In order to make it possible to conduct model experiments in the course of aerodynamic studies of ship and their equipment, the writer arranged a small wind tunnel. It is a Gottingen type having rectangular section as shown in Fig.1. A wooden propeller driven by 2H.P. electric motor is employed to circulate the air current in the tunnel. Speed of the wind is altered by three kinds of pulleys and measured by an inclined-tube-manometer combined with a pitot tube. Maximum speed of the wind is 22m/sec and power coefficient is 4.085. Figs.3-5 indicate the distribution chart of speed at the central section of the measurement part. Then, the drags of spheres supported as shown in Fig.6 were measured to ascertain the turbulence in the air current.

抄録全体を表示

As a part of studies on the aerodynamic characteristics of rectangular sails, the writer performed wind tunnel experiments on the sail models indicated in Table 1. A sketch of the apparatus used in measurements of lift, drag and centre of pressure to various angles of attack is shown in Fig.1. Table 2 indicates the Reynolds Numbers and effective angles of attack α in each measurement. Their coefficient about each model expressed by equations (1), and the stalling angles and maximum lift coefficient with parameter camber are obtained as shown in Figs.2-7. Then, making use of these results obtained by the writer, coefficients of maximum thrust C_t and side force C_s at the same time expressed by equations (2) against θ_a, the directions of apparent wind from bow, are shown in Figs.8-9, and its angles of attack α_m are indicated in Fig.10. Some discussions of the findings are presented.

抄録全体を表示

A radio telemetering system for the ship's rolling motions has been designed and it was discussed in the previous paper. In the present paper, the method for analysis of the ship's rolling record which was obtained by means of the above mentioned system was discussed ; an analyser for the application of this method was designed and examined. Change in the value of transverse metacentric height (=GM) of the ship is the most useful information for judging of the safety of the ship's stability in the seaway. Generally, according to the relation between GM and the rolling period of the ship, if the transverse radius of gyration of the ship (=κ) or coefficient c (=κ/B) is given as a constant value, the value of GM and the change of GM (=ΔGM) are calculated by equation (1) and (2), respectively. As to Tables I and II in which the practical ship's data are shown for drifter and pelagic fishing boats respectively, by calculating of GM for each datum in accordance with equation (2), their mean values are found to be 0.209m for drifter and 0.0972m for pelagic fishing boats against 1 second change of the ship's rolling period. Concerning the results of the above calculations, though the mean values of GM are from 20% to 30% for the value of GM, it is necessary to know the value of GM within 10% for the value of GM at least, from the practical view point. According to the relation of GM and the value of the change of the ship's rolling period (=ΔT) which is shown in equation (2), it is required that the rolling period of the ship should be taken within the precision of one-fourth second. In the above mentioned meaning, in order to presume the rolling period of the ship from the record of the ship's rolling, the method making use of the spectrum is more practicable than the method by means of the apparent period. The author discussed the several methods for calculating the rolling period from the record of the ship's rolling, and designed an analyser which consists of a function generator and a frequency analyser. It was found that this analyser is sufficiently effective for the above mentioned purpose.

抄録全体を表示

"Wash cement" has been chiefly painted in fresh water tanks of ships for corrosion prevention etc. We know that it will be better to change water in tanks two or three times to make suitable drinking water when new wash-cement was painted. The number of times, however, are not decided by sure reasons for suitability of drinking water but human taste etc. So, it is necessary to make a study of abovementioned problems for seamen. Then, authors measured pH of fresh water in some model wash-cemented tanks as a method of the study, and reported the results with some discussions and proposals in this paper.

抄録全体を表示

The present paper gives the results of full-scale trials on one of ship bower anchor which were carried out on board the training ship "SHIOJI MARU". The tests were conducted on JIS-type anchor in general use in Japan to-day, and the tensions on chain were measured by means of wire strain guages while the ship's engine was being reversed. The types of sea bed in these trials were mud and sand. From the results of the tests, the authers have come to the following qualitative conclusions. (1) The holding power is found out to be superior in sand to in mud. (2) The rotational instability is not observable. (3) It is desired to drop anchor as slowly as possible in case the bottom is soft. (4) It is most desirable to use sufficient scope of chain, the amount of which is to be determined by taking the depth of water into consideration. (5) The ship can be best held when the anchor is brought up firmly. It is, however, rather difficult at times to determine when the anchor bites into the bottom. (6) When the ship begins to drag the anchor along the bottom, the pull on the chain falls to approximate constant value to be determined by the type of the bottom. (7) It is reasonable to define the so-called holding power of an anchor as the maximum pull on chain which will be reached just before the moment the anchor begins to drag.

抄録全体を表示

Authors consider principal questions of navigational and steering control instrumentation, and a plan of a ship control consol installed on the bridge of the auto-controlled ship. They report of a trial consol fitted to the bridge of the training ship "Shioji Maru", and compare it with those of foreign made.

抄録全体を表示

To decide the ship's position on the chart, the following method sometimes has been used ; select three objects whose positions are accurately given on the chart. With sextants, measure simultaneously the horizontal angles between the center object and the right and left objects, then set angles to the 3-arm protractor. Then place the protractor on the chart with its center at about the estimated position of the ship with the straight edge of the fixed arm passing through the plotted position of the center object. Move the protractor about until the straight edges of the right and left arms pass through the plotted positions of the right and left objects. The center of the protractor is now accurately at the position of the ship at the time the sextant angles were taken. But this method being pretty complicated, it is scarecely used except for the hydrographic survey. The instrument I have invented is operated as follows. Setting the instrument, with two sextants, to measure simultaneously the horizontal angles between the center object and the right and left objects, the index arm of one sextant is moved until the right obiect coincides with the center one below and the other moved until the left object coincides with the center one below. Next switch on an electricity without watching the graduation, and by synchro-motor, twice as large as these angles on two sextants are reproduced to this instrument, which has been made to record the position of the ship. Repeating this means the course will be recorded. The principle of this instrument and the direction for use are illustrated by Fig.1. Its construction is illustrated from Fig.2 to Fig.6.

抄録全体を表示

In the case of transfering the angle on the sextant to the other instrument such as three arm protractor, we used to read the graduation first then transfer it to the instrument. I devised to transfer the angle by using a sychro-motor, electric transfering apparatus, without reading the graduation. One of the aims of this apparatus is to connect it with "course-recording apparatus of the coasting", explained on this book. Fig.1 is the sextant connecting with a sending synchro-motor. Fig.2 is the wiring figure of a synchro-motor. Fig.3 is the connecting apparatus of the receiving svnchro-motor and gear.

抄録全体を表示

The accuracy of a Loran sky wave line of position depend chiefly upon the accuracy of matching and reading the signal on receiver-indicator, the accuracy of the sky wave correction and the geometrical factor of precision. We discussed the accuracy of matching sky wave by many observations and found that the influence on the accuracy of a position line is not so large compared with the other two effects. The distributions of the probable error of practical Loran sky wave position line about the several Loran pair at north pacific are calculated. The sky wave accuracy patterns are also shown. From these patterns, the navigator can see the accuracy of a Loran sky wave posision line at once.

抄録全体を表示

When sounding a lake or an artificial lake of electric power plant by an echo sounder installed on a boat, the error due to inaccuracy of positions, is large because of difficulty of determination of accurate positions, and moreover, great efforts are needed. On a frozen lake it is easy to determine positions with accuracy. Besides, echo sounding from the surface of ice is possible. Therefore, sounding from it is more speedy and accurate than that by a boat. The pond-smelt can be detected from the surface of ice, too. The se are new methods of sounding of lake and detection of fish school on the frozen lake, which have never been published. It is pointed out that easier sounding is possible by using the latest transistorized compact fish finder.

抄録全体を表示

Recently, the Japanese translation of sea terms is in the abnormal condition, and their meanings of each word are very various and difficult by the authorities or the writers. I, the present writer, tried to study about the source of this subject.

抄録全体を表示