On the Anchoring in Strong Wind at Single Anchor of the Variable Pitch Propeller Ship

摘要

The training ship of the Nagasaki University Faculty of Fisheries, the "Nagasaki-maru" on her training voyage, happened to be overtaken by Typhoon No.17 (Rubby), at Hongkong on September 5, 1964, and, being under the gusts of the maximum momentary velocity of 40m/s for about 2 hours, recorded the maximum momentary wind velocity 54m/s and the minimum atmospheric pressure 966mb. Among the vessels at anchor there, 3 ships sank after grounding, 14 ships grounded and 120 junks sank. Owing to the operation by the angle regulation of the variable pitch propeller and the remote control of the main engine revolution, " the Nagasaki-maru" succeeded in keeping anchoring through the storm for about 8 hours without dragging the anchor. From these experiences and records, some studies were made on the anchoring in strong wind at a single ancdor of the variable propeller ship, and the results are reported here. (1) During the anchoring of 7 hours and 41 minutes, the regulations of the propeller pitch angle and the engine revolution were performed 726 times, that is, 1.6 times per minute; and in every five minutes, 14 times were maximum and 2 times were minimum. (2) During the time, the anchoring was kept with the ship speed at 4 to 6 knots under the wind blowing at the maximum momentary velocity of 30 to 40m/s and at 6 to 8 knots under the wind at the maximum momentary velocity of 40 to 50m/s. However, the ship speed must be regulated properly according to the gustiness. When the gust changed its direction suddenly at the velocity of about 50m/s, the helm was changed to head against the wind with the ship speed of about 11 knots. (3) The chief officer must be posted at the forecastle to report about the direction and the tension of the anchor chain. This is very important when the engine is operated in anchoring. And the ship is necessary to have an equipment furnished to connect the bridge with the forecastle. (4) The anchorage must be set up at a broad area of the sea without obstacles because the ship moves in a large scope using th engine, But it must not be positioned facing an open sea. It is needless to say that the type of the bottom is desirable to be good for holding the anchor. (5) The anchor chain should be slackened as long as possible. This serves not only to increase the holding power of the anchor but also to enlarge the action radius of the ship. (6) It is necessary to keep anchoring, knowing the position of the anchor by a buoy or a light buoy on the anchor. (7) When the variable pitch propeller ship tries to anchor using the engine, the engine can, of course. used easily. But it is left to a future study which is the more suitable, anchoring at a single anchor under the operation of the engine; or anchoring using another anchor as a preventive of yaw under the operation of the engine, for example, as the hammer lock moor, without letting the ship move so much