This report is dealing about the results of open water tests at the Ship Research Institute for two series of model propellers, each having the expandeda area ratio of 0.35 and 0.50. The shapes and the principal dimensions of the propellers are shown in Fig. and the results are given in Fig. 2 Two kinds of design diagrams constructed from these results, one according to Admiral Taylor's method and another to Dr. Schmidt's method, are also given in Fig. 3-6.

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When a ship, which is rolling among waves around the steady heel due to wind, is attacked by a sudden gust, sometimes accompanied by the rudder action, if the work done by the gust and rudder action be greater than the reserve of her stability, she capsies. The condition, that the capsize may not occur, can be expressed by the following relations:
C'=S_d/C_wD_w(θ_r+2θ₀)+2D₀θ₀+1/2mθ₀²>1……(A)
where S_d: dynamical stability arm, i. e. the area of t e stability curve divided by the weight of the ship, D_w: heeling moment arm (the speed of the gust assumed to be 1.4 time of the mean wind speed), θ_r: range of the stability curve, C_w: reduction coefficient determined from the fact of the reduction of wind speed near the sea level, θ₀: rolling angle. D₀: heeling moment ar_??_n due to the rudder action, m: metacentric eight.
Being given the speed and the rolling period of a ship, the waves (length and height) and wind speed, which cause the severest conditions to her reel, are to be found from the curves given in the paper. C' in (A) should be at least greater than unity, but, considering the other conditions which are not taken into account in the deduction of (A), the permissible lowest value of C' must be taken much greater than unity. C' is called in this paper the safety criterion, and can be considered as like the factor of safety in the strength of materials, and its permissible lowest value should be determined from the experiences of actual ships. Values of C' are calculated with several small-typed vessels, and given in the Table.

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[in Japanese]

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It has elapsed many years since the water tube boilers were introduced into marine use, with full success in European countries and in America. In Japan, on the contrary, this type of boiIer has been used for some large cargo ships before the war and for a few kinds of War-time Standard Type of Ship under instruction of the former Japanese Navy during the war, but now no positive demands.
It is generally recognized that through the possibility of high pressure and high temperature steam using the water tube boiler, the higher thermal efficiency and weight reduction in total engine part are gotten. This fact makes us profitable to adopt the boiler in this country where fuel and steel are excess bly short. Nevertheless, there are hesitations in our ship world to adopt this type for marine boiler due to li anxiety of reliability and difficulty of handling.
The prob ems on reliability and difficulty in handling, are as follows;
(1) Danger of low water,
(2) Trouble through feed water,
(3) Easiness of coal burning.
In this paper, the above problems should be investigated to clarify the reality, and if possible new design on the water tube boiler and finally the remedy to solve these problems will be protested.

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It is theoretically clear that the improvement of the heat engine depends upon the following three factors: high combustion speed, high compression ratio and high air excess. As to the present engines these factors are inevitably restricted due to its own characteristics upon which the writer explains in details by the actual and a so numerical data.
Deducing from this explanation, remarkable improvement of the thermal efficiency will be attained by the separate compression system, which cycle will be generated as follows:
1. Necessary air for combustion is compressed in one chamber to hlgh pressure and high, temperature,
2. Fuel is injected into inert burned gas medium separately in another chamber, and compressed to high pr ssure and high temperature,
3. Then these air and gseous fuel mixture are communicated to each other, and instantly ignited of tself,
4. After combustion, the burned gas expands, and develops work done.
This system of the internal combustion engine will be formed in two types, the positive and the negative. In the former type two cylinders are used for air and fuel respectively, and gaseous fuel mixture is compressed positively to high compress on ratio, but in the latt r type only one cylinder is used to compress the air, and fuel is gasified and heated to high tempe ature in a small chamber near the cylinder top, in which the inert high pressure and high temperature b rned gas remains separately from the main cylinder shut out by control valve during the expansion stroke. By the above mentionedl systems air will be compressed to about 40 atmospneres and 600°C, and fuel will be gasified easily to 15 atmospheres and 1000°C. Such condition of air and fuel gas, when communicated to each other, possess excessive high potential combustibility, which was called in some extent “detonation” in gasoline engine. Three principal factors for improvement of thermal efficiency; high combustion speed, high compress on ratio, and high air excess, will be rea ised by this separate compression system, which has been patented recenetly. The writer is convinced that this system will contribute to improve the fuel problem both in- and out-land.

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Vast application of electric welding to ship works for weight and labour saving has required good h gh tensile steels, as HT and D steels being satisfied for ord nary practice, are unsuitable for very high temperature treatment of arc welding due to their high contents of carbon and manganese.
So 13 sorts of high tens le steel of various contents are studied to improve the demerit.
Invest gat ng the test result of these samples against mechanical properties, weldability, and strength of welded joint, Si-Mn steel (C 13%, Si 1.0% Mn 0.8%) proved to be the most su table one.
As to the test for weldability, it seems to be necessary to examine for hardening ratio of test pieces heat-treated similar to affected zone by welding heat to raw material, and moreover to investigate the condit on of ruptures of test pieces heated actually by the same manner as weld ng.

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During the last five years the authors have supervised 11 series of exposure tests, ranging from 6 to 25 months, of Japanese cedar samples tested in various ways to prevent attack by marine borers. Some of the new methods were applied to more than 20 ships sailing to the southern seas, but unfortunately most of them were lost or destroyed before ade uate tests could be completed.
Protective methods generally in use for saving wooden ships from borers are either chemical or mechanical. The chemical method kills the borers by painting or injecting preservatives or toxicants into the wood. The mechan cal method prevents borers from reaching the timber by sheathing it with sheet metal or specially treated fabric. Observation of exposure test on materials treated by these two methods have given the following results:
1) Painting the exposed surface with a chemical substance harmful or disagreeable to marine borers such as copper paint, is commonly practiced as the most effective and practical method in use at present. This method is not permanent because the protective substance either gradually leaches out, or the coating itself is destroyed by abrasion in a very short time. Subsequently frequent docking and renewal are necessary.
2) Sheathing the bottom with an outer board w th an intervening layer of tar paper has been considered resistant, but their experiments show it quite ineffective against both sh p-worms and boring crustaceans over a two year period.
3) Impregnating the wood with pre ervatives and toxicants is cons dered better than co ting, but the large amounts of impregnants neces ary, and the increase of weight to the ship are undesirable.
4) So far as the weight i concerned, sheathing the bottom of a ship with thin wood impregnated with creosote or copper hydroxide is better than injecting the hull itself. But the impregnated boards lengthen the life of the ship only until the in ected tox cants leach out of the thin wood, which is usually within a year.
No chemical method depending on tox city lasts over one or two years.
Next they tested various methods of applying soluble urine resin compounds, which may be so treated as to make a hard, unsoluble outside layer, giving mechanical as well as chemical protect on. Results were obtained as follows:
1) Test pieces pa nted with urine resine compounds were not attacked by the borers after one and one half years. and fter two years the test pieces were attacked slightly only at one corner where the coating abraded. The method is more effective than painting with copper.
2) The two year tests of an interven ng layer of urine resin compounds give complete protection against the borers. Veneer plates with two or three protective layers of urine resin compounds may be applicable for the outer protective boards of ship.
3) Samples sheathed with thin boards injected with urine resin compounds lasted two years against borers.
4) Another important result of this method is the waterproof quality imparted to the woodtself. The weight of samples after two years test in the sea showed only 10-20% increase remakably lower than that of the other methods which allow sometimes up to 120% increase in weight.

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