92 



HYDROGRAPHIC MANUAL 



sen bottles, and instruments of similar size- 

 and weight. Heavy duty winches now under 

 development will be capable of storing up- 

 wards of 40,000 feet of tapered cable (% to 

 34 inch) and exerting a line pull of 30,000 

 pounds at 130 feet per minute. Traction de- 

 vices separate from the storage drums are 

 required. The winch will be used for obtain- 

 ing large cores, deep dredging, or for an- 

 choring in great depths. 



The oceanographic winch is mounted on 

 deck so that the cable can be lead directly 

 outboard to an "A" frame or boom. When 

 deep casts are made a dynamometer or ball 

 breaker device should be used to indicate 

 when the bottom has been reached. 



3-112 Bathythermograph winch. — The 



BT winches now in service are powered by 

 3 HP single speed electric motors. This pow- 

 er is inadequate to utilize the full working 

 strength of the %.j-inch cable. The winch 

 is being redesigned to incorporate electro- 

 hydraulic drive powered by a 5 HP motor 

 (Fig. 31). This will provide greater flexi- 

 bility in the use of this equipment and it 

 should be suitable as an all-purpose oceano- 

 graphic winch for small survey vessels. 



The winch is designed primarily for use 

 in lowering a BT both while underway and 



Figure 31. — Bathythermograph winch. 



when drifting or anchored on station. The 

 reel will hold approximately 3,000 feet of 

 % 2 -inch 7X7 stainless steel aircraft cord 

 which has a breaking strength of 1,500 

 pounds. The winch may be used for a variety 

 of purposes in appropriate depths ; such as : 

 Nansen bottle casts, bottom sampling with 

 small samplers, lowering cameras or plank- 

 ton nets, and as a sounding machine. 



3-113 Dredging winch. — Any available 

 winch may be modified to serve as a dredg- 

 ing winch in moderate depths of 200 to 400 

 fathoms. The winch should have a storage 

 capacity of 900 fathoms of Yn-inch cable or 

 500 fathoms of '/o-inch cable and a level 

 wind device to lay the turns evenly on the 

 drum. A power supply sufficient to exert a 

 pull of about 5,000 pounds is required. There 

 should be an indicator to show the amount 

 of cable paid out. 



Two methods have been used on C&GS 

 ships to provide a dredging winch which 

 meets the above requirements. The wire rope 

 drum on the anchor windlass may be adapted 

 for the purpose, or a boat hoisting winch 

 may be used. See Section 3-131 for a de- 

 scription of dredges. 



3-114 Bourdon type bathythermograph 



(BT).— The bathythermograph (Fig. 32) 

 consists essentially of a thermal element and 

 a pressure or depth element so constructed 

 that a staballoy coated or smoked glass slide 

 driven by the pressure element moves at 

 right angles to a stylus which in turn is 

 driven by the thermal element. A trace 

 showing temperature with relation to depth 

 is drawn on the slide as the BT is lowered 

 and raised. 



The BT may be lowered while underway or 

 when lying to on station. BT's are furnished 

 for three ranges: 200 feet, 450 feet, and 

 900 feet. A BT should never be lowered 

 deeper than its designed range. BT slides 

 shall be marked and lacquered in accordance 

 with instructions contained in the manual 

 furnished with each BT. 



A special grid is supplied for each instru- 

 ment for converting the stylus trace to tem- 

 perature and depth readings. These grids 



