The fluid motion raised by a ship has been theoretically investigated by various researchers under the assumption that the deformation of the surface of water is negligibly small. But results obtained under this assumption do not wholly agree with experimental one, Then it seems to be indispensable to regard on the finite deformation of the free surface. Dr. Kreitner made some considerations on this problem for one dimensional cases. In the present paper the writer gives an expanded theory for the two dimensional problem uuder the assumption that the vertical acceleration can be neglected in comparison with that of gravity. The results obtained from this theory shows that there is a critical range of finite extension for the fluid motion even when the breadth of the water way is not restricted. This result could not be obtained from the linearised theory considering the surface deformation so small that it could be neglected.

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The theoretical investigation of wave-making resistance of ships have been almost completed in this twenty years with many elaborate papers of Havelock, Hogner, Wigley and Weinblum etc. In these papers, however, it was only discussed about the relation between ship forms and coefficient of wave-making resistance, and not noticed how the resisting pressure distributes on ship surfaces and how varies this distribution with ship forms.
The chief object of this paper is to analyse these relations, illustrating some interesting properties of wave-making resistance, and this suggests how the ship forms must be designed on the standpoint of wave-making resistance.
Lastly, this paper has the theoretical grounds for Yourkevitch form and somewhat wavy waterplane form, both may be the forms of least resistanse on the consideration of surface distribution of resisting-pressure.

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The author gives a purely theoretical method to calculate oproximately the change of hydrodynamical pressure at the sea-bottom generated by a vessel in motion, and makes numerical calculations for some cases of examples.

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The author proved that the method of navigation with minimum fuel consumption is to navigate with constant horse-power inspite of the sea condition, when a ship goes on a given route with a given time, and that the constant service horse-power is approximately equal to the one corresponding to the given mean-speed and the daily meaned “sea-margin” of the route. With this theorem, he proposes the resonable method to determinate and to criticize the economical horse-power (or designed horse-power) of liner.

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On Aomori-Hakodate sea line wind is very strong in winter and train ferries often suffer from unfavourable effect of wind on their manoeuvering. To investigate the wind effect on ferries contributing to putting out plans for the reconstruction or for the new design of them, wind-tunnel experiments were carried out on some typical types of them. Changing the direction of wind relative to ship-model in whole range, wind forces and moments acting on ship body above water line were measured. The results of experiments are somewhat different from what are believed generally.

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Recently the superstructures of train ferries are made gradually larger, consequently the manoeuvering becomes difficult or sometimes even impossible in Aomori-Hakodate line, where the strong winds blow in winter. The train ferries need regular arrival and deperture in order to perform their service, so they are required the high manoeuverability. To satisfy this requirement, we must make clear the effects of wind on the manoeuverability of train ferries and find the measures for reducing or preventing that harmful effects.
Many able researchers have studied on the directional stability and the turning motion of vessels, and it seems that some of them have attempted to obtain the relation between the directional stability and the turning motion but none has been successful in his attempt. Notwithstanding the fact that the nature of directional stability or turning motion has been made clear to some extent, we have not been able to consider the problem of manoeuverability for practical cases. For instance, it has been said that the manoeuvering of trawlers and drifters is difficult under strong winds, but this subject has not been analysed and has not been able to discuss in detail.
The author supposed that a vessel will take a stable course and advances on this course after a long time, and that she may be said to be manoeuvered when she is possible to turn to both sides. Then the author considered the steady motions of a vessel and investigated their stability; by this study the relation between the directional stability and the turning motion was made clear, and it became possible to discuss the effects of wind on the motion and manoeuverability of vessels. In this paper, applying these results, the author discussed this subject on the case of train ferries.
The results obtained from this study are as follows.
(1) The train ferries has the tendency to turn windward except in the case when the strong adverse wind blows diagonally. This tendency agrees with the actual experiences in Aonzori-Hakodate line.
(2) The manoeuvering is possible at high speed and becomes impossible at low speed as compared with wind velocity. Namely a train ferry will be in the following ranges according to the value of wind velocity/ship speed:
(i) When the wind blows diagonally from behind,
(a) the range where she is manoeuverable,
(b) the range where she turns windward.
(ii) When the adverse wind blows diagonally,
(a) the range where she is manoeuverable,
(b) the range where she turns windward,
(c) the range where she is manoeuverable,
(d) the range where she turn leeward.
(3) To widen the range where the manoeuvering is possible, the following are effective:
(a) To make smaller the force by the wind and the moment by the wind blown diagonally from behind.
(b) To make larger the moment by the adverse wind blown diagonally.
(c) To enlarge the effectiveness of the rudder.
(d) To make directionally stable, namely to trim by the stern and to attach dead wood to the stern.
The above results were obtained for train ferries. Some kinds of vessels may have the opposite tendency.
Still there are many unknown factors, so this subject must depend upon the further experimental studies.

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The writer has been studying in the manner of expression of the damping properties of the rolling motion of ships and the method of analysis which is simple and is to be employed in various calculations, having just achieved some of the results as follows. In the general case of the curve of extinction to be expressed by an arbitrary function of amplitude θ as having an entire approximation the expression of the damping properties of the rolling motion of ships is considered to be appropriate as explained in the following sequence.
(1) In order to express, of the first significance, the damping properties of the motion peculiar to hulls the number of swing for the rolling to decrease to one-half amplitude μ is employed in the amplitude θ=10°. Furtheremore to express the degree of increase in the damping of the rolling for the augmentation of amplitude, μ₂/μ₁, ratio of the number of swing for the rolling to decrease to one-half amplitude μ₂ and μ₁ in amplitude θ=20° and 10° is employed.
(2) The value of these μ₂ and μ₁ can be obtained directly from the experimental result of the rolling motion.
(3) The damping properties of the rolling motion among waves are expressed by maximum amplitude in synchronous rolling θ_max in the simplified imaginary standard condition on the utmost audacious assumption. In this case the damping forces among waves are taken for those in the still water and that which is learnt from Zimmermann's study is taken for the standard condition of waves.
(4) If the damping properties of the rolling motion of ships are expressed by the number of swing for the rolling to decrease to one-half amplitude μ in an arbitrary amplitude, μ is found from μ₁ and μ₂/μ₁ as shown below;
μ=1/a_e(1+Δ_eθ){1-1/2(1+Δ_eθ)}
where{a_e=2/3μ₁(1-1/μ₂/μ₁) Δ_e=0.15/2μ₂μ₁-1(1-μ₂-μ₁)
(5) The maximum amplitude in synchronous rolling among waves θ_max is found by graphic method from the following expression.
γΘ_w/θ=2/πa₂(1+Δ_eθ)
where{Θ_w; the slope of the surface trochoid γ; the coefficient of the effective wave slope a_eΔ_e; by using the above expression can be round μ₁ and μ₂/μ₁.

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The problems of the virtual mass of the vibrating body floating or submerged in the water are classified as following:
1. Effect due to the advance speed of the vibrating body.
2. Effect due to the form of the vibrating body.
3. Effect due to the frequency. (Free water effect)
4. Wall effect.
We studied the problem of the 4th category theoretically and experimentally. We solved it by the method of successive approximation and compared with the virtual mass obtained by the experiment of a uniform cylindrical body floating on the shallow water. We had a good coincidence between these two values.

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The datas of the damages and ruptures of the Liverty ships. which were built during the war, give us many hints to the welded ships which shall be built in future, In reading the Journals of the American Welding Society, which were presented by Mr. Harry W. Plerse to the Japanese Welding Society, we can know these datas and many reports to these problems.
I think that we must know the characteristics of the plastic deformation, to know the rupture sufficiently. In the past few years, we have published some reports about the plastic deformation and now in the stage to the study of rupture.
In this report, we discussed some phenomenon of rupture under the three foundamental stress-distribution, such as tension, compression and twisting and from these studies we could put first step to the study of rupture.

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Goal-Post Mast is usually equiped on board of large cargo ships. It is regarded as a rigid frame under space loading conditions. But the process of calculating the stresses produced by loading is very complicated by usual method of analysis such as strain energy method.
The simple procedure of stress analysis is developed in this paper by using of generalized slope deflection formulae for space rigid frame proposed by author taking account of bending moments, twisting moments, axial forces and shearing forces acting on the extremities of members. Taking the slopes and deflections of nodsl points as the statically indeterminate quantities, the fundamental equations of equilibrium are easily solved by successive substitutions.
This method shows simpler process to solve the problem than by the strain energy method. And author shows simple formulae of stresses. Numerical study are performed on the goal-post mast fitted to Japanese standard cargo ship of A-T type.

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