APPENDIX 

 MODIFICATION OF ELECTRIC WAVE STAFF ( HYDROGRAPHIC OFFICE MODEL MARK I) 



The Electric Wave Staff (Hydro graphic Office Model Mark I) has 

 been modified to improve its watertightness, eliminating the major 

 weakness of the instrument in the past. The modification consists of 

 imbedding the res5stors of the step-resistance gage in Scotch Casting 

 Resin within Micarta contact stems and connecting each set of the 

 resistors by plastic-covered wire. Thus the electrical circuit of 

 the step-resistance gage is coinpletely water proofed except for the 

 contact points. The aluminum tubing is flattened around the holes 

 where the contact stems enter to provide a good seat. The contact 

 stems are inserted and attached by means of Micarta hex nuts and 

 washers. The tubing itself is coated with paint and Scotch electric 

 tape to insulate the tubing from sea water in the vicinity of the 

 contact stems. This is necessary to insure as long an external 

 current path between contact points as possible, taking into con- 

 sideration the water draining from the stems and tubing after the 

 wave surface recedes. The contact surface is situated on the top 

 of the stem near its extremity and all surfaces other than this 

 are plated with DCU silicone compound which breaks the surface 

 water film rapidly. These provisions reduce the lag t?me following 

 the recession of the wave surface to a fraction of a second. Working 

 drawings are included in figure 6. 



The Electric Wave Staff (H. 0. Model Mark I) as modified ha3 

 been tested aboard the Chesapeake Bay Institute Vessel MAURY and 

 found to operate satisfactorily. Six instruments of the new design 

 have been prepared. 



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