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tradmanclimbs
Sep 1, 2005, 5:14 PM
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I just bought a spool of 5mm maxim spectra cord to tie off forged friends with. the info provided with the cord recomended tripple fisherman knott for maximum strength . It did not say that the doubble fishermans was not recomended it just said that for full strength to use the tripple. I promptly decided that the tripple is too bulky for this aplication. Tied off a loop of 5mm with doubble fishermans, fired up the 83 F150 plow truck and had a quick test. wrapped a tow strap arround a tree, tied a few figuer eights in some retired 8.6mm beal doubble rope lead line. the lead rope attached to the tow hitch with figuer eight, the loop of 5mm spectra in the middle attached to the lead line and the tow strap with old retired chiounard light D biners. Promptly broke two ropes with this set up and have full confidence in the doubble fishermans for this aplication. The doubble knott even though it makes a sharper bend than the tripple is obviously pleanty strong enough to break lead rope without faliuer of the spectra.. so it is certainly stronger than most cam placements and in my OP satisfactory for the aplication.
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dudemanbu
Sep 1, 2005, 5:22 PM
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gotta love experimental data. Thanks a bunch.
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veganboyjosh
Sep 1, 2005, 6:01 PM
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In reply to: fired up the 83 F150 plow truck and had a quick test. In reply to: some retired 8.6mm beal doubble rope lead line In reply to: the tow strap with old retired chiounard light D biners In reply to: The doubble knott ... is obviously pleanty strong enough
obviously.
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glowering
Sep 1, 2005, 6:02 PM
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FWIW I think the triple is recommended because spectra is more slippery than nylon. So it's not strength that's the factor but the knot slipping or coming undone. So if you do use this knot tighten it with as much weight as possible (2 peop's body weight?) and keep an eye on it to make sure it stays tight.
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mcfoley
Sep 1, 2005, 6:03 PM
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I think the trippled knot is reccomended because spectra is more "slippery" and rigid than standard cord, so it has more of a tendency to untie over time.
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vegastradguy
Sep 1, 2005, 6:13 PM
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In reply to: I think the trippled knot is reccomended because spectra is more "slippery" and rigid than standard cord, so it has more of a tendency to untie over time.
correct. cyclic loading on the double fishermans on spectra cord can loosen more quickly due to the nature of spectra.
keep your tails long and inspect frequently and you should be fine.
personally, though, i do use a triple fishermans, because following the recommendations of the manufacturer usually gets you a better case in court should you have to sue.
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g_i_g_i
Sep 1, 2005, 7:09 PM
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I suggest reading http://www.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf
according to the experimenters, the mechanism of failure is different between a double and a triple fisherman knot: what breaks in the double fisherman knot is the sheath, and when the sheath has broken, the core slips through the knot. The sheath can get tensioned and be close to rupture even if you don't see the knot get loose, or the tails get progressively shorter, so I'd suggest to always use a triple fisherman.
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tradmanclimbs
Sep 1, 2005, 7:12 PM
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They actualy recomened either a doubble fishermans, figuer 8 or tripple fishermans. then they state that testing has shown improved performance with the tripple fishermans. the wording led me to belive that the concern was the fibers in the tech cord are weaker when bent at sharp angles. I did notice some slippage in my red neck test.
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slobmonster
Sep 1, 2005, 7:49 PM
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In reply to: I did notice some slippage in my red neck test.
Hope you're well, Nick.
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climbingeek
Sep 1, 2005, 8:21 PM
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This is merely a variation on the idea conveyed by g_i_g_i:
A couple years back, Todd Vogel and Alan Jolley went into the Bluewater lab and tested high strength cords. A double-fishermans was not strong enough in Spectra (Titan, etc.) to prevent the core from backing itself out of the knot. Once the core backed its way out, the sheath promptly broke.
The triple fishermans knot did not exhibit the same failure.
NOTE: Spectra and "Maxim Tech Cord" are quite different (including diferences in materials, diameter, heat dissipation and handling characteristics). Vogel & Jolley's test did not include Tech-Cord.
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climbingeek
Sep 1, 2005, 10:56 PM
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Thanks g_i_g_i for the link. That article on high-strength cords was super informative!
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tradmanclimbs
Sep 2, 2005, 4:50 PM
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Gigi, In your labrotory test they pull the tech cord to failuer. In my redneck test I put the tech cord into a system much as it would be used in actual climbing. the doubble fisherman knott was NOT the point of failuer in my test. the climbing rope broke before the knott had a chance to fail. In a real life climbing application used as a gunks tie off, the cam placement would possibly fail , the chances of generating enough force to breake the climbing rope are nill as well. my conclusion is that your recomendation to allways use a tripple fishermans VS a doubble has little merit in the world of actual climbing.
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sixleggedinsect
Sep 2, 2005, 5:11 PM
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while we're on the subject:
i also reslung a couple cams with one of the techy cords. forget which one, but id like to say 5.5 dyneema. its a thin purple-looking cord (speckled blue/red/black, IIRC) that ive seen around a lot.
what is the word on the street for the appropriate amount of tail for these cords, assuming triple fisherman weighted to body-weight.?
id like to keep them as short as possible to reduce the bulk and catchiness, but dont wanna' kill myself.
thanks,
anthony
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tradmanclimbs
Sep 2, 2005, 5:58 PM
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I only tested the maxim tec cord and I did only break 2 ropes. I used 1.5 inch tails on the test that I did. and that was barely sufficient. the cams that I slung I left 2" tails. Place cam in bomber placement then vigerously bounce test with static spectra daisy. that should set the knott fairly well. I will most likely re test soon.
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catbird_seat
Sep 2, 2005, 9:26 PM
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If you decide to use the double fishermans knot, rather than the triple, you can do the following. Buy some waxed nylon cord, or what sailors might refer to as "marline". Put a 1/2" long seizing on the tails. You are basically locking the tails so they can't slip. This would be as strong or stronger than the triple knot.
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papounet
Sep 4, 2005, 11:03 PM
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Dear tradmanclimbs,
Your red neck tests do not address the 3 issues with aramid fibers:
low resistance to cyclic loading
sliperiness
fiber cross-cutting.
(manufacturer have lessened the sliperiness and have almost negated the uv- issue by protecting the aramid fibers within normal nylon.
You did break twice a old double rope used as a single (as far as i understand your setup). a good start...
Tom Moyer tested many more setups many more times. His tests demonstrates that the tech cord are the ones that suffer from the worst degradation of peformance when knotted. The french cavers association just published exhaustive tests on dynema 5.5 mm cord. (I published the links some weeks ago).
The issues with those fibers does not occur during the first tests.
a/ Knots come undone when repetadly loaded and unloaded
b/ a cord tied/united several times becomes noticebly weaker
c/ small radius knots cause fibers cross cutting
(which may be of concern if you pass the cord through the hole in the stem a forged friend),
d/ knots done with high-tch cord may miss the dynamicity provided by the elasticity of simpler material and the tightening of the knot, which in turn mays cause failure in brutal shock loading.
In other words, I am no convinced that your tests represent the conditions in which the cord will be used.
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tradmanclimbs
Sep 5, 2005, 1:14 AM
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i do agree that only two tests is not enough. As for representing the actual in the field use my red neck tests are a whole bunch more realistic than any of them darn labrotory geek fests :roll: They use maqchines to break their shit but none of em ever think to use actual climbing rope. It don't mean phooey if you break the tech cord with a darn machine. when was the last time you took one of them there gear breaking machines climbing? Now most of us do take a pickup climbing so I got you beat on that one without even gitting started 8^) I regulerly logg with old climbing rope and test all kinds of stuff like knotts and such. One thing I have learnt is that if you really yard on a rope with an F150 there ain't no knott made that yoiu can undoo without a knife. That leads me to belive that if you ever experience a factor 2 fall you better have a knife handy even if you do tie in with a pansy assed bowline :twisted: The thang that makes my red neck tests more accurate than Geek tests is that I put old biners and rope in the system. Any old geek can break Tec cord with a machine but can you break it with a pickup and old biners and climbing rope? If the old biners or rope breaks before the tech cord then your test is a moot point. The chances of the actual gear placement ever being subjected to the same forces is zero therefore your geek test don't mean shit :D Next test I will use 10.6mm marathon! That el be a hoot :twisted: Hope I don't blow a clutch :?
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jimdavis
Sep 5, 2005, 5:07 AM
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In reply to: i do agree that only two tests is not enough. As for representing the actual in the field use my red neck tests are a whole bunch more realistic than any of them darn labrotory geek fests :roll: They use maqchines to break their s--- but none of em ever think to use actual climbing rope. It don't mean phooey if you break the tech cord with a darn machine. when was the last time you took one of them there gear breaking machines climbing? Now most of us do take a pickup climbing so I got you beat on that one without even gitting started 8^) I regulerly logg with old climbing rope and test all kinds of stuff like knotts and such. One thing I have learnt is that if you really yard on a rope with an F150 there ain't no knott made that yoiu can undoo without a knife. That leads me to belive that if you ever experience a factor 2 fall you better have a knife handy even if you do tie in with a pansy assed bowline :twisted: The thang that makes my red neck tests more accurate than Geek tests is that I put old biners and rope in the system. Any old geek can break Tec cord with a machine but can you break it with a pickup and old biners and climbing rope? If the old biners or rope breaks before the tech cord then your test is a moot point. The chances of the actual gear placement ever being subjected to the same forces is zero therefore your geek test don't mean s--- :D Next test I will use 10.6mm marathon! That el be a hoot :twisted: Hope I don't blow a clutch :?
Three words: Git 'er dun!
I think both of those tests are helpful in learning about how the stuff works.
When you really start worrying about whether something breaks at 25 or 26kn, that's when I stop caring.
SO...replace the shit if you take several good whips on it, tie a tripple fishermans, and call it good.
Cheers,
Jim
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tumblemark
Sep 5, 2005, 9:35 PM
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Before all y'all science guys get too far out on the gang plank, be aware that yer throwin' around fiber factors fast 'n loose.
Maxim 5 mm Tech cord is made with interior fibers of Technora (an aramid) and a sheath of polyester. There's no Spectra in it.
Spectra (same thing as Dyneema) webbing is made by combining UHMW polyethylene fibers with nylon (polyamide) fibers; 'cept probably Mammut's new 6 mm (yes 6!) slings don't have much nylon.
Spectra/Dyneema and Technora are not the same fiber and they have very different properties when it comes to flex/knotting resistance, temperature resistance, UV resistance, etc, etc.
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tradmanclimbs
Sep 6, 2005, 1:11 AM
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I Like jims analogy about splitting hairs and gitting your panties all in a bunch over a kn or 2. I did crank er up this morning and went ahead and broke a good sized chunk of 10.6 marathon rope. That is one burly rope guys and gals so I ain't too worried about my system. I will have way bigger worries than the integrity of my gunks tie off if i start breaking rope that beefy without my plow truck :shock: I had a loop of the maxim 5mm tec cord tied with a doubble fishermans vigoursly tighted by bouncing in aiders while attached to a pull up bar. The same two 19 yr old bail biners were still in the system. The doubble fishermans did just fine and broke thet thar rope sweet as can be. allmost no slippage this time
8^) gotta love that ol ford 8^)
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cracklover
Sep 6, 2005, 2:06 AM
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I reslung all my hexes and my forged friend with 5.5mm high-tech cord.
I used triple fishermans, and neither I nor any of my partners have ever noticed it being too bulky. Whats the matter - you got stingy and didn't buy enough cord? ;)
But now to the important question - how do you get your pullup bar to stay up for much more than bodyweight. I can't do even a moderate bounce test on mine without it dropping me on my ass!
GO
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papounet
Sep 6, 2005, 8:36 AM
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In reply to: Before all y'all science guys get too far out on the gang plank, be aware that yer throwin' around fiber factors fast 'n loose. Maxim 5 mm Tech cord is made with interior fibers of Technora (an aramid) and a sheath of polyester. There's no Spectra in it. Spectra (same thing as Dyneema) webbing is made by combining UHMW polyethylene fibers with nylon (polyamide) fibers; 'cept probably Mammut's new 6 mm (yes 6!) slings don't have much nylon. Spectra/Dyneema and Technora are not the same fiber and they have very different properties when it comes to flex/knotting resistance, temperature resistance, UV resistance, etc, etc.
As I posted in an earlier thread, technora is of the aramid family. It has improved fatigue resistance over kevlar (once thought the magic can-do-everything man-made fiber).
Tests published this June 2005 by the french cavers' association in both static and dynamic situations of 5mm dyneema cordelette new and old
in french
http://perso.wanadoo.fr/misch/spelehautjura/dossier/dyneema.htm
http://www.ecole-francaise-de-speleologie.com/get/dyneema/dyn.htm
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tradmanclimbs
Sep 6, 2005, 1:04 PM
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slung hexes and gunks tie offs are two different animals. with the gunks tie off you need room for your fingers in the crack when you are cleaning the cam. also I never tied a tripple before as I never had a need to. the doubble has worked just fine for as long as I have been climbing. 22yrs. My tests show that the doubble still works just fine.
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