59°50' 59°40' 59°30' 



Figure M-3. Drogue plots. 



up or sink witliin .a period of several days, and 

 in some cases, the drogues have been lost be- 

 cause, they could not be. located. Since the above 

 operations are improvised, it is expected that 

 parachute drogue techniques will be improved; 

 nevertheless, the dii-ections given, if followed, 

 will enable inexperienced personnel to obtain 

 excellent results. 



M-7 Ekman Current Meter, — The Ekman 

 current meter was developed by Dr. V. Waif red 

 Ekman, a Swedish scientist, whose original de- 

 sign, although modified, remains basically un- 

 changed. The meter, shown in figure M-4, is 

 designed to give current speed and direction at 

 any depth. The speed-measuring mechanism 

 consists of an impeller, or screw, and a shaft con- 

 nected to a set of dials which indicate impeller 

 revolutions. The direction device consists of a 

 magnetic compass and a compass-ball recepta- 

 cle. The receptacle is divided mto 36 chamters, 

 each representing 10° of azimuth. As the im- 



peller rotates, bronze balls fall, one at a time, 

 from their reservoir onto the top of the com- 

 pass needle and, depending on the heading of 

 the meter, are guided to one of the 10° direction 

 chambers. This gives the direction toward which 

 the current is flowing. 



The current ineter is lowered by either the 

 oceanographic or bathj^thermograph winch, 

 using %2-, %2-5 or %6-inch wire. The impeller 

 is locked while lowering and hoisting. One mes- 

 senger is sent down the wire to unlock the im- 

 peller and set the meter in operation. A second 

 messenger is sent down to lock the impeller be- 

 fore hoisting. The platform from which the 

 Ekman current meter is suspended should be 

 anchored to obtain valid measurements. 



M-8 Assembling the Ekman Current 

 Meter. — The following components, spare 

 parts, and accessories for the Ekman current 

 meter are contained in a cari-ying case : 

 Main body of the meter. 

 One tail section (vane and two brass tubes) . 

 Two impellers and shafts. 

 Compass box and compass laeedle. 

 Two compass-ball receptacles. 

 Two messengers. 



One metal container of bronze balls. 

 IVIiscellaneous items including a graduated 

 reading frame, a special wrench, tweez- 

 ers, bronze-ball loading tube, and small 

 weight. 

 The meter is assembled for operation as 

 follows : 



Step 1. Attach the vane to the two brass tubes 

 (left-hand threads), and attach the tubes to the 

 main body of the meter by right-hand unions. 

 A special wrench is provided for tightening the 

 unions. 



Step 2. Open shutter by pressing tripping 

 mechanism arm (A) (fig. M-5). Depress catch 

 (B) and release the impeller forward bearing 



SHUTTERS 



COMPASS 

 BOX 



COMPASS -BA 

 RECEPTACLE 



VANE 



Figure M-4. Ekman current meter. 



Change 1—1970 



M-3 



