ABSTRACT 



Five integrated faired towline configurations based 

 on a blunt nose fairing design were experimentally 

 evaluated in the David Taylor Naval Ship Research and 

 Development Center deep-water towing basin to determine 

 the general towing characteristics of each configuration. 

 Mathematical expressions of the normal drag and side force 

 coefficients are developed from the measured data. 



ADMINISTRATIVE INFORMATION 

 The work described in this report was sponsored by the Naval Air Systems 

 Command under Naval Coastal Systems Center WR21203 of 5 October 1981, David Taylor 

 Naval Ship Research and Development Center (DTNSRDC) Work Unit 1-1541-076. 



INTRODUCTION 



The David Taylor Naval Ship Research and Development Center (DTNSRDC) has 

 been tasked by the Naval Air Systems Command (NAVAIR) to develop towlines for 

 helicopter towed sonar systems with high speed and deep depth requirements 

 exceeding the practical capabilities that can be provided with bare, ribbon or 

 sectional faired towcables. To achieve the speed/depth requirements with a 

 towline length that can be handled in the space limitations of a mine- 

 countermeasures (MCM) configured helicopter, the towline should have a high 

 tensile strength load-carrying element, a small bending radius, and minimum drag. 

 Integrated towline concepts have demonstrated the necessary high-strength, low- 

 drag characteristics, but in many cases have demonstrated susceptibility to 

 hydrodynamic/mechanical instabilities and shape asymmetries which result in 

 excessive towline kiting. 



Integrated towlines developed previously were designed using established 

 symmetric airfoil shapes such as the NACA 0020 and NACA 63A022 profiles. A 



modified version of the NACA 0020 towline was evaluated at sea and demonstrated 



1 A 



acceptable towing characteristics . Figure 1 presents a cross-sectional view of 



the NACA 0020 towline, showing the typical features of the integrated towline 

 design which include a fiberglass strength member, an elastomeric afterbody 

 fairing, electrical conductors and a DacronCS^cloth skin. Although this design 

 provides a very high axial strength-to-size towline, it also produces a high 



References are listed on page 39. 



^-"^ Trade name of DuPont de Nemours, Inc. 



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