The recent surge of interest in various ways to create loops and splices in fly lines is a positive development. It's helping us to get the maximum performance and versatility out of our fly tackle. Like others, I've been trying to upgrade my skills and knowledge in this area. But I'm concerned that there's a lack of scientific rigor in testing and comparing results. (This is also true of knot tying, with some people content to rely on inferior knots that Grampaw tought them.)
How many of you have actually tested and compared your results? From what I've seen in several articles, imperical testing of knot and line strengths is dificult, requiring machinery that is not available to most of us, and methadology that is complex and tedious. But without test results, how do we know if our connections are reliable?
Let's start with a fundamental question: how strong is a fly line?
That's our base line, and I've never seen a figure in print. (I guess, and it's only a guess, that it's approx. 35-40 lbs., perhaps less for the tapered ends and running lines.)
I've been told that it's not an important issue, because the static lifting strength of even heavy duty fly rods, expressed in pounds, isn't all that much. That's missing a point: Almost all of us snag bottom from time to time, and have to break loose (with a direct pull that doesn't put our rod at risk, of course!). Usually the tippet will break first; but even in freshwater we frequently use stout tippets for salmon and steelhead. And if a sinking tip is jammed between rocks, well, we're going to find out how strong our connections really are.
These are non-comprehensive but realistic tests that we can duplicate. I've been testing my connections recently, using mono of various sizes tied to trees in my back yard. It's been a relief to find that blind splices, served loops, and double catch loops in 50 lb. braided line, thread-whipped and coated at the back end, are all stronger than 35 lb. mono. I think that's strong enough for most purposes. I still need to test blind splices in running line, and knots in backing.
Regarding welded loops: the attraction of sleek, professional-looking loops may be concealing a weakness. Welded loops are mostly plastic melted to plastic, without the braided core contributing any strength to the loop. Or am I missing something?