Isaacs—Faughn—Schick—Sargent: Deep-Sea Moorings 281 
may be estimated from towing and wind-drag curves for the hull, and approxi- 
mately equals the way that the hull would make before the same wind. The orient- 
ing effect of this initial velocity at the approach of a comber is a very important 
factor and demands some wind drag in the design. 
As the next comber will start to break at the point where the preceding one 
terminated, it is necessary that the surface float return part way toward its orig- 
inal position before the next comber breaks. Otherwise it will be carried farther 
from its original position, putting additional stress on the system and risking 
dangerous disorientation. The criterion of safe performance is that the stressed 
system shall move the surface float approximately 14 of the distance it was dis- 
RADAR REFLECTOR 
SKIFF 
DANGER ORANGE 
500 FT. PENNANT WITH SMALL WHITE NUMERAL 
ORANGE FLOATS NEAR SKIFF 
Fig. 4. Deep-moored instrument skiff. 
placed by the first comber in the interval between the moment that the first comber 
breaks and the moment that the succeeding comber breaks. For safety, then, the 
surface float must move about 4% of a wave length in % of the wave period, or at 
an average velocity of %45 of the phase velocity. The elasticity of the pennant 
provides the larger part of the available restoring force. Thus a 10 per cent 
elongation of a half-inch nylon rope in new condition will provide a restoring 
force of 700 pounds, or 10 per cent of the ultimate strength. A 20 per cent elonga- 
tion would result in a restoring force of 2,000 pounds, which is undesirably large 
in most circumstances, and should be avoided by proper design. The maximum 
force available is the sum of the maximum wind drag and the additional force 
exerted on the pennant by a displacement of the surface float over a distance equal 
to about 25 per cent of the wave length. In making the calculation, it is best to 
assume that the maximum current drag exists at all times. Details of the caleula- 
tion of the restoring forces are given in the Appendix. 
