1/2in Stable Braid vs True Blue

Matt J Leppek

Matt J Leppek

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Which do you think has the higher WLL? True blue with the stretch, or stable braid with the superior tensile?

I think true blue will have better WLL for negative rigging, but personally I'd rather take it a bit smaller and know that a bit of stretch isn't going to get intimate with a house.
 
The WWL is just a percentage of the tensile strength which isn't effected by how much each stretches.

If both are used with blocks the stable braid would be stronger.

Using crotches, the true blue would be the better choice.
 
I'm not to sure. This question originated with a conversation with my old boss. He believes true blue is a stronger rope because of its stretch, and that stable braid will fail before true blue would in negative rigging. I disagreed with him at first, but I think it does hold some ground. When the rope stretches it dissipates some of the force, where stable braid has nearly no stretch to it, absorbing the full impact on the rope and rigging point.

I thought of it like locking off the porty with stable braid, and letting it run was the true blue equivalent.
 
The true blue may stretch longer but it will only do so to it's breaking strength of 7,300 lbs. The stable braid breaks at 10,400 lbs without stretching as much.

Stretching doesn't add strength it's a characteristic of its construction.

To be clear are you talking about natural crotch or block rigging?
 
I'm talking about block rigging.

Originally I believed similarly to what you stated Brock, that the stretch only effects the rope up until the breaking strength. My boss is generally very knowledgable about rigging forces, so I didn't want to disregard what he was saying, though I had my doubts (which is why I posted here).

Thanks for the responses so far!
 
I think if you are looking at stable braid vs dynasorb or similar you will find more "cycles to failure" with the dynasorb. Not sure how that applies to two almost completely different ropes like 12strand vs double braid. I think each has its own set of uses and comparing the two is a bit apples to oranges.
 
In pull tests true blue may elongate more before breaking at 7300 pounds but stable braid breaks at 10,400 lbs. There's no doubt that stable braid is stronger. Now, in real life rigging scenarios, true blues stretch or elongation may be a more appropriate choice when blocking down to reduce forces on the standing stem as long as the pieces are not heavier than the rope can stand...
I'll take a good rope man and stable braid over true blue any day.

Reed Wortley
CTSP #01739
ISA CA #SO-6953A
 
Brocky said:
Stretching doesn't add strength...
Click to expand...

Actually, it does... shock forces on a low-elongation rope are much higher than on a high-elongation rope. Since tree work seldom involves the rope only being subjected to static loads, the tensile strength can be very misleading. In drop tests, a nylon rope will always outperform a polyester rope of the same diameter, regardless of what their tensile strengths in a straight pull test are. The higher elongation, and especially when it occurs allows nylon to absorb an enormous amount of energy that a polyester rope can't.

Whether that is helpful or not, depends entirely on the nature of what you're doing with the rope. Polyester's greatest asset is its superior abrasion resistance, which is also very important in tree work.

Video of both rope types during drop testing has been posted in other threads on the board, and I believe is still available on some of the rope manufacturers sites.
It can be a real eye opener, watching a 7,000-lb. tensile rope take 6 drops without breaking while an 11,000-lb. tensile one breaks on the first drop.
 
JeffGu said:
Actually, it does... shock forces on a low-elongation rope are much higher than on a high-elongation rope. Since tree work seldom involves the rope only being subjected to static loads, the tensile strength can be very misleading. In drop tests, a nylon rope will always outperform a polyester rope of the same diameter, regardless of what their tensile strengths in a straight pull test are. The higher elongation, and especially when it occurs allows nylon to absorb an enormous amount of energy that a polyester rope can't.

Whether that is helpful or not, depends entirely on the nature of what you're doing with the rope. Polyester's greatest asset is its superior abrasion resistance, which is also very important in tree work.

Video of both rope types during drop testing has been posted in other threads on the board, and I believe is still available on some of the rope manufacturers sites.
It can be a real eye opener, watching a 7,000-lb. tensile rope take 6 drops without breaking while an 11,000-lb. tensile one breaks on the first drop.
Click to expand...
Nylon degrades severely when wet or subject to UV. That being said, I don't give a shit about Nylon.

You make a good point @JeffGu but Nylon or high stretch ropes are not stronger but may be more resistant to breaking in some instances.

Reed Wortley
CTSP #01739
ISA CA #SO-6953A
 
Well, I guess... most people I think would say that dyneema is stronger than nylon, based on tensile strength. If you were lifting a static load with 22kN, 120cm slings, one dyneema and one nylon, you would expect them both to hold 80kg without breaking... and they would. But if you want to toss the 80kg off of a tree limb 50 feet up, you'd quickly find that "strength" is about a lot more than how strong something is when the load isn't moving fast.

DMM already tested that one... seee the video on THIS page.

And Yale certainly seems to understand that "strength" for a rope is about the work required to break it, if THIS page is any indication, and that a static pull test to derive tensile strength numbers is only part of the picture when it comes to rope strength.

I guess it just depends on what you believe constitutes strength. I certainly don't want to argue semantics.
 
Thank you Jeff, this is the post I was looking for. After I thought about the stretch factoring into the rope from my convo with boss man, I figured that it would affect the real life situation WLL negative rigging puts on a rope.

On paper tensile strength looks good, but there are a lot of factors that go into the forces a rope is able to handle.
 
So this thread should lead me to the belief that stable braid rope or ropes with with less stretch have shorter life spans and number of cycles before failure?


Sent from my iPhone using Tapatalk
 
From what I understand the cycles will be moderately similar so long as you're not bombing big chunks on them. If you have to bomb big chunks, a rope with more stretch will absorb the impact better, thus prolonging the life compared to a less stretchy rope.

Longevity factors for me seem more about UV factors and rope wear, so long as you stay within the WLL.
 
Brocky said:
The WWL is just a percentage of the tensile strength which isn't effected by how much each stretches.
If both are used with blocks the stable braid would be stronger.
Using crotches, the true blue would be the better choice.
Click to expand...
NickfromWI said:
I agree with Brock. If natural crotch rigging, you're old school and should use and old school rope! [emoji4]Otherwise go with double braid
Click to expand...

Getting clear on the terminology is so crucial here... I'll take stretch over strength in a rigging line any day!!!!! The real danger is not in the additional force on the rigging system that static rigging lines create relative to dynamic lines. ITS THE ADDED FORCE ON THE TREE THAT CAN KILL YOU!

And as far as calling NC old school, IMO there's an evolution that gets past rigging with blocks alone.. hybrid systems using NC, blocks, shackles, rings etc... together with near balance tie offs and appropriate cuts could expand your horizons..

PS ... I recently dyno tested an 1,100 lb chunk of oak on true blue.. 4 wraps and locked off purposefully so there was no run... peak load was 2,300 lbs.. watch the yale video and you'll realize your boss knows his stuff.. Stronger isn't better

stay safe out there brothers.....
 
True blue does you no good when lifting a storm damaged limb off a house or positive rigging... it's not the single do all rigging rope...
The initial conversation is not about strength (tensile) it's about appropriate rigging system choice. Know your limits and don't approach them. The rope should be the weakest point in the system...
Semantics are huge, being detailed is important.

Reed Wortley
CTSP #01739
ISA CA #SO-6953A
 
Both true blue and stable braid are both made of polyester so I don't see the relevance of bringing up nylon and dyneema.

If you dropped a load of say 20,000 # on both ropes separately which one will break first?

Not time wise but by tensile strength: edit.
 
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