to 6 feet. The most severe waves expected were those generated by the underwater ce:onations themselves. The forces onthe moor from these waves were calculated, using the wave ne:ghis and velocities estimated in Reference 21. The required depth for the subsurface float was determined by calculating the orbital motion of normal surface waves at depth using the formulas (Reference 72): Hg = Ho e- (27d/L) and L = = & a7 yi where Hg is the diameter of the orbit at depth d; H, is the height of the surface wave from trough to crest; L is the length of the wave from crest to crest; g is the acceleration o. gravity; and T is the period of the wave. Thus, for periods of 2 and 9 seconds, the depth at which the orbital motion is 1 percent of surface is approximately 60 and 300 feet, respectively. A ‘depth of 150 feet for the subsurface float was selected as the best compromise between expected extremes. Although the hydrostatic pressure at this depth is relatively insignificant, calculated overpressure due to the detonation required that close-in subsurface floats be capable of withStanding pressures of about 2,000 psi. The maximum capability of the floats finally used tn these locations was calculated to be 1,450 psi, using a modified Timoshenko formula. This strength proved sufficient. To maintain a deep moor on either a sloping or a flat bottom, the weight of the anchor used by SIO (Reference 35) was doubled. The maximum horizontal force Fy that can be sustained by the deep moor may be expressed as a function of the anchor weight in air W, as follows: Fy = (bW-T) cos 6 (f cos 9~ sin @) . where b is the buoyancy factor characteristic of the anchor material; T is the vertical component of tension in the mooring cable; 6 is the angle of the bottom; and f is the coefficient of , friction. Assuming an angle of friction of 45°, this maximum force was calculated for iron and concrete weights on a number of bottom slopes (Figure 2.12). At the cable tensions and anchor weights used (tension approximately 500 pounds, anchor weight approximately 1,500 pounds in air), the difference in density between iron and concrete permits a smaller weight of iron to be used for a given bottom reaction. Furthermore, the compact shapes obtainable with iron weights permit greater lowering speeds. Both minimum and maximum values for wind and water drag forces were calculated for the coracle. The maximum case for water was calculated, using the profile drag coefficient fora flat disk whose diameter was equivalent to the coracle diameter at the waterline, and the profile drag coefficient for a flat plate was used in calculating the maximum case for air. These maximum and minimum drag forces onthe coracle, presented in Table 2.3, bracket those actually observed for the winds or currents encountered (Figure 2.13). Similarly, the expected drag forces on various possible mooring components were calculated for the assumed surface and subsurface currents and are also summarized in Table 2.3. The maximum and minimum excursions were then determined for a number of possible moors and are tabulated, together with the approximate subsurface float depressions, in Tables 2.4 and 2.5. A safety factor greater than that employed by STO (Reference $5) was incorporated in the specified mooring cable, since calculations showed that this increase was possible without materially altering drag forces or cable costs. Selection of the final moor represented a compromise between various opposing factors as demonstrated for a 1,200-fathom moor in Figure 2.14. The final system is schematically represented in Figure 2.15. In brief, the specifications for the major components are from the bottom up: a bottom detecting device (SIO drawing E-834), a No. 16 grapnel, a 1,500-pound 69 $2)