The Knot Strength Thing — Can knot strength be calculated? Does it matter?

by | Jan 9, 2022 | 34 comments

Knots come with opinions. They come with failures and with baggage. And they usually come recommended by someone else. You try the knot, and it works or it fails you. So you keep it or move on.

But because the world’s collected information (and opinion) is now at everyone’s fingertips, many anglers use another approach — research. Instead of tying the knots and fishing, they read about them, find charts and videos, look for breaking strength tests and failure rates for fluoro and nylon, comparing and contrasting a time-cost/benefit analysis that factors knot strength, difficulty and reliability.

I’ll be candid. A lot of that might be overthinking things.

Find a knot your buddy recommends. Learn to tie it at home. Fish it hard for a few outings, and see how you like it. Maybe that’s all you need to do.

That said . . . here comes some advice and a long-jump down the rabbit hole of knot strength. I think it’s appropriate, because there seems to be a common anxiety about trying new knots, and a fear of the simplest knots breaking.

I love the Davy Knot. And I’ll use this as Exhibit A for knot anxiety. Why? Because there’s a widely circulated myth out there, claiming the Davy isn’t as strong as the others.

Is it? But . . . does that really matter?

READ: Troutbitten | Use the Davy Knot — Here’s Why

From Your Fingers or From Mine?

Some of the knot tests that you’ll turn up with a Google search are pointless. They really can’t be relied upon, for a bunch of reasons that we’ll get to in a moment.

A while back I did my own tests for the breaking strength of fluorocarbon tippet material. It wasn’t a knot test but a tensile strength test. It was unscientific, it happened at my fly tying desk, but I trusted my results because I did it myself.

READ: Troutbitten | Fly Shop Fluorocarbon Too Expensive? Try Invizx

If you don’t have an expensive, scientific machine for testing tensile, then your stats for breaking strength are dubious at best.

Even with such a machine, data about knot strength is suspect. Why? Because knots are personal. How you tie your Clinch might be a bit different than how I tie mine. Sure, we each take five turns around the main line and then finish through that loop. But maybe you’re more careful about how you tighten the knot. Maybe I burn mine a little with too much friction. Maybe the angles are a little different.

Let’s get back to the Davy for a minute: The Davy Knot will fail if you pull on the tag at all while tightening or clipping. Inevitably, when people tell me their Davy Knots fail, this is the problem. Just a slight pull on the tag accidentally loosens the knot. And with so few wraps in a Davy, there’s really no room for error. It’s one of the simplest knots out there, but it must be tied with precision.

Photo by Josh Darling

Material Matters

Gear fishermen will tell you this all day — some knots are great for nylon and bad for fluorocarbon. Some knots are an excellent choice for small and medium diameter lines but bad choices for thicker lines. And some knots are not a good choice for large diameter hooks. (The Davy is one of them.)

It’s silly to expect one knot to do everything. And it’s folly to compare knot strength without factoring everything in.

Many years ago, I had a spool of Dai Riki nylon. It was sold on brown spools and green ones — two varieties. I liked what they called “Dynamic” on the green spools best, but I bought a spool of brown because it’s all my local fly shop had. How could it be much different, right?

I painfully remember sitting on the bank the next day, after trying to tie a simple Clinch Knot with that stuff, over and over. Nothing complicated — just a Clinch. But every time, the knot slipped as I tightened it. I tried wetting the knot as usual, and I tried it dry. I tied with more turns and less. I cinched down fast and slow. It was maddening. And I cannot remember another time when I was so frustrated and exasperated on the water.

I still don’t know what was wrong with me or that tippet. But, I’ll be damned if I couldn’t tie a good knot with it when I tried a month later, either. So I threw out the brown-spooled stuff and stopped thinking about it.

What’s my point? Sometimes, certain materials just aren’t a good fit. There are intangibles in this confusing sport, and often, it’s better just to accept them.

Photo by Josh Darling

Does Knot Breaking Strength Matter?

Sure it does. But for me, it’s not the most important thing.

In my rigs, I have multiple knots, from the fly line to the fly. Set aside the fact that I tie my own leaders and there are many knots, tapering down to a thinner line. Instead, let’s look only at the tippet section.

In my favorite Harvey Dry Leader, I have knots at 3X, 4X and 5X, then to my fly. (That’s very general, but hey, just for conversation.) Those knots are Double Surgeon’s Knots and I do not  want them to fail before the Davy knot to the fly. If I hang in a tree, I want the knot at the fly to break first. If it breaks anywhere else, I’ll lose more material and more time on a rebuild.

Likewise, if I add a nymph dropper to the dry, I would like the knot at the nymph to break on a snag instead of the knot on the dry. Makes sense, right?

How about a nymphing rig with two flies, with one on a tag dropper? The same principles apply. I build my rigs so the weakest point of connection is at the point nymph. And I can achieve that with material and with my knot choice.

It’s helpful to have that control.

Back to Me and You

Knots are personal. Your Davy might be stronger than my Clinch or my Uni-Knot, and that might be for a variety of reasons.

Personally, I don’t believe any of the knot strength tests because there are too many variables. And what I know about the performance of my favorite Davy, for example, conflicts with the myth of its inferior breaking strength. My Davy’s are strong. But I don’t know about yours. That’s for you to find out.

So find your system. And choose with purpose. Learn by experimenting rather than believing in some online chart. Trust your fingers and your choices.

Fish hard, friends.

 

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Enjoy the day.
Domenick Swentosky
T R O U T B I T T E N
domenick@troutbitten.com

 

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Domenick Swentosky

Central Pennsylvania

Hi. I’m a father of two young boys, a husband, author, fly fishing guide and a musician. I fish for wild brown trout in the cool limestone waters of Central Pennsylvania year round. This is my home, and I love it. Friends. Family. And the river.

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34 Comments

  1. The original (single) Davy knot has slippage problems when there is a significant diameter disparity between a thin tippet and relatively heavy gauge hook wire.
    The Double Davy with just one extra turn solves this problem with just an extra two seconds of effort. When using the “Pinch Method” the Doubly Davy can be tied in less than 10 seconds and simply will not slip regardless of hook wire diameter, results in a very small footprint, wastes little tippet material, and is very reliable.

    Here’s the best way to conduct a fair and accurate test of relative knot strength:

    Knot vs. Knot Comparison Testing

    Knot strength is measured in the lab using motorized force testing machines like a Chatillion TCM. Tension is slowly and steadily increased until the knot fails. Hi-tech testing machines can measure breaking forces with great precision.

    However, under actual fishing conditions, knots seldom fail from the slow, steady pull of a fish. Knot vs. Knot is a simple test that can be used to accurately compare the strength of flyfishing knots when stressed by the impact forces exerted by hook sets or sudden fish surges.

    Required equipment includes 2 vise-grip pliers, protective eyewear is must, two of the same style and size hook you commonly use, a spool of your preferred tippet material, a measuring tape or ruler, and paper and pencil for recording the results.

    This is a test that pits Knot vs. Knot in a best of 10 competition – and it compares your personal tying techniques and skills using the actual hooks and tippet material you fish with. No force gauge is required as this is a comparative test designed to determine relative knot holding strength. Testing wet knot strength can of course be accomplished by soaking your tippet and knots before testing.

    This test does carry a risk of serious eye injury if safety precautions are not followed, so protective eyewear and locking vise-grip pliers are a must.

    Here’s how the Knot vs. Knot test is conducted:

    Cut a 24” piece of new tippet material. Tie a hook to each end with competing knots. Secure each hook in a locking, Vise-Grip plier. Apply a series if sharp pulls, increasing force until one knot fails. Mark the winner with a slash tally mark. Repeat nine more times and declare a winner. In my case if the Double Davy wins it will move on to compete against the most popular tippet-to-fly knot – the Improved Clinch Knot.

    Different tippet splicing knots and different brands of tippet material can be comparison tested as well. As a general rule the traditional tippet splicing knots (Blood and Surgeon’s) are the weakest link in the system, unless you are still using the Clinch.
    The new Infinity Tippet knot is the best on stream splicing knot I know of; it is fast, reliable, and stronger than all the others.

    Reply
      • This is why I went to the double davy. You just don’t have try to do things perfectly, from judging whether tippet and hook are a good match, to pulling on just the right parts while cinching it down. I just tie it and done. There is a part I have to do just so or else I’ll have to pull on the tag to finish cinching it, thereby having more waste, so I’m contradicting the above sentence just slightly, but it will not slip, in either case. I think I tried the davy 3 times. The 3rd time it slipped and that was it, no mo’!

        Reply
  2. To complicate things a bit, I’ve found that different brands react differently to different knots. And, the same brand will be reliable in thicker diameters with a certain knot but not in thinner ones. I suggest anglers experiment a bit and then decide on their core knots for given applications.

    Rick, thanks for the infinity knot. I believe that this is the same knot that the British call the figure of eight knot. It seems that we Americans see infinity where the Brits just see eight.

    Reply
    • The Infinity Knot = the Orvis Tippet Knot. Same, I believe. And I agree, I use the it all the time:
      — Can use the up-tag without breakage.
      — Can use the added in line to form the tag.

      Cheers.
      Dom

      Reply
      • I *think* I tie the orvis tippet knot. The one I studied online, and use, they called it the “j knot”. When I looked up the OTK recently, it looked like the same knot. In any case, I like it a lot.

        Reply
  3. I have been fly fishing for 65 years and can say without any question that I have only had 2 knots fail while engaged with a large fish (20″+). I single clinch knot, tied with floatant on my fingers and a Davey knot with dry hands. I have tied nothing but the double clinch knot ever since I lost the second fish. Why chance losing a large fish of a lifetime for the extra 10 seconds it takes to tie a double clinch knot?

    Reply
    • Hi Mike,

      My reply is not me trying to change your mind about any knot. It’s just an answer to your question:

      “Why chance losing a large fish of a lifetime for the extra 10 seconds it takes to tie a double clinch knot?”

      We choose knots other than the Clinch to:
      — Save material , which saves time building rigs. (Example: we can tie a Davy about 1.5 inches of material.) Knots that waste material force us to rebuild a lot more often. It’s not just about the one knot.
      — Have a lower profile knot to the fly. (Example: I don’t use a loop knot to streamers, because the Davy is so small, it allows for extra flexibility.)

      More here:

      https://troutbitten.com/2017/09/17/fifty-fly-fishing-tips-8-use-the-davy-knot-heres-why/

      That said, my first recommendation has always been to find knots that work for you. And I know that you’ve obliviously done that. Excellent.

      Cheers.
      Dom

      Reply
  4. The best knot Is the one You can tie consistently correct. I love the Davy knot and I tie it correctly at least 85% of the time, the other 15% is when i hook a big fish….So I find that a Pitzen knot, sometimes called a 16/20works best for me.

    Reply
    • Right on. Use what works. That’s why there are so many knots, right?

      My trouble with the Pitzen is that it adds another layer of mass to the Clinch — and more time.

      I think knot mass is an underrated factor — not because the fish care what the knot looks like, but they do care how much movement the fly has. Knots with more mass permit less wiggle.

      Cheers.
      Dom

      Reply
  5. I have guided for 26 years in the BWCA. I once had a tarpon tournament flyfisher who had a very accurate digital scale with him. He gave me the scale,hooked his fly on it which was attached to a 7wgt rod and walked back about 50-60 ft. He then applied pressure and bent the rid into a complete C, almost to the breaking point. The scale registered just over 2 lbs! Try it some time. You are 100% correct, It’s how well you tie the knot, not which knot you use.

    Reply
    • Right on. I often take a client’s fly and hook it to my hemostats, then I walk back and pull hard — like a big trout. A fly rod is designed to protect the tippet. We can exert a LOT of pressure on a fish before the tippet breaks. The flex of the rod diminishes the force of the pull. That’s a pretty amazing example that you gave there. Thanks, Steve.

      om

      Reply
    • Most knot failures come from impact forces not steady tension. Break offs can also occur due to tippet abrasion, from sharp teeth or gill plates, or entanglement in wood or around/under rocks. Maximum pulling force with a rod is produced with a very low, downward facing rod angle, not a tip up “C”. Suggesting that tarpon anglers cannot place more than 2lbs. of force on a fish is misleading. Nonetheless, for most trout anglers the weak point is the tippet splice unless the inferior clinch is used.

      Reply
  6. My Davy knots fail far less than my double surgeons (snagging trees, etc., that is). Sucks to lose and retie more tippet after that. I also love that I can tie a Davy on a smaller piece of tag end then with other knots. If I feel I need it “stronger”, I’ll make it a double Davy.

    Reply
  7. I am convinced that most break-offs occur either from abrasion (especially at the eye of the hook), or from “wind knots”, an overhand knot accidentally introduced by poor casting technique (or wind) and not knots. Twenty years ago, while killing time in my fly shop, we performed comparative knot strength tests using the method you describe with the vise grips. Fluro was relatively new at the time and our main concern was Flurocarbon strength versus mono. (BTW 5X Fluro was much weaker than mono 5X, although I am not sure this would still be true). We also learned that a simple overhand knot anywhere in the line in Fluro or mono reduces the breaking strength by nearly half. Bill

    Reply
  8. Years ago I switched from double to triple surgeon’s knots for my tippet-to-tippet connections and have had far fewer knot failures at those connections since then.

    For tippet to fly I like the Orvis knot because you don’t have to worry about tippet vs hook wire diameter creating slippage, for instance if I want to try a few drifts with a thick wire woolly bugger.

    Reply
  9. I really like your approach and thoughts. There is no magic knot, time put in will reveal what works best on the water. I think that attention to detail is often ignored with knots. I see that many anglers have no system for tying/checking knots. For me every knot I tie is lubricated, tightened, visually inspected, and then I give is a firm pull to test it’s strength. By going through these steps I have a high level of confidence in the knots I am fishing. Weak knots are weeded out by me rather than by the fish. A good at home test to reveal the difference can be in the details is tie a blood knot in some 5x tippet and tighten it down without lubricating it. Then pull on the knot until it breaks. Next tie a blood knot in the same tippet, lubricate it thoroughly, then tighten and pull on the knot until it breaks. In my findings the lubricated knot is often twice as strong.

    Reply
  10. Im a professional mariner and went to a 4 year Maritime college where amongst all the classes we took was a semester class on knots, bends, uses etc. Long story short, every time any material bends or wraps around, over, under itself or anything else etc. IT WEAKENS, period. (doesn’t matter which material) the strongest any line will be is when it is straight. A seven turn clinch knot is weaker than a five turn clinch. Knots work on the principal of compression. As a line with a knot is stretched it pinches (compresses) down on itself. Compression or Bending = Weaker. The best knots are those that have the least number of compression points and don’t slip. Always give your know a good tug before the first cast.
    I’ve used the Double davy for 10 years and never had one slip. I keep track of the distance between the last knot in the leader and the fly. In 10 years I’ve broken a fish off twice at the knot.

    I use a single Davy for brookie and small fish water cuz it’s that much faster.
    The other consideration is abrasion . If you’ve cast 100 times on the same knot, it is weaker than when you started.

    Reply
    • Merchant Mariner? Appreciate the info. My brother went there and turned me to on to fishing. good conversation Dom.

      Reply
  11. Your point about knots being personal is dead on. For a decade, I worked for a fishing tackle manufacturer that produces millions of miles of fishing line per year. Hundreds of tensile tests are performed each day to measure the straight break and knot break strength of the nylon, fluorocarbon, and braided line being produced. Round-robin tests have been done that involve numerous people testing various lines on various testing equipment. Straight break strength is not heavily influenced by the person doing the testing. Knot break strength, on the other hand, is greatly affected by who tied the knot. The “best” knot, poorly tied, may fail before the “worst”, well tied. To your point, learn to competently tie whatever knot you chose to use.

    Reply
  12. Thanks for another great article. I am a big fan of the Davy knot which I learned about from your blog. I regularly strength test my knots with a size 18 hook and scale and have found that on 5x and 6x tippet, a double Davy is about 10% stronger so I always tie it as it only takes a few more seconds. Of course this is based on how I tie it. Other things I have found is that a double Davy is better than a clinch and comparable to an orvis knot in strength, but a Davy is much easier for me to tie. Also I have found that material matters, especially on 6x where nylon is much stronger for knots than flouro (again for me).

    Reply
    • Some knot tying tips worth passing on:
      Always maintain tension on a newly tied knot for at least 10 to 15 seconds to help seat it,
      then give the tippet a few sharp tugs to test it. A poorly tied knot will reveal itself when pre-tested and could save the fish of year. One feature of the Davy knots is that if tied incorrectly they fail the pre-test every time. If you want to see the hands down fastest version of the DD check out the “Pinch Method” video on YouTube. Takes longer to thread the eye than tie the knot using this one-handed technique.

      Reply
  13. I was a clinch knot tier for years as that was the only knot that I knew how to tie. It wasn’t until reading this blog that I discovered the Davy. I now use it for most of my flies. I got to see the strength of this knot and 5x fluoro a few weeks ago when I snagged a 6″ diameter limb on the stream bottom. I managed to pull the limb in without losing anything. Cheers!!

    Reply
  14. The best way to dramatically improve knot strength is to trade in your 7X and 6X tippet spools for 5X and better yet, 4X. Going long and strong is a much, much better way to fight big wild trout properly (quickly) and will go a long way to ensuring a safe and healthy release.

    Reply
  15. Great topic! Funny in that I am heeding some of the tips on your site, and have been practicing the Orvis Tippet Knot and the Davy Knot the last couple of days. I’m going to try them tomorrow.

    I was showing a friend who said he was having issues with the top tag breaking when that hook got hit by a big fish. We tried the Orvis (using nylon for practice) and could break it fairly easily. He said he used nylon on his surgeons. I said “hold on”, ran out to the garage and got my lanyard, a cut off a piece of fluoro. Tied the Orvis with that, and couldn’t easily snap the the upper tag. He was sold-there clearly was a big diff between nylon and fluoro. Another reason to only use fluoro underwater.

    Thanks for all of your great articles, and I love the podcasts!

    Reply
  16. Almost all the time I use a 16/20 aka pitzen knot for tippet to hook eye. it’s not because its the strongest but because I can tie it with a pair of forceps. Years of using a mouse to program computers has left my right hand with a tick. it takes a little more line but at 69 I want to fish the rest of my life it lets me stay in the game. Sometime the game goes not to the swift or strong but the persistent.

    Reply
  17. About 25 years ago, I went to a Labrador fly-in lodge for big brook trout fishing. The guides were Newfoundland dudes who spoke an English I could barely recognize, but they were damn smart fellows. We fished streamers and a mouse they tied that they referred to as “the shaving brush”. It was end-of-season, the fish were in gorgeous spawn colors, and dry-fly fishing was over a month ago. I was doing my usual blood knot tie for tippets, and the guides just laughed at me. “Here,” they said. “Watch this.” They tied their tippets with double surgeon knots. In their experience, they said that that their knots took much less time to tie, and were the equal or the stronger of the blood knots. So, I started following their advice. I’ve followed it for 25 years, without regret. I will only tie blood knots now when constructing leaders, and I only do that because I have the time and I’m nostalgic.

    Reply
    • I agree on all points. However, another point that matters is knot size. Blood knots are streamlined and go through the guides nicely. Surgeon’s Knots are the opposite of that. So in anything larger than about 1X, I choose blood knots. That’s me.

      Cheers.
      Dom

      Reply
  18. Another great article Dom. I discovered the Davey knot on the Troutbitten site while searching for an answer to my knot problems. I had just changed my mono leader tippet from Maxima ultragreen to a brand name copolymer. I loved the copolymer performance but my trusty clinch knot was constantly failing. The tackle store advice was more turns on the clinch knot but it got to the point where I wouldn’t change flies because tying a 9 turn clinch knot on the water was a complete pain in the butt. So when I discovered Troutbitten and the Davey knot and also the articles about choosing knots and systems that were versatile and ones that you could do simply and fast on the river, it totally changed my fishing game. Through going down countless Troutbitten rabbit holes in the last 3 years, I have gone from fishing mainly dry flies and standard dry dropper to tight line mono rigs, all the dry dropper styles and trying my own Harney dry leaders. It’s dramatically increased my catch rate but maybe even more importantly, I’ve loved the process of learning and experimenting and trying all these new theories out on the water. What an awesome sport this is and what an awesome resource Troutbitten is. Cheers Dom and the TB crew.

    Reply
  19. Dom, I love this thread.

    For some aesthetics matter. There is just something aesthetically pleasing about a well tied blood knot for a line to line connection.

    Kinda like the appreciation for someone else’s uppercut as they repeatedly hit you in the face.

    Reply
  20. To me, by far the most important thing you can do if you want to have confidence in your rig is to practice tying knots at your bench until you can get repeatable results. If you can’t tie repeatable knots in the comfort of a chair with good light, your chances of doing it streamside are poor at best. And as to the knot comparison idea – spend the time to get to the point that you can quickly tie each knot. If you can tie it quickly, you have done it enough times that you are probably doing it the same way each time. And if you find that the knot is inconsistent, spend some time experimenting to see if you can identify the small variation that is causing the difference.
    One final observation – I did lots of knot comparisons and really liked the Orvis knot. One of my most important criteria was consistent strength – that I could trust the knot every time. When I started using it in fishing it seemed to be breaking much too easily – the difference was when it got wet – it lost a lot of strength. Something to watch out for.

    Reply

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Domenick Swentosky

Central Pennsylvania

Hi. I’m a father of two young boys, a husband, author, fly fishing guide and a musician. I fish for wild brown trout in the cool limestone waters of Central Pennsylvania year round. This is my home, and I love it. Friends. Family. And the river.

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