Mythbuster busting

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Mythbuster busting

Postby hank moon » Nov 19, 2014 12:52 pm

OnRope1's Myth#11 is not a myth. Two locking carabiners provide redundancy and help safeguard against accidental unclippping from the rope. Many accidents have occurred, mostly in artificial climbing walls, in which the climber became unclipped from a single locker and fell. Arguably, these accidents might have been prevented if 2 carabiners had been used.

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Re: Mythbuster busting

Postby GroundquestMSA » Nov 19, 2014 1:14 pm

hank moon wrote:OnRope1's Myth#11 is not a myth. Two locking carabiners provide redundancy and help safeguard against accidental unclippping from the rope. Many accidents have occurred, mostly in artificial climbing walls, in which the climber became unclipped from a single locker and fell. Arguably, these accidents might have been prevented if 2 carabiners had been used.

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The argument (I assume Mr. Smith's) is that anyone using two locking carabiners should orient them identically, not opposite and opposing, as is commonly preached for non-lockers. I can't quite imagine what difference it makes. I was considering a post about some these myths myself. More in a minute.
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Re: Mythbuster busting

Postby GroundquestMSA » Nov 19, 2014 1:32 pm

OnRope1 Myth#2
If a harness has a belay loop for attachment, by-pass the belay loop with a carabiner; connecting the waist belt with the leg loops.


Bruce goes on to say, "No one has ever advocated using a "by-pass" carabiner, replacing/supplementing the harness belay loop." --Obviously someone has, or this wouldn't be a "myth".

Next, "This engages the waist belt, engaging all the wearer’s internal organs, as a life support element instead of transferring the force to the legs like the harness’s belay loop is designed to do... Using the 'belt' for life support can damage the spleen, liver, kidneys, pancreas, appendix and breathing capacity." --The belay loop on one of my climbing harnesses has the same diameter as a large carabiner. There is no difference in weight distribution to leg loops or waist belt whether I use a biner or the belay loop. Clearly, the waist belt has to be engaged to some degree, or the belay loop wouldn't pass through it at all.

Also, "Belay loops are also affixed to the center of the harness to assist in keeping you centered on the rope in normal use or a fall. A "by-pass" carabiner can move to the side under a fall or even normal loading, causing you to dangle from the side, rather than the center." --This is curious indeed. A carabiner placed next to and bypassing the belay loop will self-orient in exactly the same way the belay loop itself will.

Personally, I don't care about this myth. I trust the belay loop (though they (old ones) have broken and hurt (killed?) climber(s?)). At the same time, I prefer the way an atc is oriented when I bypass the loop.
Last edited by GroundquestMSA on Nov 19, 2014 2:10 pm, edited 1 time in total.
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Re: Mythbuster busting

Postby GroundquestMSA » Nov 19, 2014 1:49 pm

See Myth#4 "A High Strength Tie-off (Frictionless Hitch) needs 3 wraps around the anchor."

I won't argue the claim that two wraps is often enough, but my goodness, doesn't the Incorrect!!! caption for a perfectly fine rig seem a bit overdramatic? And the "terrible waste of resources"... Boy. That extra 2 seconds and four feet of rope used. What a tragedy.
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Re: Mythbuster busting

Postby Scott McCrea » Nov 19, 2014 4:29 pm

GroundquestMSA, Bruce is correct. Don't bypass the belay loop WITH A CARABINER. A carabiner attached to a harness thru the waist band and the leg loops would be tri-axially loaded. That should be avoided, if possible. Belay loops don't just break. The only one I know of that has "failed" was damaged and knowingly used despite the damage. Belay loops are incredibly strong and durable. They are not decoration. The smart people that study, design, and test harnesses feel they are necessary and should be used.

There are many times I wish I had two extra feet of rope. More than two wraps could cause some twisting/torquing forces. Some anchors might not like that.

As with just about all advice, it can be summed up with, "It depends."

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Re: Mythbuster busting

Postby hank moon » Nov 19, 2014 5:51 pm

GroundquestMSA wrote:
hank moon wrote:OnRope1's Myth#11 is not a myth. Two locking carabiners provide redundancy and help safeguard against accidental unclippping from the rope. Many accidents have occurred, mostly in artificial climbing walls, in which the climber became unclipped from a single locker and fell. Arguably, these accidents might have been prevented if 2 carabiners had been used.

Image


The argument (I assume Mr. Smith's) is that anyone using two locking carabiners should orient them identically, not opposite and opposing, as is commonly preached for non-lockers. I can't quite imagine what difference it makes. I was considering a post about some these myths myself. More in a minute.


Several of these "Myths" are poorly worded/defined in that they don't make a clear claim or statement one way or the other.

I am not sure what the intended message of Myth#11 is, but the way it's worded, not a myth.

All that said, I love the Mythbusters' general intent and hope this discussion can lead to improvement.

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Re: Mythbuster busting

Postby hank moon » Nov 19, 2014 5:59 pm

GroundquestMSA wrote:OnRope1 Myth#2
If a harness has a belay loop for attachment, by-pass the belay loop with a carabiner; connecting the waist belt with the leg loops.


Bruce goes on to say, "No one has ever advocated using a "by-pass" carabiner, replacing/supplementing the harness belay loop." --Obviously someone has, or this wouldn't be a "myth".

Next, "This engages the waist belt, engaging all the wearer’s internal organs, as a life support element instead of transferring the force to the legs like the harness’s belay loop is designed to do... Using the 'belt' for life support can damage the spleen, liver, kidneys, pancreas, appendix and breathing capacity." --The belay loop on one of my climbing harnesses has the same diameter as a large carabiner. There is no difference in weight distribution to leg loops or waist belt whether I use a biner or the belay loop. Clearly, the waist belt has to be engaged to some degree, or the belay loop wouldn't pass through it at all.

Also, "Belay loops are also affixed to the center of the harness to assist in keeping you centered on the rope in normal use or a fall. A "by-pass" carabiner can move to the side under a fall or even normal loading, causing you to dangle from the side, rather than the center." --This is curious indeed. A carabiner placed next to and bypassing the belay loop will self-orient in exactly the same way the belay loop itself will.

Personally, I don't care about this myth. I trust the belay loop (though they (old ones) have broken and hurt (killed?) climber(s?)). At the same time, I prefer the way an atc is oriented when I bypass the loop.


re: "no one has advocated..." - I think he means "no manufacturer has ever advocated..." or similar.

yeah, curious indeed about the migrating carabiner claim. Maybe he means the carabiner can slide around the belt on some harnesses, like the Black Diamond Alpine BOD? Without more details of intent, seems a weak or nonsensical claim at best.

The death of Todd Skinner was due to belay loop failure, but note that the belay loop that failed was a worn-out loop on a worn-out harness that should have been retired well before the accident occurred. His partner, Jim Hewitt (who also used to cave in TAG), reportedly tried without success to convince Todd to not wear that harness. Todd's death was fully preventable and entirely due to human factors.

A true tragedy.
Last edited by hank moon on Nov 19, 2014 6:11 pm, edited 1 time in total.

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Re: Mythbuster busting

Postby hank moon » Nov 19, 2014 6:09 pm

GroundquestMSA wrote:See Myth#4 "A High Strength Tie-off (Frictionless Hitch) needs 3 wraps around the anchor."

I won't argue the claim that two wraps is often enough, but my goodness, doesn't the Incorrect!!! caption for a perfectly fine rig seem a bit overdramatic? And the "terrible waste of resources"... Boy. That extra 2 seconds and four feet of rope used. What a tragedy.


ha ha...indeed a tragedy. Bruce is a man of elegance and the overwrapped tensionless hitch obviously offends his sensibilities.

Here's a myth for ya: "the tensionless hitch is the best way to rig to a tree," or how about "it's important to use a full strength rig whenever possible."

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Re: Mythbuster busting

Postby GroundquestMSA » Nov 19, 2014 6:32 pm

Scott McCrea wrote:Belay loops don't just break. The only one I know of that has "failed" was damaged and knowingly used despite the damage. Belay loops are incredibly strong and durable. They are not decoration.

Yep, yep. Again, my preference for bypassing the loop is a matter of utility, not mistrust.

Scott McCrea wrote:Don't bypass the belay loop WITH A CARABINER. A carabiner attached to a harness thru the waist band and the leg loops would be tri-axially loaded

Nope, nope. Well, not unless one component of the harness gets hung up on the sleeve or something. If your imagination won't do the trick, go out and bypass the loop with a carabiner. Sit on it.


Not that there are any definitive answers to be found anywhere, or even desired, but this thread by folks far more familiar with climbing harnesses than I or many cavers is at least interesting.

Scott McCrea wrote:More than two wraps could cause some twisting/torquing forces.

???

Scott McCrea wrote:As with just about all advice, it can be summed up with, "It depends."

Which is why you can't, even if you're an SRT master (as Bruce indeed is) make weakly supported arguments in a dogmatic fashion... unless you want an on-rope-every-once-in-a-while know-nothing kid to pick at them. :big grin: No disrespect to Mr. Smith is intended. I don't know much, and won't, no matter how much I read and think and fiddle, until I can get some real significant experience. I do believe, though, that building an intellectual basis for techniques that I can't regularly practice still has merit.

hank moon wrote:All that said, I love the Mythbusters' general intent and hope this discussion can lead to improvement.

Me too.
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Re: Mythbuster busting

Postby GroundquestMSA » Nov 19, 2014 6:40 pm

hank moon wrote:Here's a myth for ya: "the tensionless hitch is the best way to rig to a tree,"


For me it is, because I'm an inelegant ignoramus who feels no sympathy for skinned trees, and the tensionless hitch is as easy as it gets. I would love to learn a better way if it's really better.
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Re: Mythbuster busting

Postby Scott McCrea » Nov 19, 2014 6:50 pm

GroundquestMSA wrote:I would love to learn a better way if it's really better.

It depends.
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Re: Mythbuster busting

Postby GroundquestMSA » Nov 19, 2014 7:31 pm

Scott McCrea wrote:
GroundquestMSA wrote:I would love to learn a better way if it's really better.

It depends.


Hee hee hee.

Scott McCrea wrote:Congrats on 1k posts!


Dear. That's embarrassing. At least I won't make it to 2k before this forum is abandoned entirely.
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Re: Mythbuster busting

Postby OpRescue » Nov 19, 2014 9:03 pm

GroundquestMSA wrote:See Myth#4 "A High Strength Tie-off (Frictionless Hitch) needs 3 wraps around the anchor."

I won't argue the claim that two wraps is often enough, but my goodness, doesn't the Incorrect!!! caption for a perfectly fine rig seem a bit overdramatic? And the "terrible waste of resources"... Boy. That extra 2 seconds and four feet of rope used. What a tragedy.



I would argue that two wraps is not neccessarrily enough, and there exists too many variables to phrase myth (#4) the way they did. I am glad that this "myth" was pointed out. The great part about most things we do within rope craft especially within rope rescue involves physics...and equations...and makes it easy for us to call BS. Anytime we wrap rope around any object (like a tree for an anchor, a descent device, or a carabiner) we create an equation in which we can determine the friction gained. As for the High-Friction Tie-Off anchor in myth #4, the success and physics behind this, is the capstan equation.

As a rope bends over a small segment of a drum (Tree), the tension in a rope will increase from T to T+dT in an angle dθ. The normal force is the differential dN, since it acts on a differential of area. The frictional force is μdN, and acts to oppose slippage.

Equilibrium in the x direction requires the sum of forces in the x direction to equal to be zero.

It is the capstan equation and principles that become relevant when discussing the High Friction Tie Off, clove hitch and the static and kinetic coefficient of friction properties of the munter hitch. The factors influencing the success or desired result in these techniques are; 1. Tension on rope, 2. Coefficient of friction, and 3. the total angle of contact.

So two wraps may work, but it depends on the weight of those on the rope and the estimated amount of force (tension) they place on the rope which will pull on the wraps. Next is the coefficient of friction between the rope and the object the rope is wrapped around (tree or whatever object is your anchor). This is almost impossible to precisely figure out. Wet rope, new rope, old rope, muddy rope, bark on tree, etc all play a role in the coefficient of friction. Lastly is the contact angle. This is the total "degrees" of angle produced by your various amount of wraps.

Heavy rappellers = more wraps. Wet ropes or wet anchor = more wraps. Smaller diameter tree = more wraps

Preaching 2 wraps = not true

A great way of thinking about the criticality of contact angle is the munter hitch. When the munter is in the break position (ropes are parallel)you or your load are in hanging in a static coefficient of friction. When you begin to move your break strand out by decreasing the contact angle of the rope and carabiner your load moves (kinetic coefficient of friction).
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Re: Mythbuster busting

Postby caver.adam » Nov 19, 2014 10:58 pm

How about this: Read the manual that comes with your harness. That is the correct way of using your gear...not some random guy who says he knows something. There are some harnesses that call for using a biner, but they don't have belay loops.
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Re: Mythbuster busting

Postby caver.adam » Nov 19, 2014 10:59 pm

I've done a tensionless with one loop of rope before. It was around a huge fricking boulder and the extra 20 feet of rope for a second wrap would've mattered.

GroundquestMSA wrote:See Myth#4 "A High Strength Tie-off (Frictionless Hitch) needs 3 wraps around the anchor."

I won't argue the claim that two wraps is often enough, but my goodness, doesn't the Incorrect!!! caption for a perfectly fine rig seem a bit overdramatic? And the "terrible waste of resources"... Boy. That extra 2 seconds and four feet of rope used. What a tragedy.
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