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Discussion in 'Tech Tips and Gear' started by Canyonero, Oct 5, 2015.
No argument there.
You've got a single point of failure now. The catastrophe knot will stop you because it jams in your rappel device if the ascender fails. No device, no backup. I find it easy to down prusik after rigging my rap device and locking it off, so I guess I don't see the advantage of doing what you describe. Sounds harder and more dangerous.
The impact force of a static rope will be (a lot) higher than a dynamic rope.
Mini example: if you have rappelled on a static rope with toooo much friction, like on an ATS, you can get 'jack-hammering'.
The rope is sort of catching, then letting go in the rappel device giving you small 'drops' of maybe 2-6 inches or so.
Especially if you are wearing a pack, this can hurt! (Now imagine dropping 2-6 FEET).
Jack- hammering just does not occur with a dynamic rope- you can get a jumpy rappel but there is no 'hammer' in the jack
(more like bounce). The dynamic rope 'eats' the shock up.
I agree with you about it being easier to down-prusik to weight the rap device in the case where one is using an ascending setup such as the type where the waist prusik is above the foot prusik.
In the setup where there is a tethered-footloop-prusik above a micro/mini traxion or garda knot on the harness, the belay loop gets crowded and it is tempting to remove that garda or MT from the belay loop prior to attaching the rap device (they often compete for the same space). If you've clipped into a knot on the rope when you were 15 feet lower and still working your way up (a practice commonly recommended in "the literature") then at this point you'd have a 7.5 foot bight of rope dangling below you. It's tempting to take comfort in that and think that all that will happen if you fall on that will be a painful jolt. I still don't really know what would happen if one had to fall on that backup knot. For me it's an open question but I suspect the answer is that "it's really bad, don't do it".
Gotcha. Seems like a different ascending system is in order ...
Agreed. But the fall factor doesn't change, that's just the distance fallen divided by the length of rope catching the fall.
The fall factor concept/model applies to typical climbing falls onto dynamic rope. It does not generally apply to other falls onto other supporting structures (e.g. static rope, webbing, cable, etc.). The numerical value component of the fall factor concept has been popularly applied to various other situations, and has often led to the kind of confusion seen in this thread. Speaking of "fall factor" outside of typical climbing situations has little meaning.
Fall factor doesn't change but the modulus of the rope does.
Static ropes can be 4 or more times as "stiff" as dynamic climbing ropes.
And...short lengths of ropes are typically "stiffer" as well. Shorter means higher deceleration loads.
In aid climbing, nothing worse than a short fall on a static sling. Which is why the savvy aid climber folks use a tether made from nylon rope which under high peak loads will slip. Also why a purcell prusik is so sweet.
I guess I'd disagree. Useful for understanding the concept especially with regard to slipping and falling onto an anchor from above, back up knots while ascending, rigging traverses, etc.
Minimizing the fall factor could be important for some canyon scenarios.
Funny to think about folks using dynamic ropes for canyoning...(back to that debate...ha ha). I guess I don't look at elongation % as much of a player when choosing a canyoneering rope. 2% v whatever. Compared to 8% or more for dynamic ropes.
Geek out, man!
It's important to know not to take free falls onto stuff that isn't designed to absorb the energy of a fall, right? For rock climbers, that means using a proper climbing rope. For the average canyoneer? Avoid taking free falls - c'est simple! Or maybe "stay below the anchor" when tethered, if you want. No need to put a "Fall Factor" number on it. KISS? Speaking of "Fall Factor" implies the norms of a dynamic rope (esp. predictable max. impact force), which are generally lacking w/canyoneering techniques and gear.
Of course it's useful for anyone doing this stuff to fully understand the FF concept...and that implies much more than the quotient, fall length / rope length
So I found this link which has an excerpt which reportedly came from a Petzl catalog:
"A fall of less than four feet on a static rope or sling can create enough shock force to cause serious injury or death. Bearing in mind that the human body can only handle, for a brief instant , a shock force of 12 kN without risking serious injury, you don't want to go around absorbing 18 kN. And you should know that 18 kN is getting real close to, or over, the minimum limits set by the UIAA on all the gear in your safety system."
So unless you're Vesna Vulović I guess maybe don't rely on a backup knot tied every 15 feet for fall protection.
Also -- side note -- as a reminder, be mindful of how much slack you've got on your tether at the anchor. If you're tied in with a double length sling and there is a bunch of slack... don't slip. Cheers, have fun, be safe.
Sure. And...there's things we can do to mitigate that risk. Not just "because I said so", but, because a higher fall factor increases the forces.
Like...get below an anchor. Get low on an anchor prior to a down climb. Maybe consider a belay for a climb from above to below an anchor. And so on. If its easy, add a layer of safety "just in case". Folks screw up. Add a bit of safety net if you can.
When folks say, "why?"...I think its nice to provide them with a reason besides..."hey, its important."
Reminds me of a friend who didn't have much experience skiing big, exposed, high elevation peaks (Foraker) in Alaska. He asks the seasoned guy, "any advice?" "Yeah, don't fall."
And there ya go.
The fall factor concept does help one conceptualize why a short fall close to the anchor is so much worse than the same fall in a top-roping situation with 50 meters of rope out.
Core memory -- good enough for faking a moon landing...
'You do have skills, training and practice, right?
I do not. I joined the group outing because canyoneering is just having fun sliding down ropes. I don't know where we're going, what the beta is or what could go wrong, and I don't know what a contingency plan is.
Taking formal, qualified rescue classes - acquiring skills, training and practice - also teaches you how much not fun it is to have to rescue in the first place and makes planning ahead part of the having fun.
Tom's point is much more important than the details of what you carry, IMO...
if you just want to have fun sliding down ropes, sport rappelling is a lot easier.
The sliding down ropes part can be "fun", yes, but ultimately it's just a means to an end. It can also be pretty daunting, at times.
The canyon and environment is the true attraction.
Hmm, with a username like Deagol, shouldn't your tag line be "too many hobbits"?
We probably haven't met, so you're not used to my rapier-like wit - the 'just sliding down ropes' thing was sarcasm.
I like that you realize rappelling is a means to an end. I've canyoned with too many that just want to set some kind of speed record dashing through canyons.
Thanks for responding. Have fun - and be safe...
great pun (hobbies vs Hobbits), I never caught that....
Also, didn't catch the sarcasm (hard to do in writing sometimes)
we have two cats: Sméagol & Deagol. Sméagol has not killed Deagol, so far...
Glad that less people are into this for just the thrill of rappelling.
Awesome. Just don't let your kitties splash around in the river and you should be OK!
I skimmed through this thread so I apologize if some of this was already mentioned.
1: Knotting the end of your rope might not stop you from rapping off the end of your rope IF you are using a Pirana or something with a similar large hole. Overhand on a bight, or a simple EDK can be passed through a Pirana with some effort. Try it out.
2: It wasn't until my 3rd big wall that another party mentioned tying backup knots as you ascend. Their technique was tying a clove hitch to a locker on your belay loop every 10 or so feet, met a few more wall climbers that do the same since. Personally I don't tie backup knots all of the time for ascending but I am more likely to if I'm ascending on two of the same types of ascending tools. Anyone else who has had a mechanical ascender fail on them might appreciate that extra peace of mind.