process for finding the “Floodable length” by this method is as following : -
(1) A series of a floodable volume (v) of a ship's hold and the distance from the centre of the volume to the midship is found mathematically, and the floodable volume curve for the whole length of the ship is drawn.
(2) A curve, named the proportional volume curve, representing the volume of the end part of a compartment in the ship corresponding to the floodable volume, where the compartment is bisected by a transverse plane passing-through its centre, is drawn.
(3) Integral curves of the transverse sectional areas of the ship is drawn, the areas being in tegrated from both ends towards amidships.
(4) Using these curves the “Floodable length” at various points of the length of the ship are graphically found, and accordingly the floodable length curve is obtained.
This is an approximate method and the procedure is much simpler than that of the Board of Trade Method, the precision, however, may be said to be not inferior to that of the latter, in general.

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The report described below is a sequel to the paper “Design of the No. 1 Motor Lifeboat of the Imperial Japanese Lifeboat Institution” read before the Second Engineering Conference held in Tokyo in April, 1931.
The above named boat was christened “No. 1 Ryoha” and standardization, full power, 8/10, 6/10, 4/10 full power, backing, stopping and steering trials and also various test of life saving appliances were conducted between Mar. 4th, and May 22nd, 1933. In addition to this, descriptions of her followers, the second motor lifeboat (“Ijin-maru, ” 40' for Yamagata-ken) and third motor lifeboat (“Namikiri, ” 15m for Osaka-fu) were given.
The former was delivered soon after the completion of “No. 1 Ryoha, ” but the delivery and commissioning of the latter took place quite recently, the record of which is appended in this paper, though it was not published in the present meeting.

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The “Shinshu Maru” is the first ship equipped with Vulcan geared Diesel engines in Japan, and the propelling machinery consists, in brief, of two sets of Mitsubishi single acting, four-stroke-cycle, airless-injection, reversible Diesel engines of special design and two Vulcan hydraulic couplings with reduction gearing. These engines develop a total normal output of 2, 700 B. H. P. at 420 r. p. m., and this speed is reduced to 90 r. p. m. at the propeller shaft.
The trials were carried out at one fifth loaded condition, and the results were quite satisfactory as follows :
a) The maximum speed of 16302 knots was recorded with two engines at 100 r. p. m. on the propeller shaft, and 12.246 knots with one engine at 72 r. p. m.
b) The minimum speed of 3.69 knots was recorded with one engine at 25 r. p. m. on the propeller shaft.
c) Entirely uniform torque in the propeller shaft was recorded by the torsion recording apparatus.
d) Easy manoeuvering.
e) Reliability of running, etc.

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In this paper, the author ambitiously attempts to deal with various nickel alloys applied in shipbuilding and marine engineering in a very wide scope. In each section, the general properties of the metals referred to are explained and discussed metallurgically and physically with illustrations, and special references are given for practical application.
Comparisons and remarks are made for various steel materials adopted for the hull construction including high elastic limit steels not containing nickel, and for ferrous and non-ferrous nickel alloys used in the marine engine and turbine construction with special references to turbine blades, propellers, condensers etc.
In conclusion, the importance of nickel in engineering and that of the research for substitute alloys are discussed and the speedy establishment of a sound policy on nickel in Japan is suggested.
The contents of the paper are as follows : -

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