Pig Rig

[BurnCMSFD]

Piggy back system would be the correct term for what I am about to ask. When this is set up would you rather tie a knot at the anchor (on the pig) or use a carabineer in place of the knot?
Yes I realize there is more stress on the rope when a carabineer is used. We play around with it both ways, I prefer the carabineer much simpler and you can maximize your pull distance.
Just wondering how you all feel and your reasoning.

Thanks
Burn

[FIRELT03]

Hi Burn
I think you're losing me on this one. We call a piggy back system any system we attach to another one, even if it is attached to a main line for a haul or lowering system. Would it not depend on which system you are using, a three to one pig rig usually requires a pulley at the anchor where as a 4:1 can use a knot at the anchor, (depending on how it is built of course) the actual haul distance would depend on where the anchor point is for the original system your attaching to, you usually cannot pull beyond the anchor on that system. Using a pulley is obviously more efficient than a carabiner by a long shot so it depends on how much friction your looking for in the system. If we are tying back our tripod or vortex we use carabiners for more friction on the tensioning lines. Hope this aids in your discussion.

[BurnCMSFD]

Sorry about that, this would be Low Angle, it would be a 4-1 put onto a mainline via gibbs(ascender etc.) When you set the distance of the pull (or what you can pull) with your gibbs & pulley, then the rope would be tied off at the anchor at that point, correct. then the other end of the line would be brought down with another pulley and biner and attached to the knot on the other end coming out of your first pulley, correct. So what im asking is what do you think about using a carabineer instead of the knot at the anchor...?
Smelling what im stepping in?

Thanks
Burn

What part of mass you from, im originally from NH

[jmatthe2]

It sounds like you are talking about a 4:1 compound system and not a block and tackle correct?

Does that smell like what I think your stepping in and haven't wiped off yet?

[BurnCMSFD]

Yes that is correcto jmatt, before you wipe it off have you used this and what did you think?

Burn

[FIRELT03]

what your saying is correct, when we teach low slope evacuation which sounds like what your doing we tie off as you state, that is the easiest way to tie the 4:1 haul system, by tying it that way you leave all the extra rope at the anchor point out of the way, by using a pulley and carabiner instead of a knot you have really added nothing to the system so why waste the time it doesn't do anything for you. we always use the knot, jmatthe2 was/is correct it is a compound 4:1 system piggybacked onto a main line, I always use a soft link, prusik attachment point, instead of the Gibbs to connect to the main line, it is easier on the rope and when it fails, if it fails, it chirps to let you know you have overloaded your system and doesn't cause major damage to your rope if it does fail. But we shouldn't be overloading anyway, I just like them better, easier to use and much cheaper to replace.Sounds like your doing it just the way we do it here in Mass, central Mass, actually, your a long way from NH. Jmatthe2 you going to be at the NASAR conference in June?

[jmatthe2]

Now we're getting somewhere!!

The 4:1 compound is a good system. It uses fewer pieces of hardware, but most departments like to just pull the pre-rigged block and tackle out.

I was never a fan of the Gibbs being used as a rope grab. As I learned more about the product (and others like it), I realized for a some loads it is fine. I am recalling from memory here but I think it was about 3,500 lbs. that the Gibbs was showing damage to the rope. That's a considerable amount of weight that should never be seen in a basic raising and lowering rope system. I like using a Gibbs on a piggy-back MA because it makes the re-set much easier. Tie a piece of webbing to the Gibbs carabiner, then someone positioned near the load can haul it back to them for a quick re-set.

That being said...I prefer soft connections on most MA's not because of strength, but because at 35 cents a foot you get the same action.

I am hoping to make it to NASAR. I haven't looked at my schedule to see if I'll make it or not. Charlotte is a great city to come and visit, if you need help finding some places to down a pint let me know!

[FIRELT03]

seems we all agree on something then, Burn hope this answeres your question

can always use a good place to down a pint

[Riversong]

Piggy back system would be the correct term for what I am about to ask.
Depending on which authority you quote, your system is a piggy-back pig rig. By Reed Thorne's standards (who has gone a long way towards standardizing terminology), a piggy-back MA is one simple MA system pulling on the haul end of another identical system. Thus your compound 4:1 is a 4:1 piggyback system.

And any MA system ganged onto a mainline is generally refered to as a pig rig. Thus what you've described is a 4:1 piggyback pig rig, which (as others have noted) is different from the more commonly-used 4:1 jigger pig rig.

When this is set up would you rather tie a knot at the anchor (on the pig) or use a carabineer in place of the knot?

I'm not sure what you're gaining by slipping the fixed bight of the piggyback through a carabiner. You're putting 3x the hauling force onto that anchor and that's a lot of stress for a rope around a 7/16" biner. I'd stick with the knot.

As far as Gibbs vs prusik as the haul grab, I agree that its a toss-up depending on the circumstances. The Gibbs (as long as it's a #3 for rescue) does make reset easier, but if it will drag in the dirt I prefer a prusik. The Gibbs can damage the rope sheath at about 2500 lbs, and I stripped an old 11mm static line with a CMI Ropewalker at about 1700 lbs.

- Robert

[BurnCMSFD]

'I'm not sure what you're gaining by slipping the fixed bight of the piggyback through a carabiner. You're putting 3x the hauling force onto that anchor and that's a lot of stress for a rope around a 7/16" biner. I'd stick with the knot.'


Well what you gain is more hauling distance, and it can be re-positioned easily. You realize also that the rope is not moving at the biner once load is on.
Depending on the situation, with the knot at the anchor the total hauling distance is limited unless you re-tie the knot, understand what I mean? I understand your reasoning for the knot less stress, but is it? you still have a bite in your rope that is taking the 3x hauling force.

Thanks for opinions
burn

[Riversong]

Well what you gain is more hauling distance, and it can be re-positioned easily.
If you mean you gain the length of the knot before the system collapses, that's not much of a gain.

You realize also that the rope is not moving at the biner once load is on.It won't move if there's enough friction at the 'biner, but there's twice the force pulling on one side of the 'biner as the other and the rope may "chirp" through the 'biner.

Depending on the situation, with the knot at the anchor the total hauling distance is limited unless you re-tie the knot, understand what I mean?
It seems you're trying to maximize a single haul, rather than reset the pig rig at the Gibbs. Aren't you using a progress capture device on the mainline and tending that?

And, if you're going to that much trouble, why not use the mainline and the same two pulleys and configure a 3:1 Z-rig, which gives more than enough MA for a low-angle haul and doesn't require double line tending.

I understand your reasoning for the knot less stress, but is it? you still have a bite in your rope that is taking the 3x hauling force.

You're right - the force at the anchor will be the same, but the force will be static with a knot and it will try to be dynamic without it, possibly causing an unexpected and jerky slip at the 'biner.

- Robert

[BuzzCut1]

Cal Fire will not use Gibbs on any rescues due to potential rope cutting. SOP is double prussiks of 7mm preferably 8mm on a 3:1 Z rig.

we did a demo in rescue class with 2 identical ropes
one with a gibbs, one with double prussiks

we had 7 on the haul line and a z rig hooked to a z rig. we snapped the line with the gibbs [it cut at the cam]

we couldn't budge or damage the rope with the double prussik

[jmatthe2]

BuzzCut -

Let me start by saying not to take this personal. My post is not targeted at you. But...

Who ever your rescue instructor was did nothing but scare you away from using a good tool in rope rescue.

I can make a prussik fail just like this so-called "instructor" made the Gibbs fail. Do you know why these guys do these demos? So they can be validated with this big eye-opening demonstration. When you break it down, the only thing you learned was that it was OK to put 7 people on a 3:1 with tandem prusiks...READ ON!

The lesson to be learned was this:

If you have to put 7 people on a 3:1 you have a major problem!!!! Every piece of harware has its limits...EVERY PIECE. Look at it this way. If every person was able to input 100 ft.lbs into the system (for a total of 700), and it was then multiplied by the MA for a total of 2,100 ft. lbs. This is a conservative estimate as I assume all 7 of you were pulling like hell. This would put you at roughly a 4:1 safety factor! Of course the Gibbs failed. Any trained rope technician would know it could fail! What they aren't telling you is that you are also getting close to the point where your tandem prusiks will begin to clutch...which can lead to rope damage...which can lead to rope failure. Yes the prusiks give you some warning, but you are still at a point of damage to the system.

Next time Cal Fire needs to hire an instructor with a little more to offer than repition of everything that is wrong in municipal rope rescue!


I apologize for the rough tone, but this type of instructor gets me ablaze!!!

BuzzCut - A Gibbs is a good tool to have in the tool box. Don't let one persons view be the only one you look at.

[BuzzCut1]

no offense taken. It's departmental policy, we follow it.

just for reference read the text on pages 14& 15 of this document
[I believe John Dill in the head of Yosemite SAR]
http://www.basarc.org/papers/roperescue/RopeRescue2002.pdf

[Riversong]

just for reference read the text on pages 14& 15 of this document

Yes John Dill is a reliable authority, but you need to read his comments carefully:

"John Dill reports that in 50 cm. (20”) drop tests, with a rescue load, the rope was cut more often than not. Both ascenders come with warnings that they are designed for one person loads and are pull tested to 4.45 kN (1,000 lb.) ONLY. They should NEVER be used in a dynamic belay situation. In practice however, for specific applications, the Rescucender™ tends to slip, on most ropes, reducing the tension, while the Gibbs® tends to destroy the rope. The variety of newer versions of Gibbs® ascenders need more testing results."

First, every device has its proper applications and its inherent limits. A knowledgable technician knows the proper scope of use for each piece of gear.

Second, the rope breakage reported by Dills was in dynamic drop tests. No mechanical rope grab should be used in dynamic applications (such as belay) but only as a haul grab or a progress capture device (and the latter is debatable).

Third, Dill is refering to early generation Gibbs #1 and #2 which were rated for a heavy one person load (500 lbs). The Gibbs #3, #3S, #4, & #4S were all designed for rescue use (1000 lbs SWL). They're twice as strong (MBS) as the old Gibbs, and they've been tested to rope damage at 3,000 lbs. If a team is putting anything close to 3,000 lbs tension on a haul line, there's a major flaw in either technique or the system.

The typical rescuer has a grip strength of 50 lbs with a gloved hand on 1/2" rope. Assuming that one could exert 100 lbs force with two hands, it would take 10 haulers pulling on a 3:1 to impart 3,000 lbs force on the haul grab.

Is it possible to damage an older rope or a smaller rope at less force? Absulutely! I destructively tested an old, stiff piece of 1/2" static caving rope with a CMI ropewalker and it sheared the sheath (but not the core) at 1800 lbs.

If you're lifting a 600 lb rescue load, there should not be enough friction in the system to require an 1800 lb force at the haul grab. Are prusiks safer? If they're made of the right cordage and tied and used properly, probably so. But there is no way to "certify" any particular prusik as there is with any manufactured mechanical device.

The Rescucender is probably the best of the rescue-rated rope grabs, with the Gibbs #3 a close second. Use them properly and they are a good tool for their intended function. Use them improperly and they, like any device, will cause failure.

- Robert

[Riversong]

Cal Fire will not use Gibbs on any rescues due to potential rope cutting. SOP is double prussiks of 7mm preferably 8mm on a 3:1 Z rig.

By the way, 8mm prusik cordage is widely accepted as the proper size for 1/2" mainline for any general use or system application. 7mm is acceptable for personal or light use.

[BuzzCut1]

By the way, 8mm prusik cordage is widely accepted as the proper size for 1/2" mainline for any general use or system application. 7mm is acceptable for personal or light use.

poor wording on my part
double 8mm prussiks is our sop 7mm is minimum for any use