Synthetic fibres -- objective performance ratings?
 

Hi,

I find myself totally befuddled by the array of synthetic fibres on the market, particularly with regard to how they perform in practise.

• Manufacturers publish breaking strengths, but even there I wonder if they measure by the same criteria -- for example, what is Samson Average Strength as compared with Samson Min Strength?

• Stretch figures are hard to come by in general, and again, I wonder about consistency of measurement. Ditto for creep.

• UV sensitivity -- total minefield! They all say "superior UV resistance", and so forth, but that's meaningless. I want to know how UV-sensitive the fibres are -- is Vectran better/worse than Dyneema? Does PBO really self-destruct after a few months in the Sun? Do the various coatings the manufacturers use (Samthane, Armourcoat, etc.) make much difference?

• Same for chafe!

So, it seems to me that it would not be hard for someone to run objective tests on all this -- eg. set up a rig to pull ropes with weights on the end back and forth over a length of steel wire with UV lamps on them -- but has this ever been done? Is there any real quantitative objective data on how these ropes perform? Failing that, reliable relative data would be a big help -- eg. Vectran is more/less chafe-prone than Spectra, etc.

Cheers, Ian

Saw something in SAIL last month
 

Yes, comprehensive testing like this would be great.

There was some testing (around knot strength actually) in SAIL last month. I found it interesting that they developed their own baseline breaking strengths -- these were far higher than the published tensiles. I believe most published tensiles are fairly conservative. I also under understand that many tensiles are determined from a spliced sample -- so by definition a proper splice is 100% efficient.

Checkout the Layline site, they have done some elasticity testing on their "punisher".

Bob

Chafe is a bear
 

OK, here's one piece of objective data on "chafe" -- apparently bears can chew through Vectran, but not Spectra!

http://ursack.blogspot.com/

Thanks for the heads-ups, Bob & Deralte (that one re bear nibbles will be a hit with the
rockclimbing set! :) ). But, Bob, I've now checked the on-line Sail TOC's for Jan'07,
Dec & Nov 2006, and don't see a hint of any ropes or knots testing: can you please
provide a link to that? (maybe a copy ... ?)

And, yes, the Layline stretches are good to see--and have several levels of tension.
(They had at one time a video of a rope breaking--oddly over an extended few seconds.)

One should expect that the baseline is tested, not quoted, and be disappointed when it's not.
There was a test of gel-spun HMPE fishlines a few months ago, and the differences
between rated & actual strengths in the lines was HUGE--to 270%*!!! And then there
will be knot testers who presume to determine efficiencies w/o determining the material
strength? --and then such determinations get compared w/each other, and ... .
[* Sport Fishing mag., Aug.2006, pp. 62-68]

I have found it intriguing how, in a table of strengths per size of various ropes, one
might be significantly higher in some sizes, then slowly or even suddenly lose that
lead and even trail, then come back again; and how the proportion of strength per
material might be inconsistent.

The Cordage Institute made some noise about their insisting on spliced strength vs.
ISO (?) or some international standard that uses other methods. But splicing takes
skill, which varies; and, of course, one would like to know of the splice's efficiency.
(Notably pathetic, e.g., was Practical Sailor's testing in which their eye splices pulled
out well under the load ultimately borne by bowlines!!)

As for other characteristics, yes, isn't is amazing at some of the assertions: UV has
NO effect on HMPE; or is it that HMPE is only "good" but not "excellent" in UV resistance;
or "excellent" up until about 3 years when more Samthane (?) coating is needed?!
--ditto on the abrasion resistance, with various anecdotes of toughness and resistance
to cutting, yet often polyester is rated higher!?

(As for PBO, the anecdotes I've heard aren't about rapid deterioration in months, but
nearly HOURS! --and yet that material has appeared (at a price!) as part of a sheath
for frictional heat resistance!?)

.:. Ya gotta wonder!

SAIL Mag piece on Knot Strength
 

The knot story is in the Feb 2007 issue (page 82 by David Schmidt) . The testing was done at New England Ropes.

They tested 1/2" double braid nylon, 1/2" Sta-Set, and 1/2" Endura Braid with a bowline, a clove hitch backed with halfhitches, a round turn and halfhitches, a figure 8 follow though, a double fisherman's knot, and an eye splice. No details were given on the eye splice, but I assume it was to NE spec.

As expected, knots in the Endura Braid were pretty bad, they only retained about 30-40% of the strength of the rope . The tensile was tested at 19300#, I believe published is 19000#. The eyesplice broke at 20594#.

The eyesplices in the other ropes were about 78% and 88% efficient at the measured breaking strength -- the measured breaking strengths were about 20% higher than published numbers. The knots were about 50-60% efficient.

It would be interesting to see a comparison between Endura Braid and Endura12 of the equivalent size. I'd assume the cover helps some -- by adding friction.

I would have expected the knots and eyesplices in the nylon and dacron to fair a bit better. The knots were only about 25% better than the same ones in Endura Braid. I would have expected the eyesplices to be closer to 100% efficient.

Bob

PBO Covers
 

I have seen the PBO covers and inquired about the UV problem. Since the covers are not designed to be load bearing, the strength is not a factor, and apparently the heat and chafe resistance is not impacted by the UV induced strength loss.

Bob

What's weird -- to me -- about PBO, is the number of people selling PBO standing rigging systems (eg. Powerlite, OYS). Case in point: a Swan 80 rigged with PBO. OK, these are all race-oriented tweak-freaks; but even so, if it's as bad in UV as people say, they're going to be re-rigging a lot, aren't they?

Hi Bob,
I'm looking forward to seeing the article, especially to see what variables might account for the odd results (like those very low splice numbers). As it happens, two of our apprentices just got the results back from their destruction tests, and nearly all of the splices appear to have approached 100% efficiency, so I know it can be done.
Fair leads,
Brion Toss

PBO Rigging and SAIL Story
 

I have sold a bit of PBO standing rigging. There is no exposed PBO, the terminals are sortof headed and glued -- most like a Cast Lock. The balance of the PBO is covered with a thick plastic tubing.

Don't expect a lot of splice tech detail in the SAIL story. I can only assume that whoever spliced was better at the core-to-core than with a double braid splice -- maybe variables in core bury, taper, etc.

Bob

Well, Bob, Feb '07 might be "last month" for you, but the way I work
it's at least a half year in the future! (And I recently got a med. bill for
my father from April '05 (oh-five, yes)!!)

Um, again, 100% of WHAT? --note Bob's point that the actual tested strengths were
"about 20% higher" than ratings (yet apparently, at least for the Endura Braid, the
test method didn't get it all--splice topping it!) Factor that in and those "weak" splices
approach 100%, too. (If the splice is breaking, it's not 100% but something shy of it
--otherwise breaks should come arbitrarily elsewhere along the line.)

I've been impressed more than once that some tester might conceive that the test
device would care whether a Fig.8 loopknot was tied in the bight or with the end!!
Did the report show the exact form (dressing, and WHICH END WAS LOADED) of the
knot--or are we gifted with Guessland, as usual? In any case, the values are lower
than what one will find in general belief in the kernmantle world--see e.g. fairly recent
testing by Dave Richards http://www.caves.org/section/vertica.../knotrope.html
--12.5/10.5 bar graphs are of each other's data; tables are correct.

(I'll hope to find this Feb SAIL still on some store shelf, thanks!)

--dl*
====

Figure 8
 

The figure 8 follow through was described as "ideal to attach two pieces of rope together" and was tested in that way. The testing machine had the belay points where you could "wind the rope around a drum and secure with a cleat".

I have had a few splices destructively tested, and they break right at the end of the taper. My understanding is that this from the stress riser due to the splice. They have all broken above the rated tensile of the rope itself, implying we did not know the true tensile before we started.

My view is that if we can splice to rated tensile (and manufacturers deliver rope at or above what they rate) and use a healthy safety factor -- I typically use at least 3:1 for running rigging -- we will keep rigs up and people happy and healthy. I suppose the ideal would be to break a section of rope off of every spool, but this gets expensive and I think the samples could vary as you work through the spool. I feel pretty good using these guidelines and then breaking a splice here and there to keep myself honest.

Bob

Tapered splice
 

Bob,

If you have the ability to test a splice??? I would very much like to see how a tucked 12 strand spectra splice fairs. I don't know the correct name but it was the one I learned working on deck on fishing boats in AK and what I have used since. Essentially divide strands into two groups of six. Put one group through the core at the eye size. In pairs tuck strands down a parallel set of strands placing the tail of the previous under the one you are tucking. Tapering out at the end.
It seems keeping tension uniform is crucial to it coming out neat, not too much or too little. We use this splice on the boat I work on for winch hook etc with pretty severe usage and loading. Lines from 5/16" to 2". If the line comes from a supplier already splice it typically has the Brummel splice?? tucked back into the core.
Anyway just curious to know how the splice would hold up.

Thanks

Jake

Splice Testing
 

I do not have the ability to test splices myself, I have had mine broken at both Yale Cordage and New England Ropes.

I have used a tuck splice on single braid dacron -- megabraid or alike. I did six or eight tucks, how many tucks do you take in high mod?

I am guessing that the splice techniques differ in larger sizes of high mod ( I have never used over 3/8"). For instance, if we used Brion's brummel splice on 2" spectra, the bury would be 16 feet long!

Bob

The splice is indeed long about 6' I'm guessing not 16' though. Not sure exactly what the one they are sent up with is. These are Gilson lines used to hual the fish on deck approx 60 ton winch pulling over a midship gantry arch and reaching to the stern. I migrated to the much warmer engine room a while back so I just go up for fun and to bug the bosun now.

One of the reasons I liked the tucked splice is it had less waste. An issue if I'm buying the line or just don't have much. I usually do about 8-15 tucks about 4" on 1/4" and 5/16", 6" on 3/8" and 1/2"
It would probably hold with less but thats what I have been doing. I use a little Swedish fid.
and must admit I like doing them they look so neat when you are done especially the small stuff.

I think I have one in the shop maybe I'll take a pic and post it tomorrow.

Jake

Oh, thanks again, for that--in my hasty review of it ($5 is more than I want to toss
for it), I missed that point. From the knot pictured ruptured, they used what I call
the "perfect form" in "weak" loading--the inner twin taking the load instead of the
one reaching to the very end of the knot (along the axis of tension).

Results given for knots resp. in Dbl.braid Nylon, Sta-Set, Endura Braid

Cowboy Bowline: 55% 55% 38%

Clove & 2HH: 65% 63% 36% (looked to be maybe on 2" dia metal?)

RT & 2HH: {slipped @40%(5,148#)} {slipped @63%(6,492)} {slipped @29%(6,166#)}

Fig.8 BEND: 57% 52% 37%

Grapevine Bend: 54% 51% 30%

I'm REALLY surprised at the figures for the Grapevine bend!?
Too bad they didn't bother to stopper the RT&2HH (or make it 3HH) and check its
strength--or try the Anchor bend.
And with the hitches, there's a question about relative diameter of the hitched
object: some hitches will work well as ring hitches but not so well on spar-
or pile-sized objects. Note that the two polyester-sheathed ropes slipped nearly
at the same absolute load--which makes sense, if they're relatively similar in
flexibility/compressibility; the nylon, sooner.

rate of pull: 1 foot / minute

(They mention the hi-mod cordage being stronger than steel pound for pound:
heck, way stronger; sometimes as strong per diameter!)

--dl*
====

Carrick bend
 

I am disappointed that the carrick bend did not get evaluated as it is perhaps the strongest bend to use when attaching lines together and I have used it many times without failure. This bend is easy to tie and easy to break loose even after a really strong pull and shock load.

To be sure this bend is not to be trusted below water if it will be pulled and loosened and banged around without first fastening the bittern ends to the working parts, a minor inconvenience when considering that if one must join two lines together without splicing when needing maximum strength.

How did you come to this assertion?
Most tests would show the Grapevine to be much stronger. (Hence my surprise at SAIL's.)
The Carrick is used/favored, so I hear, in the hard-laid (read STIFF) ropes used for the
big crab pots (6-800# empty!) out from Alaska; I think that Rosendahl's bend would make
a good candidate for that, too.
For Carrick-like performance (but stronger, I'd think, a little), try Ashley's bend #1425 or
1452--this latter being much more secure when slack.

--dl*
====

My disappointment at the Sail test was that they failed to reference the pin diameter. The larger the diameter of the pin the greater the load on the knot. Also the diameter of the eye formed (by knot or splice) is also important info for reference.

I worked with Brion some time ago when he was reviewing knots in HM ropes. He did a write up on the subject also.

Back to the original topic of the thread. Comparison tests are only as good as the test method used. Repeatability and consistancy of the aparatus and method is the only way to make a test that yeilds usable data. There are so many ropes, tests, reviews, experts, and final applications that it is a daunting task to consider. I have seen several good abrasion test methods and know NER had done some work with these methods in evaluating chafe of mooring pennants.

The use of PBO in jackets is for its resistance to extreme heat and abrasion. The fact that its life is not much longer than that of milk when in the sun seems of little consequence to those with big budgets and high expectations.

When it comes to bears chewing through Vectran Vs Spectra - you may want to consider if this is abrasion or shear. Spectra is certainly superior in cut resistance - but that is not abrasion. My experience has been that Spectra and Vectran are comaprable in an abrasive environment. I have never done an apples to apples test to distruction of both Spectra and vectran. Spectra will certainly have an advantage with how slick a surface it is. But again - with the testing. You would have to consider under what load such abrasion would be occurring, what braid is used for each, How rough a surface etc.

I am interested in seeing more testing. Strength loss over varying radius. Tensile breaks at varying travel rates. Abrasion of different fiber types, different braid types, different loads, different abrasive surfaces. UV Degridation. Shock loading. and so on.

Ref: Dan Lehman's comments
 

Sorry Dan, I should have qualified further the reasons for my liking the Carrick bend. This bend is easy to tie, easy to untie and strong and can be used with widly varrying diameters and types of line mixed.

The bends that you mentioned are qualified by their being confined to using lines of fairly equal diameters. The Grapevine can be a bitch to untie after it has been subjected to a heavy pull in water. I do like the symmetry, however, of those that you mentioned. I truly don't know how to choose between an Ashley #1425 and the Zeppelin or Rosendahl's bend....any suggestions?
Thanks

I've seen another way, but I tie the Carrick in the capsize-the-lattice-form way,
and with different rope types, that will be somewhat tricky. I got my numbers backwards
or my "former" lattered, but #1452--what Day got started as "Ashley's Bend"--is quite
like the Carrick but for being stronger (in some misc. testing), and more secure; it has
a few ways of being dressed/oriented, though. (Another interlocked-Overhands bend,
called "Shakehands" by Harry Asher, and now in some knots books, can similarly be
seen as a derivative of the Carrick.) #1425 can also handle mismatched ropes within
as much range or more than I'd think a Carrick could.
Rosendahl's bend presents two broad, flattish faces, with ends coming out on small
sides to these, so to speak: makes for taking knocking about abrasion pretty well.

Whizz-bang tying methods have been invented for both 1452 & Rosendahl's, both of
which impress me as too clever by half--one must mind picky details in order to get
the final effect; I much prefer to form one Overhand in rope, and then choose how the
2nd gets formed into it (to make 1408 or 1452 or 1425 or ... or Rosendahl's or ... ).

Again, on the strength of the Carrick, I've not seen much testing--just a lot of echoes
of the rumor (Ashley's?); it does not LOOK so strong to my eye, in terms of material
curves (part of the picture).

--dl*
====

Thanks Dan..
 

I'll give these a try. The knots that I use under pressure are all those that I can remember to tie easily like the usual basic ones and the butterfly, carrick, prusic and, yes, I've even used a sheepshank to shorten a line that quickly will have a strain on it and, therefore, it doesn't come undone.