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Knot Strength Query


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33 replies to this topic

#1 Patriot

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Posted 02 January 2020 - 10:06 PM

I have been re-watching a few videos on fly fishing knots - mostly leader to tippet and tippet to hook - and have never learned of any explanation as to why knots break at less than the noted line strength they are tied with.  

 

Does anyone know why this is?

 

I would much prefer to use a 6x tippet (Rio Fluoro, 3.6 Lb) rather than a 5x, but will not do so if its knot will break at less than its designated breaking strength.  I normally fish the San Juan River in Northern New Mexico and these trout normally run in size L, so a stout leader is a no-brainer.

 

 

Thanks!



#2 Dave G.

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Posted 03 January 2020 - 06:13 AM

My theory when in doubt is to just go with the stronger leader and run an extra foot or two of it. I've used 6x here at home for trout but the slightly larger salmon in Maine in rivers make short work of breaking even 5x. They are fast and abrupt fish compared to our pond trout here who are prolific midge eaters compared to bait fish and caddis etc up there. That said, in some ponds I've seen 17" trout that won't take even a 6x leader and #20 chironamid, they reject them. switch to 7x and a #24 then they jump the thing. Well I'll be 70 in April, I don't tie size 24 anymore lol. We have other ponds where they will take the #20 or even an 18 on 5x. You might catch more fish with 6x but will do pretty well on a longer 5x too.

 

Half the time we jinx our own knot when we tighten it down by not lubing it, just a dip in the water or a little saliva can make a huge difference. All my leader to leader knots etc are double surgeon knots, never had one break that was tightened down right and tags clipped right. And it's lot less fussy to tie than other traditional leader to leader or to tippet knots. I generally use improved clinch knots at the hook, sometimes a loop. I've found it's most important how you tighten down the improved clinch, too much friction is the killer of this knot in my experience. The guides I know in Maine use the improved clinch as well.

 

To me it's just as important if not more how the tip of the rod acts than what knot I use but I've settled on those. Tip action, especially as the bigger fish get in close is very important imo, you want that tip to flex as the fish jerks around and shakes its head etc. Just my view. Really good tip action on the rod has saved many finer tippet to hook knots for me, where stiffer tip action has broken tippet to hook knots and on smaller fish. I hate a real stiff tip section.


John 7:38 ESV  is about "Rivers of Living Water"


#3 Dave G.

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Posted 03 January 2020 - 06:49 AM

My theory when in doubt is to just go with the stronger leader and run an extra foot or two of it. I've used 6x here at home for trout but the slightly larger salmon in Maine in rivers make short work of breaking even 5x. They are fast and abrupt fish compared to our pond trout here who are prolific midge eaters compared to bait fish and caddis etc up there. That said, in some ponds I've seen 17" trout that won't take even a 6x leader and #20 chironamid, they reject them. switch to 7x and a #24 then they jump the thing. Well I'll be 70 in April, I don't tie size 24 anymore lol. We have other ponds where they will take the #20 or even an 18 on 5x. You might catch more fish with 6x but will do pretty well on a longer 5x too.

 

Half the time we jinx our own knot when we tighten it down by not lubing it, just a dip in the water or a little saliva can make a huge difference. All my leader to leader knots etc are double surgeon knots, never had one break that was tightened down right and tags clipped right. And it's lot less fussy to tie than other traditional leader to leader or to tippet knots. I generally use improved clinch knots at the hook, sometimes a loop. I've found it's most important how you tighten down the improved clinch, too much friction is the killer of this knot in my experience. The guides I know in Maine use the improved clinch as well.

 

To me it's just as important if not more how the tip of the rod acts than what knot I use but I've settled on those. Tip action, especially as the bigger fish get in close is very important imo, you want that tip to flex as the fish jerks around and shakes its head etc. Just my view. Really good tip action on the rod has saved many finer tippet to hook knots for me, where stiffer tip action has broken tippet to hook knots and on smaller fish. I hate a real stiff tip section.

By the way if non of the above works from leader to hook try a palomar knot. It's all we use in salt water around here.


John 7:38 ESV  is about "Rivers of Living Water"


#4 niveker

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Posted 03 January 2020 - 08:23 AM

Does anyone know why this is?

 

 

As I understand it, the knot effectively is cutting into the line.  



#5 DFoster

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Posted 03 January 2020 - 09:28 AM

I like a blood knot for leader to tippet connection because it's a cleaner knot than the double surgeons.  However when it's cold a blood knot can be tough to tie so when my fingers are cold and not cooperating I'll use a double surgeons knot.

 

For tippet to fly I love the Davy knot.  As long as you use good quality tippet, correctly tie and lubricate the knot you shouldn't have an issue with them breaking.

 

I have found it's all too easy to exceed the breaking strength of any knot when fighting a fish in a strong current. 


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#6 SilverCreek

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Posted 03 January 2020 - 10:57 AM

I have been re-watching a few videos on fly fishing knots - mostly leader to tippet and tippet to hook - and have never learned of any explanation as to why knots break at less than the noted line strength they are tied with.  

 

Does anyone know why this is?

 

Thanks!

 

Every knot deforms the line because the line MUST wrap around itself, another line, or the hook. Therefore, when a solid material is "flexed" the inside arc is compressed and the outside of the arc is stretched. Therefore stress is uneven across the material.

 

Secondly the material is deformed and compressed (pinched) on both ends of the knot where the material enters the knot. Therefore the compressive force THINS the material and there is LESS material where it is pinched by the knot,

 

With a straight line pull on a line, all the molecules "feel" the same force of distraction. With a pull on line with a knot, some parts of the material "feel" a greater distractive force because it is bent and other parts have less material because it is pinched. Usually the thinned material breaks where it enters the knot. The material is weaker because there is less of it.

 

Make sense now?


Regards,

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#7 Patriot

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Posted 03 January 2020 - 11:05 AM

Thank you all for your generous and informative comments.  

 

The videos that I have watched (more than once) are these Rio videos:  Leader-to-tippet knots and tippet-to-fly knots.  In both of these videos breaking strength is noted and each tier used lubricant on each knot before tightening.  As noted, knot breaking strength varies significantly between knots.  This has always puzzled me and Rio offered no explanation.

 

I just purchased a new fly line for one of my fly rods and will have to soon make a choice as to which knot to use between leader and tippet.  I always use a needle knot (I believe that is the correct name) between fly line and leader.  The new fly line may come with a loop and I may forgo the needle knot.  Not sure about this at the moment.

 

My preferred tippet-to-fly knot has always been the turle knot.  From the videos, I was happy to learn that this is a very strong knot.  However, the hooks I am using have flat or horizontal eyes.  In other words, the eye is not bent up or down.  IMO, the horizontal eye is adding additional stress on the tippet material.

 

There must be some 'knot research' somewhere but darned if I can find it.

 

@niveker

I think your comment makes perfect sense and could well be the reason some knots break before others do.  Thanks for that bit of into.

 

@Dave G

Thanks for all of your great commentary.  Knot to pull your chain (pun intended), but nearly 90% of the food the trout eat in the San Juan River are midges.  I'm a wee bit your senior and if I could not tie these tiny flies I would have to purchase them and that would definitely make me very cranky.  I've been tying since I was a teenager and have probably purchased less than a dozen flies in my lifetime.  To be clear, I do have to use a magnifier when tying but I've accepted the fact that my eyes are not what they once used to be so this works well for me.

 

@DFoster

Thanks for the info on the Davy knot.  I had never heard of this knot.  I should get out more.  Ha!

 

Thanks again to all for shedding some light on this.



#8 Patriot

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Posted 03 January 2020 - 11:15 AM

My wife learned of some very interesting research that has been done on the very subject we have been discussing.  It appears - "Some knots are stronger than others, but scientists have struggled to explain why."  Now, who would'a thought??

 

At any rate here is the link to one article.

 

And here is another link with videos.

 

I think we should all pitch in an buy her a box of chocolates.  I will pick them out, of course.  Ha!



#9 Patriot

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Posted 03 January 2020 - 11:32 AM

 

 

 

Every knot deforms the line because the line MUST wrap around itself, another line, or the hook. Therefore, when a solid material is "flexed" the inside arc is compressed and the outside of the arc is stretched. Therefore stress is uneven across the material.

 

Secondly the material is deformed and compressed (pinched) on both ends of the knot where the material enters the knot. Therefore the compressive force THINS the material and there is LESS material where it is pinched by the knot,

 

With a straight line pull on a line, all the molecules "feel" the same force of distraction. With a pull on line with a knot, some parts of the material "feel" a greater distractive force because it is bent and other parts have less material because it is pinched. Usually the thinned material breaks where it enters the knot. The material is weaker because there is less of it.

 

Make sense now?

 

 

Your explanation makes perfect sense.  As a woodworker I understand compression and tension very well, but never thought to apply that knowledge to knots.  Lesson learned.

 

All of this said, what is your preferred leader-to-tippet knot?

 

Thank you very much for some very valuable information.



#10 steeldrifter

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Posted 03 January 2020 - 12:34 PM

The others have explained it well, and properly. You'd be surprised at just how changing the way something is rigged or knotted affects the strength. Years ago I worked as a fabricator in a wire rope shop. We use to make all sorts of lifting devices and wire rope slings. To give you an example. The 3/8" wire rope sling we use to make was basically a rope with two eyes we would open and weave into each end. If you used it in a direct pull it was rated at 1.2 tons. If you used it as a choker (put one eye through the other and pulled - basically like a fishing knot would somewhat be)  then it was rated at only .92 (so not even a ton). Yet if you looped each end around a part and had the two eye ends on the same point (making a basket) then it was rated at 2.2 tons.

 

I always found it quite interesting how just changing the way something was hooked up could so drastically change its strength.


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#11 Patriot

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Posted 03 January 2020 - 01:09 PM

@steeldrifter

 

Thank you for your insightful comments.

 

One would think that by now we would have all this knot business figured out, but alas, we apparently have not.  We tend to choose those knots which are easy to tie or  whatever other reason we conjure to justify a particular knots usage.  

 

In a week or so I will be making a fool of myself fishing in 20 degree weather.  Hopefully, I will use the correct knots.  From long ago experience, it was ice coated ferrules that were the problem and not my leader-to-tippet knot.  Cannot wait to get out there.

 

Thanks again for your help.



#12 SilverCreek

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Posted 03 January 2020 - 01:15 PM

 

 

 

 

Every knot deforms the line because the line MUST wrap around itself, another line, or the hook. Therefore, when a solid material is "flexed" the inside arc is compressed and the outside of the arc is stretched. Therefore stress is uneven across the material.

 

Secondly the material is deformed and compressed (pinched) on both ends of the knot where the material enters the knot. Therefore the compressive force THINS the material and there is LESS material where it is pinched by the knot,

 

With a straight line pull on a line, all the molecules "feel" the same force of distraction. With a pull on line with a knot, some parts of the material "feel" a greater distractive force because it is bent and other parts have less material because it is pinched. Usually the thinned material breaks where it enters the knot. The material is weaker because there is less of it.

 

Make sense now?

 

 

Your explanation makes perfect sense.  As a woodworker I understand compression and tension very well, but never thought to apply that knowledge to knots.  Lesson learned.

 

All of this said, what is your preferred leader-to-tippet knot?

 

Thank you very much for some very valuable information.

 

 

For leader to tippet I use the blood knot. The reason is that it is a slim knot and it is a knot that is directly IN LINE and not offset as the surgeon's knot is.

 

The thing about a blood knot is that most guides show equal number of wraps on each side of the knot. That is fine IF the diameters of the lines being joined are the same. However, most of the time, a blood knot joins two monos of UNEQUAL diameter. A leader to tippet knot most often joins the transition section of a leader to the thinner tippet section of the leader.

 

Now follow my logic on this next explanation. If we take an equal number of wraps of that thicker line around the thinner line on one side of a blood knot vs the same equal number of wraps of the thinner line around the thicker line on the other side, THEN the number of wraps are the same BUT the length of the line GRABBED by the wraps are NOT. The thicker line grabs a longer section of the thinner line, than the thinner line grabs of the thicker.

 

When tested, this blood knot will be weaker than a blood knot tied with an extra wrap of the thinner line which serves to "equalize" the length of line "grabbed" on each side. So in tying a blood knot with unequal diameters of line, take an extra wrap with the thinner line. Also the number of wraps on each side must be no less than 4 and no greater than 7. So 5 wraps on one side and 6 on heh other is a good compromise for unequal diameters.

 

If the diameters are way different, then double the thinner line to tie an "Improved Blood Knot." Again the doubling over of the thinner line is to equalize the amount of line grabbed on each side of the knot.

 

https://www.youtube....h?v=DyQeoWcn8FY


Regards,

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#13 Patriot

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Posted 03 January 2020 - 02:07 PM

@SilverCreek

 

Thank you once again for a very informative post.

 

After reading your comments I found a video that demoed the blood and improved blood knots plus three other knots.  The improved blood knot was the clear winner.

 

For those following this thread here is the link to the Rio video and the follow image is the conclusion.

 

Attached File  leader-tippet-knot-strength.jpeg   62.29KB   0 downloads



#14 Patriot

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Posted 03 January 2020 - 02:59 PM

 

For leader to tippet I use the blood knot. The reason is that it is a slim knot and it is a knot that is directly IN LINE and not offset as the surgeon's knot is.

 

The thing about a blood knot is that most guides show equal number of wraps on each side of the knot. That is fine IF the diameters of the lines being joined are the same. However, most of the time, a blood knot joins two monos of UNEQUAL diameter. A leader to tippet knot most often joins the transition section of a leader to the thinner tippet section of the leader.

 

Now follow my logic on this next explanation. If we take an equal number of wraps of that thicker line around the thinner line on one side of a blood knot vs the same equal number of wraps of the thinner line around the thicker line on the other side, THEN the number of wraps are the same BUT the length of the line GRABBED by the wraps are NOT. The thicker line grabs a longer section of the thinner line, than the thinner line grabs of the thicker.

 

When tested, this blood knot will be weaker than a blood knot tied with an extra wrap of the thinner line which serves to "equalize" the length of line "grabbed" on each side. So in tying a blood knot with unequal diameters of line, take an extra wrap with the thinner line. Also the number of wraps on each side must be no less than 4 and no greater than 7. So 5 wraps on one side and 6 on heh other is a good compromise for unequal diameters.

 

If the diameters are way different, then double the thinner line to tie an "Improved Blood Knot." Again the doubling over of the thinner line is to equalize the amount of line grabbed on each side of the knot.

 

 

I just checked the blood knot that I am currently using on my preferred fly line.  It appears that I used three wraps to join my 5x leader to my 6x tippet material.  I will redo that knot and use 5 wraps this time.

 

I miked both lines and got 0.15mm for the 5x leader end and 0.13mm for the tippet end.  I think it would be fair to call these diameters to be approximately similar in diameter so equal wraps should work well.

 

If my memory serves me correctly, I think that I used to coat this knot with Pliobond adhesive which smoothed out the knot.  I have not done that in years and it is probably not worth the time to do.  

 

Thank you once again for a very helpful post.



#15 tjm

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Posted 03 January 2020 - 09:42 PM

Hi Patriot, SilverCreek's explanation is pretty much what happens and almost all knots fail where the main line enters the knot. It will look like the line parted in the middle because there will be no curl or trace of knot left.

I had some time so I did the search for you. I probably didn't find all the instances of knot testing but these should give you an idea of how they did it and the resulting strength ratings.

https://www.fix.com/...t-encyclopedia/
https://www.saltstro.../fishing-knots/
https://www.knotsfor...strength-chart/
https://www.fieldand...-fishing-knots/
https://www.bassreso...ines-knots.html
https://www.saltstro...ot-vs-uni-knot/
https://mattsbucket....ot-testing.html
https://www.fieldand...-fishing-knots/
https://www.fieldand...-line-strength/
http://www.leeroysra...trong_knots.htm
https://www.bdoutdoo...h-chart.596379/
https://www.fieldand...nofilament-line

and how to tie some of them can be seen here https://www.animatedknots.com/
or here https://www.netknots.com/

 

I use nail knot for leader to line  and Double Fisherman’s Bend to join sections of leader or tippet to leader, easier for me to tie and I can step down a greater difference in diameter, I've never had these knots fail, any failures are always the tippet, it being smaller.  I did use blood knots for years and tied as Silver describes they work very well. I usually use a Duncan knot or a Double Davy knot at the fly.