C-15
C
4125 Telemetry Towfish Cable Layback Plots
The plots contained within this document have been generated under the following conditions/
assumptions:
x Sea State = 0 (no vessel heave motion)
x Ocean current = 0
x Solutions are for steady state Tow Vessel Speeds (2 to 8 knots, 1 kt increments)
x Cables Examined: .375” Soft Tow Kevlar (23080), .25” Double Armored (A304874), .32” Double
Armored (A320327), .45” Double Armored (A302799)
x Cable lengths 50m to 600m
Ocean currents will be a factor for virtually all cases in which the system is used. By following the simple
procedure below the existing plots can be used for predicting the tow fish depth when ocean currents are
present (assuming the ocean current is uniform with depth).
Tow Vessel moving into the current:
Tow Fish Relative Speed = Tow Vessel Speed + Ocean Current
Ex: Tow Vessel Speed - 5kts, Ocean Current 1 kt, ->Tow Fish Relative Speed = 6 kts; Use the 6 kts
data curve in the graphs listed within
Tow Vessel moving with the current:
Tow Fish Relative Speed = Tow Vessel Speed - Ocean Current
Ex: Tow Vessel Speed - 5kts, Ocean Current 1 kt, ->Tow Fish Relative Speed = 4 kts; Use the 4 kts
data curve in the graphs listed within
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