TRAWLING FOR FORAGE ORGANISMS IN CENTRAL PACIFIC 



279 



I V IMiU mOh PRESSED TO SHAPE 



FRONT VIEW 



Figure 10. — Construction details of the diving vane of the 10-foot Isaacs-Kldd trawl. 



are drilled on the midline and ends of the vane 

 with their centers 1 inch from the after edge of 

 the vane. 



A pipe strut 17 inches in length extends down- 

 ward from the front center of the vane (detail B, 

 fig. 10) . Lengths of 6-inch pipe are split length- 

 wise and welded together to form a faired cross 

 section. Tliis strut extends up through the leading 

 edge of the vane and is welded both above and 

 below. A 2-inch-wide center strip of i/g-inch plate 

 covei-s this point and adds stiffening to the vane. 



The tension member consists of a wire pennant 

 made from %-inch-diameter 7X19 preformed 

 stainless steel wire rope. Solid rigging thimbles 

 are installed at each end. The tension adjustment 

 is made with a %-inch closed pipe turnbuckle se- 



cured by %-inch galvanized chain shackles. Pad 

 eyes of %-inch plate drilled for %-inch shackles 

 are welded to the vane at each end. An 8-inch 

 length of %-inch pipe is bent aroimd a suitable 

 radius and welded to the lower end of the pipe 

 strut to serve as a guide for the tension member. 

 Tension on the wire should not be excessive; the 

 wire after prestretching .should be just hand-tight 

 since too much tension during towing will cause 

 the vane to buckle. 



The towing arms are hinged triangular members 

 formed by welding 14 x 2-inch plate bai-s into a 

 triangle with the towing center 6 inches forward 

 of the leading edge and 201/2 inches above the hinge 

 center. The arms are hinged by means of a V^- 

 inch diameter galvanized pin held by 2-inch-long 



