Dynamee Runner Failure

[ClimbingPanther]

That's an awful clean cut! The psychology of it may not make sense, but it's possible to have been mostly cut, and the cut hidden in the knot, unless he untied and retied the knot every morning. I wonder if he can be sure nobody was up there with a knife during the night or even while he was on rappel? 30 feet back from the edge... you're not going to see anyone. He said the ends were soft, not fused, which makes friction-related abrasion & cutting highly unlikely, and it was not in contact with the rock. He also said the girth hitch was tight. Now how could the knot be tight if it was responsible for the break? How else do you get such a pretty cut without a knife and without any heat?

 

Especially in light of other testing which has recently been discussed, I think there's something very suspicious about this failure and don't believe it has anything to do with the girth hitch. That said, it's your life not mine so believe what you want and be as safe and cautious as you want to be!

 

Someone ought to be able to reproduce that with those exact components if it was really just the girth hitch which caused the failure.

 

HAHAHAHAHAHA!!!! Look at this picture and then read the tag closely.

Edited November 3, 2006 by ClimbingPanther

[fenderfour]

Hey - I've got ten old Mammut slings if anybody wants them for testing.

[TeleRoss]

Something doesn't seem right with the picture.

so the yellow runner is girthed around the black one.

but the side that is cut is not the part of the sling that would be rubbing against the black runner, which presumably would have been the one doing the cutting. The portion of the yellow runner that is in contact with the black one is still intact.

hmmmmm.

[AJScott]

Damn! Thats a tough one, doesnt look equalized at all to me...but either way that thing shoulda held up to a couple days of rapping on it. no more clove hitching those things for me. Not guna stop using um though

[ian]

i thought the problem was that the mammut runner was doubled back (girth-hitched) on it itself and the contact between itself caused the mammut runner to fail....i'm still not sure why...was it because Sherman was moving back and forth (horizontally) across the rock face, which would have caused a 'sawing' motion? or was it just the fact that since these runner have such a small diameter that the force of Sherman's weight was enough to pinch the mammut runner to the point where one part sliced through another?....the first way seems more likely to me...(maybe because i'm just in denial and don't want to believe how easy these slings can break)

[ClimbingPanther]

Yes, ian, that is the supposed problem, but how does that happen if, like the guy said, the girth hitch was still tight? If so, then there's nothing but air to abrade it.

[G-spotter]

Aliens did it

[TeleRoss]

Ahhh...ok yeah, that makes sense...side to side motion and portion of the yellow runner that is the loop portion of the hitch cut through the strand coming out of the hitch...shite..that IS scary.

[high_on_rock]

I don't get it yet. If the two are joined they will move as one, there should be no "sawing." What am I missing?

E

[TeleRoss]

Yeah the two runners joined by the hitch will not move across each other...cuz it's essentially a knot...however, the strands of the yellow runner coming down out of the hitch can swing back and forth if the weighted rope is swinging also by the person on it going left or right, so the back and forth motion of the weighted yellow runner abrating against the loop of yellow runner forming the hitch seems to have caused the failure....YIKES!!!

[high_on_rock]

I am still not getting it. If the knot was in a non-moving position then I believe you would be right. Since the knot is also moving along with the runners, is there any sawing?

E

[TeleRoss]

Yeah I see what you're saying, it does seem like the unit would move as a whole, but I think that there is enough "free" movement of the strands of the yellow runner descending from the hitch to cause some sawing...I don't know...try it at home I guess and see if you can get any separate movement by the descending strands.

[fenderfour]

BLack Diamond does some playing in the lab: web page

[catbirdseat]

Wow, it appears that the skinnier the sling materal is, the greater the percent reduction in strength from girth hitching AND, the two alternate methods, the strop hitch and climer's (or climber's) hitch don't improve matters much.

[ClimbingPanther]

Thanks for that link, fenderfour. Plenty of good info there.

 

Mike Layton, check this out because it's way better than the slipshod work and assumptions in some of the previous links. It's interesting to note that the lowest drop-test failures are around 10 kN, way more than you ought to be able to produce rappelling. Maybe this goes down with an older sling? Regardless, the most telling result is the pictures of post-failure slings. They're ratty and frayed, not a perfect slice with a tiny fray on one side.

[layton]

yo, what does the "this" of "check this out" refer too?

[Mr_Phil]

this

[layton]

thanks

[Buckaroo]

Mammut's final word on the matter.

 

Apparently they are saying yes girth hitch drops strength up to 50% but in this case the sling was cut by a sharp object and not because of the knot.

 

LINKY

[ClimbingPanther]

Nice work finding their report! Thanks. That guy probably works in the nylon industry

[catbirdseat]

Sabotage?

[Buckaroo]

""Nice work finding their report! Thanks.""

 

Home sick from work with the cold/flu just swimming in the web sea. Started in some thread in the ice climb forum and after about 5 clicks came to this thread, the link I posted was about 4 clicks later.

 

""That guy probably works in the nylon industry""

 

It's the Mammut factory.

 

""Sabotage?""

 

Sherman said his dog was hanging around at the top, maybe someone came during the night. Or maybe he just had a worn sharp piece of gear and it brushed up against.

[ClimbingPanther]

It's the Mammut factory.

I meant the guy who owned the sling, that he wanted to spread rumors about dyneema to make nylon look better. It was a poorly stated joke. I have thought "sabotage" all along on this one.