Crimping Parameters examined- Tests & results.

[DenisB]

A journey in crimping technique:
I started my journey in crimping in the late '70s using full size A..C..D&F silverlocks with a fullsize bench crimper ( 24") in mono from 250# Jinkai ,to custom made 1200# 3.3mm.
Then later, when the mini-locks became available I started using them with a Jinkai SC-3 crimper .
In each case I proof tested the constructions to determine optimum settings.

Late last year 2011 , Marc77 responded to a post about crimp strengths & we started corresponding about crimping and Marc sent some of his crimp joins for testing ( they were indeed the strongest testing crimp joins I had seen ) . Marc then provided some crimp joins using the same materials & equipment in configurations I requested.
Marc is an accomplished & experienced crimp user.
The results were interesting & led to a further series of tests with a crimping rig I designed & made where I could set the load pressure on the crimping handles.

The original samples Marc provided were of a crimped swivel ( to suit Paulus's line test machine) using a join method of his own design and a crimping tool where he had modified the hole to optimise the results as he tested and evolved his technique.

His results were extremely good & led to questions about why they were so good & what components of the crimping dynamic contributed to his particular success.
Marc had modified 2 significant components of the join
a double pass loop thru the eye of the swivel with a single flemish twist in the eye & just enough compression of the crimp to generate enough friction to hold the package together.
He was using a Momoi mini-lock crimp & a pair of 10" crimping pliers ( without depth adjustment).
This crimping style was developed by Marc in association with Capt. Robert Wadsworth of the "Sunbeam Express" from Niantic, Connecticut.

The average join strength was 92% of tested line BS.
- all joins failed at the crossover of the flemish twist in the eye of the hook.
This compares to approx 80% for a single crimped loop.
A characteristic of this type of crimped loop join is that it can quickly generate friction on a hook eye etc & hold it in a fixed position.
this is an advantage in some rigs & a disadvantage where a freeswinging hook is desired.


So then I stated a series of tests to examine individual parameters in the crimping dynamic.and Marc was kind enough to provide a series of samples in the initial test series.

The lines & crimps used are fundamentally irrellevant to the results & implications of each dynamic examined ( as they are the same within each test series & we are comparing like for like except for the join parameter we are testing.)
Paulus did the line tests quoted in the discussions unless otherwise stated

Each individual parameter will be discussed in its own post in the thread.

[DenisB]

The effect of tension profile inside the crimp ;
this is influenced by the line path in the loop.............or a straight line to line crimp as a mid-line join.

Friction & load sharing between the components inside the crimp is influenced by the diameter shrinkage of the elastic mainline & tag under tension , & reduces the friction they can maintain under the compression of the crimp sleeve to resist slippage as the line is tensioned..
The object of crimping is to generate sufficient friction without damaging the molecular structure of the line ..........so that the inherent weakness of bending the line in a tightish radius around the eye of our terminal tackle becomes the weakest link............
the radius of the bend vectors the tension forces in the line to increase the shear forces on the molecular structure and promote failure in the bend before the straight line sections will break.
( no fishing line is perfectly uniform & there may be a section in the test length that is less strong than the section in the bend around the terminal tackle............as a general statement a bend creates a stress concentration that makes the bend the weakest point)
Similarly, line twist in a bend further increases the stress concentration in the molecular structure of the line.

Mid-line crimp join
- 59% ( failed x3 slip)

single pass loop
- 89% ( failed x3 at bend in loop eye)

Double loop pass
- 86% ( failed x3 at bend in loop eye)

Double pass loop with single flemish twist.
-92% ( failed x3 at bend in loop eye at the flemish twist )

Discussion;
- the midline crimp join subjects the lines at each end of the crimp to 100% tension & maximises line diameter shrinkage under tension within the crimp.
The tension & loadsharing profile in the crimp is 100% at each end & 50% in the middle.
The minimum compressed crimped length in O/S studies identifies a minimum length of 6 x line diameter to maximise strength of a crimped join used in this format.
ie
the crimp length must be sufficient to provide an adequate length of line at 50% loadshare & reduced tension & consequent contraction to maintain friction within the compressed ID of the crimp sleeve to resist the tension causing the lines to slip in the crimp............provided the compression of the crimping has not damaged the molecular structure of the line &/or created a stress concentration in the work hardening of the line in its compression distortion to cause the line to fail before then.
( no wonder the shorter mini-locks failed by slipping in this format, using the same crimp pressure as the looped formats ........it was only done to demonstrate the effect of changing the tension profile of the line within the crimp )

the loop formats change the tension profile of the mainline & loop ends at each end of the crimp to:-
100% in the mainline
50% ( general statement ) in each leg of the loop.
The tension profile is less radical in the crimped length of the sleeve from 100% at one end to 50% at the other , compared to the tension profile of 100-50-100 in a mid-line join.

Single Pass loop results;
these were the best I have seen & are specific to the attention to detail Marc had taken in his crimping setup.( more typical results in other tests over time have been in the order of 80% )

Double Pass loop results;
these were anomalously a little low, the loops in the tackle eye were noticed to be a little twisted & this is assumed to be the cause of the low results ( more typical results are 85% & double loops are generally better than single loops in a number of knot designs & test results )
What is seen from the loop formation is that friction in the eye of the terminal tackle & the eye of the loop improves the loadsharing in the radius of the bend which is the weakest link in the construction.
What is also of importance is the correct even length of the loop legs during crimping with the more complex loop eye designs , to ensure that the loadsharing in the loop legs at the crimp is 50:50.
Obviously uneven leg lengths under tension will move the tension profile closer towards that in a midline -join with lower strength results.
Again , the results of Marc's flemish eye construction is a credit to his attention to detail in his crimping technique.

[DenisB]

Crimping pressure:

First some useless facts about human grip strength.
Medical tests show that the average human grip strength increase with age to about 40 YO, where it peaks at 50-55kg, and then slowly declines.
For women it peaks at 40-45 kg ......IIRC.

The test rig used , applied load at the end of the handles & for equivalent leverage to hand pressure needed to be approx 20% lower at maximum ..........to not exceed average human capabilities.
( in reading the test results you need to add approx 20% to the test figure to equate to human grip strength at the position on the handle that its gripped by a human.).

More useless facts about crimper jaw compression forces & the compression strengths of crimps & mono ( so the test results & discussion make more sense )

- compression yields of potential materials in the components is:-
Nylon................45MPa
Aluminium..........90MPa
Copper..............184MPa.

You can see here that it takes twice as much force to compress copper as aluminium & twice as much force to compress aluminium as it does nylon.
The nylon is solid & its compression stength is full value of the above table, the sleeves however are hollow tubes & the compression strength of the tube of material is reduced considerably by the shape factor of the material in a crimp sleeve ( whilst at lower compression strength values ,an aluminium sleeve of the same dimensions as a copper one , will have only half the compression strength of the copper one).
During the initial stage of crimping the sleeve is compressed & then both the sleeve & the aluminium is compressed . The more they are compressed the more they work harden & the more force is required to compress them further.
When the crimp sleeve contacts the line , the line reinforces the crimp sleeve & the force required to continue to compress both the sleeve & the line is cumulative of the yield strengths.
( test results show this effect further down)

Mechanical advantage of the crimping pliers & the ratio of Jaw compression force to handle pressure in the test rig
compression magnification of Jinkai SC-3 crimping pliers ( 3 peaks brand )
- middle hole is 2.5mm dia. ( negligible jaw circumference difference on a 2.5mm rod )
Note: this is not with the jaws fully closed , but at the radius of the jaw holes..........the crimper jaws are not designed to fully enclose the crimp , they allow for the natural thickness of the flash formed at the sides of the crimp sleeve in forming an aligned circular OD of the sleeve around the lines when the crimp is fully formed.

1st stage lever arm( handle ) is 18mm/127mm = 7.05:1 leverage
2nd stage lever arm ( Jaws at middle hole) is 15mm/ 35mm = 2.33 :1 leverage
Total leverage magnification handle load to crimp sleeve load = 16.43:1
ie
*1 kg at the end of the handle = 16.43 kg at the middle hole of .SC-3
crimp compression load with 1kg pressure applied at the handle end is 4.1MPa ( at the jaw dimensions of the middle hole on SC-3)
- crimp compression load at max average male crush grip strength is 225Mpa ( Wow).

When you apply sufficient pressure to the handle to significantly contact the stop adjustment screw the leverage instantly reverses at the jaws and there is no dwell time at max crush pressure..........crimp dimensions INCREASE compared to a crush which lighty contacts the stop screw.
Dwell time at max pressure affects the crimp compression result.
It stabilises at just under 3 secs...........so I used a count of 3 as the dwell time standard for all the tests.

Note- different brands of crimper have different dimensions so the leverage magnification in their designs is different & the compression force at the jaws is different .
Size isn't everything
another hand crimper I have , thats physically bigger than the SC-#3......has:-
1st stage leverage of 7.37 :-
2nd stage leverage of 1.32:1
Total leverage magnification at the same hole size as the SC-3 of 9.73.
meaning that for the same grip pressure as a Jinkai SC-3 .............this crimper , despite being larger .............has only 60% of the crimp compression pressure of the smaller SC-3.

Now to the results:- ( Black magic 80# "tough"leader -Jinkai M ( 60-80#) sleeves ).

- 11kg Handle load- just starts to deform the sleeve.( ~45MPa) on the sleeve)
- 15kg Handle load -just stops the mono slipping under finger pressure.(~61MPa)

Crimp tests
17.77kg handle load ( 72.6MPa jaw compression) – result 14.26lb slipped
21.15kg handle load (86.7MPa jaw compression) – result 42.77lb slipped
24.15kg handle load (99MPa jaw compression) – result 52.42lb slipped
27.64kg handle load (113.2MPa jaw compression) – result 63.40lb slipped
31.06kg handle load (127.3MPa jaw compression) –result 66.84lb broke in top of crimp
34.38kg handle load (141MPa jaw compression) –result 59.87lb broke in top of crimp
37.22kg handle load ( 154.7MPa jaw compression) –result 69.07lb broke in top of crimp

Optimal handle pressure was approx 31 kg and variation below this resulted in slippage, variation above this damaged the molecular structure of the line & failure occurred at the crimp.

Subsequent DIY testing indicated that a variation in handle load of approx 2Kg from optimal affected results significantly.

This is why I make the statement that if you think you can consistently control handle pressure to within 2kg each time you do a crimp months or seasons apart you are kidding yourself.

Crimping handle pressure equates to a small change in the depth setting . Using a depth setting adjustment on your crimper produces consistent results once you have established the correct setting for optimal results by testing.





The effect of Crimp sleeve to Line fit:
Momoi 80# Hi- test leader Jinkai mini-lockM ( 60-80#) & smaller ID Jinkai mini-lock S ( 40#)
Jinkai S.........very tight push fit.
Jinkai M........ loose fit ( but not terribly loose).

Results:
Handle load 21.15kg
Jin 40 tight tested 65.2lb slipped
Jinkai m loose tested 55.41lb slipped


Handle load 24.15kg
Jin 40 tight tested 65.13lb slipped
Jinkai m loose tested 55.98lb slipped


Handle load 27.6kg
Jin 40 tight tested 74.36lb slipped
Jinkai m loose tested 83.88lb broke main linep


Handle load 34.38kg
Jin 40 tight tested 73.57lb slipped then broke main line above

The results relative to handle pressure /crimp compression force are all over the place as the crimp dimensions affect the relative deformation compression of the different crimps at the different pressures.
This identifies two things
each crimp/line combination has its optimal setting ( how many times has this been said)
The heavier wall thickness jinkai 60-80# has a higher best result.despite being a looser fit on the lines.
This is not necessarily indicative of extrapolating these results to other brands with different crimp wall thicknesses , different sleeve ID & possibly a different sleeve alloy.
It does drive home the message that each combination of crimp sleeve & line needs to be tested to determine the optimal components & crimper setting for your favorite leader materials.

[DenisB]

the effect of crimp length:
Momoi mini-locks vs Jinkai mini-locks
( Momoi 80# Hi-test leader )
Results:
Handle load 21.15kg
Jin 40 tight tested 65.2lb slipped
Jinkai 80 loose tested 55.41lb slipped
Momoi 80lb tested 80.75lb then broke

Handle load24.15kg
Jin 40 tight tested 65.13lb slipped
Jinkai 80 loose tested 55.98lb slipped
Momoi 80lb tested 82.46lb then broke

Handle load 27.6kg
Jin 40 tight tested 74.36lb slipped
Jinkai 80 loose tested 83.88lb broke main line
Momoi 80lb tested 76.65lb slipped ( anomalous result)



Momoi 80# mini lock single squeeze (4.5mm crimped section length )
vs
double squeezed ( approx 6.35mm crimped section length )
( black Magic 80# "tough" leader)
single squeeze
21.15kg 46.12lb slipped
24.15kg 61.74lb slipped
27.64kg 68.26lb slipped
double squeeze
21.15kg 72.87lb slipped
24.15kg 71.41lb slipped
27.64kg 68.28lb slipped ( anomalous result)

Whilst not a complete test result determining optimal settings in each series, these 2 series show distinct advantages in using the momoi mini-locks which enable a longer continuously crimped section by double crimping ( overlapped).
Part of the reason for some of the anomalous tests was that the tests were conducted with pressure as the variable parameter & not a depth setting.
This meant that the second overlapping squeeze on the momoi crimps was conducted by hand pressure to approx the same crimped section dimensions as the first squeeze ( to simulate an approximation of what a constant depth setting squeeze would produce at those pressures............obviously the test results idendify I did not always get it right.

What the results do show is that the momoi mini-locks achieve very good friction with less compression & distortion of the molecular structure of the line .........which is a very desirable outcome in optimising crimp strength.
That outcome is the result of the momoi mini-locks being able to be applied with a 40% longer crimped section length, with an overlapping second squeeze.
This is highlighted in the general results in the latter table where the same momoi crimps were compared with a 4.5mm long crimped section & with a 6.35mm long crimped section.


You can read & interpret those results for yourself.

The longer fullsize Jinkai/Momoi/silver locks in the A,B,C....F series are desirable for leaders above 200# due to the diameter of the line & a need to have a minimum crimped section ratio of 6:1 (length : diameter) to achieve adequate friction at the higher load levels and adequately respond to the tension-loadsharing- line diameter shrinkage in the crimped section as line tension increases.

[DenisB]

I'm done with examining the effects of the parameters in crimping. Its up to you to find the combination that suits your preferred leader brand & size and the setting that optimises crimp join strength.
You control the choice of components.
You control the consistency of your crimping technique.
Test your results...........don't guess.

Its pretty obvious that controlling crimp results by just hand pressure is not reliable , whereas using a depth setting for the jaw compression does .
So buying a crimper that has a variable depth adjustment , or modifying your crimpers that don't , to provide one , is very desirable to be able to produce consistent optimal crimp joins week by week year by year using a crimper set for the combination & using it just for that combination.

If you are optimising crimping results by modifying hole sizes REMEMBER those holes are not circular with the jaws closed, they are not fully closed when you complete forming the compressed crimp ...........the hole is circular with a gap between the jaws............and that gap is not the same for each different sized hole in multi-hole crimpers. ( it varies with the amount of flash that is squeezed out the sides of the crimp in forming the compressed crimp section with crimps of different cross-section dimensions.
If honing holes ............establish the gap that the jaws have with the hole circular ( test it on different sized metal rods /drill shanks & pack the jaws at that gap when honing holes to a larger diameter .........if you insist on using a multi-hole crimper for more than one job at the same depth setting & need to adjust the crimper compression level on a second hole in the same crimper pliers.
Been there done that ........its simply cheaper & easier to buy another pair of crimpers for the second job.

Notes about crimper brands:
crimpers for aluminium sleeves for fishing line are designed differently to crimpers for the electrical trade.
ie
crimpers designed for the electrical trade are not designed to accomodate any flash in the crimping process , electrical connections form a complete circle in the crimped section without flash at the edges as the crimp connections are designed internally with an internal sleeve to promote a round crimped section under compression.
Most crimpers in the world are designed for electrical connections not fishing line.
Quite a few crimpers out there in the market place as mono crimpers are re-branded electrical crimpers.
ie
they are not designed to allow for the flash produced by an aluminium crimp used on fishing lines

This means when you use them on aluminium crimps on your line the jaws do not reach proper alignment and the crimp itself does not reach its desired shape or distribute the compression forces properly with a fully formed crimp.
They do a <90% job of crimping aluminium crimps on fishing line, as they tend to distort the molecular structure of the mono inside the crimp unevenly.

The test of what you've got is simple
- close the jaws tight without a crimp in them
- if the hole is round , they are electrical crimpers
- if the hole is oval & you have to open the jaws slightly to get a round hole ...........they are fishing line crimpers.

No names , no pack drill , just check what you've got .................you know the brand & where you got it from.



Hope you found some useful information in this series of tests & discussion to optimise your crimping technique & join strength.

FWIW

[luna sea II]

very informative

[madday]

Denis,
can you post the picture of the joins?
Mid-line crimp join, Single pass loop, Double loop pass, Double pass loop with single flemish twist?

[DenisB]

Sorry never took any pics

Mid line join is :-
one long line line in one end of the crimp ( with a short tag exiting) & another long line in the other end of the crimp with a short tag existing the opposite end .


single loop pass :-
is putting a crimp on the leader line , passing the line thru the eyelet of say a hook , bending it back 180 Degree & into the crimp, forming a simple loop.
Ie
a simple loop


A double pass loop is:-
putting a crimp on the leader line , passing the line thru the eyelet of say a hook & wrapping it around the eyelet & back thru the eyelet again , making two turns around the hook eye , then up into the crimp.
ie a simple loop but with 2 turns around the hook eye.


A double pass loop with a single flemish twist is ;-
putting a crimp on the leader line , passing the line thru the eyelet of say a hook & wrapping it around the eyelet & back thru the eyelet again ( same as above but with a loose wrap of line) , then wrapping the tag around the loop of line before bending it another 90 degree to fit into the crimp after snugging the loop wrap with flemish twist down close to the hook eye.

You can find diagrams of flemish loops / flemish eyes, commonly used in multi-strand wire leaders, in most of the rigging sites.
A flemish loop in multi-strand wire typically uses several twists around the loose loop to give it stiffness in the loop & stop the flemish eye puling up tight on the hook.
In the mono leader construction Marc77 used there is only one flemish twist in the loose loop.

Hope that helps.

[Badfish1]

Very informative...thank you!


Thanks,

Joe

[madday]

thanks Denis....

can somebody make this thread sticky please.......