2-39 Examine the Wire and Connection to 



the BT. — Be sure that the wire is hitched to 

 the winch reel in such a manner that it cannot 

 pull loose if all wire should pay off the drum. 

 As an additional precaution, do not pay out 

 the last layer of wire when lowering the BT. 

 The wire should be wound on the drum so that 

 it pays out and reels in at the top of the drum. 

 For survey work, it is recommended that bare 

 wire and not plastic-coated wire be used. If 

 900-foot-depth BTs are to be used at least 2,000 

 feet of 5^2-inch, 7x7 stainless steel wire should 

 be used. As the plastic-coated wire usually 

 comes in 1,200-foot lengths and cannot be 

 spliced, it is not long enough for use with 

 900-foot BTs. Run the free end of the wire 

 through the towing block at the end of the 

 boom. This block is of a special counter- 

 balanced design for BT use. 



The type of cable hitch used to connect the 

 BT to the wire differs slightly with different 

 models. The instruction book accompanying 

 each BT shows the method of attachment for 

 that model. If the connection is frayed, 

 rusted, kinked, or in any way doubtful, cut off 

 the faulty part of the wire and make a new 

 connection. Check the swivel carefully. On 

 those models that use a Fiege-type swivel 

 connector make sure the Fiege sleeve is screwed 

 into the socket as tightly as possible. More 

 BTs are lost by poor connections than from 

 any other cause. 



2-40 Check the Winch.— The hand lever 

 on the winch serves as both brake and clutch. 

 It has three positions: (1) When it is vertical, 

 the winch is in neutral and the drum can be 

 turned in either direction; (2) when it is pushed 

 outboard to the engaged, or hoist, position, the 

 motor turns the drum and spools on the wire; 

 (3) when the lever is pulled inboard, or toward 

 the operator, to the brake position, the drum 

 is locked and cannot be rotated. 



With the winch lever in neutral, turn on the 

 motor to make sure the power is available. 

 The shaft bearings should be kept well lubri- 

 cated according to the instructions provided 

 with each model winch. The drum should 

 turn freely. 



The winch installation should be such that 

 the wire comes across the top of the drum. 

 The hand lever should move away from the 

 operator to engage the motor and toward the 

 operator to set the brake. On some earlier 

 model winches, the hand-lever operation is 

 just the reverse; i. e., the brake is away and 

 the clutch is toward the operator. Check 

 these operating positions to make sure that the 



installation is correct and that the drum 

 revolves freely in neutral. 



2-41 Put the Slide in the BT.— Remove 

 the waterproof cover from the box of smoked- 

 glass slides and take out one slide at a time, 

 holding the slide by the edges to avoid removing 

 the smoke film. Do not remove the waterproof 

 cover from the box until actually ready to use 

 the slides. This will prevent the oil from drying 

 out. When the slides get too dry, the smoke 

 tends to wash off more readily. 



Insert the slide into the hole on the side of 

 the BT and push it into its bracket. The 

 edge of the slide with the bevelled corners goes 

 in first, the longer bevel toward the nose of the 

 BT, making certain that the smoked surface 

 of the slide is toward the stylus. Push the slide 

 all the way in against the stop pin. It is im- 

 portant that the slide is fully in, otherwise 

 the temperature will be recorded fictitiously 

 low. Occasionally check the grooves of the 

 slide holder to make sure they are clean, free 

 of glass chips, and that the spring holds the 

 slide firmly against the opposite groove. With 

 the slide fully in, the stylus will be brought 

 against the smoked surface when the sleeve is 

 moved back to cover the opening. To reduce 

 extraneous scratches on the slide, do not move 

 the sleeve back until the BT is ready to be 

 put over the side. 



2-42 Put the BT over the Side.— After 

 permission has been obtained from the officer 

 of the deck to make a lowering, and the depth 

 of the water has been determined, pick up the 

 BT, pull the sleeve down over the slide holder, 

 and set the winch lever in neutral. With one 

 hand hold the BT at the rail and with the other 

 take up the slack in the wire by rotating the 

 drum. When all slack is in, set the brake. 



Turn on the winch motor so that power is 

 instantly available for the rest of the operation. 

 Lower the BT into the water to such a depth 

 that it tows smoothly just below the surface. 

 Put on the brake and hold the BT there for 

 one minute to enable the thermal element to 

 come to the temperature of the surface water. 

 Set the winch counter at zero. 



2-43 Take the Bucket Temperature. —While 

 the BT is being towed at the surface, take the 

 bucket temperature of the surface water and 

 record it on oceanographic log sheet B as shown 

 in chapter 14. Special bucket thermometers 

 are supplied for U. S. Navy surveys by the 

 Hydrographic Office. These are more accurate 

 than the thermometers issued with the BT kits 

 and are to be used in place of the latter. These 

 thermometers are read to the nearest 0.1° F. 



H. O. 607 



19 



