306 Bulletin, Scripps Institution of Oceanography 
the really difficult problems occur. A surface pennant must be highly elastic if it 
is to be vertical, or, if nonelastic, it must be allowed to float for some distance on 
the surface, where it is liable to fouling by ships. Moorings with slack surface 
pennants are easy prey to theft or to retrieval by helpful itinerants, and the 
installation of transducers along a slack surface pennant is not satisfactory, be- 
cause their depth cannot be controlled. 
In an attempt to solve some of these problems, a somewhat different type of 
mooring is now under development, using a 34-inch taut nylon mooring line with- 
out a submerged float. In order to maintain the station-keeping ability of the 
taut-wire mooring, the new nylon mooring is designed to be under a tension of 
300 to 400 pounds at all times. To achieve the desired tension the mooring is 
installed so that the line is stretched about 15 per cent. This requires prior knowl- 
edge of the depth where the mooring is to be installed. 
In order to support a vertical mooring line with 300 to 400 pounds tension a 
new catamaran-type instrument float (fig. 12) was designed with the mooring 
line attached nearly amidships. The catamaran has other advantages over conven- 
tional boat-shaped floats. It permits the mooring line to be fastened below the 
deck in such a manner that theft or retrieval by unauthorized persons is difficult. 
It affords a large, flat, stable deck, which facilitates servicing or repair, and it is 
not very attractive to potential pirates. 
Use of a taut nylon mooring line assumes that the nylon will have sufficient 
elasticity to withstand the wave-induced excursions of the surface float. Our experi- 
ence indicates that the nylon retains its elasticity for periods of at least one year, 
and exhibits no measurable creep or shrinkage after installation. We have made 
two successful installations of this type of mooring in 300-fathom depths, and they 
are still performing satisfactorily. 
Basic CoMPUTATIONS FOR DRAG FORCES ON THE MOORING 
Depending on the stage of planning, we will require either (1) first approxima- 
tions for determining feasibility and as a basis for further consideration, or (2) 
precise information of the type required for the placing of orders for materials. 
For most purposes the simplified formulas given in the section on system design 
will, when used with discretion, provide the degree of accuracy required for 
estimating the forces on a mooring. These formulas, however, should be applied 
with some eaution, as the following discussion indicates. Additional background 
may be found in Rouse (1946). 
The foree exerted by a fluid flowing past a submerged object at a steady rate 
may be expressed as 
F=Cp(W/2g) AU? (19) 
where F is the fluid force, usually referred to as the total drag force (a combina- 
tion of skin drag and form drag) ; Cp is a dimensionless drag coefficient; W is the 
specific weight of the fluid (weight per unit volume); g is the acceleration of 
gravity; A is the projected area of the object that intercepts the flow; and U is 
the undisturbed speed of the fluid. Strictly speaking, this equation applies only 
when the object is small compared with the dimensions of the fluid, far from the 
boundaries, and only when the undisturbed velocity of the fluid is uniform as well 
