Journal of the Kansai Society of Naval Architects, Japan

On the previous report, the authors gave an outline of the wooden harbour launches which also served as tug. With regard to those small boats, few papers and reference data are available at present. Moreover, since the publication of the first report various kinds of light scantling boats and small harbour launches have been launched at Kobe Port. The authors present in this report the design and some particulars concerning the high speed boats out of those. To the technical progress on wooden ship building this record will make some contributions.

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The experiments made on a recently built mechanical trigger are reported in this paper. They were made at first on the condition only with the first lever of the trigger and then at the launching of two vessels. By these experiments stress distribution over the surface of the first lever, starting force, frictional coefficient of launching ways, etc, were measured. The results are as follows :- (1) Strength of the cover plate of the mechanical trigger being insufficient, displacement of the cover plate should be reduced by reinforcing it. (2) The variation of the starting force during the preparation stage of launching can be explained. (3) Frictional coefficients of launching ways for the M.S. Elsborg and the M.S. Rosborg are 0.0208 and 0.0191 respectively.

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1. The height of wave that rises ahead of a column, such as periscope of submarine, running across the water surface is nearly equal to the velocity head (V^2)/(2g) of the column, when the speed is comparatively low. However, when the speed becomes higher, the height of wave crest, followed by splash resulting from its crumbling, is less than the velocity head. The relation between the wave height H, or velocity head (V^2)/(2g) (V is the speed of column and g acceleration of gravity), and Froude's number 〓 is shown by the authors as follows : For 0 < 〓 < 3.4 [numerical formula] and for 3.4 < 〓 < about 9 [numerical formula], and the ratio of the wave height H to the diameter D is [numerical formula] 2. The number of Karman vortices generated behind the column in expressed, as is commonly known, by the following formula :(ND) / V �� 0.2 where N is the number of vortices generated in a unit time, D the diameter of the column, and V its speed. Our experiments carried out at Reynolds' numbers over 10^5 reveal, however, that (ND) / V is not always about 0.2.

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The selection of steam conditions for marine turbines is influenced to a great degree by the fuel economy. The curves in the paper show the reduction in steam and fuel consumption by the adoption of the high pressure and high temperature steam. Next, the main features of the modern Mitsubishi-Westinghouse turbines are described, especially oh their excellent reaction blading, with some efficiency curves. The "5600" type reaction blading has developed principally for the geared marine turbines destined to operate over a wide speed and load range with high efficiency.

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