grid spaced 2 by 2 in. was taped on the front glass wall of the tank (nearest 

 to cameras) for a reference in analysis of the videotapes. White paper was 

 taped to the back glass wall of the tank to enhance visibility of the recorded 

 waves. A stopwatch was placed in the viewing area of each camera to synchro- 

 nize review of the two videos. A photograph of the video equipment is shown 

 in Figure 22. 





BHPW ** 



^^^^^^^B **__J jdi^^^^^HI^: 



•m* wm 



^^^i^^ m 1 iS **^ Was ' <I^1H^I 



^r Mi 



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Figure 22. Video equipment used in study 



94. A 35— mm camera provided general documentation for each test. Two 

 still photographs were taken of the bar in the tank, and approximately ten 

 photographs were taken of waves transforming over the structure. 



95. Bars were constructed of 3/4 -in. marine plywood. A schematic of a 

 typical bar is shown in Figure 23. The seaward and shoreward faces of the 

 structure were connected with strap hinges, and the two ends were anchored at 

 the correct length with predrilled 1/4-in. steel bars. Observations during 

 preliminary tests showed that sections of longer bars flexed under the waves. 

 To minimize this condition, the longer structures were supported by legs 

 attached underneath to prevent flexing or "breathing" of the seaward and 

 shoreward faces due to wave action. Styrofoam was placed in the opening at 

 the crest and taped in position to maintain a flush surface. Styrofoam also 

 was used to seal the sides of the bar against the walls of the tank. Prior to 



61 



