





















k^tf 



* 







6 





_ No. 

































167-175 Original form * 











































•x, 









^^ 



























o 































z 



o 









a 

























VJ 























































M ■ Total mooring line load in pounds 



H|" Incident wove height in feet 



L^ Incident wave length in feet 



Y' Specific weight of water in Ibs/cuft 



B* Width of Trap In feet 



d » Depth of woter In feet 



o 





















6 7 8 9 10 



Mooring Line Force Parameter, Md/yBH.l/ 



Figure 163. 



Mooring line force versus wave steepness for Wave Trap membrane- 

 type floating breakwater concept by U.S. Rubber Company (after 

 Ripken, 1960a). 



b. Wave Blanket . Ripken (1960a) investigated the effectiveness of the 

 Wave Blanket, a proprietary design of a wave absorber also developed by U.S. 

 Rubber Company. The design consists of a moored blanket of permeable material 

 designed to float just below the surface of the waves. The concept of the 

 design assumes that the orbit and translation velocity of the wave will force 

 a flow through the permeable structure of the blanket; the flow resistance of 

 the dense permeable structure should induce enough energy loss to dissipate 

 parts of the wave energy. 



The blanket units in Ripken's (1960a) tests were assembled from sheets of 

 three-dimensional fabric woven from stiff plastic fibers varying from 0.014 to 

 0.020 inch in diameter. The fabric used in the two-dimensional wave tests was 

 designated 4-ply "Trilok," about 1/2 inch thick; the total thickness of the 

 various units tested ranged from 8 to 24 inches. The nature of the fabric, 

 which is slightly buoyant in freshwater, is shown in Figure 164. The blanket 

 assembly consisted of two sheets of Trilok fabric. The upper sheet had a 

 corrugated or sine waveform, and the lower sheet lay flat. The two sheets 

 were lashed together with plastic cording to form the unit blankets, which 

 were then attached to form various test assemblies up to 50 feet wide. 



Ripken's (1960a) initial tests demonstrated that where waves had a length 

 greater than the blanket width, the blanket was subjected to substantial 

 alternate tension and compression across the width. In tests using multiple 

 layers of the basic blanket unit, the individual layers were securely lashed 

 at close intervals around the outside edges of the blanket units and at spaced 

 intervals in the interior. Mooring stiffeners were provided across the front 

 of the top and bottom layers of the stacked units. Tests were conducted with 

 the one-, two-, and three-layer blankets at a total thickness of 8, 16, and 24 

 inches, respectively. Figure 165 is a schematic diagram of the Wave Blanket 



223 



