a problem waiting to happen.

I've used 8mm Bee-line with I2I locked brumel with tapered, tucked tails for a while now. I've always used them with a Schwabisch hitch and had very good results. Lately I began to experiment with the Valdotain and had a problem on two separate occassions. Both occurred in the descend mode. In both cases, I looked at the Bee-Line and realized the cover had pulled away from the eye, and had slid up the core a couple of inches. Here's what I think is going on.

The Valdotain contacts the Bee-Line splittail quite differently than a Schwabisch. The coils of a Schwabisch provide the friction and the cover has little pull against it. OTOH, the Valdotain has braids that tend to run almost parallel to the climbing rope and friction between the rope and the splittail is pulling almost directly upward (i.e. trying to pull the cover away from the eye). It appears to be a contest between the securing of the cover to the eye and the force (friction) trying to pull the cover up the core (with the rope). Note that this could not happen with a double braid splice, but a double braid splice could have it's own set of problems. So what's all this mean?

I think it means that the cover has to be really secured to the core with stitching (not my recommendation) or very strong, secure whipping or actually I think it is serving. It also means that a Valdotain will always be producing a tug-of-war against the cover securement. It may just be a matter of time until the friction wins. The good news is even if the cover slips, the strength is not compromised since the strength of a I2I locked brumel is in the core alone. However, the core is exposed if the cover slips up and will not handle abrasion well at all.

So why not stitch the cover to the core? In the pull tests I did, it appeared that under heavy loading, the stitching tears the fiber of the core and cover - that does compromise the integrity of the splice. Over time, it may be that accumulated "stitch stressing" gradually breaks core fibers.

BTW, in one of the pull tests Hunabku and I did, we applied about 1000 lbs to an 8mm Bee-Line locked brumel I2I WITHOUT TUCKING OR SECURING THE TAIL IN ANY WAY, and the brumel did not fail.

Very good info Ron, and a valid concern too. I may have to consider beefing up the way I secure the cover in my splices. Moss has got one I did and I know he uses an XT a lot. Similar forces apply, I think. I don't use VT's or XT's much so I haven't ran into that much. On some of my older 8mm Bee-line I2I's that I stitched I got some weird bunching in the core strands near the stitching. That's one of the things that caused me to look for other ways to secure the cover. I'll try to remember to post some photos of them later this evening.

So your out climbing on a VT huh? The wonders never end. I sure wish I was out there with you. Tell Marion I said I miss her and her cooking and tell June that "I never did".

Yeah, I'm concerned about this - this may be a problem surfacing, or it may be that we just need to be sure the cover is really secured to the core.

I'm wondering if I'm not whipping strongly enough or if it's just a matter of time until any whipping or stitching treatment is going to come loose with a Valdotain. I tend not to really clamp down on the whipping and maybe my findings are a harbinger (been waitin' for years to use that word ) for even for more tightly secured covers.

Yeah, stitching is problematic. I believe stitching is the worser of the two methods. With the whipping, no harm is done to the core or cover and it is clear that something has happened and needs attention. With stitching, core fibers are likely being distorted and/or broken and with repeated use, could become a hidden failure - well, hidden until it happens.

This sure makes a guy think about I2Is using double braid splicing.


I wish you were here too!!!! How about Chinese tonight?

LOL, guilty - I'm out VT-ing, although the last climb (29June2009) was on 11mm KMIII using a RADS implemented with a small I'D. I have to say I was pretty impressed. The I'D gives really good control for descending and a secure lock-off for work positioning. I was in a tree about 2 hours on it, pulling up a limb with a 3:1 block and tackle, tensioning the transfer line with a Z rig, controlling the transfer speed with a control line anchored via a 3WP, and controlling the vertical (drop) with a third line anchored the same way. I put the limb down right where I wanted it - while I was still in the tree and I had no help on the ground at all. I'm gonna do a detailed post about it as soon as I can get a demo rig set up and take some pics.

And, the next time you're here, we're gonna set this thing up and you can use me as the limb and transfer me somewhere - anywhere along the sloped transfer line, stop me and lower me. You can even lower me, then move me to a different location along the line, raise me back up as if you were dodging obstacles.

I'll pass that along to Marian and June!

Ron

VT and XT have the same dynamics where the finishing braid (just above the eyes) contacts the climbing rope. So far climbing on Hunabs spliced eyes with a very secure whipping I'm seeing no problems developing, and don't anticipate them. I'll let you know if I notice any cover creep.
-moss

This is the way that I did them in the past.


You can see how the creeping cover would cause the stitching to distort the strands of the core as it "combed" through them. In this state even under load some of the strands remain "puffed" indicating to me that they are sharing none of the load. Dipping them also seemed to lcok the strands into a position they wouldn't be in under load. I didn't like that either. I quit climbing on them, and changed my method.

The way I am doing them now allows the core strands to "free float". This allows the core strands to equalize and share the load. I'm whipping the cover down on top of tubular webbing that protects the eye and facilitates "free floating". Hopefully it will hold up. If it doesn't the cover will expose a core with a locked brummel, tail buried splice. And it will do this without the stress of stitching combing through the strands.

Moss, if you get some cover slip please do let me know. I am considering adding one wrap of rubber tape between the whipped down cover and the tubular webbing to add some security to the cover position while still allowing for "free float".

I'm confident that this situation is due to the stitching technique. The 8mm beeline eye-to-eye is my most purchased sling. I've got a couple hundred of them floating around the world with nary a complaint.

Ron (or Hunabku) mentioned the stitching tearing the rope fibers. If climbers/riggers are at the point where that is happening, they have other, bigger concerns that they need to rectify.

The cover fibers should poke out the top of the whipping a bit. The cover needs to be braided underneath the whipping. Where I've seen people have problems is when they whip over a ravelled cover and then the stitching (serving) isn't locking the cover down. It sorta like a comb getting pulled through your hair. You want the hair tangled so the comb (the whipping) doesn't just slide.

Something like this should do the trick: http://picasaweb.google.com/nickaraya/M ... dWhipping#

LOVE THE MACRO LENS!!!!

love
nick

Nick,
There may be two ways stitching can alter the strength of the core - with a Valdotain. One, a heavy load and two, an accumulation of lighter loads over time that continually pull at the cover and it's securement.

No matter how you slice it, the heart of the matter, for a Valdotain, is that the force generating pull on the cover, pulls directly against the cover securement. IF the loading on the cover becomes great enough the the securement can be compromised and the cover may start to slip. Notice in a DdRT valdotain, the pull on each strand of the split tail is in the 50 - 75 pound range and it is in that range that both Hunabku and I have seen problems. Hunabku is seeing it in stitching due to accumulated use and I am seeing cover slippage.

Granted, we can secure the cover tightly enough to prevent slippage and perhaps with a combination of stitching and serving, a long enduring securement for a Valdotain split tail. But that's not the only scenario to be concerned about. Suppose a climber decides to use his '8000 lb' I2I brumel spliced split tail in a Valdotain anchor for a Z rig. Immediately, the pull on the cover and hence the cover securement is doubled from the 50 - 75 pound range to a 100 - 150 pound range. Is the cover securement still strong enough. Now lets add a force of 400 lbs to the Z rig and the force in each Valdotain line moves to 200 lbs. Let's think about what that might do to the stitching, etc. in the eye.

The security of the cover fails when the weakest link in the splice fails - so what is the weakest link? It's either the stitching or the serving - that's all. The core and cover are plenty strong so as more and more pull force is applied to the cover, via the Valdotain, the closer it comes to failure or even perhaps worse invisible damage. Lots of things can happen. The stitching can break, core fibers can break, serving can stretch, all compromising the cover securement. And with repeated use....

Then the climber takes this same piece of Bee-line and starts to climb on it. The up side is that the most likely thing that will happen is that the cover will slip as I have seen on two occasions. But cover slippage does not effect the strength of a locked brumel, tail-tucked, tail-tapered eye splice.

My primary purpose for starting this thread was to point out that the Valdotain puts much more stress on the the cover securement than any other friction hitch I know of.