TM No. 306 



DESCRIPTION OF THE DROGUES 



Parachute drogues were designed that would have a large drag area 

 (approximately ^5 square meters) at the depths where the water currents 

 would be measured^ as contrasted with a drag area (approximately 3 

 square meters) where the surface float would be exposed to the surface 

 water and the wind. At the same time the float and structure of the 

 drogue above the water was designed to be clearly visible at the surface. 

 A diagram of this d«sign^ which is comparable with that reported by 

 Ref o 1, is shown in Figure h.- : ' . 



The surface floats were constructed of styrofoam (3 feet long^ 

 2 feet wide^ and 1 foot thick) covered with 3/8-inch marine plywood, and 

 ballasted by a 50-POi^nd weight suspended 8 feet below the float. Each 

 float supported a mast which extended approximately 2k feet above the 

 water and consisted of a 20-foot length of aluminum pipe and a 15-foot 

 bamboo pole. 



The aluminum pole^ with the 50-POund ballast weight mounted on 

 the lower end, was positioned through a center hole in the float, and was 

 held in- place by a clamp and shackle combination above the plywood 

 cover and by a l/i+-inch manila line bent around the float and secured 

 through the shackle (see Figure 5A) . 



The bamboo pole was fastened to the upper end of the aluminum 

 pole with hose clamps. Two flags, a wire mesh radar reflector, and 

 a blinking light were attached to this pole as shown in Figure k. 

 The upper flag, used for locating the drogue, was about 1.0 by I.5 

 meters, and international (day-glo) orange in color. The lower flag, 

 used to identify the individual drogues, was a standard Wavy type 

 signal flag. The blinking light was fabricated using a socket, flashing 

 light bulb (gE type h-07) , lamp cord and 6-volt hand lantern-type battery. 

 The lights normally gave no trouble, but occasionally they stopped 

 flashing after a day or two of operation because of breakdown of the 

 bimetallic strip in the bulb. Batteries and bulbs were replaced at 

 the termination of each transect. The longest period of operation 

 was approximately k days. 



A harness of l/4-inch, stainless, 7x19 wire rope was run through 

 the center hole in the float alongside the aluminum pole. A loop was 

 fashioned at each end, and the wire rope was attached to the ballast 

 weight below the float and to the aluminum pole above the plywood 

 cover (see Figures k and 5A) . The upper loop was used in retrieving 

 the floats, and the parachute suspension wire was attached to the 

 lower loop by means of a splice-type fitting as shown in Figure ^B. 

 Any strain on the harness was transferred to the float by a l/ij— inch 

 cable-clamp and a l/4-inch shackle resting on the 3/8-inch marine 

 plywood cover above the mast hole. 



