286 Bulletin, Scripps Institution of Oceanography 
square feet of form drag area, or about that of a large barge. Fortunately, water 
velocities at great depths are low, and hence the total horizontal drag force over 
most of the length of wire is small. 
ULTIMATE TENSILE STRENGTH OF WIRE PS. 
0 100,000 200,000 
2 We OCEAN DEPTH 
ALLOWABLE DEPTH 
OF MOORING 
DEPTH (FATHOMS x10 °) 
O 10 20 30 40 50 60 70 80 90 
CUMULATIVE FREQUENCY DISTRIBUTION OF OCEAN DEPTHS 
Fig. 7. Ultimate tensile-strength requirement. 
250,000 
As horizontal forces increase, wire with a greater ultimate strength must be 
used to limit excursion and dip of the system. Hence the strength/drag ratio of 
the wire is important. For wires of the same specific gravity and construction 
this may be expressed as follows: 
T = (1/k) s (2/4) t? 
where 
T =maximum allowable tension on the wire 
k =safety factor 
s =ultimate strength of wire in psi 
t =diameter of wire in inches 
D~t 
where 
D = drag force on the wire in pounds 
R =szt?/4D, the strength/drag ratio (T/D) 
Therefore 
R~ s(x/4) (t?/t) or 
R~ st 
(1) 
(2) 
(3) 
(4) 
The higher the strength/drag ratio, the more nearly vertical a mooring may be 
made for a given current profile. 
