The author examined the nature of the resistance of bilge keels by the towing experiments of thin plates and ship-models fitted with bilge keels, and the following general conclusions were obtained:
(1) The amount of resistance of bilge keels moving through water parallel to the stream lines is smaller than that of thin plates having the same nature of surface and area calculated by Professor Hiraga's formula. From this fact, it appears that the“corner effect”, so to call, is existing at the joining parts of the bilge keels to the plates.
(2) Taking the above-mentioned “corner effect”into account, the frictional resistance of bilge keels having sharp edges can be expressed by the following formula:-
(R^-_f)_t°=KS(1+<2L'x/S-4Ly/S)V^1.90(ν_t°/ν_15°)^•165……(1)
where (R^-_f)_t°……Frictional resistance of bilge keel at t° C in kg.,
K……Coefficient of frictional resistance depending upon the nature of surface,
=.04577 for polished metal surfaces,
=.04857 for painted surfaces,
S……The area of bilge keel in m².,
L……The length of bilge keel in m.,
L'……The length of bilge keel excluding the aft round-up portion of it,
x……Edge effect in m, taking from Prof. Hiraga's paper,
y……Corner effect in m, depending upon the breadth of bilge keel as shown in Fig. 6,
V……Towing speed in knots,
ν₁₅°……Kinematic viscosity in m²×sec^-1 at 15°C
ν_t°……Kinematic viscosity in m²×sec^-1 at t°C.
(3) The amount of the corner effect depends upon the breadth of bilge keel and it is independent of the sectional form, length and speed,
(4) For bilge keels fitted to ship-models, the frictional resistance calculated by the formula (1) amounts to about 97% of the measured increase of resistance due to bilge keels.

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The present knowledge on the rolling of a ship on waves is only qualitative, and the results of theoretical calculations can not be compared with experiments. In this paper, firstly the solution of the forced rolling on permanent waves with the resistance composed of the terms, proportional to the angular velocity and its square, is obtained, and by comparing the theoretical results with tank experiments, the validity of the assumptions usually adopted is investigated. If we assume the resistance to be the function of the absolute angular velocity and compare the theoretical values with the experimental ones, the resistance on waves increases a very little from that for free rolling, and the effective wave slope coefficient, which is theoretically deduced by the statical conditions, should be reduced by quite a large amount. If we take the resistance to be the function of the relative angular velocity, the increases of resistance on waves are rather irregular, the amount being generally larger than in the previous case, but the reduction of the effective wave slope coefficient is similar as in the previous case. Lastly, a new expression for the synchronous rolling is obtained, and compared with the experiment.

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(1) Showing the tensile properties, impact figures and thermal expansion at the high temperature, the characteristics of welding stainless steel are compared with the common steel.
(2) The change of the micro-structure, hardness and mechanical properties by reheating the stainless steel are described.
(3) Reactions between the metallurgical structure and hardness distribution on the vicinity of the welded parts are shown.
(4) Mechanical properties of the welded pieces are tabulated.

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Singular point is defined as a point at which the direction of principal stress is indeterminate, and divided into 3 kinds, viz. zero-point, pole and point of discontinuity. It is usually so difficult in the well known experiment of photo-elasticity to determine the stress-curves in the immediate neighbourhood of singular points, that the features of the stress-curves near the singular points have not been ascertained up to date. In this paper they are studied analytically with some experimental verifications, paying special regard to how the direction of principal stress changes, when we go around a singular point along any closed curve. As the result, we obtained an effective resort in the experiment of photo-elasticity to determine, to what sort of singular points a point in question belongs, by observing only the surroundings apart enough from the point, without necessarily closing about it.

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Other than the usual buckling by bending, the torsional instability and wall buckling may occur for the thin walled struts under axial compressive load. The wall buckling strength of thin plane-walled profiles and the torsional instability of thin plane-walled open profiles were treated summarily, abstracting from the theoretical and experimental studies of the anther.
For the given strut length and axial load, the graphical and calculation methods for the determination of the sectional dimensions of minimum weight were described for the pre-assumed profile form in taking account of these kinds of elastic instability. The figures of merit for the profile form and material were determined.

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By introducing the following stress function in polar co-ordinates for the section in problem
Ψ=1/h.(rⁿ-a²ⁿ/rⁿ)cosnθ-r²+a²,
we can work out the stresses:-
zr=-1/2rG(na/H)(R²ⁿ-1)/Rⁿ⁺¹•sinnθ and zθ=-1/2rG(a/H)[n•R²ⁿ+1/Rⁿ⁺¹cosnθ-2HR]
where n=integer or fraction number,
a=radius of a circle,
h=constant concerning the profiles,
R=r/a, and H=a^2-nh.
Between two stresses, it is necessary to consider the resultant stress in our case. Generally, the maximum stress occurs at the inner periphery on the line of polar axis.
For such a treatment, reference may be made to “Torsion of Rod with a Section of Regular and Curve-sided Palygon” on the Transactions of the Society of Mechanical Engineers, Japan, Feb. 1935.

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The contents of the present paper are as follows:
I Introduction.
II Electrical equipments for driving the model towing truck before the installation of the automatic voltage regulator.
III Several methods of obtaining constant voltage direct current source.
IV Course of adoption of the automatic voltage regulator.
V Automatic voltage regulator using grid-controlled ionization tube.
VI Running performance of the model towing truck after the installation of the automatic voltage regulator.
VII Preliminary experiments for adopting the second automatic regulator for constant speed operation of truck.
VIII Conclusion.

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