RESISTANCE AND STABILITY TESTS OF THE WOODS HOLE OCEANOGRAPHIC 

 INSTITUTION CURRENT-INDICATOR BUOYS 



by 

 R.A. Ebner 



ABSTRACT 



The Woods Hole Oceanographic Institution has developed an instru- 

 ment which in principle uses the drag of a buoy to measure current velocities. 

 At their request the David Taylor Model Basin measured the drag of l/3-scale 

 models of three proposed forms for the buoy and a full-scale model of one of 

 these forms to determine which of the forms was best suited to their purpose. 

 The full-scale model was also tested for stability. From the tests conducted 

 Buoy 1 was found to have the most satisfactory performance. 



INTRODUCTION 



At a conference held at the David Taylor Model Basin (1 ),* repre- 

 sentatives from the Woods Hole Oceanographic Institution explained a proposed 

 device for obtaining measurements of the vertical distribution of velocity in 

 ocean currents in water up to 200 feet deep. A system for determining this 

 distribution was proposed. A buoy which was attached to an anchor by means 

 of a mooring line was to be released from the ocean bottom. As the buoy slow- 

 ly ascended to the surface the angle of the mooring line at the buoy was de- 

 termined by the resultant direction of the weight, buoyancy, and drag forces 

 acting on the buoy. A recording pendulum for indicating the angles which the 

 cable assumed at various depths was to be attached directly under the buoy on 

 the mooring cable; see Figure 1 . From the angles obtained, the drag of the 

 buoy could be computed. Hence, if the drag of the buoy was known as a func- 

 tion of the current velocity, the recorded angles would be made a direct 

 measure of the velocity of the current. 



It was requested that the Taylor Model Basin make resistance tests 

 of three l/3-scale model buoys and one full-scale model. The models were 

 supplied by the Woods Hole Oceanographic Institution. It was also requested 

 that tests be made to determine whether the presence of various towing bails 

 attached to the buoys had an appreciable effect on the drag, and that a test 

 be made to observe the stability of the full-scale model when it was towed 

 from an underwater towpoint, simulating actual moored conditions. 



* Numbers in parentheses indicate references at the end of this report. 



