Page 357 equipment and instruments 4466 



After the taut-wire apparatus has been prepared for use (see 4465), the ship is 

 maneuvered to a position near the extension of the range between the two stations 

 marking the distan(3e to be measured. The ship's heading should be approximately 

 that of the azimuth of the range, the distance from the nearer station depending on the 

 depth of water (see 4468). The ship is either slowed to mere steerageway or stopped 

 completely while the taut-wire anchor is released. 



Two men are required when the anchor is lowered. One man lowers the anchor 

 into the water ready to be dropped, while the other man attends the brake of the taut- 

 wire apparatus by which the anchor is held suspended. The signal to drop the anchor 

 is given by the bridge; it is usually one short blast of the whistle unless other sliips are 

 in the vicinity, when the loud-speaker system or a messenger should be used. At the 

 signal, the taut-wire attendant releases the tension on the brake, allowing the anchor 

 to descend slowly to the bottom, and notifies the bridge when the anchor strikes bottom. 



After the anchor is on the bottom the ship moves slowly ahead, gathering speed 

 very gradually to avoid dragging the anchor. A ship equipped with pilothouse speed 

 control is best adapted to measure distances with the taut-wire apparatus, for the rate 

 of increase in speed can be controlled on the bridge. If the speed is controlled by tele- 

 graph signals to the engine room, a routine must be established for increasing the speed 

 gradually and steadily at such times. The engineer on watch should be notified when- 

 ever a taut-wire measurement is to begin and how many minutes he should use in work- 

 ing up to standard speed. The engines should be started veiy slowly and thereafter 

 the officer-in-charge need only notify the engine room when he judges the speed is being 

 increased too fast or too slowly. The maximum speed on a taut-wire measurement 

 should not exceed 9 knots, for the revolution counter of the instrument is difficult to 

 read accurately at greater speed. As the speed is increased the taut-wire attendant 

 must increase the brake tension gradually until at standard speed a tension of 36 to 40 

 pounds is indicated on the dynamometer scale. If the sea is rough and the ship rolls 

 considerably, the tension should be adjusted near the lower limit in order to avoid ex- 

 cessive strain on the wire and the risk of draggmg the anchor. 



The ship is steered on the range toward the first buoy station, but when it is near, 

 the course is altered slightly so as to pass it on the down-current side at a distance of 

 15 or 20 meters. When the ship is within approximately 400 meters of the buoy, 

 the officer- in-charge on the bridge must notify the personnel at the taut-wire apparatus 

 to stand by on the alert to read the revolution counter. They may be notified through 

 the loud-speaker system or, if no other ships are in the vicinity, by very short blasts 

 of the whistle in conformity with the passing signals of the Rules of the Road; one short 

 blast if the station is to be passed to port and two short blasts if it is to be passed to 

 starboard. 



The two observers, assigned to read the revolution counter, stand by while the 

 approach to the station is watched by the taut-wire attendant, who should station 

 himself where he can give the "mark" to read the revolution counter when the station is 

 abeam. A deckhouse or any thwartship structure conveniently located may be used 

 for alinement to mark the station when it is abeam. All the stations in a consecutive 

 measurement should be marked from the same position. 



The accuracy of a taut-wire measurement depends on the maintenance of a straight 

 course throughout the distance to be measured. A taut-wire measurement is always 

 simplified if the traverse stations have been anchored approximately in a straight line, 

 for the ship may then be kept on course by the use of the forward range. Where a 



