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Article type: Cover
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Published: March 20, 1959
Released on J-STAGE: February 24, 2018
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Article type: Cover
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Published: March 20, 1959
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Hidehiko AYA
Article type: Article
Pages
1-7
Published: March 20, 1959
Released on J-STAGE: February 24, 2018
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Recently classification societies developed the rules for mammoth tankers, but no definite theory is established for their structural arrangement. In order to find out the most effective structural arrangement an investigation has been made to analize the structural rules from the standpoint of saving the material. The conclusions are as follows : 1) The requirements of longitudinal strength are slightly different between the classification societies, and the Lloyd's rules are advantageous on weight saving as far as the mammoth tankers are concerned. 2) The depth of ship and the spacing of deck and bottom longitudinals are to be kept maximum as far as possible. 3) Two longitudinal bulkheads are to be arranged in cargo oil tanks unless otherwise required. 4) When the horizontal ring system is adopted, it is better to give each cargo oil tank an equal breadth. 5) To adopt long tank length is advantageous.
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Kazusuke MATSUNAGA, Kanichi SUIZU, Takeo YASUDA
Article type: Article
Pages
8-19
Published: March 20, 1959
Released on J-STAGE: February 24, 2018
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The straightness of flame cut edge is often quite unsatisfactory to a great extent, and this is causing many troubles in the works done after cutting, especially in the submerged-arc welding. In this report the authors have clarified the factors affecting the straightness and the efficiency of the water cooling method which we have tried to obtain perfectly straight edge. The essential particulars of the results are as follows : (1) Besides the accuracy of the machine itself, there exist three major factors affecting the straightness. The first is the plate motion in lateral direction, the second is distortion during cutting and the third is shrinkage distortion after cutting. The former two cause deviation of the line to be cut from the path of the cutting tip. (2) Of course these distortions are caused by the cutting heat, and experimental formulas, which can predict the heat absorbed by plate and the consequential distortions, have been obtained. (3) The water cooling reduces these distortions, and under the optimum cooling condition the straightness is improved very noticeably. This condition can be learned by a calculation. (4) The beneficial water cooling like this, on the other hand, lowers the notch toughness of the steel in as-cut condition. This seems to be due to the more intense quench-hardening of the cut edge by accelerated cooling. However, this behavior is of little significance as the cut edge will be welded subsequently.
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Mitsuo NAKANO, Iwao FUTAMI, Ikuo UEMURA
Article type: Article
Pages
20-28
Published: March 20, 1959
Released on J-STAGE: February 24, 2018
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The repairing work consuming about 300 tons of steel of Liberty type ship, the "D0NG HAE", which ran aground off Imaharu, Shikoku, on account of a dense fog, was done in the space of time from the 20th of May to the 3rd of August, 1957, in Kawasaki Dockyard. In order to shorten the docking period and to save the repairing cost, the damaged double bottom construction, which was the major damaged part of the ship, was renewed in the following manner. At first, as far as the strength of the hull permited, the damaged part of the inner bottom was removed while the ship was afloat for the purpose of shortening the docking time. At the same time, renewed double bottom parts, including bottom shell, were assembled on assembling platform in the form of four double bottom blocks which weighed about 16.8, 38.6, 31.7 and 72.5 tons respectively. After assembling, these blocks were arranged beforehand in the position which would be directly under the damaged part of the ship when it was docked in. The damaged part being removed, these four blockes were lifted up one after another by a 200 ton floating crane, and fitted on to their proper positions. As a result of this method, the time the ship spent in the dock including the days of docking in and of undocking was actually 23 days, and man-hours were also saved by 52%.
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Yoshiro KASAMA, Rinichi WASHIMI
Article type: Article
Pages
29-31
Published: March 20, 1959
Released on J-STAGE: February 24, 2018
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At the Marine Engineering Committee of the Kansai Society of Naval Architects the designing method of a marine propeller and shafting is now under consideration, and on the key fixing the propeller upon the propeller shaft its standard dimension sand the method of calculating its strength have been determined. We are going t oreport the decision on behalf of the committee. The formulas calculating its stresses are as follows. [numerical formula], [numerical formula] where T = torque of the engine at M.C.R. (kg-m) D_m = mean diameter of the propeller shaft in the cone port (m) D_c = D_m - (H_c)/(100) (m) L_a = effective length of the key (cm) B = width of the key (cm) H_c = effective depth of the key way (cm) τ = shearing stress of the key (kg/cm^2) σ = compressive stress of the key (kg/cm^2) The allowable values are τ = 400 kg/cm^2 and σ = 1500 kg/cm^2.
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Yoshiro KASAMA, Rinichi WASHIMI
Article type: Article
Pages
32-36
Published: March 20, 1959
Released on J-STAGE: February 24, 2018
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Since the tug boat works under various towing and free running conditions, its propeller is to be so designed that in every condition it may develop enough towing force and at the same time enough free running speed. On the other hand the main engine can work neither over a certain maximum torque nor over a maximum revolution. The common rigid pitch propeller cannot make use of the full power of the main engine, restrained either by torque or by revolution except at the designed full power speed. In the case that the type and dimensions of the ship and the power of propulsive engine are known and either the diameter or revolution of propeller is given, we have found that the power is most effectively utilized if we design the propeller so that it can absorb the full power of the engine at the three quarters of the ship speed expected at free running condition. According to this idea propeller for the tug boat by the commonly used systematic screw series diagrams, i.e., √<B_p> - δ design diagram.
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Yoshinao HOSOMURA
Article type: Article
Pages
37-44
Published: March 20, 1959
Released on J-STAGE: February 24, 2018
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In the paper read before the autumn meeting in 1955 of the Kansai Society of Naval Architects under the title, Experimental Research on the Corrosion of Propeller Blade and Sleeeve, the author referred to that zinc plates would suppress the corrosion of copper alloys. In the present paper, the author mentions the results of experiments, by which he intended to verify the above statement. In the sea water, by making electrical circuit between manganese bronze and zinc plates, the former becomes anode and the latter cathode. By the chemical action, zinc ions are carried to the anodic manganese bronze and its surface is covered by a film of gilded zinc. In this case, dezincification of manganese bronze is suppressed and corrosion does not occur. Generally zinc plates are fitted for the purpose of protection against the corrosion of hull plate. Zinc plates are fixed on the hull plate by studs or other means, and propeller shaft, intermediate shafts and main shaft are supported by bearings through oil film. So that shafting and hull is electrically insulated. The author supposes that, if the ship hull and shafting are electrically connected, by electrolytic action between manganese bronze propeller and zinc plates, the propeller blades are covered by zinc film and dezincification of the propeller will be suppressed.
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[in Japanese]
Article type: Article
Pages
45-52
Published: March 20, 1959
Released on J-STAGE: February 24, 2018
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Article type: Appendix
Pages
53-54
Published: March 20, 1959
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Article type: Appendix
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App1-
Published: March 20, 1959
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Article type: Appendix
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Published: March 20, 1959
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Article type: Appendix
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Published: March 20, 1959
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Article type: Appendix
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Published: March 20, 1959
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Article type: Appendix
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Published: March 20, 1959
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Article type: Appendix
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Published: March 20, 1959
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Article type: Appendix
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Published: March 20, 1959
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Article type: Cover
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Published: March 20, 1959
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