Isaacs—Faughn-Schick-Sargent: Deep-Sea Moorings 273 
mounted on the bow. The depth of water must be known, and some means of 
metering the wire is necessary to permit proper laying of the anchor without 
fouling. 
When anchoring in the open sea, scopes (“seope” is the ratio of the length of 
mooring line to depth) of 1.1 to 1.6 have been used, and, when anchoring in the 
strong currents of the Gulf Stream, scopes of 2.0 to 3.0 have been used. 
The “taut mooring” was first described by Bascom (1953). Figure 1 shows a 
more recent form of this mooring, designed by John D. Isaacs, Robert P. Huffer, 
and Lewis W. Kidd, which is adapted for use in any depth of water (1957). 
The original installations were designed to fulfill as nearly as possible a require- 
ment for a rigidly fixed reference point to which water motions (waves and cur- 
rents) could be related. The submerged float served as the required point, and 
provision was made for attachment of the necessary sensing elements. The surface 
float then provided an accessible platform upon which recording units and power 
supplies could be located and serviced. 
As shown in figure 1, a typical station consists of a submerged float (1), held 
with considerable tension some 150 feet below the surface by a low-drag mooring 
line (2) connected with a suitable anchor (3). From the submerged float a slack 
rope (4) leads to a skiff (5) which floats on the sea surface and holds the recording 
instruments. The key to the system is the use of the submerged float for buoyancy 
and the taut wire of high tensile strength (and low drag) for the main mooring 
line. 
THE ENVIRONMENT 
The principal phenomena in the open sea which determine the design of mooring 
systems are (1) currents, (2) waves, and (3) the rapidity of corrosion and decay. 
Although other factors often assume great importance at some times and places, 
these three must be contended with all the time and everywhere. 
1) Currents.—If there are no currents, a subsurface buoy connected with an 
anchor by a taut mooring line will hold the line in a vertical position. If horizontal 
currents exert drag on the buoy and the line, the line will be bent into a curve 
which, to a first approximation, may be considered an are of a circle. Because of 
this change in figure, the buoy will be pulled to a greater depth by an amount 
ealled its “dip.” It will also be displaced down current by an amount ealled its 
“exeursion.” In designing a taut-wire mooring system it is necessary to know or 
to assume the actual current profile in order to select component dimensions that 
will give acceptable values for the dip and the excursion. 
The current profile from top to bottom is not a straight line; the current dimin- 
ishes with increasing depth but not linearly. Strong horizontal currents are re- 
stricted to the upper layer of the ocean where, owing to vertical mixing by wind 
and waves, the temperature and other characteristics are uniform. In this layer 
currents of one or two knots are common, and in some areas, as in the Gulf Stream, 
currents of three or four knots oceur frequently. In much of the tropics the mixed 
layer is 200 to 400 feet deep throughout the year. In mid-latitudes it has an annual 
eycle, being very shallow in summer and reaching 300 to 600 feet in winter. There 
is a tendency for the layer to be deeper in the western portion of the oceans at 
