Dropper loop knots on the Ghetto Tensile Tester

[popa_pescarul]

Test Equipment and Environment:
1 spool Izorline XXX Super Co-Polymer 40# Test.
1 Ghetto Tensile Tester, consisting of:
100# dumbell (handle wrapped with packing tape to protect line abrasion)
Shimano 50# spring scale (calibrated at 20# using 2 10# dumbell weights)
Right foot on dumbell
Factory calibrated right arm pulling on line attached to spring scale

To test main line strength containing a loop knot:
Bottom tag end of line wrapped 6x around 100# dumbell, aprox 8" line to knot under test,
aprox 8" more line to top standing end tied in a figure 8 loop knot hooked onto shimano spring scale.

To test a knot's loop strength:
Bottom standing end of line wrapped 6x around dumbell, aprox 8" line to knot under test whose
loop was hooked onto shimano spring scale, top tag end hanging free.

Each knot tested with 10 trials, raw sample data shown
/x = sample mean (average)
S = standard deviation of the sample

Test 0, for reference, breaking point (in pounds) with simple overhand knot in middle of main line:
1 2 3 4 5 6 7 8 9 10
32 34.5 33.5 32 34.5 30 32 29 30.5 31
/x = 31.9#
S = 1.853#

Test 1, Dropper Loop (main line strength)
13.5 13 16 17 16 13 14,5 11.5 15 21.5
/x = 15.1#
S = 2.8#

Test 2, Dropper Loop (loop strength)
21 26.5 22 22.5 19.5 16.5 15 13.5 16 23.5
/x = 19.6#
S = 4.215#

Test 3, Kiwi Loop (main line strength)
24.5 23.5 24.5 28 24 22 14 22.5 24 25.5
/x = 23.25#
S = 3.646#

Test 4, Kiwi Loop (loop strength)
19 42 36 18 39.5 38.5 32.5 29 15 36.5
/x = 30.6#
S = 9.879#

Test 5, Straight Surgeon's Loop [2x around standing line] (main line strength)
15 22 17.5 13 15.5 14 22 8* 9* 9*
/x = 14.5#
S = 5.033#
* knot unravelled before breaking

Test 6, Straight Surgeon's Loop [2x around standing line] (loop strength)
36 34 28.5 18.5 32 31 33.5 31.5 24 24
/x = 29.3#
S = 5.5#

Test 7, Figure 8 Surgen's Loop (main line strength)
17.5 20 25 17.5 18 18 15 17.5 17 21
/x = 18.65#
S = 2.759#

Test 8, Figure 8 Surgen's Loop (loop strength)
36.5 37.5 38 36.5 35 38.5 34.5 38 32.5 36
/x = 36.3#
S = 1.874#

Interpeting the Data:

Test 0 gave me a reference point for the relative strength of the line. It's rated 40#, but
it's actual breaking strength is unknown.
If we assume an overhand knot reduces the strength of this line to somewhere between
50% and 75% of original strength, then the 31.9# mean breaking point means our original
line strength is somewhere between 42.5# and 63.8#. I'll use 75% of original strength which
estimates the true strength of this 40# test rated line to be around 42.5# or so.
I'll use 42.5# for calculating the % results below.

The standard deviation tells us, in pounds, how much variance there was in the trials.
The overhand knot itself is pretty consistently repeatable and the standard deviation was the
lowest: 1.853#. This is less than +/- 6% deviation from the mean and probably represents the
limit of the accuracy of my ghetto tensile tester.

Test 1, The Dropper Loop, main line strength

I was suprised by how much this knot weakened the main line. The average breaking point
was only 15.1#. That's only retaining about 36% of the original strength of this line!
If you tie a line with multiple dropper loops, anything but the top loop would be subject to
this reduction in strength. The standard deviation rose to +/- 2.8#, not suprising since
this is a more complicated knot than just an overhand. Still, pretty consistent
considering as much as +/- 1.853# of that is due to GTT* tolerance.
(* ghetto tensile tester)

Test 2, Dropper Loop, loop strength

Ok, so what if you just have 1 dropper loop tied in your line (or you're only worried
about the top dropper loop) and you pull on the loop instead of on each end of the main line?
Well, it's a little stronger from the loop's point of view. But, still not very impressive.
Just 19.6# breaking point on average. Still only 46% of the line's original strength.
Interestingly, the standard deviation rose quite a bit to +/- 4.215#. I did not pay attention
to which free end of the line I chose to wrap around the dumbell to work opposite the spring
scale hooked through the loop. Maybe one side of the knot is slightly stronger than the other?
Maybe it matters which direction you tie a dropper loop knot in a dropper rig so the stronger
end is to your main line and the weaker end is to your bottom weight? Anybody know?
Maybe, I'll try testing this in a future experiment...

Tests 3 and 4, the Kiwi Dropper Loop Knot
(Kiwi platted blood loop)

For the main line test, this knot retained almost 55% original line strength, almost 20% stronger
than a standard dropper loop knot.
The standard deviation was a little higher than for the dropper loop, I think this could be
due to this knot being a little more difficult for me to tie; not being as practiced with
it as a normal dropper loop knot.
Tesing the loop strength also demonstrated the kiwi knot being quite a bit stronger than a
standard dropper loop; 72% of original line strength verses just 46% for the standard dropper loop.
The standard deviation was quite high, +/- 9.879#, and again, some of it could be that it matters
which end I chose to pull against, but I didn't pay attention. Also, I don't think my tying was
as consistent with this knot. Even so, it was so much stronger, that event with my sloppier
consistency, it would almost always turn out to be a stronger knot than the standard dropper loop.

Tests 5-8, The Surgeon's Loop Knots

I've seen 2 variations on the Surgeon's loop from different sources. Some making
2 wraps around the standing line, other sources say to make 1 wrap around the standing
line, then cross back to make 1 wrap the other way to form a figure 8 pattern.
Some sources call the 2nd version a "figure 8 loop" instead of a surgeon's loop.

From the look and feel from my experience in tying both versions of the knot,
and especially from the results measured, I'm forming the opinion that the figure 8
version is the true and correct way to tie a surgeon's loop, and the first way is
just a bogus knot and those knot tying directions are just WRONG.
Any surgeons out there who can confirm this?

The figure 8 version formed an extremely strong loop, 36.3# breaking point on average,
which is retaining over 85% of the original line strength. Pretty impressive. While
the straight version retained only about 69% original strength.
Really impressive was the consistency of the figure 8 version knot with just +/- 1.874#
of standard deviation; essentially the same consistency as the simple overhand knot and
the theoretical limit of the GTT.

For main line strength testing, pulling on each end of the standing line with the
loop knot in the middle, neither knot did particularly well. The mean of the
figure 8 version came in almost 10% stronger, and almost half the size of standard
deviation as the straight version of the knot which simply came unravelled during
the last 3 trials. This demonstrated the figure 8 loop to be marginally better than
a dropper loop for tying a loop along the length of a standing line and the straight
style surgeon's loop as something you would just not want to use at all for putting a
loop along a length of standing line.

Conclusions / Lessons Learned:

The dropper loop really lays a smack down on the strength of your line. For bottom
weighted or multiple hook rigs, use a much heavier main line than you thought you needed
in order to compensate for this. Use this with lighter weight snood style leaders, or
maybe even a 3-way swivel might not be such a bad idea after all.
(Master of the obvious? Did I just go through all this only to discover what everybody
else already knows?)

The Kiwi Dropper is indeed significantly stronger than a standard dropper loop knot,
but not by quite as much as the web site of the guy taking credit for the discovery
of the kiwi dropper loop claims.

Use the figure 8 loop for terminal loops that you want to be strong.

Use the bogus "surgeon's loop" for loops that you want to have break first;
(like a breakaway weight or something) or banish it from use altogether.
The figure 8 loop is the one true surgeon's loop!

Do NOT operate the GTT while in shorts and barefoot.


Things To Do:

Test if dropper loop knot strength is asymmetrical.

Test some other loop knots: perfect loop, blood bight, spider hitch

Test terminal knots for strength: uni, SD jam, albright, palomar, etc.

Devise tests of terminal knots for other properties: size / freedom of lure movement etc.

Need more spools of line!

Need some kind of real tensile testing machine!

[Scarleg]

good chit there bro.....

[SAGE]

Shit Randall, that's an awesome post bro.
You did some serious testing that folks here can actually put to good use.
Many thanks



edit : "Factory calibrated right arm pulling on line attached to spring scale"...Mr. funny guy : )

[branman]

It would be cool to have someone else tie the knots and see if there is any difference

Not a shot at your knot tying just it is amazing how differently people tie the same knot. I think It would be interesting

[popa_pescarul]

Originally Posted by SAGE

Shit Randall, that's an awesome post bro.
You did some serious testing that folks here can actually put to good use.
Many thanks

edit : "Factory calibrated right arm pulling on line attached to spring scale"...Mr. funny guy : )

Thanks Sage!

Unfortunately, the factory right arm calibration procedure for the GTT is covered under trade secret and I'm not at liberty to divulge it. :jo:

[locobro]

Hey man, that is a great post. Especially for knot tying dorks like myself. Simple is good. Good point made on the knot tying by an additional person. Also wondering about how lubed the knots were as they were tightened, I've been extra careful about that since a great post regarding friction and line strength being compromised because of it.

Thanks again

[popa_pescarul]

Originally Posted by branman

It would be cool to have someone else tie the knots and see if there is any difference.

Not a shot at your knot tying just it is amazing how differently people tie the same knot. I think It would be interesting

I AM AN INDEPENDENT VARIABLE!

[OBfishguy]

pretty impressive post, lots of spare time?
what about the time and accuaracy of each knot, a spider hitch is not as strong as a bimmini however it can be tied in a fraction of the time and is suitiable for most purposes? Dropper verses Kiwi, what is the time in tying difference and how many times does it get ugly when it is tightend? pretty knots are better than ugly knots
Then again I have a prefference for quick pretty girls rather than complicated ugly ones or complicated pretty ones in fact I guess I just like quick and easy even if I break them off more often!!
good work on the post!!

[popa_pescarul]

Originally Posted by popa_pescarul

I AM AN INDEPENDENT VARIABLE!

ammm....attempt at little math humor?

Seriously, yes, it would be great to gather multiple samples from different knot tyers. This would help remove me from any bias in the data.

It would be interesting to see if others conduct a similar experiment, if they get similar relative strengths between the knots.

Even better, if there's a remote possibility that there's other geeky fishing nerds as me out there, we could team up and compare different knot tyers on the same set-up.

It's ridiculously tedious alone, but a couple or few people working together could probably run through a lot of trials fairly quickly.

This all started when an already unhealthy obsession to get on the Izorline Knot-Tying Competition leaderboard got completely out of hand...

[popa_pescarul]

Originally Posted by locobro

Also wondering about how lubed the knots were as they were tightened, I've been extra careful about that since a great post regarding friction and line strength being compromised because of it.
Thanks again

Lubrication protocol also covered by trade secret.

:jerkoff:

[ZZZZZ]

Offshore I use a rubber band.

Ground fish I tie dropper loop. Hmmm I don't recall breaking many but I wonder what mine break at.

Interesting.

[popa_pescarul]

Originally Posted by OBfishguy

pretty impressive post, lots of spare time?

Sad huh? Well, when I can't be out fishing, at least I can do something somewhat related to the sport.

Originally Posted by OBfishguy

what about the time and accuaracy of each knot, a spider hitch is not as strong as a bimmini however it can be tied in a fraction of the time
and is suitiable for most purposes? Dropper verses Kiwi, what is the time in tying difference and how many times does it get ugly when it is tightend?

Those a really good points. I find a lot of resources that list tying instructions for many different versions of fishing knots, but they don't go into much
detail about why I might want to choose to use one over the other.

I think the standard deviation might be a useful indicator of the accuracy of a particular knot. The lower the std. dev., the more consistent the knot is.
If you get a really wide std. dev., then either the knot itself isn't very predictable, or the tying technique isn't very precise.
Having some hard data like I tried to assemble above might be a valuable tool for helping to make an intelligent choice about which knot to
use, or whether you're tying it well. If you knew, for example, the relative strength and reliability data of the spider hitch, uni-to-uni, and the bimmini twist,
you would know if the spider's "good enough" for your application, or whether you should choose something else.

In the case of the dropper vs kiwi:
The dropper was moderately easier for me to tie and is hands down, the best looking knot.
The dropper's wraps lay tight and flat against the main line, the loop comes off at a nice right angle.
The kiwi's plaits were not as tight and compact and the body of the knot is more football or torpedo cigar shaped
than the even wraps of the dropper loop. The loop came fairly straight off the main line, but it's just not quite as
nice and tight of a hot little hardbody as the dropper.
If you want a more compact, good looking knot: use the dropper loop.
If you're willing to invest a little bit more knot tying effort and don't mind a slightly looser, bulkier knot
in exchange for one that's probably 20-30% stronger: use the kiwi.
If you don't mind if the knot isn't pretty or symmetrical at all, the loop doesn't stand off the main line at a right angle,
but is really easy to tie, a little stronger than the dropper loop in the main line, and a lot stronger than the dropper loop
when pulling from the loop: use the figure 8 surgeon's knot.

Originally Posted by OBfishguy

pretty knots are better than ugly knots
Then again I have a prefference for quick pretty girls rather than complicated ugly ones or complicated pretty ones
in fact I guess I just like quick and easy even if I break them off more often!!
good work on the post!!

Here's to swimming with bow-legged women!