|
retep
Aug 18, 2007, 11:20 AM
Post #1 of 39
(15832 views)
Shortcut
Registered: Oct 13, 2006
Posts: 19
|
Has anyone done any drop tests with the blake's hitch? I've found one paper, with promising results, but it was done under conditions closer to arborist work than climbing.
I ask because I currently use a prussic on a short sling for solo top-roping, however a blake's hitch could be made self-tailing and would use even less hardware.
|
|
|
|
|
retep
Aug 18, 2007, 5:02 PM
Post #3 of 39
(15739 views)
Shortcut
Registered: Oct 13, 2006
Posts: 19
|
That's the paper I was referring too. Unfortunately they only tested blake's hitches in doubled rope configurations, rather than single rope. The tests were also done with static arborist rope, rather than dynamic climbing rope. On the bright side, a factor 2 fall didn't break the hitch, only caused it to be welded the rope due to slippage, anything less and nothing was damaged.
|
|
|
|
|
russwalling
Aug 18, 2007, 8:44 PM
Post #4 of 39
(15700 views)
Shortcut
Registered: Jun 12, 2002
Posts: 239
|
In reply to: I currently use a prussic on a short sling for solo top-roping, however a blake's hitch could be made self-tailing and would use even less hardware.
Please don't do this. There are much better, safer, and just as cost effective methods.
|
|
|
|
|
retep
Aug 18, 2007, 9:47 PM
Post #5 of 39
(15672 views)
Shortcut
Registered: Oct 13, 2006
Posts: 19
|
In reply to: Please don't do this. There are much better, safer, and just as cost effective methods.
You mean like clove hitches? They're much more annoying to feed.
Petzl shunts aren't approved for that usage by industrial rope access bodies.
Ascenders shred ropes in falls.
Gri-gri's require modification to really work properly. Nor would I want to trust one to catch as much as a tight prussic.
Soloists... they sound great, but are expensive.
Remember, I'm talking about a *tight* prussic on a very short sling, tied such that it can't loosen much, that is manually moved up. The only thing I see that can go wrong is grabbing it during a fall. (well, that and rope-abrasion issues common to all rope-solo setups) The tests in the above paper show quite clearly that even under severe, factor 2 falls, (which if I'm careful near the anchor aren't going to happen in a top-rope setup anyway) prussic knots don't fail.
Rant aside, what are your alternative suggestions?
|
|
|
|
|
Tree_wrangler
Aug 18, 2007, 11:37 PM
Post #6 of 39
(15636 views)
Shortcut
Registered: Feb 8, 2007
Posts: 403
|
You're right that the prussic system is solid, but it does have the theoretical "nylon on nylon" flaw. Whether that is actually valid when it comes to the forces encountered during a typical climb, using a prussic is another question though..........
If you're an arborist (and it sounds like you might be), then you know that prussic belay will actually take lead falls, and HAS NEVER FAILED in the arborists setting. This actually says a great deal, since tree climbers are industrial workers and put a great deal more wear on gear than the vast majority of rock climbers.
To be fair though, the prussic belay system might be severely flawed if taking long alpine-scenario or giant big wall falls though. I'm uneducated about the history of the system in extreme circumstances, but I suspect that it is actually much safer overall than it is reputed to be. There are a lot of variables in the system, such as diameter of prussic cord, so the information that IS out there may well be garbage anyhow....(i.e., someone was using thin cord for ascension, fell, broke the cord, died, and everybody jumps to the conclusion that the prussic system doesn't work.) But, like I said, I'm no expert. I'm using a Silent Partner these days.
If you're familiar with the blake's, then you probably know how it's used in arborists' work. Using the "hip thrust" technique, you basically take short, 6" or so static falls on the knot repeatedly. I've never seen it slip under those circumstances. It's likely that the knot will grab even harder with dynamic line, so you're probably OK. I said probably OK......Why not take your system to a safe environment and practice jumping on it a little? Get some crash pads, etc. under a tree or gym wall, and let yourself drop onto the knot?
Another suggestion, that eliminates the prussic controversy is to put a loop-knot in your rope every 5' or so. Put two locking 'biners on your harness, and as you climb, clip into the loops. Rather than clipping both 'biners into one loop, you use the two biners to avoid ever being unclipped. So, as you climb, clip the higher loop to a 'biner before you release the lower loop from the other 'biner. This oughtta be just as easy as the prussic system, and will eliminate any worries about the security of that system, given the histrionics that occur everytime it's mentioned.
|
|
|
|
|
russwalling
Aug 19, 2007, 5:54 AM
Post #7 of 39
(15608 views)
Shortcut
Registered: Jun 12, 2002
Posts: 239
|
In reply to: Rant aside, what are your alternative suggestions?
Forget it. You seem to have it all figured out. See you on the other side.
|
|
|
|
|
k.l.k
Aug 19, 2007, 2:25 PM
Post #8 of 39
(15557 views)
Shortcut
Registered: May 9, 2007
Posts: 1190
|
Russ is right-- if you are regularly relying on a Prussik, you are screwed.
Summer 1988: I am at Mt. Erie, jug soloing a new route (top rope). Soloing with a jumar always made me nervous--never liked it, even though I was always super finicky about the set-up, testing, etc. The climb is about a thirty-foot steep face but it's high up on a ledgy cliff system of fourth and fifth-class rock faces broken up by bushy ledges. While resting on the top ledge, two guys rap down to me. They leave their ropes fixed and announced that they are going to solo back up them using Prussiks.
Me: "Please don't do that.
Them: "Perfectly safe, it's done all the time, I have a feeling it's much stronger than most folks think" (Or something along those lines.)
Their proposed climb is about one-hundred feet, the first forty overhanging, maybe 5.10--clearly too hard for them. They set off. I pull myself as far under the hang as I can--the ledge is only about three foot wide at that point.
Sounds of struggle. The grunting of a gumbie shoving along a Prussik. Panting. Then WHAM! The guy smacks down from forty feet, hits the ledge, and bounces almost three feet high before settling down in a pile of mangled soloist less than a foot away from me.
The Prussik didn't even slow him down. He's alive and conscious. I take his pulse, check his pupils and feel for broken bones. The most obvious damage is his knee: He's completely ruptured his patellar tendon and it's folded back to expose the knee joint--looks like an illustration in an A&P manual. He's also messed up numerous other places and obviously can't stand, walk, or even crawl. His buddy is completely freaked out. It's a lovely scene. So I spend the next three hours setting up rappel anchors; improvising a litter; and lowering/rapping/carrying this bleeding dude down about six hundred vertical feet of 4th and 3rd class terrain that also happens to be landscaped with blackberry bushes.
I left their ropes fixed as a temporary monument to Prussik soloists.
|
|
|
|
|
majid_sabet
Aug 19, 2007, 3:09 PM
Post #9 of 39
(15544 views)
Shortcut
Registered: Dec 13, 2002
Posts: 8390
|
KIK
Was this on two or three wrap prusik ?
|
|
|
|
|
k.l.k
Aug 19, 2007, 3:48 PM
Post #10 of 39
(15526 views)
Shortcut
Registered: May 9, 2007
Posts: 1190
|
I can't recall if they used two or three wraps, but their Prusik set-up was visually fine. Straight out of Freedom of the Hills. I watched to make sure they knew how to set their knots before I took shelter.
|
|
|
|
|
majid_sabet
Aug 19, 2007, 4:15 PM
Post #11 of 39
(15514 views)
Shortcut
Registered: Dec 13, 2002
Posts: 8390
|
KIK
There is big different in 2 or 3 wrap prusik. loading pruisk and dressing it correctly with proper size cord and material to catch is another important key elements where most climbers forget to do. prusik is heavily been used in mountain rescue operation and there has been tons of testing on prusik and how they catch a falling load. If there is a problem with prusik or its function, I am sure rescuers are more interested to know than any one else on earth.
(This post was edited by majid_sabet on Aug 19, 2007, 4:17 PM)
|
|
|
|
|
retep
Aug 19, 2007, 8:48 PM
Post #12 of 39
(15454 views)
Shortcut
Registered: Oct 13, 2006
Posts: 19
|
In reply to: I can't recall if they used two or three wraps, but their Prusik set-up was visually fine. Straight out of Freedom of the Hills. I watched to make sure they knew how to set their knots before I took shelter.
Their prusiks did have long tails on them though correct?
In my testing before I started using prussiks I quickly found that long tails can easily creep back into the knot, at which point a loose prussik won't catch.
Loosened up the maillion is directly against the fishermans knot, yet, the prusik is still tight enough to reliably catch. FWIW it's actually a 4-wrap prusik as well.
Of course, if you grab the prusik, as those guys may very well have, your going down.
Did you see the condition of the prusik? Was it melted inside? Was it loose? How did the rope look? Stiff ropes or floppy? I found that stiff ropes make for a much less reliably system, both the ropes in my picture are cheap and floppy.
|
|
|
|
|
retep
Aug 19, 2007, 9:19 PM
Post #13 of 39
(15446 views)
Shortcut
Registered: Oct 13, 2006
Posts: 19
|
In reply to: If you're an arborist (and it sounds like you might be), then you know that prussic belay will actually take lead falls, and HAS NEVER FAILED in the arborists setting. This actually says a great deal, since tree climbers are industrial workers and put a great deal more wear on gear than the vast majority of rock climbers.
I'm not a professional arborist, though I do climb trees for fun, and to make up for me having no car and living rather far away from the nearest real rock. :)
In reply to: If you're familiar with the blake's, then you probably know how it's used in arborists' work. Using the "hip thrust" technique, you basically take short, 6" or so static falls on the knot repeatedly. I've never seen it slip under those circumstances. It's likely that the knot will grab even harder with dynamic line, so you're probably OK. I said probably OK......Why not take your system to a safe environment and practice jumping on it a little? Get some crash pads, etc. under a tree or gym wall, and let yourself drop onto the knot?
That's exactly what I did with the prusik idea in the first place. Drop tests with 30lb weights at first in my apartment, which lead me to the idea of keeping the tail of the prusik as short as I have it. Then gradually taking some falls in a safe environment. I still need to do some better full scale testing, mainly with less rope out to get the fall factor higher, but then again, I've only used it on climbs and with techniques where I've felt that falling is unlikely. (As in, ooh, that section looks hard, I might fall, I'm going to sit down now and just ascend past it/do another climb)
I'll definitely be doing the same with the blakes hitch of course. If it's known to chop ropes though, I'd rather know in advance and save me some money! :)
In reply to: Another suggestion, that eliminates the prussic controversy is to put a loop-knot in your rope every 5' or so. Put two locking 'biners on your harness, and as you climb, clip into the loops. Rather than clipping both 'biners into one loop, you use the two biners to avoid ever being unclipped. So, as you climb, clip the higher loop to a 'biner before you release the lower loop from the other 'biner. This oughtta be just as easy as the prussic system, and will eliminate any worries about the security of that system, given the histrionics that occur everytime it's mentioned.
I thought of that system too... As a backup it's a decent idea, though I'm uncomfortable with exposing myself to such large falls while soloing due to the chance of injury while alone. I also don't like how difficult it would make retreating off the climb, with my prusik system I carry a petzl stop and an ascender w/ footloop, so I simply sit down on the prusik, rig the stop under it, and use the ascender to take weight off the prusik. Fairly fast and hopefully easy if I were to get injured. Also enough gear to get up the climb, handy, as most of what I've done has been in a bit of a canyon where the only approach is from the top.
Absolutely nothing wrong with it as a backup though in a separate line. I'll likely make up a dedicated small diameter backup line, pre-knotted, one of these days.
|
|
|
|
|
majid_sabet
Aug 19, 2007, 9:45 PM
Post #14 of 39
(15435 views)
Shortcut
Registered: Dec 13, 2002
Posts: 8390
|
for prusik to catch a rope , the diameter of prusik cord must be correctly chosen otherwise pruisk either fails to catch or catches and melts if smaller dia is chosen. The correct diameter ( based on what type of rope its going to be used on ) should be between 60% to no more than 75% of rope's diameter.if you have a 10 mm rope and you use a 8 mm prusik cord, most likely prusik will fail to catch and generally this due to larger loop on prusik wrap. just because you have a prusik in there, it does not mean it will catch the falling load.generally prusik moved 6-12 inches before it locks on rope as shown with red tape /marker . See images below.
[URL=http://imageshack.us]
[URL=http://imageshack.us]
(This post was edited by majid_sabet on Aug 20, 2007, 5:14 AM)
|
|
|
|
|
k.l.k
Aug 20, 2007, 1:22 AM
Post #15 of 39
(15385 views)
Shortcut
Registered: May 9, 2007
Posts: 1190
|
Majid-- The point of my post is not to suggest that the Prusik is a wicked knot. It was standard for SAR at the time, the one I learned (and used), and the only reason I didn't use it on that rescue is that I had Jumars. But it was considered dicey, even at the time, for rope soloing.
The guys in the story had the same set-up that everyone in northwestern Washington had learned: 7mm on 11mm ropes. Their ropes/perlon were not new and stiff. I cannot swear that they used three rather than two wraps, but it's most likely they were using three--otherwise I probably would've commented (they probably would've responded that they knew better), and I probably would have remembered that detail. I certainly remember their responses to my attempts to talk them out of it. But I could not attest to three wraps in court--let's say there was a ten percent chance that they were using only two. I watched the start of the pitch, enough to see that the guy knew how to hand set a knot. I did not see the rest, except for the last few feet of the fall.
I did not break down the accident scene. The guy was in bad shape, and although he was responsive, with a forty-foot decker you always suspect head and internal injuries/bleeding. That means the clock is running.
The Prusik was still attached and intact. The rope sheath was intact. The knot had slid the forty feet without fully catching. He had not pulled up a loop and clipped off presumably because, as is common on difficult ground (whatever difficult means for you), he had not found a good enough stance.
OP-- I would listen to Russ.
|
|
|
|
|
majid_sabet
Aug 20, 2007, 5:19 AM
Post #16 of 39
(15344 views)
Shortcut
Registered: Dec 13, 2002
Posts: 8390
|
KIK
The prusik must be managed and set to react manually by some one's hand otherwise it will not catch and i bet it will fail 85% of the time. I wish you know what size cord or how many wraps were there when that happen.
Either way, I do mind doing a 40 footer test on prusik in the next 3 months with a dummy to see how it goes.
MS
|
|
|
|
|
Tree_wrangler
Aug 20, 2007, 3:10 PM
Post #17 of 39
(15288 views)
Shortcut
Registered: Feb 8, 2007
Posts: 403
|
In reply to: Sounds of struggle. The grunting of a gumbie shoving along a Prussik. Panting. Then WHAM! The guy smacks down from forty feet, hits the ledge, and bounces almost three feet high before settling down in a pile of mangled soloist less than a foot away from me. The Prussik didn't even slow him down.
All "theoretical" discussion aside, this single event oughtta create concern for using the prussic belay all by itself. Your idea of using a separate rope with a "bottom-line" backup is a good one. I do the same thing.
|
|
|
|
|
k.l.k
Aug 20, 2007, 4:00 PM
Post #18 of 39
(15257 views)
Shortcut
Registered: May 9, 2007
Posts: 1190
|
Majid-- That is correct. And that is precisely one of the reasons that a set-up taught as best standard practice in specific rescue situations was NOT considered a best standard practice for rope-soloing.
|
|
|
|
|
petsfed
Aug 20, 2007, 4:28 PM
Post #19 of 39
(15233 views)
Shortcut
Registered: Sep 25, 2002
Posts: 8599
|
Didn't Royal Robbins almost die from using a pair of prussik for self belay? Or was that because he was using them to lead something solo?
|
|
|
|
|
billcoe_
Aug 21, 2007, 1:47 AM
Post #20 of 39
(15157 views)
Shortcut
Registered: Jun 30, 2002
Posts: 4694
|
russwalling wrote: In reply to: Rant aside, what are your alternative suggestions? Forget it. You seem to have it all figured out. See you on the other side.
ROTFLMAO! 
Good one.
|
|
|
|
|
retep
Aug 21, 2007, 2:34 AM
Post #21 of 39
(15141 views)
Shortcut
Registered: Oct 13, 2006
Posts: 19
|
In reply to: Didn't Royal Robbins almost die from using a pair of prussik for self belay? Or was that because he was using them to lead something solo?
I've heard of that one before from http://www.rockclimbing.com/...cgi?post=17937#17937 from passthepitonpete he took a lead fall on them, and they melted. No other info on the conditions.
As an aside it occured to me that a really simple system would be to basically setup a normal top-rope/gri-gri combo and then clip the gri-gri to your own belay loop... The moving rope would avoid wear issues common to all fixed lines. However, I'd be even more reluctant to trust the gri-gri to lock off given that the force on it would be halved. A grillon http://en.petzl.com/...Produits?Produit=311 would be a much better choice as they aren't spring loaded so even the slightest load causes them to lock up. Same goes for the standard gri-gri rope-solo system. Pretty expensive option though, ~$140, at least you get a free lanyard with it.
Of course, the above does make the possibly deadly assumption that grillion's are just gri-gri's minus a spring and handle. Petzl says grillions are for work positioning, not fall arrest, and therefore can't handle a fall greater than 0.5m. They don't say if it's due to the design of the grillion, or the rope that they are provided with. (likely the rope, it's semi-static)
Google "grillion rope-solo" turns up nothing. I've only briefly seen one in real-life.
(This post was edited by retep on Aug 21, 2007, 3:35 AM)
|
|
|
|
|
majid_sabet
Aug 21, 2007, 5:39 AM
Post #22 of 39
(15117 views)
Shortcut
Registered: Dec 13, 2002
Posts: 8390
|
KIK
Sometime ago during a seminar, someone mentioned, for prusik to catch on rope, prusik requires two important things
1- Person to activate the locking part
2- A minimum of a 30 degree bend on the rope below the last 3 warps.
According to this theory ( I can not be sure on his statement), this rope bend below the last 3 warps momentarily slows the prusik movements and allow a short time for the center cord to apply tension on all wraps. Without this critical angle, the chances of prusik to fail are much greater.
I wonder if any one else ever heard of this before or what you guy think about this?
[URL=http://imageshack.us]
[URL=http://imageshack.us]
[URL=http://imageshack.us]
(This post was edited by majid_sabet on Aug 21, 2007, 5:41 AM)
|
|
|
|
|
microbarn
Aug 21, 2007, 12:18 PM
Post #23 of 39
(15084 views)
Shortcut
Registered: May 12, 2004
Posts: 5920
|
retep wrote: In reply to: Didn't Royal Robbins almost die from using a pair of prussik for self belay? Or was that because he was using them to lead something solo? I've heard of that one before from http://www.rockclimbing.com/...cgi?post=17937#17937 from passthepitonpete he took a lead fall on them, and they melted. No other info on the conditions. As an aside it occured to me that a really simple system would be to basically setup a normal top-rope/gri-gri combo and then clip the gri-gri to your own belay loop... The moving rope would avoid wear issues common to all fixed lines. However, I'd be even more reluctant to trust the gri-gri to lock off given that the force on it would be halved. A grillon http://en.petzl.com/...Produits?Produit=311 would be a much better choice as they aren't spring loaded so even the slightest load causes them to lock up. Same goes for the standard gri-gri rope-solo system. Pretty expensive option though, ~$140, at least you get a free lanyard with it. Of course, the above does make the possibly deadly assumption that grillion's are just gri-gri's minus a spring and handle. Petzl says grillions are for work positioning, not fall arrest, and therefore can't handle a fall greater than 0.5m. They don't say if it's due to the design of the grillion, or the rope that they are provided with. (likely the rope, it's semi-static) Google "grillion rope-solo" turns up nothing. I've only briefly seen one in real-life.
all of that sounds like a crap ton of work, a whole lot of maybes, hopefullies, and coulds ....AND your cost is up to $140.
Why aren't you getting a soloist or another device DESIGNED to do what you want?
|
|
|
|
|
binrat
Aug 21, 2007, 1:22 PM
Post #24 of 39
(15065 views)
Shortcut
Registered: Jul 27, 2006
Posts: 1155
|
Top rope soloing using prussiks does not make sense. You have to keep the prussik tight on the rope, which means that you almost have to two hand it up as you ascend. I've seen a microsender attached to the rope and the climber had a purcell prussik as a connector in the system.
|
|
|
|
|
retep
Aug 22, 2007, 7:14 AM
Post #25 of 39
(15005 views)
Shortcut
Registered: Oct 13, 2006
Posts: 19
|
In reply to: all of that sounds like a crap ton of work, a whole lot of maybes, hopefullies, and coulds ....AND your cost is up to $140. Why aren't you getting a soloist or another device DESIGNED to do what you want?
None of the three devices designed for soloing on the market are designed to be used with the moving rope setup I outlined above. If it works it could offer advantages in areas with lots of sharp rock, like where to date I've done most of my rope-soloing. That's enough reason for me to want to try.
Besides, many people still use gri-gri's as solo devices even when alternatives exist. Might as well see if you can make an incremental improvement, given that a grilion is so similar and could offer a big advantage.
The soloist wouldn't have been invented in the first place if they just listened to people ranting about "soloing? sounds like a crap ton of work..."
|
|
|
|
|
|
|
|
|
1
