The updates:
I stopped by On Rope 1 and showed Bruce the pics and graphs. Two things came up:

1- The melting point of Technora. Bruce had some 5mm 'tech cord' which is a Technora core with a nylon cover. We went to the back with my Bee-Line cover (75% Technora and 25% Polyester) and he found a short length of Tech cord. He first put a piece of nylon webbing under his hot knife and it melted through it like the proverbial hot knife through butter. Then he did the same with the Tech cord. It instantly melted through the nylon core and just sat there. I demonstrated how a cigarette lighter would melt a Technora strand in the Bee-Line cover. He put the Bee-Line cover under the hot knife and it just sat there not doing anything. He stated his knife was at 1200°F!

But, there's more to it than appears. The spec I looked at (http://www.teijinaramid.com/smartsite.dws?id=91) says, "...Thermal decomposition threshold of 500ºC (932°F), so Technora can be used at 200ºC (392°F) for long periods. At 250ºC, (482°F) it maintains more than half of its room-temperature tensile strength." If I understand the implication of this, it says that Technora's strength diminishes dramatically at elevated temperatures, i.e. 482°F it's retains half its tensile strength. I suspect it's a proportional thing as well. I.e. as the temperature goes from room temperature to 480°F the strength goes down somewhat inversely proportionally.

2- A of the natures of aramid fibers: as I understand it, aramid fibers are self abrasive. That suggests that when aramid fibers are used in knots and splices, they deteriorate just by rubbing against one another. This would imply that the tensile strength of aramid fibers deteroriate with use.
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The following answers are based on recent tests performed on 8mm Bee-Line on a 20,000 lb tensile testing machine. The tests in most cases are a single test of one knot or splice, in some cases two and even three samples were tested. So…

The following answers/opinions reflect what happened, and cannot be used as statistical samples or testing. These answers/opinions are for information/discussion/entertainment only and no claims of safe or unsafe operating conditions are implied or suggested. Each can form his or her own opinions and conclusions about how the data/tests should be used and applied.

I make no claim that the results/data/opinion, et al, are accurate, scientific, rigorous, nor exhaustive. Use at your own risk.

1. A- 8000 lbs – basis: manufacturer and distributor catalog specs. This parameter was not tested.

2. Believe it or not the most accurate answer is 350°. Basis: The core is Vectran, spec’d at 900°. The cover is 75% Technora and 25% polyester. The maximum operating temperature of technora is about 350°. Hunabku looked this up on the web for me. Polyester, according to Bruce Smith at On Rope 1, starts to go ‘plastic’ at about this same temperature.

3. D. about 4500 lbs or about 56% of the spec’d tensile strength of 8mm Bee-Line Basis: Two tests, both eye-to-eye locked brumels, Hunabku whipped and stitched his I did not. Both had between 6” to 7” tail tucks. Here are the charts of the tests and pics of eyes.

The X axis is extension in inches, i.e. how far the machine has pulled.

Hunabku’s splices:

Hunabku’s graph:

My splices:

My graph:


Kinda far from the impression one might have of splices in Bee-Line. Notice in Hunabku’s graph, the splice slipped slightly at 600 lbs and slippage and recovery increases almost proportionally to loading until a load of about 4500 lbs is reached where it abruptly drops to about 1300 lbs. More after we look at the graph of my splice

Notice in my graph, my splice shows the first very slight sign of slippage at about 1100 lbs. Remember my splices are not whipped or stitched. In a similar fashion to Hunabku’s splice, slippage and recovery continues and seems to be proportional to loading. But my no whipping-no stitching splice holds up to almost 5800 lbs before it essentially fails catastrophically. However, even at the recovery point it is still supporting a bit over 300 lbs.

It is extremely interesting that both charts reveal numerous cycles of strong recovery from a significant slip/failure. When Hunabku and I examined his splice, it looked like the cycles were influenced to some degree by stitching. It is unclear whether the stitches are popping loose or the stitches are ‘cutting’ some of the Vectran fibers.

4. B, 5. A or D - The cover is about as strong as the core – surprised? I was, but Hunabku pretty much had this one nailed. He’s said all along there had to be a lot of strength in the cover and he was very right! The reason I put A or D for number 5 is that the rope broke at about 5600 lbs because of the splice, but the splice itself did not fail or slip for that matter. Basis: See for yourself:

As shown in the pic, this is simply a length of cover with the core completely removed and tucked tails between 6”-7” long. There is a light whipping and this pic is after the sample was tested:

The eye:


The failure:


The graph:


First, the little glitch at about 1.3" was due to a fixture shift and not cover splice slippage. Notice the stretch profile as I believe this has significance to knots. Pretty impressive that a simple tail tuck in the cover held to right at 5600 lbs!

The failure is extremely interesting as how and where it failed. The failure occured at what appeared to be the middle of the line! Hunabku noticed an interesting thing though: the cover broke exactly where the untapered tail ended. I don't believe that's at all viewable in the pic because you have to manipulate the line to see what happened. I had tapered one tail and for some reason I didn't the other. I may rerun this test with well tapered tails - it should be be even stronger. BTW, as best as I can tell, neither splice slipped at all and this thought is also supported by the graph. Notice there are no slip/recovery indications in the graph.

6. D. – Another surprise? I was surprised and disappointed. The scaffold hitch failed at about Like every other knot/rope I’ve ever pulled to failure, the failure occurred right where the loaded line enters the knot; in nearly 50 pulls I have never seen a failure in the eye, even with less than 1:1 ratios. Ratio in this context is the ratio of the diameter of the rope to the diameter of the device the eye is attached to. E.g. I did a number of pulls of 1/4" rope using a 3/16” screw link; the eye still wasn’t the weak point.

Anyway here is the scaffold hitch and failure:


Here is the graph – you can form your own opinions about this:

It’s probably helpful to note that a lot of the extension is due to the hitches (one on each end) drawing up.

7. D – Well, another disappointment – failure of an 8000 lb line at about 3000 lbs. While 3000 lbs is more than sufficient to provide a safety margin of over 10:1, the disappointment is that it fails far below (about 38% of the published tensile strength of 8mm Bee-Line) the 60% (4800 lbs) typically claimed for the bowline. Hunabku offered an opinion that I concur with – the Vectran is an armid fiber and is self abrasive. It’s very likely destroying itself under the pressure produced by the load.

Here’s the knot and failure:


And here’s the graph:


BTW, the reason there’s no bowline in one end of the line is that I told a buddy watching the test that which ever bowline survived that he would likely be able to untie it without a lot of trouble. He put my claim to the test and easily untied the bowline after it had been subjected to a 3000 lb load!!!!

8. D – Similar to the bowline with the tail inside the eye. It failed at about 2900 lbs

The knot and failure


And the graph, once again you can form your own opinions on this thing????


I think this puts to rest the idea that bowlines slip and indicates that it doesn’t make a lot of difference whether the tail comes out inside the eye (classic form) or outside the eye. I tend to use the outside on footloops etc.

9. Well, I may have discovered a mess up on my part. I have two samples we tested – one was single brumels whipped in both ends with 6-7 inch tail tucks but somehow I didn’t seem to make it home with the data for this test. So if I may, I’ll defer to a locked brumel versus a tail tuck that I do have data for.

Here’s a graph of the data – remember this is a lowly tail tuck with modest whipping only for security:



Looks to me like the tucked tail faired about as well in maximum strength as the locked brumel in previous tests. I don’t believe any other splice or knot made it to 5800 lbs. Of course, again, there’s the issue of what might happen if the load was constant instead of dependent on the machine’s essentially static position.

My personal opinion based on what Hunabku and I have seen and discussed, it looks like the winner is the locked brumel without stitching. The stitching seems to detrimentally affect the strength of the splice.

In some of the failed samples, it appears to me that perhaps a longer tail tuck, 7 – 8 inches would increase the strength of the splice.

But remember – this is all experimental, opinion, and the tests are by no means conclusive or exhaustive. HENCE, you are own your own as to how you use these results. The one thing I think is safe to say is that splices in Bee-line are not as strong as we might think!

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A word about knots, hitches, splices and tensile machines. The tensile machine I used cannot replicate an actual free weight on the rope. E.g. the machine applies force by moving the upper beam upward, hence applying force to the rope. As soon as a knot or splice slips, the load is greatly and abruptly decreased because the machine cannot, nor is it designed to try, to move nearly fast enough to maintain a constant force. A free weight OTOH, would apply a constant force and since the force would be constant, the knot/hitch may not recover as it did on the machine. However, in actual applications, the rope, hitches and knots should never experience such high loads as produced by the tensile machine. But if a fall produced say a 3000 lb force in the rope, there is reason to wonder if recovery is possible.

But the second reality is, if a fall produced a force of 3000 lbs, it wouldn't much matter whether you hit the ground or not; the shock to your body produced by a 3000 lb force would likely be fatal in itself.
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A question, where is failure indicated on the graphs, I'm seeing all of the peaks and valleys (representing load and slippage over time?), when does failure occur?

I'm not a fan of using 8mm Beeline as a single leg open split tail. A rope of similar diameter and construction to the climbing rope (if it is not a static) works great for this application. In a closed split tail the load is distributed across both legs so even at the lowest quoted break figure (for scaffold hitch, splice or cord) capacity is still equal to or over 15:1 (to working load).

I'm puzzled as to why anyone would spend the money on expensive cords like Beeline for an open split tail when the same diameter (as the main climbing rope) polyester arb rope is quite safe and probably performs better (smoother grab and release).

I'm probably in the minority here but I don't like splices on my closed split tail, the bury doesn't allow me to optimally tune my hitch, especially in the length department. Shorter overall length from harness attachment to the top of the friction hitch is what I'm looking for.
-moss

Just a point of clarification here: I think the issue with the Bowline is as a harness attachment point, when it is unloaded it can loosen, as happened with the climber who fell and mangled his arm. Don't think anyone has ever said the Bowline fails by slipping in a pure loading scenario. The Bowline is backed up to prevent it from loosening and failing during an "unload/reload" cycle.
-moss

Excellent question. I have a definite answer - I'm not sure . But, referring to the first graph (locked brumel splice), I would have to consider failure at the first major, sudden drop on the graph - at about the 0.75" extension mark. The prior slippages are almost too small to classify as a failure. But, the first major failure (at 0.75") may be catastrophic under real load conditions. Meaning that if a continuous force of about 4400 lbs were applied the splice would have failed completely. I'm pretty sure what's happening is a 'failure' allows slack which unloads the line ON THE MACHINE and gives it a chance to recover.

Then again, how would we ever get a 4400 lb load on a line while climbing or falling for that matter.



I understand. The data, etc. is not intended to endorse any kind of climbing method or system, but rather to report what happen as force was applied to Bee-Line in various configurations under controlled conditions. I don't and don't know of anyone that uses Bee-Line in a single leg open split tail, although I suspect it is used that way.


Well, again, the test results have no implications about how the Bee-Line should be used. For the most part, it is my impression that Bee-Line is most often used in a closed split tail for DdRT.

Two things have emerged from these tests, and one, the maximum operating temperature (about 350°F) of the cover was discovered independently from the tests. The other is that although 8mm Bee-Line is rated at 8000 lbs, there is no practical way to capture that strength because of the dramatic reduction in strength due to knots and splices. I'm convinced as Hunabku opined, that because armid fibers are self-abrasive, the fibers self destruct in knots and splices under heavy loads, thereby reducing the useable strength of the Bee-Line to something close to 8mm nylon accessory cord both in strength and temperature. The only difference would be that Bee-Line doesn't have anywhere near the stretch that nylon does.


I don't know about being in the minority, but I too have noticed the trade off between spliced split tails and knotted split tails. The splices take up much less room on the terminating carabiner, but the tails do extend up the line further and could interfere with the grip, etc. But, Hunabku has one Bee-Line split tail that has overlapping tail tucks and it offers no slippage in anyway.

OTOH, knots do take up a lot of space on the terminating carabiner, but don't otherwise interfere with line wrap etc.

BTW, one of my applications for Bee-Line is, and maybe was, as an extension tether from my upper ascender to my harness in a Texas SRT system. In this application the splices have a distinct advantage over knots. I actually have a locked brumel splice directly to the hole in my ascnender and the other end is connected directly to my pear screw link on my belt. Not only is that configuration more compact, it eliminates two carabiners. Oh, the core at both ends is protected by a 1/2" nylon sleeve in the eye.

Other than this one case you refer to, I'm not aware of bowlines failing under any conditions. In his book, Bruce Smith, endorses the use of bowlines on long descents and reports of no failures of bowlines under any conditions.

I do agree that it is theoretically possible for a bowline to release under the right conditions of slack. I have tried numerous times to simulate a failure due to slack and have not been able to except by very extreme manipulations. However, bowlines are not as secure in some types of rope as it is in others. E.g. I would be reluctant to use a bowline in PMI EzBend, yet Bruce endorses the bowline and cavers typically use PMI MaxWear rope which is stiffer than EzBend, and Bruce does not use backups on knots.

When I use a bowline, which is quite frequent, I do use the mountaineer version, but I'm not sure why.

The 6mm tech cord tied into a sling (double fisherman's) and girthed onto the ascender (and harness) is also excellent for this use. Takes a little getting used hanging on this skinny stuff but the 5000 lb. rating is reassuring, especially doubled in a sling. As I've mentioned in the past I rounded the cross-section on the attachment point on my Petzl Ascencion with moldable epoxy to minimize the chance that the ascender would cut cord on a shock load. I've climbed many hours on this system and have seen no wear on the sling cord from the ascender. The advantage of the girthed attachment to the ascender and harness is easy on/off removal and separation of components and no hardware between the ascender and harness attachment point. One of the skinny high strength webbing slings will also work but it can be difficult to find a length that's right for your arm stroke, and the webbing is a little more bulky than the tech cord.
-moss

A visiting arborist traveling without gear climbed with me on gear that I provided. They normally terminate their 1/2" 16-strand arborist rope with a Bowline tied to the carabiner attached to their harness. They tried this configuration using my 11mm Fly and immediately rejected the the Bowline. It would not set tightly enough. Bear in mind that for tree climbing it is desirable for the bight to grab the carabiner tightly so that the eye won't slide and cross the gate. In caving this would not apply. I think that a Bowline with a larger bight can be tied safely in most ropes.
-moss

New England's Tech cord, it's available in 3 & 5 mm would be good for my application, although I'm trying to avoid using a loop or sling. Loops seem to be prone to becoming 'involved' in other lines and gear, hence my reason for a single line of Bee-Line. That plus Bee-Line can be easily spliced to minimize bulk at the termination points. Beyond that, the 5mm, 5000 lb Tech cord should be sufficient as a single line tether which would also avoid a loop, and a compact, protected knot at the ascender wouldn't be a problem, and maybe an anchor hitch or scaffold knot at the harness wouldn't be too much bulk with 5mm line.

Looks like a Tech cord test will be coming in the near future - stay tuned. know a good place to buy Tech cord?

I like the easy-on/easy-off of the setup you described.

That's right, it's only 5mm. I like it doubled just for the good redundancy of it all and the sling allows the girth attachment. I still try to keep all my life support stuff up in the 5700 kn or better range.

I climb through some pretty tight situations in conifers with it and haven't had any trouble getting the sling hung. I'd just Google it until you find the best price, I buy it from a different source each time based on best price.
-moss

You meant 5700 lbs perhaps?

I'll probably give it a try, depending on what it costs. Samson's Ultra-Tech looks pretty good too.

Yep, 5700 lbs is what I meant.
-moss

Ron,

Many thanks for your efforts. As you know I think some very valuable information is coming out of your research.

I'm going to stop stitching my eye spices for one. It is just fastenating to me, to see such a strong cord fail at such low forces when it is manipulated.
I think Ron and I both agree that B-line is great stuff. I love it and I hope no one thinks the intention of this report is to discourage the use of B-line. I highly recommend it.

I have a much better understanding of the limitations of aramids now, though. Altough they are extremely strong and light they lose much of those benifits under practical use.

The test of the cover only blew my mind. Even though I have always maintained that the cover had to be some pretty stong stuff, I didn't expect for it to have the fairest curve of all the plots.
It is amazing to me that the spliced cover alone had almost twice the strength of the scaffold knotted complete cord. To me that is testament to the self abrasive nature of these fibers.

This gives me all sorts of ideas for what to do with all the extra cover I end up with.

Keep up the good work Ron!!!

Agree with Hunabku, great work.

Now that I've had time to re-read the post and study and absorb the charts I'm starting to get what's happening during the tests. Each peak on the graph represents maximum load, the valleys represent slippage but not failure over multiple recovery cycles until total failure occurs, except the spliced-eye cover test where theres is a gradual increase to max load then failure. Also the scaffold knot test has a similar curve though as indicated it's probably because of knot slippage on both ends of the cord.

Ideally it would be good to isolate the bowline and scaffold knot tests to just one knot on one end of the cord.

I'm not a splicer but I thought the the question of whether to stitch or not had to do with the stability of the spliced eye when not under load. I thought the max load difference between a stitched vs. the unstitched eye was acceptable considering the tradeoff for a more secure splice when not loaded. As long as the climber is maintaining a high ratio of (theoretical) failure load to working load for the use of the eye all is good.

Not that Ron has unlimited time and materials to refine these tests... here's what I'd like to see tested:

Pull test of 8mm Beeline in a closed split tail configuration on a 11mm 24-strand arb rope. Maybe test with 3 of the commonly used hitches using scaffold knots and a spliced eye. Would be very interesting to see where failure would occur. I suspect that the Beeline/hitch combo wouldn't fail but would slip on the rope (not a bad result if that's what happens). To simulate a "real world" DdRT rig you'd want to include both legs of the climbing rope in the system being tested.
-moss

Thanks guys, it's quite interesting and enlightening to do tension tests.

Just to confirm Hunabku's thought about the purpose of the tests and Bee-Line - I love the stuff. I have some reservations about using it as a single line tether as I have been in a Texas system, but that resevation is not due to the pull tests but due to the nature of aramid fibers being self-abrasive. I don't see even that as a problem when Bee-Line is used as a split tail since the load is shared by two legs of Bee-Line and two splices/knots.

I'll be back at school for the Fall semester about the 15th of August and after I get through the first week of administrative obligations, I should have about a week before classes start that's a bit slower and I can do some more tests. One of the first tests I'm gonna do is about 200 - 300 cycles of loading to 220 lbs and fully unloading. Then after the cycles are complete, I want to pull the test specimen to failure. The purpose is to see if cycling, e.g. using it as a life tether in a Texas system, gradually weakens the cord. We've already seen what non-cyclic loading does so we have something to compare to.

Probably the next thing I'll do is what moss suggested - pull a friction hitch on a climbing rope. I think our tensile machine has just enough travel to handle a very short 'climbing' rope. I won't be able to simulate a full DdRT rig, for one reason because I won't be able to simulate the limb radius and the sleeve/limb friction. But, I figure what we are really looking for is where the friction hitches start to slip or destroy something and I can measure that. Now all we need is some short pieces of climbing rope

BTW, for friction hitches, I thinkin' a Schwabisch, Distel, and a Valdôtain, if the machine has the travel to handle the Valdôtain. As I recall, it stretches out some.

And a comment about the test results:
1- the tests were high loading, pull-to-failure tests. Hence all the loads were way above normal climbing loads.

2- The failure modes are what happened at the very high loads.

3- No conclusions can be made about the effect of cyclic loading at low loads, i.e. 200-250 lbs.

4- According to Bruce (On Rope 1), when he examined the graphs they were pretty much what he expected! He stated that some of the early slippage, i.e. 600 - 900 lbs, was likely due to knot take up and setting under loads that could not be realized by normal knot setting means. He also stated that much of the recovery was realistic, i.e. the cordage/knots slip, and do actually recover.

5- My observation: once there is give in the rope anywhere, the load will be reduced simply because the distance between the terminating points on the machine is essentially the same, but due to the slippeage, the rope between the two terminiating points is longer which can dramatically decrease the load and even look like a complete failure, when in fact it may not have been. If the same tests were performed with actually weights, slippage would still occur, but the 'unloading' due to the increased length of cord would not produce the same unloading as it did on the machine because the load would still be applied. The bottom line is, it is very possible that those deep unloading points are not failure in any sense, but simply the inability of the machine to keep a constant load on the line when it slipped. Of course the opposite is true too. It may be that if and actual weight had been used, the knot would not have recovered and may have failed catastrophically. But again, these are mostly at very high loads.

beelines....total rip-off. i bought an eye to eye prussik and i burnt it within 30 climbs. i have about 5 of those generic yellow ones from sherrill and they all are still solid....and half the price.