Safety Tethers / Purcell Prusik

[rcwild]

Most canyoneers understand the importance of having a safety tether. It is used primarily to secure yourself to a precarious anchor while rigging for rappel. If sized correctly, your tether can be used for ascending. Some tether variations can be used for other purposes as well. For example, a double tether with two different lengths can facilitate knot passing, transitions (ascend to rappel or rappel to ascend), and some rescue techniques (like the balancier).

It's hard to beat the Petzl Spelergyca (formerly called Energyca) if you are looking for a double tether. The long side is a nice length for clipping into anchors and, for most people, about the right length for ascending. The short side can be made a bit shorter by tying an overhand knot in the middle. This modification makes it an ideal length for knot passing, transitions and balancier.

Some canyoneers like to use daisy chains (or adjustable daisies) as safety tethers. They work well, but some caution should be exercised. The long daisies found in most climbing shops can create problems: (1) The excess length can easily catch on branches and rocks, in cracks, etc. This can be life-threatening if caught under water. (2) The excess length can set you up for a severe shock load on your anchor. (3) If a shorter length is desired, clipping through loops incorrectly can result in failure when loaded during a fall.

Personal opinion: Using a daisy longer than your reach should be avoided. 24 inch daisies are available and the ideal length for most people. They can be girth hitched to your harness with a carabiner clipped to the end. Easy to avoid excess loops (that could snag) when not in use by clipping the carabiner to gear loop on harness. This length is about right for ascending. When a second, short tether is needed, simply clip your canyon quickdraw to your harness.

[ratagonia]

...Some canyoneers like to use daisy chains (or adjustable daisies) as safety tethers. They work well, but some caution should be exercised. The long daisies found in most climbing shops can create problems: (1) The excess length can easily catch on branches and rocks, in cracks, etc. This can be life-threatening if caught under water. (2) The excess length can set you up for a severe shock load on your anchor. (3) If a shorter length is desired, clipping through loops incorrectly can result in failure when loaded during a fall.

...

As a climber, I'm a big fan of daisy chains - for climbing. They are not good in canyons. Since 'adjustable length' is not needed very often, the main feature of a daisy chain just gets in the way. Buy a Spelegyca, or rig up the equivalent using slings.

Tom

[John Styrnol]

I've tried the daisy chain thing, did not care for it. I will be trying the sling deal next. If I do not care for it, I will try the Spelegyca.

[rcwild]

Check out these photos showing bad vs good gear racking.

http://www.canyoneering.net/forums/showthread.php?t=263

People who use daisy chains for tethers typically clip multiple daisy loops into one carabiner on their gear loops in an attempt to carry it more efficiently. Ugly bundle of webbing that is difficult to access when needed.

[rcwild]

Question asked via private email:

Q: I like to dangle my pack from a really long leash, say 6 feet, which would require me to sling from a Spelergyca. I'd like to have the safety of being able to quickly disconnect from my harness with one hand if my pack becomes wedged. For this reason, wouldn't it be better to use a carabiner to connect the Spelergyca to my harness, rather than a rapide?


A: If I understand your question correctly, you are planning to extend your Spelergyca with a sling. Long end of Spelergyca is around 24 inches, so you would add a 48 inch sling to total six feet. ?? Not a very good solution.

Instead, girth hitch your old (semi-retired) daisy chain to the haul loop of your pack. Clip the other end of the daisy chain to your harness with a carabiner. If your pack gets stuck, unclip this carabiner. No need to detach your Spelergyca.

[sonnylawrence]

I use a Purcell prussik. It has a lot of utility, not just as a pack tether. I can use it as one of two rope grabs to ascend a rope. It could be used as a cow's tail or to build an anchor. Since it is a Purcell prussik, it has some energy absorbing qualities. I make the end loop large enough that I can do a triple wrap prussik on 11 mm rope. The length of the total Purcell depends on what I am using it for. So, for example, I also use these for my mountaineering axe wrist loop. In this case, the length will be measured to the bottom of my axe. I use them for snow pickets, etc. I usually make them out of 5 or 6 mm cord.

For caving or canyoneering, I can change the length of the tether by sliding the prussik-on-itself portion of the Purcell. The end loop is girth hitched to the pack. The prussik-on-itself end is carabinered to me.

I unsuccessfully tried to load a picture to this site from: ahsrescue.com/pc-1211-105-personal-purcell-prusik-system.aspx

[skianddive]

Here's the image that Sonny wanted to show....

[rock_ski_cowboy]

Well I just bought the spelegyca! Darren at Mountainworks had some around that apparently haven't sold for a long time so he gave me one for 15 bucks. Cool. Anyhow, now i have one, I'd like to know what I can do with it. Safety clipping for anchors and pack tethers are the obvious ones. As it will probably be the end of the season or later by the time I can afford some ACA training, I'd like to know what makes the Spel so ideal for canyoneering, and what is commonly done with it. Also which loops to attach the quicklink to on the harness-- What size quicklink and what to hook it through? I have a standard climbing harness with belay loop, upper and lower loops, etc.

Ben

[ratagonia]

Well I just bought the spelegyca! Darren at Mountainworks had some around that apparently haven't sold for a long time so he gave me one for 15 bucks. Cool. Anyhow, now i have one, I'd like to know what I can do with it. Safety clipping for anchors and pack tethers are the obvious ones. As it will probably be the end of the season or later by the time I can afford some ACA training, I'd like to know what makes the Spel so ideal for canyoneering, and what is commonly done with it. Also which loops to attach the quicklink to on the harness-- What size quicklink and what to hook it through? I have a standard climbing harness with belay loop, upper and lower loops, etc.

Ben

Use a 5/16" Rapid Link to attach the center of the Spelegyca to your belay loop. Clip in your rappels above this. Put a locking biner in each end of the Spelegyca. I use BD Quicksilver 2 Lockers, but for general use would put one of those on the long side, and a Petzl Attache on the short side.

What can you do? Uh, all sorts of things. The main advantage of it is you are already to go. I hang a sling on my pack, and clip the sling for rappelling. Guided rappels - just clip in. anchor - just clip in. Providing a Sequence anchor - toss the long side around your side for the next person to clip in to. Rappelling with the Rope Silo or pull cord bag - clip on the side, or shorten it up by putting it through the handle and clipping to a gear loop on your harness.

Rescues - even more uses, but, hard to explain here. Take the classes, learn the stuff.

Hope that helps.

Tom

[rcwild]

During our Technical Canyoneering Course, students see a few uses for the Spelergyca. A few think it's cool enough to buy one. During our advanced workshops, students see many more uses (transitions, knot passing, etc). Several students decide they have to have one. During our Canyon Rescue Course, students see how indispensible it is for some techniques and everyone buys one.

Tree anchor? Pass the ends around oposite sides of the tree and clip the 'biners to each other. You're instantly secure while you set up webbing around the anchor.

Long end is perfect length for most people to use on their harness ascender. Put ascender on rope, clip in with Spelergyca, go.

Much more.

[sonnylawrence]

Last week I saw some spectra daisey chains that had been drop tested with Fall Factor 1 or 1 1/2 falls. The loop the biner was clipped to broke. Lovely!

Last year we drop tested an old Spelegyca that belonged to a caver who would no longer use it out of fear it would fail. We had Fall Factor 2 falls. It sustained many falls, slowly unzipping the stitching.

[rcwild]

Sonny,

Any chance you could turn me on to some data re breaking nylon daisies? Most of the excessively long daisies I see used in canyoneering are nylon. More energy absorption than Spectra, but the length is much more likely to set user up for fall factor 2.

[mtngoat59102]

As many times as this subject has been gone over in the last year you think the point would start to get across. Daisy chains are not the best option for your personal leash.

[rcwild]

Please respond to the attached poll: What do you use as your safety tether?

Add comments regarding the reasons for your choice. Thank you for participating.

[beadysee]

Please respond to the attached poll: What do you use as your safety tether?

Add comments regarding the reasons for your choice. Thank you for participating.

I use a sewn shoulder length sling. Usually a spectra/nylon one.

I like it because its usually something I have with me, its optimum length for reaching the anchors, I can rappel from it, use it as an ascender, hang my pack with it, leave it, cut it up.

I dislike daisy's because they aren't slings. I hate thinkin' I could cross clip a pocket. They are usually too long and get in the way. And, specialized type daisies are too specific to anchoring (ie, if it doesn't serve several functions, then, not as likely to be in the kit).

-Brian in SLC

[hank_moon]

yah, stay away from daisies for lanyards - 'specially the spectra ones...

[charlybldr]

I recently attended the International Technical Rescue Symposium in Fort Collins Colorado. ITRS is a yearly event where rescue professionals from around the world meet to exchange ideas on advances in rescue equipment and techniques. There was an interesting paper presented this year that directly pertains to this thread.

Research was done by Mike Gibbs of Rigging for Rescue in Ouray Colorado on the results of shock loading daisy chains and other commonly used positioning lanyards. In addition to being the owner of one of the premier rescue training organizations in the country (R4R), Mike is an active climbing guide as well as a member of the Ouray Mountain Rescue team. Mike performed dynamic testing on daisy chains as well as a number of positioning lanyards commonly used in climbing and rope rescue. The results of this testing were informative, to say the least. After reading this post, many of you may want to reconsider your choice in positioning lanyards.

Mike designed a drop test representative of what could take place in the field that would provide some indications as to the capabilities and/or limitations of positioning lanyards. A common example in canyoneering would be slipping from a stance when starting a rappel with the anchor at your feet resulting in dynamically loading your safety lanyard. The purpose was to examine the magnitude of peak forces as well as the integrity of the connections on certain commercially and user-created lanyards in a dynamic event. The drops were conducted with 80 kg and 100 kg mass simulating the weight of a climber or climber with a heavy pack and fall factors from 0.5 – 2.0. The surprise was how easily daisy chains and some other lanyards resulted in catastrophic failure on relatively short drops.

Test results were sobering at best. Particularly considering how many canyoneers still insist on using the daisy chain (almost 30% of poll responders) as their primary positioning lanyard. Daisy chains failed in short falls (FF 0.5-1.0) and slings made of Spectra/Dyneema webbing exhibited alarmingly high impact forces (>12kN) and catastrophic failure at surprisingly low fall factors. In canyoneering this could easily happen at any rap anchor below chest level. One slip and bang, you’ve dynamically loaded the anchor.

Nylon slings (not nylon daisy chains) and the Purcell Prusik came out on top as a result of their shock absorbing abilities. Typically, nylon slings held falls with reasonable impact forces (<10kN). The Purcell Prusik did best holding up to factor 2 falls with impact forces of less than 12kN. (FYI acceptable impact forces: CE 6kN, CSA/OSHA 8kN and UIAA 12kN).

I would urge all of you using daisy chains as your primary positioning safety lanyard to stop immediately! And those of you using Spectra/Dyneema slings for this purpose do the same. I would recommend you switch to something like the Petzl Spelegyca, Imlay Clipster, Purcell Prusik or nylon accessory cord or tape sling that has at least some dynamic shock absorbing ability.

Charly

[bobeck]

I use Purcell Prusik (s) because they are CHEAP, STRONG, ADJUSTIBLE, SHOCK ABSORBING, DISPOSIBLE, ASCEND-DESCEND(ING). LOAD RELEASING....overall.....because they work and are safe..... Did I say that they are CHEAP?

[ratagonia]

How long of what size cord to you use for one of those things? Is there a good diagram anywhere, showing how to tie it up?

Tom

[rcwild]

Tom, did we play with Purcells during your Canyon Rescue course?

[DJ Meding]

Rich,
Any test results using omni sling as a tether?
Dave

[rcwild]

I don't think OmniSling was included in the test data presented at the technical rescue symposium. I'll be in Moab with Charly and Dave over the weekend. I'll ask them if they know of any such data.

[hank_moon]

How long of what size cord to you use for one of those things? Is there a good diagram anywhere, showing how to tie it up?

Tom

http://www.geocities.com/r_riversong/Purcell_Prusik_tying_technique.jpg

[ratagonia]

Tom, did we play with Purcells during your Canyon Rescue course?

Mike Mello had some and used them to good effect.

Interesting at the Canyon Rescue course, everyone applies their own style and gear to the lessons and problems. Bill tried to do everything with one locking biner and those three prusiks he found. Mike used the stuff he carries as a rescue-type guy. I'm willing to carry new gear, as long as it is light and compact. Etc.

I'm still not converted to prusiks, and insist on doing everything with over-the-shoulder slings. But, it is good to know HOW to do it.

Tom

[DJ Meding]

Ok I can figure out the left end but having trouble tieing the big loop prusik end. Can anyone help?
Dave

[sonnylawrence]

Okay, I will give it a try. To make a standard set of short, medium and long Purcells, it takes about 10 meters of 5 or 6 mm cord. I normally just make two shorts (different lengths) and a medium. If this write up doesn't work, maybe Joe Bugden will make us a video of it being tied in an X or R canyon!
1) Tie a figure 8 on a bight with a loop about 8 inches long. This will be the part that attaches to the main rope to ascend. The loop size depends on the rope and cord diameter. If you use 11 mm rope and 8 mm cord, you need a bigger loop than if you use 5 mm cord. Tie the knot loose, you'll see why later.
2) To measure, put the loop in your crotch. This is to make what is called a medium Purcell. Otherwise measure to your nipple for a long Purcell. Note, a short Purcell is just a simple loop tied with a double fisherman's. usually it should be from nipple to top of head.
3) From your crotch, let the cord drop to the floor, go under your foot and over your foot. It helps to wear shoes you will use on rope. Pinch the cord on top of your foot. This point will become the bridge on the prusik-on-itself as Hank shows in his diagram link.
4) Hang the bridge over the top of your middle finger, left hand.
5) Wrap cord three times clockwise around your little finger.
6) Wrap cord three times counter clockwise around your thumb.
7) Touch thumb to little finger.
8) Pull bridge off middle finger and onto doubled cord.
9) Slowly open up the 6 wraps of cord into a 'tunnel.'
10) Pass the figure 8 from #1 through the 6 wrap tunnel.
11) Pass the rest of the tail of the cord along with #10.
12) Cinch the Purcel prusik. This just formed your foot loops. They can be used on one foot or separated for two feet. (And many other things not related to ascending.)
13) Feed the tail of the cord backward through the figure 8 knot. Thus the figure 8 knot will be made of three strands of cord.
14) Clean everything up. Insert foot. Hold to crotch. Ascertain all is well before cutting off cord.

Note: Nathan Schara and Ken King have tied this with either a double fisherman's or triple (fisherman's in between the usual double fisherman's) instead of a figure 8 knot.

[DJ Meding]

Huh !!!!!!!!

[DJ Meding]

Sonny,
Thanks, but I need a visual on this one.
Dave

[sonnylawrence]

Yeah, I did too. When I see Chandler Dayton next, I will ask her to make a video clip.

[bobeck]

I believe I have specific Tying Instructions at work and will try to scan them and send them to a file for viewing. Its a bit confusing to tie them because you begin with 10 meters of 6 mm and tie the first prusik without cutting the 10 meter length until it is finished. Then you tie the second prusik without cutting the 6 mm again until it is finished. Basic Measurement of the Prusiks is done with the foot prusik on and secured and the bight of the rope prusik to your nipple on the longer of the 2, and the shorter coming up to your crotch. The 3rd and final prusik is measured as a single prusik loop that measures from your nipple to one hand (spread) width above the top of the head. 10 Meters of 6mm= give or take $9 and an investment of 1/2 hour to tie,. I think it slips at about 2-3 kn...will look at my specs. Very easy to adjust for length and have 2 sizes to choose from. I recently created a single strand "double" prusik system based on the single Purcell, that is a twin adjustible, 2 point anchor clip in prusik; Its really cool! If your anchors are staggered, it gives the ability to clip each anchor and even out the force on each anchor point by using only one prusik attached to your harness. Probably not necessary , but could be used to clip a "piggy back" while still clipped to the anchor without the need of a second "strap". Maybe not a nobel prize winner but I've found it handy!

[sonnylawrence]

I recently created a single strand "double" prusik system based on the single Purcell, that is a twin adjustible, 2 point anchor clip in prusik;
This is interesting. Could you post of picture of it? Thanks,

[Eshi-1]

1. Click on the small picture for a bigger version:
http://www.ahsrescue.com/pc-1211-105-personal-purcell-prusik-system.aspx

2. Purcell tie in photo gallery
http://www.pbase.com/phil_box/purcell_tie_in

[DJ Meding]

That did the trick. A picture is worth a thousand words. Now I would like to see a few pictures for it's differnet applications. Also would it not be better to have have a double looped eight on the tie in end? It would make girthing the loop to your harness a little bulkier but add some redundancy to the rig. Just questioning the strength of 5-6mm cord. Does anyone have numbers on that.
Dave

[hank_moon]

1. Click on the small picture for a bigger version:
http://www.ahsrescue.com/pc-1211-105-personal-purcell-prusik-system.aspx

2. Purcell tie in photo gallery
http://www.pbase.com/phil_box/purcell_tie_in

Note that the adjustment "Prusik" shown in #1 is not a true Prusik. Wonder why? Anyone using this "off-Prusik" care to comment?

[DJ Meding]

Hank,
I will take a stab and guess that a true prussik has an even amount of wraps.
Dave

[sonnylawrence]

Note that the adjustment "Prusik" shown in #1 is not a true Prusik. Wonder why? Anyone using this "off-Prusik" care to comment?
Some people feel that by having a "3 and 2" loop prusik on what is esentially a foot loop, it grabs and releases better as the person is standing in it to ascend a rope. I have used "3 and 2" and "2 and 2." For my weight of 162 pounds on either 5 or 6 mm cord, I can not tell the difference.

[sonnylawrence]

Also would it not be better to have have a double looped eight on the tie in end? It would make girthing the loop to your harness a little bulkier but add some redundancy to the rig. Just questioning the strength of 5-6mm cord. Does anyone have numbers on that.
The double looped eight you mention might interfer with using it via a standard prusik attachment to the mainline. The strength of the system would be that of the 5 or 6 mm cord (5.5-7 Kn), doubled (hence 11-14 kN) then times ?% for the figure 8 knot made of three strands. Assume that knot is at 60%, so the Purcell prusik might hold 6.6-8.4 kN. That is when it is attached as a prusik. When girthed to a belay loop, it could be half of that. Somehow you have to factor in the fact that the Purcell will slip when loaded, increasing the safety factor by some amount.

[hank_moon]

I will take a stab and guess that a true prussik has an even amount of wraps.

Bingo! Also, a true Prusik is spelled "Prusik" (capital "P", one "s") and pronounced "Proozik" :)


Some people feel that by having a "3 and 2" loop prusik on what is esentially a foot loop, it grabs and releases better as the person is standing in it to ascend a rope.

Not following you here. This loop (with the "3 and 2" Prusik) is ideally only adjusted once before the climb, eh? No grabbing and releasing during the climb.

[sonnylawrence]

Not following you here. This loop (with the "3 and 2" Prusik) is ideally only adjusted once before the climb, eh? No grabbing and releasing during the climb.
I did not do well at explaining. Sorry. The Purcell prusik has two ends. One is a simple loop formed by the figure 8. It is used to attach to the main line. A prusik hitch (and other hitches like Hedden, Klemheist) can be tied with any simple loop, including this one. The other end of the Purcell is a "prusik on itself." It forms the foot loop. It is adjustable for different size boots, leg lengths, etc. For ascending, once the length is set, it should not need to be adjusted, but can be. In my attached picture, the blue cord has four wraps forming the prusik, the red cord has 5. The red cord has 3 wraps on one side, 2 on the other. Hence it is a "3 on 2." Supposedly this bites better when weighted. I have not had problems. I usually tie them 2 on 2.

The Purcell prusik can be used for more that ascending a rope. It is a safety tether on a harness, tether for a pack, attachment to a snow picket, attachment for ice axe, used to tie people into a litter, used around a tree to climb, used in building anchors, etc. Advantages are cheap, adjustable length and shock absorbing ability. When used to ascend a rope, both loops can be put on one foot or separated, allowing one foot in each loop.

One problem I see with canyoneers is that many do not have a cord system pre-rigged to ascend a rope. The need to ascend arrives, out come a variety slings and cords. The person gets exhausted trying to get up the rope. This is the wrong time to be inventing an ascending system. Being able to quickly adjust the length of the Purcell foot loop is nice. There are of course many other ways of accomplishing the same task.

[bobeck]

I use a wrap 3 wrap 2 prusik and yes they work better at grabbing and are easier to break...The wrap 3 side is always on the locking side and the wrap 2 side is on the non locking side. Works the same for Purcells as it would for progress capture (or ratchet). Not easy to hitch onto the body of a rope but can be done using a strand and not a loop. Much simpler though to just use a double or triple wrap prusik. FWIW

[bobeck]

Just posted a picture of a creation of mine. A "double" wrap 3, wrap 2 Purcell Personal Anchor System. "It works Good Mikey!" In the photos "Members Gallery"

[NSchara]

Just posted a picture of a creation of mine. A "double" wrap 3, wrap 2 Purcell Personal Anchor System. "It works Good Mikey!" In the photos "Members Gallery"

It looks like you should double the loop on the left side. That would give you equal strength on both sides of the knot. Unless you're only intending to use one of the carabinered stands at a time, which may be the point. Either way, I'd probably prefer two normal Purcells for their more general utility.

Also, as Sonny mentioned previously, Ken and I independently came up with a different knot for the Purcell. Ken used a normal double fisherman's, except with the third strand of rope also running through the middle of the knot. This leaves the top loop and bottom loop slightly adjustable by sliding the connecting strand through the knot. I used a sort of triple knot double fisherman's. The middle strand that is shared by both loops is tied with a double overhand. The free end from the top loop is threaded through this first double overhand and tied with another double overhand around the strand exiting the first. The free end from the bottom loop goes up through both previous knots and ties in a double overhand around both strands of the top loop. This triple knot prevents the loops from resizing. The primary advantage of this type of knot is that it cleans up a little tighter and neater than the figure-8. However, it is much harder to untie if the cord is needed for something else.

After actually using my first Purcell to asecend (only 8 ft) this weekend, I think I'll be making another.

[hank_moon]

Sonny

Thanks for the detailed explanation of the wrap issue. I've never had a problem setting or releasing a Prusik, so I'll probably stick with the "original flava" variety if I ever make a set of those oh-so-trendy Purcells.


One problem I see with canyoneers is that many do not have a cord system pre-rigged to ascend a rope. The need to ascend arrives, out come a variety slings and cords. The person gets exhausted trying to get up the rope. This is the wrong time to be inventing an ascending system. Being able to quickly adjust the length of the Purcell foot loop is nice. There are of course many other ways of accomplishing the same task.

I've only had to ascend a few times in (non-exploratory) canyoneering. Biggest prob I've seen out there is that folks just don't have good technique, regardless of the equipment used. Purcells ain't gonna solve that...only a fair amount of real-world practice. One practice routine could be to find a good canyon for fixing ropes, drop a few raps, ascend back out, repeat w/increased #of drops, etc. Start with short drops and move up. Start w/ dry drops, then go wet. Efficient ascending is not a skill easily gained by most people - lots of struggle at first.

Quickie contest: what's the number one ascending mistake made by a beginner that prevents upward progress? Winner gets...uh, a smilie or something.

[sonnylawrence]

Quickie contest: what's the number one ascending mistake made by a beginner that prevents upward progress? Winner gets...uh, a smilie or something.
I consider myself an eternal beginner. A few weeks ago I had to take my annual intermediate personal vertical skills test for SAR. It involves ascending, passing knots and rebelays, changeovers ("transitions" a la ACA). I used my frog caving system. I kept pushing up on the handled ascender. I was going nowhere fast. Finally it occurred to me I was supposed to have my foot in the foot loop. I wasn't even hypothermic! That was pretty stupid on my part.

[bobeck]

It looks like you should double the loop on the left side. That would give you equal strength on both sides of the knot. Unless you're only intending to use one of the carabinered stands at a time, which may be the point. Either way, I'd probably prefer two normal Purcells for their more general utility.


I have been using Purcell Prusiks as emergency and sar work for almost 9 years and I love them, but my intention with this "Double Prusik" was not as an ascender, however I can use it that way, but to create a double point anchor for myself, and found that it made an ideal system to clip a pack for a piggyback while still connected into the anchor. This illiminated the need of a separate sling to be girthed onto my harness. As for the strength? 5mm BW accessory cord is rated 5.7 kn x 2 strands= 11.4 kn - 30% at the knot is roughly 7-8 kn. I dont have a problem with that for a personal anchor.

[bobeck]

Forgets to unclip from the anchor???????

[rcwild]

Howdy Bo

I noticed quote tags missing in a couple of your posts. There needs to be a "start quote" and "end quote" tag for the quote to appear correctly ...

Start quote tag is -- left bracket, "QUOTE", right bracket. End quote tag is -- left bracket, then "/QUOTE", right bracket.

[hank_moon]

I kept pushing up on the handled ascender. I was going nowhere fast. Finally it occurred to me I was supposed to have my foot in the foot loop.

So close!!!

[hank_moon]

Forgets to unclip from the anchor???????

Good guess...but this mistake can be made w/o clipping into an anchor.

[charlybldr]

So. What do you recommend for an adjustable length tether?


I use a Purcell Prusik. It is about 18" long in its short adjustment and is infinitely extendable up to arms length. It also acts like a load limiter in a dynamic loading situation improving your odds when using less than bomb proof anchors. I use a canyon quickdraw when I need to clip in shorter than 18".

[ratagonia]

I use a Purcell Prusik. It is about 18" long in its short adjustment and is infinitely extendable up to arms length. It also acts like a load limiter in a dynamic loading situation improving your odds when using less than bomb proof anchors. I use a canyon quickdraw when I need to clip in shorter than 18".

I know people SAY that a Purcell Prusik acts as a load limiter, but it probably does not.

In many rescue systems, Prusiks are used and act as load limiters. Should the load exceed X, the Prusik slips. In this kind of system, the slipping of the Prusik results in a decrease of the load, so the Prusik slips a bit, then recatches when the load is somewhat under X.

When used as a leash, however, the mechanics are quite different. Take a tumble off that stance and land on your PP, and if the Prusik starts to slip, it will likely go all the way to the end, and create a larger shock load. For you equation-using physicists, compare the energy absorbed by the Prusik moving along itself with the energy put into the system by your body falling the addition length. Without measuring it is hard to say, but it seems like the energy input is WAY higher than the energy absorbed.

Or, alternatively, the Prusik sliding could melt through, and thus you fall to your death.

You (meaning Sonny, of course) could test this. Use steel plates as a drop weight, hook up your pretty stout anchor, and drop the plates Factor 1 fall. My claim is that if the Prusik starts sliding, it will most likely go all the way to the end. Result?

Nothing wrong with using a Purcell Prusik, just don't think it is giving you "load limiting" or "shock absorbing" capability, because it is not.

Tom

[sonnylawrence]

You (meaning Sonny, of course) could test this. Use steel plates as a drop weight, hook up your pretty stout anchor, and drop the plates Factor 1 fall. My claim is that if the Prusik starts sliding, it will most likely go all the way to the end. Result?


Okay, I will take the challenge. I will have to wait until my Stealthrubber covered steel toed boots are delivered.

[charlybldr]

Nothing wrong with using a Purcell Prusik, just don't think it is giving you "load limiting" or "shock absorbing" capability, because it is not.

Tom

A rather difinitive statemtent there Tom.

I mentioned in a previous thread (Safety Tethers Poll), that Mike Gibbs owner of Rigging For Rescue in Ouray Colorado has done some testing on individual safety tethers. Mike has presented his findings at the International Technical Rescue Symposiums in 2005 and 2006. He also recently presented this paper again at the Mountain Rescue Association meeting in Salt Lake City last week.

The original paper presented at ITRS 2005 entitled “Daisy Chains and Other Lanyards: Some Shocking Results when Shock Loaded” involved testing a number of commercially available lanyards as to their ability to withstand shock loading. They did two independent drop test series conducted in 2002 and 2005 which examined the effects of a shock load on various commercially made and user-configured lanyards.

Rather than test to the OSHA standard (which is a slow pull test to determine ultimate strength) Mike did a drop test using fall factors ranging from .25 to 2.0 in an attempt to simulate a real life situation such as a climber or rescuer falling from a stance in which they had some slack in their primary lanyard attachment. Scenarios could include a climber standing up to adjust some rigging while at a belay station, a rescuer lanyard climbing a ladder on a tower rescue or a litter attendant scrambling up the side of the litter to adjust some rigging during a vertical lower/raise operation, very similar to a canyoneer slipping at a rappel station with anchors at waist level with slack in the lanyard or below, such as an anchor at your feet.

Concerns addressed:

1. the magnitude of peak forces on certain lanyards and/or lanyard configurations in a dynamic event.
2. examining the integrity of the connections on certain commercially available as well as user-created lanyards in a dynamic event.


The commercially available lanyards tested did not perform very well where the Pursell Prusik performed admirably. Following are a few results representative of the range of testing.

Lanyard Fall Factor Max Arrest Force (kN) Result
Metolius PAS 1. 0 19.2 catch
Metolius PAS 1.25 20.9 failure
Yates Spectra Daisy Chain .25 9.0 catch
Yates Spectra Daisy Chain .5 11.3 failure
Climb High nylon Daisy 1.0 12.8 catch
Climb High nylon Daisy 1.5 17.0 catch
Climb High nylon Daisy 2.0 19.9 catch
Purcell Prusik 1.0 9.1 catch
Purcell Prusik 1.5 12.7 catch
Purcell Prusik 2.0 12.9 catch

Note that the “daisy chains” not only exhibited catastrophic failure at very low fall factors but also exhibited unreasonably high impact forces and that the Purcell Prusik in every case performed as intended sliding to a catch before full extension with more reasonable impact forces.

*All test data above copyright 2005 Rigging For Rescue.

This testing prompted Mike to specifically look into the Purcell Prusik in greater detail. At the 2006 ITRS he presented the paper “Drop Testing on Purcell Prusiks: A Critical Evaluation of Their Capabilities as a Positioning Lanyard in Rescue and Climbing” which focused primarily on evaluating the Purcell Prusik as an alternative to the daisy chain and similar lanyards.

For this test Mike chose acceptable Max Arrest Force at fall factor 1 to be less than or equal to 8kN with lanyard integrity OK. In other words the lanyard needed to retain its function after the test.

Out of 39 test drops at a fall factor of 1 the Purcell Prusik exhibited absolutely no failures with all but three exhibiting impact forces less than 8 kN. An additional eighteen drops at fall factor 1.5 resulted in only 2 failures neither of which were catastrophic. The two failures exhibited enough glazing to prevent further use of the lanyard.

FYI. Following are maximum impact force standards set by internationally recognized organizations.

CSA Industry 8 kN (no injury)
OSHA Industry 8 kN (no injury)
CE Industry 6 kN (no injury)
UIAA Recreation 12 kN (survivable)

A representation of results from additional testing of the Purcell Prusik at higher fall factors.

Lanyard Fall Factor Slide Distance Max Length Max Arrest Force
Purcell Prusik 2 28.5 cm 70 cm 9.024 kN
Purcell Prusik 1.5 22 cm 71 cm 9.516 kN
Purcell Prusik 1 10 cm 68.5 cm 7.913 kN

Note the Purcell Prusik performed as intended, sliding to a catch before ultimate extension resulting in Max Arrest Forces under the UIAA 12 kN max in fall factor 1.5 and 2 falls. Well under UIAA and under the CSA and OSHA 8 kN maximum.

How did some of the other commercially available lanyard perform in this test?

Lanyard Fall Factor Max Arrest Force (kN) Result
Metolius PAS 1 20.219 kN held
Metolius Monster Daisy .5 11.885 kN held

*All test data above copyright 2006 Rigging For Rescue.

By the way the above Metolius lanyards are made of a Nylon/Dyneema blend. Note that Max Arrest Force barely comes in under the UIAA max of 12 kN (survivable) at a fall factor as little as .5 and quite excessive (you’re gonna get hurt in this one) at fall factor 1. Fall Factor 2 resulted in catastrophic failure of all Spectra or Dyneema lanyards. Can you say “dirt me”?

Although I have never taken a fall on my Purcell Prusik, personal experience has convinced me of its superior versatility and performance when used as a personal safety lanyard. The fact that this device has been universally accepted by the International Rescue Community reinforces this position. Results of Mike’s testing has convinced me that it is reasonable to assume the Purcell Prusik will indeed catch a fall keeping Max Arrest Force at acceptable levels while stopping before ultimate extension. In fact, allowing the Purcell Prusik to continue to be used. I am curious to see whether or not Sonny’s testing supports this conclusion.

[Paul Nelson]

Do you have a link to the results of that study?

I would like to read the full report.

[charlybldr]

I have a hard copy of the paper and test results from ITRS. Was told it was posted on the MRA website but I haven't been able to find it there. I'll keep looking.

[sonnylawrence]

You (meaning Sonny, of course) could test this. Use steel plates as a drop weight, hook up your pretty stout anchor, and drop the plates Factor 1 fall. My claim is that if the Prusik starts sliding, it will most likely go all the way to the end. Result?


Paul Stovall, Jason Martinez and I did some testing on prussiks (AKA prussicks, prusiks, prusics) . Warning: this was NOT an exhaustive test. No specific conclusions can be made from these experiences. This information should serve to cause a person to ask more questions, generate discussion and signal a system that either is or is not useful.

Please see other discussions on this forum on Purcell Prussicks.

The image in picture seven is how we tied the Purcells. Specifically they had a 3 on 2 configuration. The cord we used was either 5 or 6 mm. In some tests we attached the Purcell to an 8 mm cord or 8 mm Imlay canyon rope. Otherwise the Purcells were clipped into very large rapides or steel locking carabiners. The item we dropped to simulate a person weighed 160 pounds (0.7 kN). It was rigged vertically above a door frame. In that way, a (roughly) fall factor 1 or 2 fall could be generated. The anchor was built of 1 inch tubular sling. However the strain gauge tension member which read axial stress was inserted between the anchor and the falling load. The information generated was sent to an oscilloscope. Thus the load seen by the materials being tested was measured. However it is possible some fraction of peak forces for the total system was dissipated by the tubular sling.
1) A 5 mm 3 on 2 Purcell tether was girth hitched to the load. It was dropped with a Fall Factor 1 (FF1) fall. The Purcell slipped 3 &#189; inches. No breakage.
2) The system in #1 was reset with FF1 and tried again. This time instead of attaching the tether to the “climber” with a girth, the simple loop was clipped into via the rapide. The Purcell slipped 2 7/8 inches. No breakage. These two tries were used to set up the strain gauge.
3) The system from #2 was reset with FF1. The Purcell once again slipped 2 7/8 inches. It took 1430 pounds (6.4 kN) to make it slip. It did not break.
4) The system from #3 was reset. This time a Fall Factor 2 (FF2) fall was generated. The cord broke at 2025 pounds (9 kN) at the girth hitch.
5) A new 5 mm tether was tied. A FF2 fall caused the Purcell to slip 4 5/8 inches at 1650 pounds (7.3 kN). No breakage.
6) The system from #5 was reset. It broke with a FF2 fall at 2025 pounds (9 kN) at the figure eight knot in the middle of the tether.
7) A 6 mm tether was attached with a girth hitch. With a FF2 fall, the Purcell knot fused at 980 pounds (4.4 kN). There was a time delay of 6 msec. The cord broke at the figure 8 knot at 1530 pounds (6.8 kN).
8) Another 6 mm tether was attached by girth hitching into the loop with the rapide. With a FF2, the Purcell slipped 4 7/8 inches at 1200 pounds (5.3 kN) and the system saw a total load of 1580 pounds (7 kN). It did not break.
9) The system of #8 was reset. It revealed a spike at 1830 pounds (8.1 kN). 173 msec later there was a second spike at 640 pounds (2.8 kN). The girth hitch apparently broke in two stages, hence the two spikes.

Observed patterns: A) The cord broke at the girth, simple loop or figure eight knot. Notably it did not break at the Purcell prussick portion. B) The prussick portion seemed to always slip. This could be observed with the tracing on the oscilloscope. It was possible to estimate the amount of energy dissipated by the slippage of the Purcell. This would correspondingly lower the total impact force the system saw. This likely would be significant in preventing the anchor and the human from seeing high peak forces.

In the picture one sees the weight, a white safety rope (back ground) to stop the falling weight from creating a crater under the building, a dark rope used to raise the weight and the blue Purcell being tested. The Purcell is attached to a black carabiner which is attached to Paul's strain gauge.

[tj_wetherell]

Sonny and Charly Thanks for the info/testing

So it looks like the Purcell is absorbing a healthy chunk of energy.

Can you guys clarify: all the cord used for the Purcells was nylon/perlon accessory cord. I'd like to see a test out of Maxim Tech Cord/BW Titan / Gemini. It would be really interesting to see how the handling/knotability of the stiffer cords affects the ability of the Prusik to grab the rope. Maybe it slides more, but absorbs more energy. Of course, depending on the slippage for your energy absorption isn't the greatest idea (thinking as he types) since if you have the tether fully extended you have the potential for the highest FF fall, and would then be relying solely on the material's ability to absorb through elongation....must.think.about.this.

Based on the Girth/F8 connections breaking is there a better way to join ANY tether to the harness? I personally use a Rapide, but for a knot would a F9 be better?

-tom (w)

[ratagonia]

Excellent testing Sonny! I love it when my firmly held beliefs are blown to shreds by actual testing.

Tom

[sonnylawrence]

The question that came up yesterday in the lab was the effect of a girth hitch on a belay loop. Would the belay loop/girth combo fail easier than a carabiner/girth combo. If someone can send me more belay loops (Tom Jones?) I will be glad to test them. It is interesting that girth hitches are on the weak side yet prussiks are stong. That extra wrap makes all the difference. A girth hitch has the "pulley effect" and cuts itself. So Tom, one possible answer is to prussik the tether to the rapide rather than girth it.

If someone wants various materials tested as Tom mentioned in the previous post, let me know. I will give you an address to send them to.

As to figure 8 vs. figure 9 knots, I think Paul Stovall looked at that once with no signifcant difference in strength, just easier to untie. I will check.

One idea that comes from this discussion is the size of cord used to make the tether. I tested 5 and 6 mm. I suppose someone who is worried about fall factor 2 scenarios might use 7 or 8 mm. Many cavers use 11 mm dynamic rope cow's tails (tethers).

The bigger concern in my mind is the whole concept of fall factor. Any of these tethers are fine for a low fall factor (say 0.25). Part of the education of a beginner is his/her position relative to the anchor. Hence courtesy anchors for difficult rappels are important so only the last person is at risk. Or have a grab line set up so most people lower themselves onto a rappel if the anchor is lower than them. Or teach people to down climb to the rap rope, perhaps on belay. Or...........

[jmart]

Regarding Sonny's drop tests: We also video taped the drops. For anyone who is interested in reviewing them, you can check them out on Google Video.

http://video.google.com/videoplay?docid=6574377271438976427

http://video.google.com/videoplay?docid=8526721436407716815

Jason

[sonnylawrence]

Can you guys clarify: all the cord used for the Purcells was nylon/perlon accessory cord.

The 5 and 6 mm cords were nylon, purchased at Sport Chalet's rock climbing department.

[charlybldr]

Can you guys clarify: all the cord used for the Purcells was nylon/perlon accessory cord.

Yes.
Mike's 2005 test used 7mm nylon accessory cord from PMI tied in a 3 wrap prusik.

The 2006 series used 6mm nylon accessory cord from both PMI and Sterling tied in a 3 wrap prusik.


I'd like to see a test out of Maxim Tech Cord/BW Titan / Gemini. It would be really interesting to see how the handling/knotability of the stiffer cords affects the ability of the Prusik to grab the rope. Maybe it slides more, but absorbs more energy. Of course, depending on the slippage for your energy absorption isn't the greatest idea (thinking as he types) since if you have the tether fully extended you have the potential for the highest FF fall, and would then be relying solely on the material's ability to absorb through elongation....

I doubt Titan/Gemini cord would work very well because it is so stiff. Both of these cords have a nylon sheath however neither cord stretches very well. I think you need both the function of the prusik as well as the stretch of nylon for the system to work properly.




Based on the Girth/F8 connections breaking is there a better way to join ANY tether to the harness? I personally use a Rapide, but for a knot would a F9 be better?

The Girth hitch will always be a potential weak point. I wonder if a prusik girth hitched to a hard link like a carabiner or rapid link (in testing) ends up being putting more force on the Purcell Prusik than when it is tied to a soft anchor point on a harness as would happen in real life?

[ratagonia]

... The bigger concern in my mind is the whole concept of fall factor. Any of these tethers are fine for a low fall factor (say 0.25). Part of the education of a beginner is his/her position relative to the anchor.....

One of my pet peeves, but the testing is so good, let me state it less peevishly than usual.

The testing by dropping steel plates is a model of what happens in the field. The people I canyon with tend to be somewhat softer than steel plates. This will decrease the loads substantially, especially when looking at short falls. (When falling 2 feet, the energy absorbed by your body flexing is substantial; when falling 100 feet on your lanyard, the energy absorbed by your body flexing is not of consequence).

Fortunately, we have no one in the community who is foolish enough to offer themselves up as the crash test dummy, so it is very hard to quantify the relationship between dropping humans and dropping steel plates. The testing represents an upper bound on the forces produced, and is interesting in how the various systems respond to it. In the real world, we know that falls onto leashes produce smaller forces than those stated. How much smaller? My guess is 50% less, but the accuracy of my guessing has recently been shown to be not so hot. YMMV. I think we can all agree that falling onto lanyards is not a good idea. This testing shows that of the various lanyards available, a Purcell Prusik might be a good choice.

Tom

[ratagonia]

Mike's 2005 test used 7mm nylon accessory cord from PMI tied in a 3 wrap
The Girth hitch will always be a potential weak point. I wonder if a prusik girth hitched to a hard link like a carabiner or rapid link (in testing) ends up being putting more force on the Purcell Prusik than when it is tied to a soft anchor point on a harness as would happen in real life?

Most likely. After the test, the Prusik was probably cinched down to a 1/4" diameter or something. Around a fat carabiner or rapide it would expect to be substantially stronger.

I wonder if a multi-wrap girth hitch might prove stronger. A two-wrap or three-wrap would start to look a lot like a prusik!

Will try to find some belay loops.

Tom

[Canyon Kelp]

Sonny,
Thanks, but I need a visual on this one.
Dave

This is my interpretation of how to tie this.

http://pctmap.homeip.net/DATA2/Slideshows/CANYONEERING/Matt_Maxon/Purcell%20Prusik/index.html

Canyon Kelp

[sonnylawrence]

This is my interpretation of how to tie this.

http://pctmap.homeip.net/DATA2/Slideshows/CANYONEERING/Matt_Maxon/Purcell%20Prusik/index.html

Canyon Kelp

Close but not quite. You started with a grapevine to attach the ends of the cord. Instead, you would tie a figure 8 on a bite. The tail of the cord gets rethreaded through the figure 8, making it quite thick. Then the Purcell is tied, very much like you showed. You demonstrated a 2 on 2 Purcell. You might consider a 3 on 2. One side would have three strands. The other would have two. I would love to shows pics but I won't have access to the right equipment until Friday.

[sonnylawrence]

Here is a link that shows the entire Purcell system used for ascending.
http://www.amrg.org/purcellprusiks.pdf

[charlybldr]

I've been using the Purcell Prusik for a few years now. When first saw it I thought it was pretty slick. Then repeated exposure convinced me of its versatility in addition to what I feel is its superior performance as a canyoneering lanyard. I also admit that Tom's initial statement regarding the Purcell Prusik lit this fire under me. And now the pot seems to be boiling over...

I have a pet peeve too.

38% of the people in the poll above state that they use either a daisy chain, a daisy chain like product or lanyard/daisy chain made of non-stretch webbing. We've known for quite some time now how easy it is to incorrectly clip into a daisy chain. It is also common knowledge that slings and ropes made of non stretch materials have little or no shock absorbing abilities. Climbers think we're nuts, but as canyoneers we accept the fact that sometimes we use less than bomb proof anchors. It's all part of the game we play.

Yet I regularly see canyoneers using daisy chains and Spectra/Dyneema slings as personal restraint lanyards seeming to give no regard to their improper application. To date, there have been no catastrophic failures of any of these products in the field. How soon will it be before we see the first one?

[John Gowans]

Close but not quite. You started with a grapevine to attach the ends of the cord. Instead, you would tie a figure 8 on a bite. The tail of the cord gets rethreaded through the figure 8, making it quite thick. Then the Purcell is tied, very much like you showed. You demonstrated a 2 on 2 Purcell. You might consider a 3 on 2. One side would have three strands. The other would have two. I would love to shows pics but I won't have access to the right equipment until Friday.I believe this post by Eshed from 11-19-2005, with its associated links, shows the correct sequence for tying it:

--------------------------------------------------------
1. Click on the small picture for a bigger version:
http://www.ahsrescue.com/pc-1211-105...ik-system.aspx (http://www.ahsrescue.com/pc-1211-105-personal-purcell-prusik-system.aspx)

2. Purcell tie in photo gallery
http://www.pbase.com/phil_box/purcell_tie_in
--------------------------------------------------------

~JG~<!-- / message --><!-- sig -->

[mdd]

I've been using the Purcell Prusik for a few years now.

Charly, can you bring one with you when we meet up tomorrow? I wouldn't mind seeing one in action, and learning to tie one. From photos I always figured they were a bit complex to tie, thus increasing the chance of screwing something up when tying them, thus increasing the chance of failure. But I've never tried to actually tie one so I figure I could be mistaken.


M

[ratagonia]

I believe this post by Eshed from 11-19-2005, with its associated links, shows the correct sequence for tying it:

--------------------------------------------------------
1. Click on the small picture for a bigger version:
http://www.ahsrescue.com/pc-1211-105...ik-system.aspx (http://www.ahsrescue.com/pc-1211-105-personal-purcell-prusik-system.aspx)

2. Purcell tie in photo gallery
http://www.pbase.com/phil_box/purcell_tie_in
--------------------------------------------------------

~JG~<!-- / message --><!-- sig -->

Interesting. Using the "Figure 8 bend made with bight and tail", you end up with a single loop of cord for your tie-in point. You could, however, do a "Figure 8 bend made with 2 bights" and get a double loop at the end. This would perhaps double the strength of the weakest point in the system.

Now, if you plan on attaching the top loop to a rope with a prusik (which is kind of the original idea) then a single loop makes sense. If you plan on using it solely as a safety leash, then a double loop might be better.

Sonny - you tracking? More test time?

Charly - how long is your Purcell when fully extended? Do you girth the top end to your harness ring or belay loop?

Tom

[sonnylawrence]

Sonny - you tracking? More test time?



Good idea! I won't be able to test it until after the holidays.

[rcwild]

I've seen people using Purcell's as safety tethers two ways. The adjustable double loop end needs to be on a metal interface (carabiner or rapide) so it will slide when length is adjusted.

1. Attach the adjustment end to the harness with a metal interface and clip the single loop end to the anchor with a carabiner. Doesn't need to be girth hitched to the carabiner (maybe a small Petzl String could be used?). When the tether needs to be lengthened, the prusik is pulled toward the user.

OR

2. Attach the single loop end to the harness. Usually girth hitched, but could be attached with metal interface. Clip the adjustment end to the anchor with a carabiner. When the tether needs to be lengthened, the prusik is pushed away from the user.

Note: the Purcell can be lengthened when weighted, not shortened.

[rcwild]

Interesting. Using the "Figure 8 bend made with bight and tail" ...

I've also used a "dogbone" double fisherman.

[charlybldr]

Charly - how long is your Purcell when fully extended? Do you girth the top end to your harness ring or belay loop?

Tom

I girth hitch the PP to my belay loop with a carabiner on the adjustable end (Rich's #2). Fully extended with the carabiner in hand, the PP matches the length of my reach.

[charlybldr]

Charly, can you bring one with you when we meet up tomorrow? I wouldn't mind seeing one in action, and learning to tie one. From photos I always figured they were a bit complex to tie, thus increasing the chance of screwing something up when tying them, thus increasing the chance of failure. But I've never tried to actually tie one so I figure I could be mistaken.


M

Will do.

[tj_wetherell]

Ok - *slight* tangent here. I've been playing with the Purcell with the goal of having the adjustable side *and* a static short length to extend my rap device. I would use the Spelegyca, but I can't get two Petzl Attache's through the short end which is what I like for varying friction to suit the rappel. So, I made a longer Purcell with the loop joined with a triple fisherman's, then a F8 tied with a bight like Tom was suggesting. (edit: from L. to R. you have the Purcell side, the f8 in "middle" for the connection to the harness, and then a shorter loop with the fisherman's in it). This seems fine for most of my intended use, but If I were to anchor the short end, and load all the way through to the Purcell end I'd be rolling the F8. So I now have a Butterfly tied with two strands instead of one to join the tether to my Rapide. Butterly's like both ends loaded, so I am wondering how folks here would accomplish this. Since the bight has a rapide through it, neither knot has anywhere to "roll" to.

I'll add photos tonight if that would help.

-tom (w)

[rcwild]

Hi Tom (W),

Not totally clear about what you're describing, but I have another suggestion.

Use a Purcell or Clipster for your long tether. Use a variation of a canyon quickdraw for your short tether. You can buy a quickdraw sling that has a tight loop on one end and a bigger loop on the other. Connect the tight loop end to your harness with a rapide or carabiner. The big loop end will be large enough to hold one or two Attaches as the situation dictates.

[tj_wetherell]

Rich.

Thanks. That is basically exactly what I do now, except that I us the Met-PAS on the tether side. Probably headed toward a Purcell to replace that though.

-t

[rcwild]

Rich.

Thanks. That is basically exactly what I do now, except that I us the Met-PAS on the tether side. Probably headed toward a Purcell to replace that though.

-t

People are using the PAS in two different ways, too.

1. Connect long section end of PAS to harness and use PAS as one long tether. When extending the rappel device is desireable, clip it into small loop where long section connects to daisy loops.

OR

2. Connect the long section to the harness using the small loop where it connects to daisy loops. This in essence creates a Spelegyca-type tether with the daisy loops serving as the long end and the long section of the PAS serving as the short end.

[Marc McDonald]

"I've been using the Purcell Prusik for a few years now. When first saw it I thought it was pretty slick. Then repeated exposure convinced me of its versatility in addition to what I feel is its superior performance as a canyoneering lanyard."

I'm not sure exactly how you're proposing using the Purcell Prusik as a lanyard. The "Rigging for Rescue" notes show the harness attachment to be a simple piece of 6 or 7mm cordage tied off with a grapevine knot to form a loop. In the classic use this would be tied with a prusik knot to a rope and then clipped into the harness to serve as either part of an ascender system or as a guided self-belay. I'm assuming (and I know that assumptions can get us killed) that what is being proposed here is using the middle-length foot prusik as the lanyard. I'm further assuming the figure 8 bight is clipped into the harness and the loop formed by the prusik that is doubled back on the cord is clipped into the anchor and used to vary the length of the lanyard. Is this correct, or am I off base?

One further note on the Purcell Prusik as an ascending system. I tried to use this system once and found I preferred a modified Texas Prusik system, which uses a short harness prusik like the Purcell system and an identical, except for the length, foot prusik which is girth hitched around the foot. I found having one foot free of the ascending system was useful and having a simple cord loop allowed more flexibility in varying the number of wraps as necessary for the rope used and/or the conditions.

Marc

[bobeck]

I use a Purcell Prusik. It is about 18" long in its short adjustment and is infinitely extendable up to arms length. It also acts like a load limiter in a dynamic loading situation improving your odds when using less than bomb proof anchors. I use a canyon quickdraw when I need to clip in shorter than 18".

If you clip a carabiner to your harness belay loop and then clip it through the prusik loop you will be able to adjust yourself all the way up to the anchor for the short "clip in". Just a tidbit!

[charlybldr]

I'm assuming (and I know that assumptions can get us killed) that what is being proposed here is using the middle-length foot prusik as the lanyard. I'm further assuming the figure 8 bight is clipped into the harness and the loop formed by the prusik that is doubled back on the cord is clipped into the anchor and used to vary the length of the lanyard. Is this correct, or am I off base?

Marc

This is pretty much how I use the PP. There are a couple of rigging options. See Rich's post #73 for clarification.

[bobeck]

This is pretty much how I use the PP. There are a couple of rigging options. See Rich's post #73 for clarification.

Don't know if you caught it in a previous post, but there were thoughts that the purcell was finitely adjustible. It is infinately adjustible if you girth hitch the "figure eight bight" to your harness and put another carabiner into your belay/rappel loop. Clip the anchor with a carabiner attached to the prusik end of the purcell. This gives you a fair amount of adjustment in and out, but doesn't allow you to suck right up to the anchor. To get closer to the anchor, just clip the carabiner attached to your belay/rappel loop to the loop of the prusik and it will allow you to adjust as close as you want to the anchor without ever being disconnected from the original anchor.

[Canyon Kelp]

I used a Purcell Prusik on Saturday (6/30/07) in Birch Hollow, & yesterday (Sunday 7/1/07) in Keyhole Canyon and liked it very much and wished I'd brought it along for Pine Creek on Friday.

I used ½ of a 30ft Bluewater 7mm accessory cord REI item # 729698

I made the corrections to my tying technique making it 3x2 not 2x2 and the figure 8 for the tie-in.

It would be better for me if I used a bit less cord as it hangs below my knee and tangled me up a few times.

I noticed my partners having to extend the anchor to their safety with a sling which happened to be a dyneema sling on a girth hitch making it the weak link in the extension.

Matt
<script type="text/javascript">theprice = "$11.95" ;</script>

[ratagonia]

It would be better for me if I used a bit less cord as it hangs below my knee and tangled me up a few times.

I noticed my partners having to extend the anchor to their safety with a sling which happened to be a dyneema sling on a girth hitch making it the weak link in the extension.

Matt

Gotta say... putting a sling on the anchor for everyone to clip into is standard procedure where I do rappels. That way, everyone can have a tether that is a comfortable (arms length at full extension) distance, yet everyone can clip in and have some operating room.

I'm not sold on the anchor sling needing to be adjustable in length. Once in a while, it could be nice, but I'm not sure the extra complexity is worth it for me. (Which, of course, me being a capitalist, has little effect on whether YOU should buy a pre-tied Purcell Prusik Adjustable Safety Lanyard (6mm x 36") from CanyoneeringUSA.com).

Tom

[rcwild]

(Which, of course, me being a capitalist, has little effect on whether YOU should buy a pre-tied Purcell Prusik Adjustable Safety Lanyard (6mm x 36") from CanyoneeringUSA.com).

Just checked again, Tom. I see computer hardware, games and toys, electronics, gifts ... but not Purcell Prusiks. When ya gonna get that store fixed?

Extend the Anchor Tie-In (http://www.canyoneering.net/forums/showthread.php?t=1649)

[sonnylawrence]

I'm not sold on the anchor sling needing to be adjustable in length. Once in a while, it could be nice, but I'm not sure the extra complexity is worth it for me.

With the goal of multi-use for various items: Purcell prusiks can do a lot. They can be part of your ascending system. It is adjustable which is nice. So this could be a leg loop. If the simple loop that is girth hitched to the harness is large enough, it can be attached even to 11 mm rope via a standard prusik. The Purcell end becomes the foot loop.
They can be used as a pick off strap.
If used as a pack tether, it is adjustable.
Yada, ya......da.............

[rambler-joe]

I'm not sold on the anchor sling needing to be adjustable in length. Once in a while, it could be nice, but I'm not sure the extra complexity is worth it for me.Tom
As I see it there are three basic problems with the Purcell prusik.
1) 10 meters is a lot of cord to carry around and get tangled up.
2) The whole thing is too difficult to tie. That means it's too easy to make a mistake.
3) Attaching it to a rope via a classic prusik means pulling the whole thing through the figure 8 bight at least twice.
It's basically a very messy system with limited use.:(

Remedy.:)
Using 2 to 2.5 meters of cord you can build a short Purcell.
1) Form the loop using a Blakes hitch. The Blakes is one of the few hitches that will grip on it's own diameter. A classic prusik, or kleimheist, like the rope to be about 20% to 50% bigger.
2) Use a Blakes hitch to connect the Purcell to the main rope.

The longer Purcell can be made with around 3.5 meters of cord. The length of cord is determined by how long you want the loop to be (shortest overall length times 2) plus enough for two Blakes hitches.

I have tried this as an adjustable safety tether, with 6mm nylon cord, and it works fine. I do not have the facilities to try a drop test. Maybe Sonny could do this. Tying it this way makes it much less messy but really doesn't increase the usefulness at all.

Rambler-joe

[Marc McDonald]

Don't know if you caught it in a previous post, but there were thoughts that the purcell was finitely adjustible. It is infinately adjustible if you girth hitch the "figure eight bight" to your harness and put another carabiner into your belay/rappel loop. Clip the anchor with a carabiner attached to the prusik end of the purcell. This gives you a fair amount of adjustment in and out, but doesn't allow you to suck right up to the anchor. To get closer to the anchor, just clip the carabiner attached to your belay/rappel loop to the loop of the prusik and it will allow you to adjust as close as you want to the anchor without ever being disconnected from the original anchor.

I tried this suggestion last weekend and it worked perfectly. There aren't many times I feel the need to be that close to the anchor, but it's a nice trick to know.

Marc

[rcwild]

Remedy.:)
Using 2 to 2.5 meters of cord you can build a short Purcell.
1) Form the loop using a Blakes hitch. The Blakes is one of the few hitches that will grip on it's own diameter. A classic prusik, or kleimheist, like the rope to be about 20% to 50% bigger.
2) Use a Blakes hitch to connect the Purcell to the main rope.

Rambler-joe

Cool idea. Reason to practice tying that Blakes hitch again.

[bw_rambo]

Hi,

I wonder if following System may work as a adjustable lanyard: Take 2-3 m of thin dynamic rope (~9mm), in one end a figure of eight loop. The other end connected to itself with the blakes hitch. So there should be no problem to hold a factor 2 fall.
I´d use single rope but maybe 1/2 would work too.

Bye

bw_rambo

[rcwild]

That should work. Same principal as a Purcell Prusik, but with only one strand instead of two.

[bobeck]

Hi,

I wonder if following System may work as a adjustable lanyard: Take 2-3 m of thin dynamic rope (~9mm), in one end a figure of eight loop. The other end connected to itself with the blakes hitch. So there should be no problem to hold a factor 2 fall.
I´d use single rope but maybe 1/2 would work too.

Bye

Would your body sustain a factor 2 fall????????????????????:worried:

[rcwild]

Posted earlier in this thread. Wondering if the single-strand with blake's hitch idea will perform as well as the Purcell ???


I recently attended the International Technical Rescue Symposium in Fort Collins Colorado. ITRS is a yearly event where rescue professionals from around the world meet to exchange ideas on advances in rescue equipment and techniques. There was an interesting paper presented this year that directly pertains to this thread.

Research was done by Mike Gibbs of Rigging for Rescue in Ouray Colorado on the results of shock loading daisy chains and other commonly used positioning lanyards. In addition to being the owner of one of the premier rescue training organizations in the country (R4R), Mike is an active climbing guide as well as a member of the Ouray Mountain Rescue team. Mike performed dynamic testing on daisy chains as well as a number of positioning lanyards commonly used in climbing and rope rescue. The results of this testing were informative, to say the least. After reading this post, many of you may want to reconsider your choice in positioning lanyards.

Mike designed a drop test representative of what could take place in the field that would provide some indications as to the capabilities and/or limitations of positioning lanyards. A common example in canyoneering would be slipping from a stance when starting a rappel with the anchor at your feet resulting in dynamically loading your safety lanyard. The purpose was to examine the magnitude of peak forces as well as the integrity of the connections on certain commercially and user-created lanyards in a dynamic event. The drops were conducted with 80 kg and 100 kg mass simulating the weight of a climber or climber with a heavy pack and fall factors from 0.5 - 2.0. The surprise was how easily daisy chains and some other lanyards resulted in catastrophic failure on relatively short drops.

Test results were sobering at best. Particularly considering how many canyoneers still insist on using the daisy chain (almost 30% of poll responders) as their primary positioning lanyard. Daisy chains failed in short falls (FF 0.5-1.0) and slings made of Spectra/Dyneema webbing exhibited alarmingly high impact forces (>12kN) and catastrophic failure at surprisingly low fall factors. In canyoneering this could easily happen at any rap anchor below chest level. One slip and bang, you've dynamically loaded the anchor.

Nylon slings (not nylon daisy chains) and the Purcell Prusik came out on top as a result of their shock absorbing abilities. Typically, nylon slings held falls with reasonable impact forces (<10kN). The Purcell Prusik did best holding up to factor 2 falls with impact forces of less than 12kN. (FYI acceptable impact forces: CE 6kN, CSA/OSHA 8kN and UIAA 12kN).

I would urge all of you using daisy chains as your primary positioning safety lanyard to stop immediately! And those of you using Spectra/Dyneema slings for this purpose do the same. I would recommend you switch to something like the Petzl Spelegyca, Imlay Clipster, Purcell Prusik or nylon accessory cord or tape sling that has at least some dynamic shock absorbing ability.

Charly

[indieandie]

I gotta ask! What makes a daisy chain unsafe as a tether? (The same salesman led us right to them when we asked about a safety tether.) Thank you for increasing my awareness.

[rcwild]

I gotta ask! What makes a daisy chain unsafe as a tether? (The same salesman led us right to them when we asked about a safety tether.) Thank you for increasing my awareness.

Those damn climbing gear salesmen! :taz:

One of many topics we will discuss during the Basic Skills Workshop next Friday. In more detail then, but the short answer has two parts: (1) the loops tend to snag on things, dangerous if you happen to be under water at that moment; (2) daisy chains tend to be made of materials that are not capable of absorbing impact.

There is another thread in the forum about safety tethers. I will move these posts to that thread in a few minutes.

[Paul Nelson]

I gotta ask! What makes a daisy chain unsafe as a tether? (The same salesman led us right to them when we asked about a safety tether.) Thank you for increasing my awareness.

As Rich mentioned, a daisy chain is not designed to be a part of a protection system which can withstand high loads. In addition, as the video shows if you short clip the loops improperly and then take a fall which breaks the bar tacks, you are no longer attached to the daisy chain. :eek:

http://www.bdel.com/videos/daisy.html

For those using daisy chains because they like to shorten the tether, they should use something like Sterling Rope's "Chain Reactor" which does not have the problem of magic trick detachment of the daisy chain, and is rated at 12.4KN. However, the Chain Reactor is not a shock absorbing system so if you are above the anchor and fall, it will result in severe shock loads.

Using a piece of dynamic rope makes a good safety, or get one of the manufactured load absorbing safety tether.

[rcwild]

For those using daisy chains because they like to shorten the tether, they should use something like Sterling Rope's "Chain Reactor" which does not have the problem of magic trick detachment of the daisy chain, and is rated at 12.4KN. However, the Chain Reactor is not a shock absorbing system so if you are above the anchor and fall, it will result in severe shock loads.

Sterling Chain Reactor and Metolius PAS are both inappropriate as safety tethers as they are both very prone to snagging.

[Carl Armstrong]

Sterling Chain Reactor and Metolius PAS are both inappropriate as safety tethers as they are both very prone to snagging.
I don't agree. Even your picture of "efficient gear racking" has the potential to be very prone to snagging with the dozen or more points I count that could easily be snagged.

http://www.canyoneering.net/content_img/rack_good.jpg

[rcwild]

I don't agree. Even your picture of "efficient gear racking" has the potential to be very prone to snagging with the dozen or more points I count that could easily be snagged.

Of course, Lee. Any gear you are carrying has the potential for getting caught on things. So you should carry as little gear on your harness as possible and you should avoid individual pieces of gear that are especially prone to snagging.

Which do you think is more likely to snag on a branch or get caught in a crack and hold you underwater until you drown – a Spelegyca (single strand, 24" long) or a Chain Reactor or PAS (multiple loops, 36" long)? I'll give you a hint; it's not the Spelegyca.

The BEFORE photo:

[bobeck]

Those damn climbing gear salesmen!

Hey! I are a "damn" climbing gear salesman!:mad:
I don't push daisey chains! I am 100% sold on Purcell Prusiks Period........ I have been pushing the system for over 9 years now. In moving water just be sure to attach the shortest purcell as your anchor tether, and if needed, "knot" it to shorten it. I have not had a daisey chain in my personal inventory for 9 years and likely will never have it again.

[indieandie]

yessir:OK OK OK Rich--take a Valium. I promise in the future to consult my canyoneering gurus before buying anymore equipment. Want to exchange a daisy chain for a prusick??? :bigeyes::cry::

Two more days to prepare for one of our most exciting expeditions. I know all you guys out there are accustomed to this stuff...but its new to us and we are loving it.

Doug, 14, will be attempting to get his climbing badge for his Boy Scouts. I know climbing is not canyoneering but the badge includes most of the needed skillls to become a really good canyon cat.

Now Rich, its time to forget all those "other" salesman, and think exclusively about the Moose Drool. Now, don't you feel better. :happydance:

[indieandie]

OOOPS!!! Sorry, Bobeck--thought that Rich was the salesman....but you can have a Moose Drool too. Hope to meet you at the rendezvous.

[rcwild]

OOOPS!!! Sorry, Bobeck--thought that Rich was the salesman....but you can have a Moose Drool too. Hope to meet you at the rendezvous.

Bo accepted the climbing gear salesman monicker, but he's also a canyoneering gear salesman. That makes him a fine exception. You would have purchased all the correct gear at his store. :2thumbs:

We won't be seeing Bo for the rendezvous until we get to Zion. I guess we could save one Moose Drool for him ... assuming you have now decided to bring several cases.

[oldno7]

I'd trade you a purcell for a daisy chain or you could bring some 6mm cord to the rondy and have someone show you how to make your own.
or you could have the redheadedselfappointedcanyonGod sell you some at the rondy and make your own. Or you could listen in his class and he'll convince you that you need neither.:teacher:

[oldno7]

http://www.geocities.com/r_riversong/Purcell_Prusik_tying_technique.jpg

[oldno7]

http://www.pbase.com/phil_box/purcell_tie_in

there, now you can have one tied up ahead of time. Soak it in red muddy water before coming to give that broke in, well used look. (thats what I do with all my gear):devil:

[brucefrombryce]

Hey Bo I would not totally rule out a daisy chain for a specific instance, and that is in skinny canyons where it is inefficient to wear a full harness.

1. A daisy chain closed with a locking biner around your waist and attached to your pack is an a great way to have your pack ready for hanging from a shoulder or below you should, and it will, the need arise.

2. a daisy chain in similiar canyons is an excellent tool for lowering individuals under control where is in not prudent to jump or slide into a pool with a lot of speed due to the unknown below the surface. That way it is not necessary to pull out that long rope you are carrying.

FWIW,

bruce :)

[bobeck]

Hey Bo I would not totally rule out a daisy chain for a specific instance, and that is in skinny canyons where it is inefficient to wear a full harness.

1. A daisy chain closed with a locking biner around your waist and attached to your pack is an a great way to have your pack ready for hanging from a shoulder or below you should, and it will, the need arise.

2. a daisy chain in similiar canyons is an excellent tool for lowering individuals under control where is in not prudent to jump or slide into a pool with a lot of speed due to the unknown below the surface. That way it is not necessary to pull out that long rope you are carrying.

FWIW,

bruce :)

Agreed Bruce! But a Purcell does even this better!:)

[sonnylawrence]

I am with Bo. I use Purcells a lot. The one down side is absorbing water. I have had them freeze in the winter.

[ratagonia]

Hey Bo I would not totally rule out a daisy chain for a specific instance, and that is in skinny canyons where it is inefficient to wear a full harness.

1. A daisy chain closed with a locking biner around your waist and attached to your pack is an a great way to have your pack ready for hanging from a shoulder or below you should, and it will, the need arise.

2. a daisy chain in similiar canyons is an excellent tool for lowering individuals under control where is in not prudent to jump or slide into a pool with a lot of speed due to the unknown below the surface. That way it is not necessary to pull out that long rope you are carrying.

FWIW,

bruce :)

Yes, but... Works just as well with a regular sling or chain of over-the-shoulder slings, and they are a lot stronger, less resistant to using incorrectly, and tend to get in the way a lot less. I don't see a real advantage to using a daisy chain in these circumstances - and lots of downsides.

Tom

[rcwild]

The only application I can think of where a daisy chain shines is for dangling your pack below you while stemming. Girth hitch the daisy to your pack and clip it to your harness with a carabiner. When it's dangling too high or too low you can move it to another loop on the daisy. Your pack does not need a full strength loop like your body does.

I described an application for a Metolius PAS in another thread titled Extend the Anchor Tie-In (http://www.canyoneering.net/forums/showthread.php?t=1649).

[indieandie]

Geez! Hope I remembered to pack the Moose Drool! Probably, one case for Rich is all I can afford. Maybe, he will share with the rest of ya. Personally, I am a wine drinker but I understand guys and their beer. Hope you all have fun~~see you all in a few...Andie

[charlybldr]

Carl,

Regarding the problem of using either the Metoleus PAS or Sterling Chain Reactor as a personal lanyard, both exhibit excessively high impact forces in dynamic loading.

I am currently traveling and so do not have access to Mike Gibbs test data. When I get home this weekend I will look up the numbers and post here.

Regarding the Blake's Hitch technique described above, although the BH works well with double braid arborist rope it doesn't work so well with canyon rope. The stuff is too stiff and the BH tends not to grab when you want it to. Even dynamic kernmantle rope seems to be too stiff.

[bobeck]

Carl,

Regarding the problem of using either the Metoleus PAS or Sterling Chain Reactor as a personal lanyard, both exhibit excessively high impact forces in dynamic loading.

I am currently traveling and so do not have access to Mike Gibbs test data. When I get home this weekend I will look up the numbers and post here.

Regarding the Blake's Hitch technique described above, although the BH works well with double braid arborist rope it doesn't work so well with canyon rope. The stuff is too stiff and the BH tends not to grab when you want it to. Even dynamic kernmantle rope seems to be too stiff.

I hope you check your voicemail regularly. I am in need of some info. regarding St. George Fire Dept. Maybe you are travelling south and can stop by to give the necessary training so that I (we) can profit mutually?

PURCELL PRUSIKS RULE! Forget the moose drool and whatever else that accumulates.

[rcwild]

Forget the moose drool ...

NOOOOOOOOO !!! :worried:

[sonnylawrence]

Regarding the Blake's Hitch technique described above, although the BH works well with double braid arborist rope it doesn't work so well with canyon rope. The stuff is too stiff and the BH tends not to grab when you want it to. Even dynamic kernmantle rope seems to be too stiff.
I have played with this quite a bit. As Charly said, stiff ropes don't work. Otherwise I don't see a pattern. Some ropes will perform surprisingly well. I have used the Blake Hitch with nylon and Spectra webbing. A downside, once it is set, it may be difficult to untie.

[rcwild]

Regarding the problem of using either the Metoleus PAS or Sterling Chain Reactor as a personal lanyard, both exhibit excessively high impact forces in dynamic loading.

I am currently traveling and so do not have access to Mike Gibbs test data. When I get home this weekend I will look up the numbers and post here.

I don't think Sterling's product existed yet when Gibbs conducted his tests. Sterling simply copied the Metolius PAS design, but made it with nylon instead of the Dyneema/nylon blend of the PAS. Being made of nylon, impact forces should not be as high when dynamically loaded.

[charlybldr]

The test data to which I refer was presented at two separate International Technical Rescue Symposiums (ITRS) November 3-6, 2005 in Ft. Collins Colorado and November 2-6, 2007 in Golden Colorado by Mike Gibbs of Rigging For Rescue out of Ouray Colorado. The 2005 presentation critically evaluated several commercially available lanyards in various shock loading scenarios, many of which tested poorly at relatively benign fall factors. The 2006 study focused primarily on evaluating the Purcell Prusik as an alternative to daisy chains (and other similar lanyards) as a positioning lanyard for rescue and climbing.

Mike's 2005 presentation paper states:

"The introduction of high performance fibers into climbing and rope rescue equipment has some worthwhile applications. However, the use of HMPE* like Spectra or Dyneema in the construction of daisy chains is simply a bad idea. The properties of HMPE include the benefits of high strength, the ability to float and excellent resistance to chemicals and UV degradation. However, HMPE properties also include very low elongation at break and a low melting point. It is these last two properties that are likely the key contributing factors to:

1. the high peak force values observed in our testing of lanyards constructed out of these materials.
2. the breaking of these same lanyard types on certain drops."

The paper continues:

"A primary attachment lanyard in rescue work as well as climbing is an ubiquitous piece of equipment. The selection of that piece of gear should be made with careful considerations of the desirable characteristics for the activity {e.g. easily adjustable, lightweight, multi-function, etc.}."

To quote from Mike's 2006 presentation paper:

"Several of the lanyards examined in 2002 and 2005*** demonstrated serious shortcomings in a shock loading scenario due to either (1) excessive MAF and/or (2) the lanyard failed or its condition was severely compromised."

"One of the lanyard configurations tested in 2002 and 2005 that showed some promise was the Purcell Prusik. Our intent in the 2006 drop test series was to conduct a number of drop tests on Purcell Prusiks in order to gain a better understanding of their capabilities and limitations as a personal restraint lanyard in a shock loading scenario. Our hope was to identify a suitable alternative choice to traditional lightweight personal restraint lanyards such as the daisy chain, for example."

Suggested Performance Guidelines:

1. Acceptable MAF** at a fall factor of 1 - less than or equal to 8 kN.
2. Lanyard integrity OK at a fall factor of 1"

Summary
Out of 39 test drops the Purcell Prusik exhibited NO FAILURES at FF1 and MAF of less than 8kN in all but two drops (both of which were <9kN). FF1 drops on other lanyards consistently exhibited higher MAF and in some cases catastrophic failure.

Examples

lanyard, material, MAF, comments
Metolius PAS, Dyneema/nylon, 20.2 kN, fusing between chains
Metolius PAS, Dyneema/nylon, 17 kN, catastrophic failure
Metolius PAS, Dyneema/nylon, 19.5 kN, no visible damage
Metolius Monster Daisy, Dyneema, 11.8 kN, three blown pockets
Metolius Monster Daisy, Dyneema, 10.6 kN, three blown pockets
Metolius Monster Daisy, Dyneema, 12.1 kN, one pocket away from failure
Black Diamond Daisy, Spectra, 9.1 kN, catastrophic failure

Mike's conclusion:

"When selecting a lanyard either to purchase or construct:

1. avoid the use of low-elongation high performance fibers.
2. choose one that limits MAF to a reasonable level.
3. keep in mind that a lanyard that reduces MAF, subjects the user to other hazards due to increased fall distance.
4. select one that retains function even after a severe drop."

and:

"When using a lanyard as the only means of attachment to an anchor:

1. keep unnecessary slack out of the lanyard, thereby keeping the potential fall factor low."

The above research sheds interesting light on commercially available personal safety lanyards which are often the choice of canyoneers. Each of us will choose our own lanyard for canyoning based on a number of criteria. The data presented above indicate that lanyards made of HMPE are not suitable because of their inability to hold MAF within acceptable levels and the possibility of catastrophic failure.

Considerations in your lanyard choice should also include weight, compactness and tendency to "snag" or "catch" on hazards in the canyon environment. Additionally, the tendency for a daisy chain to be incorrectly clipped makes this design unsuitable as a personal safety lanyard for canyoning.

Accordingly, my personal favorite choices for a personal safety lanyard are:
Petzl Spelegyca
Imlay Clipster
Purcell Prusik


*HMPE = high modulus polyethylene
**MAF = maximum arrest force
***two independent drop test series

[tj_wetherell]

Charly,

Very interesting. Is there a way to provide the full report (legally). I would very much like to read it. I'm interested in the test setup and instrumentation used to take the measurements.

While the study evaluated the PAS and some Daisies, It would be interesting to see what forces the Spelegyca and Clipster see.

-tom (w)

[charlybldr]

Mike Gibbs of Rigging For Rescue in Ouray Colorado has most graciously given us permission to publish his research on Personal Safety Lanyards and the Purcell Prusik.

"Daisy Chains and Other Lanyards: Some Shocking Results when Shock Loaded" was presented at the 2005 ITRS conference in Ft. Collins Colorado from data obtained in two independent drop test series conducted in 2002 and 2005.

A number of the lanyards examined in these tests demonstrated serious short comings. One of the lanyard configurations however, did very well.

"Drop Testing on Purcell Prusiks: A Critical Evaluation of Their Capabilities as a Positioning Lanyard in Rescue and Climbing" was presented at ITRS in 2006 from drop tests earlier that year. These tests were done in order to better understand the capabilities and limitations of the Purcell Prusik when used as a personal restraint lanyard in a shock loading scenario.

The two papers are now attached to this thread for those of you who are interested in closer examination of Mike's research.

Mike Gibbs is an active climbing guide and volunteer member of the Ouray Mountain Rescue Team as well as owner of Rigging For Rescue offering technical ropework seminars and consulting out of Ouray Colorado. For more information on R4R please visit their website at: http://www.riggingforrescue.com/

[beadysee]

"Daisy Chains and Other Lanyards: Some Shocking Results when Shock Loaded" was presented at the 2005 ITRS conference in Ft. Collins Colorado from data obtained in two independent drop test series conducted in 2002 and 2005.

That's pretty darn interesting stuff. Thanks.

There was a thread on the supertaco climbing website which started, I think, with a video/photo's from BD on the dangers of daisy chains.

A guy from Metolius posted this:

"Standard webbing isn't strong enough to achieve the strengths needed. Therefore we had to design a custom webbing and order 5000 yds (per color) of it just to start the project (that’s a fair amount of PASs). It requires an extra heavy duty nylon/dyneema blend (16mm) as the loops are in contact with one another throughout the chain. This system creates a lot of friction (when under load) and needs a very robust webbing to achieve the strength number. 4050 lbf. is the PAS's rated strength, stronger than the stringent UIAA harness standard of 3600 lbf. There are 6 hot cut parts that are combined with a total of 62 bar tacks and a box of straight stitching. Plus one small label. Then it gets inspected and every tack and stitch is recounted. Once it passes inspection it goes onto a well thought out piece of packaging which is die-cut and specifically shows how the PAS is used. Without the packaging we felt like people wouldn't understand the reasons why daisy chains were being misused. The packaging also shows how the PAS is to be used correctly. At the end of the day our margin is quite low, but we feel like it is an important enough item that we needed to do it regardless of how much we actually made. We hope this answers a few of the questions you all have had.
Cheers,
Metolius Climbing"

What I'm curious is if the PAS has changed in material construction since the testing done? Its not 100% dyneema but a mix of nylon and dyneema. Anyone know??

Its a little troubling that the PAS doesn't hold up to a 1.25 fall factor and busts in the sub 20kN range (imparting that much load into a belay system wouldn't be a good thing, methinks).

I like the PAS. Well made and very functional. Now I'm kinda rethinkin' my tether use, and, may consider a swith to a 6mm purcell prusik with the Mammut pro cord. Have to see how bulky and functional it would be.

Good stuff. Thanks for attaching those documents, Charley.

-Brian in SLC

[Marc McDonald]

Charly,

Thanks for posting the PDFs of the lanyard tests. The results are very interesting and should be sobering to anyone still using a daisy chain or PAS as a personal lanyard system.

Marc

[Gertjan]

Hello canyoneers,

I'm reading with big interest most of the discussions on the ACA forum as European canyoneer.
It’s interesting to see how many sorts of lanyards are used in America especially the purcell-prusik. This sort of lanyard is real American I believe, never seen yet in European canyons.
In Europe there are three sorts of lanyards mainly in use. The Petzl Spelegyca, the Beal Dynadoubleclip and selfmade lanyard of dynamic rope in 9 til 11mm. In 2006 there was an test for the most used lanyards in Europe, sortlike as the tests of Mike Gibbs. The tests are done by the French Cave and Canyoning Organisation EFS.
Who is interested, you can read the results on the next site:
http://efs.ffspeleo.fr/get/longes/longes.pdf
It’s only in French, so I don’t know how wel your French is.
About a week I’am going canyoning or canyoneering how you call it for 2 weeks in France and Spain. I will try the purcell as lanyard.
Canyongreetz from Europe

[W. Kay]

I've been following this thread and am now curious as to the strength of the safety tether I use.
I tied a daisy chain from webbing as per instructions in Craig Luebben's "Knots for Climbers" book. It takes about 15-20 minutes to make at home on the couch and is a lot cheaper than other options. I'm thinking that the webbing will take more energy to fail than I am capable of building in a full tether length, worst case fall. This is pretty much the same stuff we're using to anchor with. The loops are isolated with overhand knots. The end loop is a water knot with the tails sewn back into to the loop to bar any slippage back into the knot. The sewn tails was my own idea. I feel secure that the issue of popping bar tacks and releasing the biners when clipped into the center loops of a standard daisy chain is of no issue with this setup. There is a knot between each loop. I attach an off center loop with a triangular link to the belay loop on my harness. This gives me two unequal lengths that can be used with biners in a number of ways. I'm also not limited to two clip off lengths.
Am I living a lie? Is this less secure than I believe it to be? I'm interested in finding out.

[charlybldr]

What I'm curious is if the PAS has changed in material construction since the testing done? Its not 100% dyneema but a mix of nylon and dyneema. Anyone know??

To the best of my knowledge the PAS's in Mike's testing were the same webbing as that which is currently being used. (a blend of dyneema and nylon)


I like the PAS. Well made and very functional. Now I'm kinda rethinkin' my tether use, and, may consider a swith to a 6mm purcell prusik with the Mammut pro cord. Have to see how bulky and functional it would be.

I would like to make it clear that my intention is not to demonize either the daisy chain or Metoleus PAS with this information. Both products are perfectly suitable when properly used as they were designed for their intended purpose (to clip in short to support body weight when aid climbing).

Neither of these products were designed to withstand a dynamic loading, nor are they intended to. When used as a personal safety lanyard, either in rescue situations or when climbing or canyoning, dynamic loading is a real possibility. I see people using daisy chains when canyoning all the time! I am pretty sure these people have no idea they are using their daisy chain improperly nor are they aware this could put them in a compromising situation. Ditto for Spectra or Dyneema runners.

The Purcell Prusik is not the perfect solution. Although in my opinion, it's a pretty good one. The Petzl Spelegyca and Imlay Clipster are good alternatives too.

[charlybldr]

Am I living a lie? Is this less secure than I believe it to be? I'm interested in finding out.

Without seeing some kind of test data to confirm I can't say for sure but I would expect your approach (daisy chain tied out of nylon webbing) to be a more reasonable alternative as tied pockets are more than likely stronger than sewn pockets and nylon webbing at least has some shock absorbing ability.

But I then ask, how much is your life worth?

If it is a matter of cost, the Imlay Clipster is an inexpensive solution. Purcell Prusik's aren't that spendy either. I used a Spelegyca for years and still like this product. But I will say it again...

The daisy chain was developed to clip in short when aid climbing. It was not developed to be used as a personal safety lanyard. Use the right tool for the job.

[beadysee]

I would like to make it clear that my intention is not to demonize either the daisy chain or Metoleus PAS with this information. Both products are perfectly suitable when properly used as they were designed for their intended purpose (to clip in short to support body weight when aid climbing).

Neither of these products were designed to withstand a dynamic loading, nor are they intended to. When used as a personal safety lanyard, either in rescue situations or when climbing or canyoning, dynamic loading is a real possibility. I see people using daisy chains when canyoning all the time! I am pretty sure these people have no idea they are using their daisy chain improperly nor are they aware this could put them in a compromising situation. Ditto for Spectra or Dyneema runners.

Hmm. The PAS is being marketed and sold for anchoring besides aid climbing. I think the PAS' purpose is to replace all those daisies folks are using for something besides (and in addition to) aid climbing. They surely don't limit the PAS use either on their website, or, on sellars websites either. And, when I bought mine direct from them (OR show), they indicated it was for any anchoring use with regard to climbing.

Web info and sellar info below.

I still like it. Played around a bit with some 6mm cord and I think too bulky for my use, perhaps, and maybe not as user friendly. I like being able to quickly clip a PAS and then back up by clipping in further down on it from another anchor.

Also, constructed a quasi PAS from a triple shoulder length piece of dyneema from Mammut (which appears a bunch thicker than the advertised 8mm?). Very low bulk. With figure eight knots, I'd imagine it would have some sort of shock absorbing ability (hopefully reducing peak load).

I guess I'll have to consider dynamic load limitations with regard to these items' use. Hmmm....

If anyone can read French, please attempt to summarize the conclusions in that attached article, if possible. Or, if there's a word or another cut-and-paste version available, might be easy to stuff into an on-line translator.

-Brian in SLC

The PAS is yet another example of Metolius’ commitment to products that are safer by design. It is designed to give the climber a high-strength anchor connection while threading for the lower, setting up a rappel or belaying. The PAS should replace the daisy chain that many climbers wear affixed to their harnesses for belay change-overs. Daisy chains should NOT be used because they are full-strength only when loaded in the end loops (intermediate pockets are only 300 lbf/1.3 kN). The PAS is super convenient and easily adjustable--just clip the loop which puts you at the correct height and . . . voila! When not in use, just leave it girth-hitched to your tie-in points, gather the extra loops and clip to the side for compact storage. The PAS is constructed from our super-strong, proprietary Power Webbing™.

Description:
The innovative PAS (Personal Anchor System) from Metolius provides climbers with a strong, adjustable system for conveniently attaching the climber to any anchor.
Features:
• It's constructed of chain linked 16mm Dyneema/ Nylon webbing that is rated at 4050 lb.
• At a two bolt sport or rappel anchor, it can be clipped into one bolt at the appropriate length and the remaining tail can be clipped into the other bolt as a backup
• The PAS is easily stowed by clipping the loops on to a biner then into a gear loop

[charlybldr]

I have no real argument with the PAS design. Each loop being full strength addresses the "less than full strength loops" of the daisy design as well as eliminates the problem of improper clipping. And you could argue any safety lanyard is bulky and could get in the way. It's the use of low-elongation high performance fibers that gives me pause. For two reasons:

1. Slings made of these fibers tend to exhibit higher peak force values in dynamic loading as they are not able to stretch to absorb any of that energy. The energy's gotta go somewhere. Think "less than bombproof anchor".

2. Add in that fiber rubbing against fiber thing. When these slings break the ends of the fibers exhibit signs of melting. And Spectra/Dyneema melts at considerably lower temperatures than either nylon or polyester. Spectra in direct contact with more Spectra? The all-nylon Sterling version is probably a better choice.

But in your case Brian, you know how to use a daisy (or equivalent) properly. I would be willing to bet the chance of you dynamically loading your safety lanyard is slim to none. It's the less experienced canyoners out there who walk into an outdoor store and see the daisy chain hanging on the wall as the answer to their prayers that worry me.

[charlybldr]

Hello canyoneers,

I'm reading with big interest most of the discussions on the ACA forum as European canyoneer.
It’s interesting to see how many sorts of lanyards are used in America especially the purcell-prusik. This sort of lanyard is real American I believe, never seen yet in European canyons.
In Europe there are three sorts of lanyards mainly in use. The Petzl Spelegyca, the Beal Dynadoubleclip and selfmade lanyard of dynamic rope in 9 til 11mm. In 2006 there was an test for the most used lanyards in Europe, sortlike as the tests of Mike Gibbs. The tests are done by the French Cave and Canyoning Organisation EFS.
Who is interested, you can read the results on the next site:
http://efs.ffspeleo.fr/get/longes/longes.pdf
It’s only in French, so I don’t know how wel your French is.
About a week I’am going canyoning or canyoneering how you call it for 2 weeks in France and Spain. I will try the purcell as lanyard.
Canyongreetz from Europe

Both these lanyards look like they would work well. Particularly if they are made of dynamic rope. Lanyards similar to these (made of dynamic climbing rope) are commonly used among IRATA Rope Access Technicians.

[tj_wetherell]

Again, We have a great thread going here....

Charly (and Mike) Thanks for posting the test results. I haven't had time to go through it carefully, but there were some interesting findings, including the force plots when they used the Yates Screamers....

Brian, I think the Purcell just as compact as the PAS and maybe a bit less prone to snagging - but then I never wore the PAS like Metolius shows (bunched up) - PAS was my previous tether. I tend to wear mine wrapped around my waist (full extension) or down through the legs and clipped to a rear gear loop.

One of the things I really like about the Purcell is that you can clip two anchors simultaneously and yet load the anchors equally. PAS lets you clip 2, but only one is weighted. I won't try to post pics here, but here is a link to some I just took: http://tinyurl.com/4syaun. (As a side, I think it might be a great solution to equalizing anchors or multiple pieces of gear).

The first photo shows the Purcell "collapsed". Notice I don't girth hitch it to my harness - I use a large aluminum rapide - no strength reduction. I also tie mine with a triple-fish instead of an F8.

The second pic shows the Purcell clipped to (2) horizontally placed anchors. I tie an overhand just after the "Prussik" so that if one leg or anchor fails, both strands still pull on the knot to clamp the standing legs.

Third pic is with an "anchor" failure.

Forth pic shows the ability to equalize with "anchors" at different "heights" (one bolt higher on the wall than the other.

Fifth is just a close-up.

Now I don't actually know if this setup achieves what I want it to, I don't have the ability to test the survivability when one leg is allowed to fail, but it seems to work...

Anyone have any comments?

-tom(w)

[beadysee]

Brian, I think the Purcell just as compact as the PAS and maybe a bit less prone to snagging - but then I never wore the PAS like Metolius shows (bunched up) - PAS was my previous tether. I tend to wear mine wrapped around my waist (full extension) or down through the legs and clipped to a rear gear loop.

One of the things I really like about the Purcell is that you can clip two anchors simultaneously and yet load the anchors equally. PAS lets you clip 2, but only one is weighted. I won't try to post pics here, but here is a link to some I just took: http://tinyurl.com/4syaun. (As a side, I think it might be a great solution to equalizing anchors or multiple pieces of gear).

The first photo shows the Purcell "collapsed". Notice I don't girth hitch it to my harness - I use a large aluminum rapide - no strength reduction. I also tie mine with a triple-fish instead of an F8....
Anyone have any comments?

I looked at 6mm for the Purcell rig, and, especially with a high profile knot likt he triple-fisherman's, its way bulkier than the PAS. I gave thought to tying one with a flemish bend, as its quite a bit lower profile.

Can't see your pictures, but, my guess is you are clipping the Purcell like an "atomic knot" type arrangement? Ie, bowline on a bite where you eat the bite and create two loops to clip to. The PAS is easy to clip single to a primary anchor, then follow up by clipping a lower loop.

Equalizing anchors is easier for me if I tie a power point to the anchors, rather than try to equalize from my harness tether.

Adding a rapide to my harness isn't desirable. Heavy and not as easy to remove the tether if need be. My bet is the Purcell rig, with rapide, weighs and takes up a bit more space than a single PAS.

I wear the PAS by clipping an intermediate loop (as well as the end loop) and attaching it to one of the back side gear loops on my harness. Doesn't seem to get in the way too much.

Note: I mostly climb, so, my application is primarily for climbing. But, I've used Tom's clipster in combo with a sling for canyoning. Sweet.

Cheers,

-Brian in SLC

[charlybldr]

Again, We have a great thread going here....
Brian, I think the Purcell just as compact as the PAS and maybe a bit less prone to snagging - but then I never wore the PAS like Metolius shows (bunched up) - PAS was my previous tether. I tend to wear mine wrapped around my waist (full extension) or down through the legs and clipped to a rear gear loop.

"In use" I wear my Purcell Prusik girth hitched to the primary attachment point on my harness, then clip it back to a gear loop on the right side of my harness. Simply unclip from the gear loop and clip into the anchor. Adjust to length. Voila.

When not in use, I wrap it snugly (like you would a prusik or sling) and hang it off one 'biner clipped to my harness either around back and out of the way or clipped inside the top flap of my pack (really out of the way).


One of the things I really like about the Purcell is that you can clip two anchors simultaneously and yet load the anchors equally. "snip" (As a side, I think it might be a great solution to equalizing anchors or multiple pieces of gear).

This method of clipping in is not the way the PP is conventionally used and certainly not the way Mike tested it. The Purcell Prusik's shock absorbing ability depends on the prusik knot slipping as it tightens down. I am afraid your method of clipping two anchors simultaneously will interfere with this and would not recommend it. Rather, you should equalize your anchor to a single attachment point. Clip into this point with your lanyard.


The first photo shows the Purcell "collapsed". Notice I don't girth hitch it to my harness - I use a large aluminum rapide - no strength reduction. I also tie mine with a triple-fish instead of an F8.

The second pic shows the Purcell clipped to (2) horizontally placed anchors. I tie an overhand just after the "Prussik" so that if one leg or anchor fails, both strands still pull on the knot to clamp the standing legs.

I find it interesting that you use a rapid link instead of a grith hitch to attach the PP to your harness, then clip the loops to separate anchors both weakening the system and diminishing the PP's ability to absorb a shock load. This appears to me to be nothing more than a mis-guided attempt to personalize the system. I'm afraid your getting off track here.


Forth pic shows the ability to equalize with "anchors" at different "heights" (one bolt higher on the wall than the other.

Tying a knot in the Purcell Prusik definately negates its ability to absorb a shock load.


Now I don't actually know if this setup achieves what I want it to, I don't have the ability to test the survivability when one leg is allowed to fail, but it seems to work...

I'm not sure how you conclude that it " seems to work". Yes, you can rig the PP in all the ways you show but I seriously doubt in the end that these methods will actually work.

[tj_wetherell]

Guys, thanks for the replies....


"
The Purcell Prusik's shock absorbing ability depends on the prusik knot slipping as it tightens down. I am afraid your method of clipping two anchors simultaneously will interfere with this and would not recommend it. Rather, you should equalize your anchor to a single attachment point. Clip into this point with your lanyard.

For the purposes of comparison with the PAS I proposed that concept as a benefit. With the PAS it is not possible to spread the load over two anchors. Brian probably uses his tether in the same way I do. When climbing, having reached the anchor, but not yet having rigged anything with a power point like a cordelette or equalette (or for threading the chains and rapping or lowering). If I want to clip both anchors, what is my alternative? I could clip both anchors through both "legs" of the Purcell, but then I have formed a "death triangle", or I could use remaining gear, or the lead rope. If I am using a Daisy or PAS I clip one anchor and then another - but if one blows, the other gets the "shock" load. Typically I clip the Purcell into one anchor, then clove the lead rope to the other. The idea of using the two legs independently is a *concept* which has not been proven - I present it here for discussion.


"
"I find it interesting that you use a rapid link instead of a grith hitch to attach the PP to your harness...

Why? tying a knot weakens the cord. The Girth Hitch has been shown to weaken joined *slings* significantly ~30%. Chris Harmston did some testing of this. Admittedly this is not exactly the test setup, but why tie a knot when you don't have to. The Aluminum rapide is less bulky than the belay loop, and too narrow to rotate and cross-load. It has a nice 10mm diameter, and is rated at 500lbs SWL, around 3800lbs MBS... Note that in Mike's paper of the test samples that broke it was at the figure 8 knot (~10kn) - but since Mike didn't put a picture of the test setup I don't know if there was a girth hitch as well, or how he was anchoring the Purcell. I know there is always lots of variation in reported knot strengths... The fishermans allows the sliding necessary when you are equalizing the legs.


"
...then clip the loops to separate anchors both weakening the system and diminishing the PP's ability to absorb a shock load.

Err. No proof (yet) that the system is weaker (MBS).

Where I propose to clip into both strands individually (IMHO) you are not climbing above the anchor. I agree that for the energy absorption the Purcell needs to have range to slip, and this would certainly limit that! And as the Prusik slips, the angle between the two anchors would increase = force multiplier! This is simply to show equal versatility to the PAS, and maybe, if proven, additional versatility.


"
This appears to me to be nothing more than a mis-guided attempt to personalize the system. I'm afraid your getting off track here.



"
Tying a knot in the Purcell Prusik definately negates its ability to absorb a shock load.


Err... I'm not sure the picture was clear enough. You do mean the overhand knot right? The overhand is tied just after the Prusik. It does nothing to limit the "slip" only the extension if one leg or anchor were to fail (if two separate anchors were clipped) EDIT -> I think I just realized what you were thinking. I use the overhand to ensure that the Prusik grabs as intended, not to limit the amount it grabs (thereby reducing energy absorption)...


"
I'm not sure how you conclude that it " seems to work". Yes, you can rig the PP in all the ways you show but I seriously doubt in the end that these methods will actually work.

By "seems to work" I mean it "seems" to be a way to equalize two anchors if need be - thus the disclaimer. I agree that the additional configuration will *not* perform as the standard Purcell. What I proposing is the opportunity to make your personal anchor SERENE. The "S" (Secure) is in need of testing, the "E" Equalized is in need of testing but I believe it to be true, the "RE" (Redundant) is there if the "S" proves true, and the "NE" (No Extension) I believe to be true. If the blanks are filled in, I think this adds versatility to an already versatile system.

I'd love to test this in a fashion other than bench-racing.

-tom (w)

[beadysee]

Brian probably uses his tether in the same way I do. When climbing, having reached the anchor, but not yet having rigged anything with a power point like a cordelette or equalette (or for threading the chains and rapping or lowering). If I want to clip both anchors, what is my alternative? I could clip both anchors through both "legs" of the Purcell, but then I have formed a "death triangle", or I could use remaining gear, or the lead rope. If I am using a Daisy or PAS I clip one anchor and then another - but if one blows, the other gets the "shock" load.

I normally, when climbing up to an anchor, clip in with the rope. Kinda depends on how desperate I am for an anchor, though. Might clip a draw into one side and yell to my partner, "take!" If its steep, I might also clip in a biner or draw, clip the rope, then, one handed, clove hitch it back into that same biner. Then I'm hands free for dealing with the whole anchor thing at that point. And, really also depends on the anchor configuration. If I was building my own anchor, I wouldn't place an RP for instance, then clip the PAS into it, if my stance was poor and I was pumped...

When rappelling off a multi pitch route, is where I usually use a tether. I clip my PAS into one of the anchors, then, with a sling or quick draw, clip in lower down on the PAS (into one of the lower loops). This would seem to reduce the chance of shockloading if one side were to blow. It's really the beauty of the PAS, instead of a daisy (where the daisy alternate clipping loops might be super weak). Seems more reasonable than thinking about building a power point for a Purcell, then having to break it down when rappelling, if the anchor is not rigged into a power point to begin with.

Anyhoo, a knot in 6mm cord, especially single strand, wouldn't be very strong from the get go. Especially an over hand knot.

-Brian in SLC

[tj_wetherell]

I clip my PAS into one of the anchors, then, with a sling or quick draw, clip in lower down on the PAS (into one of the lower loops). This would seem to reduce the chance of shockloading if one side were to blow.

That is a good way to get a bit of extra safety - Thanks for sharing. I will use the lead rope unless I need it free - it is the strangest stretchiest thing I carry. Now in the canyons, it is the strongest, but very stiff.....



Anyhoo, a knot in 6mm cord, especially single strand, wouldn't be very strong from the get go. Especially an over hand knot.


In Tom Moyer, et. al - Comparative Cord paper a runner tied with a double (or triple) fishermans broke at about 180% of the average tensile strength of a single strand of 7mm nylon, in this case 5000lbs / 22kn. The overhand I use is actually a "double" used as a load limiter - how strong is it? The only testing I have seen for the overhand is as a stopper, and for joining ropes for rappel (there the strength reduction was ~40%) - however neither of these replicate using it as a load limiter (EDIT -> I meant extension limiter - not load limiter) ...which is a common use of the overhand. (EDIT-> anyone have data on strength reduction in a sling/runner with an overhand tied in it?)

-tom(w)

[sonnylawrence]

anyone have data on strength reduction in a sling/runner with an overhand tied in it?)

-tom(w)
The more I see of this type of information, the more impressed I am with the variability. The strength of the knot depends on the material and construction of the rope or sling. Nylon acts differently than Spectra. I imagine flat nylon sling acts different than tubular. My suggestion is to be careful generalizing data from one size or type of material to another.

[mecypher]

Rich I was in conversation about safety tethers this weekend with Jim & Michelle. Jim was telling us the importance of them and how to use them and why you would want them. But the truth of the matter is neither Michelle or I could remember you ever discussing these in the class and we never used them in class. Is this something that we should invest in before coming out to Zion in September?

[rcwild]

We actually did talk about them, but didn't use them. We were never in a precarious spot where we needed them. I made a comment about listening to that little voice in your head telling you when you are at risk near the edge, when the rock is slippery, on scree, etc.

Quite likely you will find yourself in situations in Zion where that little voice shouts at you - MOLLY; CLIP IN WITH YOUR SAFETY TETHER! HURRY!

http://www.wildernessadventures.com/store/index.php?act=viewCat&catId=9

[Cheese]

I use a 4 or 5 foot omnisling.

For those of you that dont know what omnisling is dont feel bad, its not that common. We found some at black diamond in SLC and got it because its basically a daisy chain without the drawback of the extra loops and double the strength. (instead of the webbing being sewn into a daisy chain, it is woven through itself, thus when not engaged, it is flat like a regular piece of webbing)

This allows me the ease of adjustment of just moving my beaner, and allows me to girth hitch the middle and have a double sided safety. Generally I keep one end longer than the other, and can easily micro adjust them, or use one for dangling a pack, etc.

I will try to take a good picture of it, so that you all can spot it next time you are at the gear store.

Stay Safe!

[W. Kay]

Jared Hillhouse operator of North Wash Outfitters has sold omnisling in the past. Check out his web site. www.northwashoutfitters.com (http://www.northwashoutfitters.com). I believe he carries 6 foot pieces just for this use. He cautioned my brother and myself not to use the last pocket at either end. He puts the locking biner in the second to the last pocket on the ends and folds and tapes the loose end over onto itself.
I'm sure that Jared will get back to you if you have any questions, he's always been good to get back with me between his jobs. He used longer pieces in his class to anchor multiple ropes and as safety hookups during the rappell training. This stuff has many uses.


W. Kay

[barleywino]

not sure whether this has already been discussed or not
http://british-caving.org.uk/rope/lanyard_tests_v6.pdf
knotted dynamic rope seems to have lowest impact force in these tests (see summary at end), not too surprising

[wiese]

At least it looks interesting, but I have never seen that in use before though.

[charlybldr]

Jared Hillhouse operator of North Wash Outfitters has sold omnisling in the past. "snip" He cautioned my brother and myself not to use the last pocket at either end. He puts the locking biner in the second to the last pocket on the ends and folds and tapes the loose end over onto itself.

The Omni Sling Jared sells is cut off a spool so the ends are not finished. There have been no reported incidents of the webbing unraveling however, no real testing has been done (to my knowledge) either. I believe this to be a good practice. BlueWater sells Omni Sling cut to specific lengths with finished ends. Costs a bit more but allows you to clip into the end pockets.


This stuff has many uses.

Indeed it does. Equalize multi-point anchors, personal lanyards and pothole escapes just to name a few.

[charlybldr]

not sure whether this has already been discussed or not
http://british-caving.org.uk/rope/lanyard_tests_v6.pdf
knotted dynamic rope seems to have lowest impact force in these tests (see summary at end), not too surprising


The IRATA Rope Access guys use knotted dynamic rope for their safety lanyards as well. 1.5m piece of dynamic climbing rope tied to a carabiner at each end. This system is proven in industry and works quite well. Also gives you something to do with those old retired climbing ropes.

[stevengines]

So I've read this entire thread a few times now along with most of the posted links to testing of the various set-ups. I've been climbing for years and I'm not ready to toss my daisy. After reading this I'll be using it differently though.

I've always loved the little details in things and this thread is full of them. I've now made a few purcell prusiks and dynamic cowtails to see the differences. I like the cowtail because you can set two ends at different lengths to give you the petzl spelegyca function with a lower impact force and tie off to both leg and waist loops leaving the belay loop free(i like the climbing harnesses). And I love the ease of use and adjustablily of the Purcell(plus they are cheap!)

I was wondering if anyone else has tried this with a Purcell Prusik though. Instead of girth hitching to the belay loop, take the loop and run it through both the leg and waist tie-in points then make it a double-figure eight (http://www.animatedknots.com/fig8loopdoublerescue/index.php)? I like this because there are two sets of ropes through the tie-in points. There is no girth hitch to ever get cinched down to worry about. My belay loop is clean. It's only slightly more difficult to attach then a girth hitch. I just push the loop back through the figure 8 pull the prusik end through the loop.

Any thoughts? I'm not trying to reinvent anything but it seems like a better way to use the Purcell as a tether.

[FredinUtah]

I have read this thread a few times & don't recall any controlled tests being reported on the Purcell Prusiks. I found this interesting and reassuring as I am using this and mine are made out of 6MM PMI cord.

Good reading.

"An Examination of Purcell Prusiks as Personal Restraint Lanyards"

http://www.marski.org/...gid=74&Itemid=26

[ewestesen]

On ascending with the Spelergyca, are you still clipping in a loop so you can 'step up' using a foot? How does that work out?

Are there any situations where you'd rather have something simpler like the Imlay Clipster (what I've been using) just because it's less stuff?

[bobeck]

I use and have used the Purcell Prusik System since 1997, and have always girth hitched the single prusik loop end into my swami and leg loops (same path as tying into a climbing rope or mainline) insuring that it is done on the left side of the belay/rappel loop as I'm right handed and wish to have the right side clear for ease of tying into a climbing/mainline rope if needed. I also use 6mm and figure it to be roughly a 9KN anchor tether. As far as dynamics? Hmmmmm? I certainly suspect that a dynamic event would see a bit of load limiting from the purcell, but then I would hope that I personally would never subject the purcell, myself or the anchor to this scenario? If I believe that there may be cause for a dynamic event at the anchor, I would then rethink how I might attach myself to the anchor? Maybe I would create a new tether by using an 8' piece of 11mm with fixed loops on each end and girth myself to one end and clip the other end to the anchor focal. By using a single 8mm prusik adjuster clipped to my belay loop I would then have a 4-8KN slip clutch load limiter? I still believe that a factor 2 fall on such system might be catastrophic, especially on so many anchors found and used in canyon hiking scenarios. I guess my thoughts on the matter is to just not let myself be put in a situation that I could shockload the anchor? Thoughts?

[charlybldr]

I guess my thoughts on the matter is to just not let myself be put in a situation that I could shockload the anchor? Thoughts?

As the saying goes: "An ounce of prevention is worth a pound of cure."

Transceivers, shovels and probes don't protect us from avalanches. Understanding snow science and avoiding dangerous slopes does.

We should always depend on our training, experience and judgment to keep us safe over relying on a piece of equipment and avoid putting ourselves in compromising positions whenever possible. I agree with Bo that a factor 2 fall in a canyoning situation could easily have catastrophic results so great care must be taken to avoid this possibility.

[charlybldr]

I have read this thread a few times & don't recall any controlled tests being reported on the Purcell Prusiks.

Mike Gibbs/Rigging For Rescue's papers referenced earlier in this thread are the only ones of which I am aware.

[bobeck]

Mike Gibbs/Rigging For Rescue's papers referenced earlier in this thread are the only ones of which I am aware.

I was first introduced to the Purcell Prusik System by Kirk Mauthner (previous owner prior to founder Arner Larsen of Rigging for Rescue). After attending 6 courses (4 under Kirk Mauthner ownership, 2 under current owner Mike Gibbs), the Purcell Prusik System is still taught and used as a multi-dimensional personal/rescue system. I have taught many folks how to construct and use this system and feel that it is one of the best, if not the best multi-purpose pieces of equipment that I carry with me in canyons, on climbs and on active rescues. I have not subjected it to shock loading, nor do I wish to, but I did use it yesterday on a multi-pitch 5.12 climb yesterday (4 pitches) and noticed that my older wrap 2, wrap 2 had a tendancy to slip when I bounced slightly while sitting on the hanging belay. Since tying my original Purcells I have started using Wrap 2, Wrap 3 and find that it is very much less apt to slipping.

[nonot]

I've had issues with slipping, but I'm using a dyneema sling so I guess that's to be expected. I had to go to a wrap 3, wrap 4 to stop the slippage but the knot is getting so long that it folds over itself and usually requires a quick dressing to get it in order. I'm thinking about ditching this idea and picking up a spelegyca. Still a good tool to have in the bag though.

[shagdeuce]

Most of the "how to tie" links in this thread are broken. I found this video on YouTube. It was just what I needed.

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[mountain man]

this is how I tie mine.

tried to place img tags but url wouldn't hotlink the image for me.

img
http://www.ahsrescue.com/popup.aspx?src=images/Product/large/1211.jpg

pic stolen from this site. click the image to get same image as above
http://www.ahsrescue.com/p-1211-personal-purcell-prusik-system.aspx

edit: and three loops to look like in this link. note the short loop is just you normal prusik cord loop tied with a double fisherman's.
http://www.rescuedynamics.ca/articles/knots/Knots.htm

[rcwild]

pic stolen from this site. click the image to get same image as above
http://www.ahsrescue.com/p-1211-personal-purcell-prusik-system.aspx

You stole it from a good site. AHS Rescue is Dale Stewart's. Great guy; certain he won't mind. :2thumbs:

[nonot]

Well I switched to the metolius PAS. I've heard the argument that it's not dynamic. I'm not upset with my choice.

[woadams123]

Steve, I have and use the metolius PAS. Do you know if one of the loops in the middle can be attached to the harness (without creating a weakness) to create a system with two ends like the spelegyca? I'm thinking of ditching mine for a purcell prusick lanyard made from dynamic rope. I am hoping to use that to eliminate using a mariner's for knot passing. Thoughts anyone?

[rcwild]

Well I switched to the metolius PAS. I've heard the argument that it's not dynamic. I'm not upset with my choice.

I saw the drop test videos from Rigging for Rescue. Pretty disturbing, but the "not dynamic" issue is not the reason for my aversion to using the Metolius PAS, BlueWater TLC or similar chains as safety lanyards. Knowing you have a non-dynamic tether, you should take steps to avoid ever being above your anchor so you don't set yourself up for a serious fall factor.

My aversion comes from the length, so it extends to the Sterling Chain Reactor (a nylon copy of the Metolius PAS). There have been a number of drownings and near-drownings resulting from excessively long daisies and slings snagging on rocks and branches under water. I also see users struggle with the inconvenience of the length -- wadding it up to clip it out of their way on a gear loop, fumbling with which loop to clip, etc.


Steve, I have and use the metolius PAS. Do you know if one of the loops in the middle can be attached to the harness (without creating a weakness) to create a system with two ends like the spelegyca?

Simplest way to create a system like the Spelegyca? Buy a Spelegyca.

Because each loop of your PAS is full-strength, you could certainly attach any loop to your harness with a rapide. You might try clipping the small hole at the "wrong" end of the dogbone (girth hitch part) to your harness. That would give you a fixed short leg and a multi-loop long leg. If you do come up with a new way to use your PAS, be sure to give it a name like SLCM.

You could use your PAS in a way similar to the Petzl illustration below. If you do, you'll have to call it WCCM.

Or you could just buy a Spelegyca.


I'm thinking of ditching mine for a purcell prusick lanyard made from dynamic rope. I am hoping to use that to eliminate using a mariner's for knot passing. Thoughts anyone?

I don't think you will like it, Bill. Made with dynamic rope (even half rope), your Purcell will be very bulky.

Time to switch from passing a knot with a mariner to using a VT. Both mariner and purcell allow lowering through the length of material used. The finite length is usually plenty, but the attachment point on the rope is fixed. You risk lowering yourself beyond the reach of the hitch. In contrast, the length of the VT remains fixed and the hitch travels, always within reach.

[woadams123]

Time to switch from passing a knot with a mariner to using a VT. Both mariner and purcell allow lowering through the length of material used. The finite length is usually plenty, but the attachment point on the rope is fixed. You risk lowering yourself beyond the reach of the hitch. In contrast, the length of the VT remains fixed and the hitch travels, always within reach.

Rich, thanks for the info and suggestions for names. Since canyoneering doesn't change with new techniques and the WCCM already invented everything anyway (they even have a book to prove it) :devil:, I'll stick to trying to learn.

I like the notion that the VT is not a fixed point. I'm going to buy and practice it. Seems it would be awkward tying a VT with one hand in an emergency when at the knot if you hadn't started down with it?

[rcwild]

Seems it would be awkward tying a VT with one hand in an emergency when at the knot if you hadn't started down with it?

Very tough tying a valdotain with one hand. Could tie a schwabish prusik with one hand, but easier to lock off and use both hands.

[nonot]

I saw the drop test videos from Rigging for Rescue. Pretty disturbing, but the "not dynamic" issue is not the reason for my aversion to using the Metolius PAS, BlueWater TLC or similar chains as safety lanyards. Knowing you have a non-dynamic tether, you should take steps to avoid ever being above your anchor so you don't set yourself up for a serious fall factor.

My aversion comes from the length, so it extends to the Sterling Chain Reactor (a nylon copy of the Metolius PAS). There have been a number of drownings and near-drownings resulting from excessively long daisies and slings snagging on rocks and branches under water. I also see users struggle with the inconvenience of the length -- wadding it up to clip it out of their way on a gear loop, fumbling with which loop to clip, etc.


I think I dug up the data you are referring to with the Rigging for Rescue tests. The fall factors were measured relative to the length of the lanyard, not the height of a person. So the fall factor for the PAS was 1-2 feet longer than the "equivalent" fall factor another device was tested at. The only failure appears to have occurred with test 29, in which a 100kg load was dropped 4 feet. I wouldn't recommend anyone try that with a static anchor, that's getting into hanger breaking ranges!

Your point about length is valid, I typically reclip into the very first loop of the PAS, I seldom have used the last one at the end.

[rcwild]

The fall factors were measured relative to the length of the lanyard, not the height of a person. So the fall factor for the PAS was 1-2 feet longer than the "equivalent" fall factor another device was tested at.

Not sure I understand your point here. Fall factor is the ratio of fall distance to length of material, so the measurement is from one end clipped to the anchor to the other end clipped to the harness. What does a person's height have to do with that?

There were multiple failures in the tests. The factor that made me question the direct relevance of the tests was the use of a solid steel mass. A human body can absorb some impact where the steel mass cannot. Nonetheless, the value of the results was in showing comparisons between materials. The Metolius PAS and other similar Dyneema and Dyneema-Nylon blend lanyards will not fail as catastrophically in real life as they did in the tests, but they will result in more severe impacts than tethers made with other materials.

[nonot]

My point was that the PAS tests had the weight being dropped heights 30-40% greater than the other devices in the test and as a result, one would expect it to have greater impact forces and be the most likely to fail. Equivalent tests were not performed clipping the PAS into, say, the 3rd loop, rather than the end loop.

You must have a different set of test data as what I found on the web indicated only one failure.

[rcwild]

My point was that the PAS tests had the weight being dropped heights 30-40% greater than the other devices in the test and as a result, one would expect it to have greater impact forces and be the most likely to fail. Equivalent tests were not performed clipping the PAS into, say, the 3rd loop, rather than the end loop.

You must have a different set of test data as what I found on the web indicated only one failure.

Fall factor is a ratio between distance of fall and the length of material that catches the fall. A 100 foot fall on a 100 foot rope is a fall factor 1. A 10 foot fall on a 10 foot rope is a fall factor 1.

If the PAS is 30-40% longer than the other devices and was dropped 30-40% farther, it is a fair comparison test.

[nonot]

When comparing static stuff, I disagree, but this is all academic, at a significant fall on static either you die breaking your spine just before the anchor fails or after the anchor fails and you hit the ground.

Fall factors are more useful in dynamic falls because of the stretch involved is in proportion to the amount of rope. Static has no stretch (or in real life, not much stretch.) The wild variations of the test data show that whatever stretch there will be on a static rope is not consistent, whereas with dynamic it is much more consistent across the tests and result in similar impact forces when the tests are repeated.

[rcwild]

When comparing static stuff, I disagree, but this is all academic, at a significant fall on static either you die breaking your spine just before the anchor fails or after the anchor fails and you hit the ground.

Fall factors are more useful in dynamic falls because of the stretch involved is in proportion to the amount of rope. Static has no stretch (or in real life, not much stretch.) The wild variations of the test data show that whatever stretch there will be on a static rope is not consistent, whereas with dynamic it is much more consistent across the tests and result in similar impact forces when the tests are repeated.

I understand your points about static vs dynamic, but I contend that if you have a static tether that is 4 feet long, it presents the potential for taking an 8 foot fall on it. To shorten it by a couple loops so you can compare it more favorably to the 3 foot tethers would be misleading.

The primary lesson in the Rigging for Rescue tests was about the ability of a lanyard to absorb impact. The Purcell performed well because the Prusik-on-itself slipped on impact. Nylon performed better than Dyneema/Spectra because it has more stretch to absorb impact.

But, like you said, it's all academic. Understand the pros and cons and use what you want appropriately. It's all good. I would rather see someone using a less-than-perfect tether and clip themselves in than to see them use no tether.

[SpencerJ]

I apologize for my late arrival into this thread (like 2 yrs late), but even though I'm only a climber, I have found this thread on the Purcell the best and most informative on the web. I've pretty much read through the entire thread and reviewed the two reports from Mike Gibbs at Rigging for Rescue. I've been using the Met. PAS for 5 or so years now, but I'm considering switching to a Purcell setup. Two questions....

1) Does the load absorption performance of the Purcell degrade if you don't leave enough slack or "slipping room" for the prusik? In Mike Gibbs' tests, the prusik seemed to slip anywhere from about 10cm to 38cm depending on the severity of the test. AND, it seems that this slipping is a key component of the Purcell's success at absorbing the load. If you have the prusik fully extended (or almost fully extended), what happens? Does the Purcell quickly lose its "strength" when you don't have any slipping room for the prusik, and you're essentially only relying on two strands of 6mm cord?

2) Could you replace the Figure-8 and the "girth hitch"-loop side with a Fisherman's Loop knot that uses two strands instead of one. I'm not sure if this is a real knot, but it creates two independent loops for girth hitching your harness (which for redundancy I like), and I'm wondering if the Fisherman's Loop knot might be slightly stronger than the F8 (but possibly at the expense of less load absorption than the F8 as it tightens down on impact). I tried to attach a picture of this, but I don't have the permissions to do that.

Thanks again for the great thread.

[sonnylawrence]

1) Does the load absorption performance of the Purcell degrade if you don't leave enough slack or "slipping room" for the prusik? In Mike Gibbs' tests, the prusik seemed to slip anywhere from about 10cm to 38cm depending on the severity of the test. AND, it seems that this slipping is a key component of the Purcell's success at absorbing the load. If you have the prusik fully extended (or almost fully extended), what happens? Does the Purcell quickly lose its "strength" when you don't have any slipping room for the prusik, and you're essentially only relying on two strands of 6mm cord?
.
The fall creates a lot of energy. It has to go somewhere. As the Purcell prusik slips on a rope or cord, it begins to glaze. It may fuse together into a hunk of nylon. Hence it is using up the energy. So yes, you need some "slipping room."

[SpencerJ]

The fall creates a lot of energy. It has to go somewhere. As the Purcell prusik slips on a rope or cord, it begins to glaze. It may fuse together into a hunk of nylon. Hence it is using up the energy. So yes, you need some "slipping room."

Thanks Sonny. This is what I expected, but my real interest is how it does when you don't have any "slipping room". Do you suddenly lose all of its strengths and excellent performance if you happen to use it all the way extended? How does it do with a FF2 (or FF1) test when fully extended? Does it do great when you have some slipping room, but if you get it fully extended, it won't survive a low factor fall, and now suddenly it's breaking (or at least performing badly) at FF1 events?

[rcwild]

Thanks Sonny. This is what I expected, but my real interest is how it does when you don't have any "slipping room". Do you suddenly lose all of its strengths and excellent performance if you happen to use it all the way extended? How does it do with a FF2 (or FF1) test when fully extended? Does it do great when you have some slipping room, but if you get it fully extended, it won't survive a low factor fall, and now suddenly it's breaking (or at least performing badly) at FF1 events?

Energy absorption is made possible by various mechanisms. Slipping is one. Prusik hitches fall under this category as do some mechanical devices.

Some products are made to absorb energy by partial failure, i.e. stitches tearing away. Yates Screamers are one example. The Spelegyca was previously called the Energyca. Name was changed because people were using it for via ferratas.

Some fibers absorb energy better than others. Nylon stretches more than polyester. Polyester stretches more than Spectra/Dyneema. Generally speaking, the more stretch a fiber has, the better it will absorb energy. The way a rope or cord (primarily the core) is braided will also affect its ability to absorb energy. There are nylon static ropes and nylon dynamic ropes; the difference is in the braid.

A Purcell Prusik tied with nylon cord will absorb energy via two of these mechanisms -- slipping and fiber material/braid. If it is fully extended so the hitch has no more slipping room, the nylon will still absorb some energy, just not as much.

Regardless of the energy absorption properties of your tether, you should take precautions to avoid FF2.

[willisj]

Looks like a Spelegyca but made with dynamic rope and with a fall indicator... Looks like it will come out sometime in 2012.
http://www.petzl.com/en/pro/new-products-0/2011/10/18/progress-progression-lanyard

[charlybldr]

Petzl has designed the new “Progress” to be used as a progression lanyard. E.g. clip the long end to an ascender with a foot-loop and use a progress capture rope grab at the waist of your harness for ascending. The dynamic rope can be expected to absorb some of the energy from accidental bouncing while climbing. You then use the short end to clip into an anchor any time you need to remove the long end from the rope. E.g. passing a knot (clip into a second rope grab) or transferring from one rope to another at an anchor point (clip into an anchor).

I think it might make a nice double length lanyard for canyoning. Caveats: Petzl clearly states “do not go above the anchor point” and the “fall indicator (green stitching) disappears when the lanyard is subjected to a major fall (improper use)”. So as with any safety lanyard used for canyoning, I would be careful and not expect full, shock absorbing “fall protection” when clipping into an anchor at your feet.

[thegrappler]

I prefer the prucell prusik. I always have one on my harness made of 10/7mm with a Petzl OK attached to the harness and a Kong Tango on the double loop side. The Prucell is generally tied as a 3on2, a 5 on 3 is being used to avoid any walking of the hitch(sliding up while not loaded). For those who are not familiar with prucells, The Prucell is a prusilk (3 on 2 prusik) tied to its self creating a double loop. This has many advantages over dasies and other PAS.
-The Prucell is adjustable, you can extend it under load. This is allowed by the 3on2. Dasies and other PAS need to be uncliped and recliped, creating a greater potential to fall. The prucell eliminates this risk, when clipped you can adjust it with our unclipping.
-Purcell has a built in shock absorber. Because of the 3on2 prusik, when over loaded/ shocked the hitch will slide, allowing energy to be absorbed and dissipated throughout the system before going into the anchor. This is like having a zorber that can be uses multiple times.
-Purcell loops can be spread to create a two point anchor attachment.
-Purcells are ideal for knot passing. If you have to pass a knot, simply descend to your knot. attach your chest purcell above your rap device with a 2 or 3 wrap prusik to the main line, and to your harness with the two loops..... tighten up the prusik ( if you locked off rappel above the knot, release your rappel device from lock position and descend to load your prucell. Attach your foot prucell below the knot, Stand up and slide the chest purcell up enough to release tension on your rap device. Now weight the chest prucell,remove your rap device, re-rig under the knot (above the foot prucell, lock off properly. Now simply slide the 3on2 prusik down on the chest prucell to load your device. Remove chest prucell (if it is out of reach, stand up in your food prucell and lower the prusik to the knot, sit into rap device and remove chest prucell, remove leg purcell, untie rappel lock off, continue to descend.
(there are a few variations of this technique, find whats fastest and easiest)

Always having a bag of purcells ( long leg short leg and chest) can get you out of anything, think of it as your get out of shit bag.

Recently i have switched the purcell on my harness to a double purcell ( like the lobster claw idea) using two knog clips, red and black (hot and cold). Red is always my main and black is back up. This is great for aid traverses, positing my self like off two anchor points (two bolts), really great for re-belays.