L3 Comminications SERIES 5000 Operation And Maintenance Manual - Appendix A: S

A-1

APPENDIX A: S

AMPLE

 T

OWING

C

HARACTERISTICS

ive

 towing characteristic graphs are included in this appendix as 

Figure A-1 through Figure A-5. Two of the graphs were generated 

without any additional weight being added to the towfish, and the other 

two graphs were made with our K-Wing II Depressor attached to the towfish. We 

believe you will find these graphs helpful in planning your surveys and equipment 

requirements.

As with any projections of this type, certain conditions and assumptions were 

made in order to generate a reasonable quantity of data with some degree of 

accuracy. Read all the conditions below before you attempt to use the data.

Data.  

Data were computer generated using programs of known prediction 

accuracy in both military and commercial towing systems. At best this type of 

data provides "ballpark" values versus absolute values. These curves have been 

checked with field data wherever possible. At best the values are within 15% 

accurate with the greatest accuracy at towfish depths between 91 m (300 ft) 

and 914 m (3000 ft) and at tow speeds of 3 to 7 knots. They are least accurate 

at slow speeds and short cable lengths.

Tow Cables.  

Tow cables having the characteristics below were used. Should 

you have a different cable, it could make a significant difference.

• 10.2 mm (0.40 in.) nominal diameter double armored, galvanized steel; 

weighing 353 kg per 1000 m (237 lb per 1000 ft) in air; 353 kN (11,000 lb) 

breaking strength.

• 17.3 mm (0.68 in.) nominal diameter double armored, galvanized steel; 

weighing 1030 kg per 1000 m (692 lb per 1000 ft) in air; 178 kN

(40,000 lb) breaking strength.

Cable drag increases with increasing cable diameter. The drag increases as the 

velocity squared (V

2

). As cable weight per unit length increases, the cable tows 

deeper.

NOTE  

Depressors have minimal effect at speeds of 2 knots or less. Boat 

motion plays a large role in shallow towing. For very deep towing, ocean 

currents can completely change the cable characteristics.

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