Class 2 fibers being used for saddle bridges

[Brock Mayo]

Hey all,
Just wanting to start a discussion about ropes used for bridges. I’m still seeing what look to be a lot of class 2 fibers being used by some manufacturers. Due to the knotting strength loss and self abrasion issues, this seems like the wrong application to me. I’m much more comfortable using a polyester double braid for my saddle bridge.
Any thoughts?
-Brock

 

[lxskllr]

Definition of class 2 fiber and example?

 

[gf beranek]

Pray tell.

 

[Brocky]

The three basic materials in the Class II are the aramids, technora, Kevlar, and Twaron, second is dyneema and the similar Spectra, and third is Vectran, kind of cross between the first two.
Covers and cores are different discussions.

 

[lxskllr]

Polyester's the gold standard for durability, no? I'm currently using a polyester kernmantle, but a 16strand should be just as good, maybe better due to even easier inspection.

 

[Tree09]

I agree wholeheartedly, and use only polyester core stuff myself, same with hitches.

 

[Brock Mayo]

I think Brocky hit the definition of class two pretty accurately. Something like synthetic winch lines (amsteel). They're super strong, but are known to self abrade, which over time makes me think not the best application for a rope bridge that is being bent by one ring usually. The main thing is to replace the bridge sooner than later, but still surprised to see the manufacturers choosing class 2 these days...

 

[Brocky]

Dyneema/Spectra doesn’t self abrade, only the aramids and vectran to a lesser amount.

The less than ideal bend radius of bridge rings should also be in the discussion.

 

[Brock Mayo]

Interesting that the self abrasion does not affect Dyneema/Spectra. I don't know much about class 2 fibers, but I figure when I see a small diameter (10mm or less) rope bridge, it's got to have some type of class 2 core. It's interesting that most of the manufactures are making it quite the mystery as to what rope/construction their bridges are made of. I'm sure it's a bit of a marketing game, but would be nice to know more about the proprietary bridges... Petzl, Buckingham, Tree Motion?

 

[Altissimus]

I trust Buckingham ...

 

[lxskllr]

I wouldn't make assumptions based on diameter. I have 10mm hitchcord(and smaller) that is poly core. You really need to know exactly what rope is used, and they don't like advertising that. My Onyx came with Platinum Protect.

 

[WoodCutr]

whats the deal with the "no hitch cord for rope bridge" rule? I could swear I heard that a while back, just not sure where

perhaps something to do with class 2 fibers?

 

[lxskllr]

Hitchcord should be alright, but it needs to be poly core. Stuff like Beeline can self abrade, and the damage is invisible under the cover til you get a surprise failure.

 

[Bart]

Brocky, you're the man. I did work decades ago testing kevlar, spectra and vectran. Abused the bejeesuz out of them till failure, but it was moderate loading parallel lay band (flat / optimal) conditions. Kevlar fuzzed as it failed. All three really tough stuff for the size. If you respect cycles to failure and pull from service accordingly there ought not be a huge difference between them except spectra is slippery. Brings back memories. Failure cycle at 1000 lbs - bang!

 

[Knotorious]

Brocky, you're the man.

The above statement is factually accurate. @Brocky is most definitely the man. Word on the street is that he eats aramid fibers every morning with yogurt and fresh fruit (his doctor said he needed more fiber in his diet) and now his GI tract has a 24Kn MBS, but only when in basket formation. I also heard that he once told his Rope Runner and climb line to install themselves and, out of respect, they did. I was also told by a reliable source that his saws start on the first pull every single time. Not trying to gossip or anything, but he's kind of a legend.

I didn't know about certain Class II fibers self-abrading. What I do know is that the bridge that comes with Treemotion harnesses is allegedly a woven 24-plait polyester cover with a Dyneema SK75 core. So, in my opinion, that sounds pretty much ideal as far as strength to weight/diameter ratio and for a high durability cover material. Of course anything made of dyneema must be retired sooner than something made from polyester or nylon because it degrades over time. I have always used polyester bridges made from segments of climbing rope, although, I have one of the stock Treemotion bridges as my second on my current saddle, which is why I'm mentioning this.

 

[WoodCutr]

I have a pulley on one bridge of my treemotion, ring on the other, its ~1 year old and looks new (im 150# with gear, 180 if im dragging a rigging bag up the tree)
other climber has a notch sentinel with a year and a half old arbormaster bridge, just starting to show some flat spotting at the rigging plates (he is 170 with gear, 200 with rigging)

I wonder how the other climbers adjustable bridge helps with wear? one side doesnt move but the other side is constantly moving, making the wear move and maybe helping keep it "new"?
never paid attention to bridge rope types, I just stuck a rope in there and hoped for the best
samson vortex lasted me a week till I retired it, too soft and seemed to not hold up, the 16 strand is bomber, now I want to try something like a spliced 3/8" amsteel (dyneema) hollow braid, but knotted rope bridge works so well


yall got me thinking

 

[Brocky]

The above statement is factually accurate. @Brocky is most definitely the man. Word on the street is that he eats aramid fibers every morning with yogurt and fresh fruit (his doctor said he needed more fiber in his diet) and now his GI tract has a 24Kn MBS, but only when in basket formation. I also heard that he once told his Rope Runner and climb line to install themselves and, out of respect, they did. I was also told by a reliable source that his saws start on the first pull every single time. Not trying to gossip or anything, but he's kind of a legend.

I didn't know about certain Class II fibers self-abrading. What I do know is that the bridge that comes with Treemotion harnesses is allegedly a woven 24-plait polyester cover with a Dyneema SK75 core. So, in my opinion, that sounds pretty much ideal as far as strength to weight/diameter ratio and for a high durability cover material. Of course anything made of dyneema must be retired sooner than something made from polyester or nylon because it degrades over time. I have always used polyester bridges made from segments of climbing rope, although, I have one of the stock Treemotion bridges as my second on my current saddle, which is why I'm mentioning this.

There must be two Brockys on here.

This is the typical bend ratio recommendations.

 

[Knotorious]

@Brocky So then if we go back to the topic of anchor rings being used on people's bridges, would it follow the same measurements as a pulley sheave? Probably not, right? Because it doesn't represent something that moves like a sheave? Or would it? What would the idea bending radius for a half inch diameter braided rope (used for a harness bridge) be? Or does it not matter because the points of weakness are at the knot for knotted bridges. But what about bridges with spliced connections? Is it ever an issue that we use rings which produce such small bend radiuses? I mean, I know it isn't a huge issue because tons of climbers do it, but is it worth companies creating a product which produces a bigger bending radius? Or does the bridge already retain most of its strength in this circumstance?

EDIT: Or is that what a "fixed pin terminal" represents? So it would need to be three times rope diameter?

 

[Brocky]

For a bridge, the pin/ring moves across the stationary rope, a 12mm rope should have a 4mm ring, or a 12mm ring should be matched with a minimum 36mm rope, according to rope companies and others.

 

[Brock Mayo]

Good discussion! Thanks for all the info... So the Dyneema core of the treemotion bridge seems to be a good choice? Does dyneema still have a shorter life than polyester/nylon?
Is polyamide basically the same as polyester?
I'm going to start using a 3/4 inch block on my bridge to attain that perfect bend radius

 

[friedrich]

The Treemotion bridge is an excellent choice. It balances weight and strength in a lower diameter offering than what you could find made from double braid polyester. It has a 24-strand poly cover and Dyneema SLK75 core. It comes with the ends melted to perfection and with the first inch and a half of each end sewn with a bar tack to prevent anyone from neglecting to leave enough tail in their knots.

Dyneema must be retired sooner than nylon or polyester.

Polyamide and polyester are both good materials for strong outdoor equipment. Here is a breakdown of some of the characteristics of both and the differences between each one...

Polyamide vs Polyester: Which One Outweighs The Other? – Banner Mattress

www.elkieark.com

Using the 3/4 inch block certainly can't hurt! Good for you for taking heed of recommendations for bending radiuses! It may be unnecessary, though. But just because it is unnecessary don't mean it isn't better. Theoretically, this should increase the strength of your bridge if you have spliced or sewn eye connection points at both ends. If you have spliced or sewn eyes on your bridge, then this will preserve close to the full strength of whatever cord you use for the bridge. If you have knotted ends on your bridge, the 3/4 block might not help anything since it is likely to fail at the knots already at 50% of MBS.

Also, your mustache is incredible. I approve!

i believe a 3/4 block on your bridge might hurt quite a bit

 

[Eric H-L]

i believe a 3/4 block on your bridge might hurt quite a bit

If you have a long bridge it might crash into your knees walking around before the climb. If you had a medium bridge it might bruise your thigh. If it was short…

 

[lxskllr]

At <$2/ft, I don't think it's worth worrying much about bridges, unless you buy the "official" bridges from the manufacturers. There isn't a lot of point in that. Much of this gear is fabricated on the fly by the user, so I don't see the logic in getting precious about the bridge. Doesn't even have to cost anything if you use pieces of old climbline. 16strand is bulletproof, and easy to inspect. A poly-poly, or poly-nylon kernmantle is bulletproof, smoother, and almost as easy to inspect. Replace it often. If you think it looks worn, change it out. Bridges cost less than harborfreight gloves.

 

[lxskllr]

Depends on the rope. How was it used? Why was it retired? Maybe you don't want to use it. Not like I'm climbing professionally, but I'd absolutely trust any of my lines as a bridge. If one isn't comfortable inspecting gear, they may be in the wrong biz. It isn't hard, and doesn't take long to inspect a few feet of rope.

edit:
I have in my hand a piece of 16strand that started as a lanyard, became a friction saver, then got cut by saw. It got cut at what looks like a perfect length for a bridge, and one day it'll be a bridge. I absolutely trust it cause I know how it was used.

 

[lxskllr]

You inspect the core by feel. Does it have weird bulges? Hollows? Is the cover doing something weird? Unless you've put chemicals on your line, polyester and nylon wear in predictable ways, and in the case of kernmantle line, hardly wear at all with an intact cover. As always, YMMV. I do what I do, and others can choose to follow or not, but it'll definitely be a cold day in hell before I pay $30 for a piece of rope blessed by a manufacturer, when I can buy the same rope for $6(being very generous on the high end here).