Spey Is The Way
What knots work for making a loop in gel spun backing?
I've used the same test method for loops. In fact, a month or so we had a long thread on loops and I pointed out the difference between the Kreh loop and the non-slip mono loop. I tested them ten times and the Kreh loop won all ten (in mono). Good enough for me. I suspect you're right regarding the materials and method of making today's braids. As Bill Nash pointed out, the Bimini is probably not the knot of choice for gel spun anyway. Lefty also made a comment on that back page column of his in Fly Fishing in Saltwaters that he'd take a true triple surgeon's loop (six times through) over any bimini for a loop in one's backing. That's when I stopped tying Biminis all together. They're no longer needed on most big game leaders nor in backing. They're fun to tie (though less so with braid) but just not really necessary any more.JR, interesting to know. On the other hand, there are so many more types of braids today than 10 years ago, that I expect the exact number of correct turns depends on the brand and pound test in question, just like mono. The braids sold for fly backing are made a bit differently and feel different than an old-school PowerPro, and now there are "fused" braids, too. They're all a bit different in knot behavior.
I don't have a testing machine, but I do test knots for the specific materials that I use. It is a reassuring way to spend an evening. Loops are the easiest to test. I make 2 different loops in a 1' length of line, insert a chopstick or screwdriver in each loop, and pull it apart. Best loop wins!
Are you using braid? And is this in your backing? I've always felt that we put way too much emphasis into fancy knots in our backing. But considering the flex of the rod and the stretch of the line and leader I doubt any of us could put more than ten pounds of actual pressure on our backing.. I don't doubt that even a standard surgeon's knot would hold. Most of us don't have the courage to do that when fighting something like a blackfin, but it would almost certainly work. What a terrific fish the blackfin is. Where do you fish yours (general area not specific?)3 turn surgeon works for me on black fin tuna and they are pull harder than a steelie.