The Improved Clinch knot is a staple of fly fishing, but you’ll also find it anywhere light monofilament lines are the go-to choice. An ideal knot for everything from panfish to trout, the Improved Clinch is strong, easy to tie, and pretty darn fast, to boot.
But it does have weaknesses. As its popular uses suggest, heavy lines and the Improved Clinch don’t play well together, and ultra-slick braid just can’t get enough bite from this knot’s loops and turns.
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The Improved Clinch knot really shines in fly angling, and you’ll find a lot of love for this knot anywhere you catch trout, steelhead, and other common fly species.
It ties really well in light lines and holds like superglue when made properly.
The downside of Improved Clinch is that knot integrity suffers in lines over 30-pound test mono diameter, and it simply won’t hold very well at all in slick braid of any diameter.
Monofilament - including fly line - is extruded from a single strand of nylon. Despite how it feels between your fingers, mono is actually pretty grippy, especially against itself. That allows it to bite and bind when formed into a knot, and it’ll hold well against itself.
Fluorocarbon is very similar to mono in terms of its surface texture, allowing good bite and grip in a knot. Where it can be problematic, however, is that it tends to be stiff for its diameter, effectively mimicking heavier line.
The Improved Clinch is a diameter-sensitive knot, and the extra stiffness of fluorocarbon is a potential problem. With lighter fluoro, you may have no trouble whatsoever, but as you step up in test strength, you’ll probably reach a point where the Improved Clinch won’t hold.
That said, as fluorocarbon tech improves, these lines are becoming more pliable. And it’s also true that the Improved Clinch and San Diego Jam are very similar knots - and the latter is well-known for holding in fluorocarbon.
My advice? Test your particular fluorocarbon. Tie the Improved Clinch, and then pull the dickens out of it on a scale to see how much integrity you get.
Braided lines are another question altogether. Woven from Dyneema or Spectra fibers, these super-strong materials are unfortunately as slick as wet ice. Essentially gripless, they just won’t bite down on themselves to create a tight knot--at least not without some very clever knot design.
Repeated tests of the Improved Clinch in braid confirm that it will not hold well.
Don’t try it!
The Improved Clinch is a very strong, fast knot that’s pretty easy to tie. But it can fail if you make one of these mistakes.