Q I have had some bad luck with gel-spun polyethylene backing on my fly reels. This past spring I hooked a heavy reef fish that my guide thought was either an amberjack or African pompano. After a half-hour of tough fighting, the line suddenly went limp. Reeling it in I found that the loop knot connected to the fly line had severed. Can you tell me what caused the line to fail?
The problem is that most gel-spun lines are slippery, and if you loop-to-loop it to the fly line, under fighting stress that loop may slip. This forms a weak girth hitch, and the gel-spun will then cut through itself.
Rod Harrison, who is a great friend and a top fly fisherman in Australia, frequently gets in fights with big billfish, tuna and other nasty critters. He is a strong advocate of gel-spun line for backing on fly reels and has developed a method that eliminates the problem. First, he has found that when you build a Bimini Twist loop in gel-spun line, you shouldn't make the normal 20 turns we associate with Dacron. Instead, make 40 or 50 twists before finishing the knot. Once you have this loop, don't loop it over the fly line once. Instead, repeat this at least six or eight times. When this is pulled snug, it will not slip.