1168 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER IfloT 



Similarly, for ascent laying of the wire on a bottom which rises less 

 steeply than the inclination of the wire (19b), we get 



sin a — sin 7 + « sin a sin 7 

 sin (a — 7) + X sin a sin 7 



1, 



which is very nearly 



— a7 



//7 



27 



(45) : 



(4G) 



Thus, in both the above cases, the error in the piano wire technicjue can 

 be closely obtained by assuming that the configuration of the wire is a 

 straight line during ascent and descent laying. This is not surprising 

 since, as we saw in Section 3.6, the deviation from the straight-hne con- 

 figuration during piano wire laying is normally small. 



Because of its smooth exterior, the normal or transverse drag coefficient 

 of the piano wire probably can be obtained from published curves for 

 flow past a smooth right circular cylinder as shown in Appendix B. For 

 typical 12 gauge (0.0290 inch diameter) piano wire, these curves yield 

 a value of Co of 1.45 and an //^ value of 25.0 degree-knots. However, these 

 values of Co and H must be considered tentative until confirmed expe- 

 rimentally. 



Ivnowing the wire's H value, we can compute the error of the ground 

 speed caused by descent and ascent laying of the piano wire by means 

 of (44) and (46). The result of this computation for H = 25.0 degree- 

 knots is showTi in Fig. 25. 



When the ascent angle of the bottom exceeds the incidence angle of 

 the wire, suspensions result and the error cannot be computed without 



6 8 10 2 



SHIP SPEED IN KNOTS 



Fig. 25 — Error during descent and ascent laying of 12-gauge piano wire. 



