Appendix C: Towing Characteristics; C.1 4125 Standard Towfish Cable Layback Plots - Edgetech 4125 SIDE SCAN User Manual

A A P P E N D I X C :
This section includes graphical plots representing the towing characteristics of the 4125 Tow Vehicle for
various cable lengths, tow vehicle speeds, and tow vehicle depths. These plots are available for equipment
selection purposes only. In addition, when selecting a particular plot, it should be verified prior to being
used for detailed survey planning.

C.1 4125 Standard Towfish Cable Layback Plots

The plots contained within this document have been generated under the following conditions/
assumptions:
Sea State = 0 (no vessel heave motion)
Ocean current = 0
Solutions are for steady state Tow Vessel Speeds (2 to 8 knots, 1 kt increments)
Cables Examined: .40" Soft Tow Cable (207551)
Cable lengths 50m to 150m
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
Example: 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
Example: 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
T O W I N G C H A R A C T E R I S T I C S
C-1