(2) Mooring Force Evaluation . Based on Ripken's (1960a) experimental 

 studies, the magnitude of the mooring force may be determined from Figure 167 

 or from the equations in the figure. These data can probably be applied to 

 scaled versions of blankets proportioned similar to those of the test unit, 

 provided the three-dimensional end effects are considered. Blankets with a 

 short width relative to the wavelength involve mooring forces that continually 

 oscillate from zero to a maximum, which is somewhat irregular for successive 

 waves. Blankets with a long width relative to the wavelength involve mooring 

 forces that continually oscillate from some nonzero value to a maximum. The 

 pattern of force variation is quite uniform for successive waves. The mooring 

 forces in Figure 167 were derived from tests with a relatively inelastic moor- 

 ing system. Other mooring systems which involve greater elastic or damping 

 action may be expected to reduce these peak mooring force requirements. The 

 mooring force for a given blanket and wave condition did not change materially 

 for variations of 1:4 to 1:10 in the mooring line slope. 



07 

 .06 



Model 

 Size 



























F*»<£ 



/ 



t A 











rest Condition 



Water t/d 

 Depth.d 



4 5' 15% 

 45' 30% 



Symbol 



Mooring 

 Slope 



110 O 

 1:10 * 

















D 



/ 



a 







- 











r> 



u / 



o / 





/ 











Lorge 

 Lorge 















/ A 



D o Xx D /< 





y 

















& 

























_ Lorge 

 Large 



30' 22% 

 45' 15% 



1:10 A 

 1:4,1:6 O 







































n 











C 

















Small 



1.0' 16% 



hlO o 















a> o $/ 



x 





























i 



\ t 



D 

 ' C 

































i 



p 













y 





D / 



































M* Total mooring line load in pounds 





O 





A 











y 









Si/- 





H|« Incident wave height in feel 











n 



' 







x 









L w = Incident wavelength in feet 





O 



O 



CDA 



- 







jy 





y ' Specific weight of woler in Ibs/cuft 

 B • Width of blanket in feet 

 d ■ Depth of water in feet 









\ -€ 







4 



• 











t ■ Blanket thickness in feet 



1 i I i i i i 



3 4 



Mooring 



Line Force Parameter, Md/yBH-L^ 



Figure 167. Mooring line force versus wave steepness for Wave Blanket concept 

 of membrane-type floating breakwater by U.S. Rubber Company 

 (after Ripken, 1960a). 



c. Thin Surface Barriers . Frederiksen and Wetzel (1959), Schwartz and 

 Watts (1959), Watts (1960), Ripken (1960a, 1960b), and Ofuya and Reynolds 

 (1967) have experimentally studied several other types of thin membranes 

 (plastic sheets, polyethylene films, and rubber material). A comparison of 

 the materials was somewhat hampered by the lack of uniformity in data presen- 

 tation. To provide a common format, Jones (1974) reanalyzed the data of these 

 researchers and presented transmission coefficients, CL , as a function of 

 relative water depth, L/d, for the parameter of wave steepness, H/L. 

 Figures 168 to 171 provide Jones' reanalysis of four different materials. 



226 



