The Canadian Drop Loop system

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The Canadian Drop Loop system

Postby Carl Amundson » Oct 4, 2007 1:35 pm

I have been researching glacier crevasse rescue techniques, with an eye to adapting them to cave rescue.
Many of these techniques lend themselves very well to minimal equipment/small party rescues.
I have come across references to the Canadian Drop Loop system.
It appears to be a variation on a z-rig, but I have not found a descent diagram of it yet. The best I have found is this:
http://books.google.com/books?id=DKOgAITSNnIC&pg=PA44&lpg=PA44&dq=%22rescue+techniques%22+%22small+party%22&source=web&ots=P4CmFUERvs&sig=w5o54usgh3EMD3VmACQohBsB08A#PPA104,M1

Does anyone out there have any additional information on this haul system?
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Postby NZcaver » Oct 5, 2007 7:05 pm

Hi Junkman,

Thanks for posting that link - I had not seen that particular material before, nor heard of the term "Canadian Drop Loop" system. Interesting.

It's tough to make sense of that diagram - and it took me a moment to realize the missing portion spills over onto the next page. This compound 6:1 is just the regular 2:1 acting on a 3:1 - you've almost certainly rigged/used one of these during one NCRC weeklong or another. :wink:

Basically, something like this (excuse my poor drawing skills, those are 3 pulleys plus 2 cams in place of Prusiks):

Image

In function, this is almost identical to the compound 6:1 [Edit - my mistake, this is actually a complex 5:1]Double Mariner system shown on the Petzl website. The term for this rigging in French is the "Mariner démultiplié." The difference with this technique is that the ropes are switched in the lower 2 pulleys (which are substituted with carabiners in the Petzl diagram). As I understand, the Double Mariner method allows for better rope management because the end you're pulling on is where all the slack goes from the haul progress. Of couse each technique will require slightly different rigging methods, especially when dealing with an already-loaded rope.

Image
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Postby Carl Amundson » Oct 8, 2007 9:58 am

Here are examples of "drop loop" haul systems I have been looking at in my research into crevasse rescue techniques:
http://www.acmgguides.com/html/tipstech ... TNumber=14

The "Drop Loop + Z Pulley" looks like it might be the "Canadian Drop Loop" system I have seen references to.
What I don't see in the "Drop Loop + Z Pulley" is an over-all "progress capture" device other then the one for the z-rig...

I really need to get to some cliffs and try some of these out.
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Postby MessedUpMike » Oct 8, 2007 4:58 pm

Unless I'm missing something it looks like it's trying to add mechanical advantage to the last end of a Z-rig. I'm not quite getting why you would go through that much hardware and not just build it up to a 4:1 or 5:1 system instead of fighting with additional changes in direction and what appears to be in the first picture 4 (?) prussicks.

I've participated in classes before where fairly intelligent guys have massively over done their systems because they over thought the problem. Looking at some of these rigs reminds me of that.
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Postby Carl Amundson » Oct 8, 2007 6:41 pm

The first one is just a 2:1 haul system.
One Pursik is the progress capture and the other two are safeties for the haulers.
Image


In the second pic. they put a z-rig on the end of the 2:1.
They are using a Garda knot as the progress capture device in place of a prusik minding pulley and prusik knots.
Image

This last one, well it's a cluster...
They added mechanical advantage to the z-rig.
They turned it into a compound 6:1 (Double Mariner seen in NZcaver post) on top of the 2:1.
As stated in the Mountaineering website "This system is high in friction".
Image


I am interested in trying out the second one (2:1 w/z-rig) and see how it performs.
For all of the above haul systems you need a cooperative patient.
Even with that, I think it is worth trying it out.
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Postby GypsumWolf » Oct 9, 2007 8:57 pm

junkman wrote:In the second pic. they put a z-rig on the end of the 2:1.
They are using a Garda knot as the progress capture device in place of a prusik minding pulley and prusik knots.
Image
---
I am interested in trying out the second one (2:1 w/z-rig) and see how it performs.
For all of the above haul systems you need a cooperative patient.
Even with that, I think it is worth trying it out.


This is a 6:1 isn't it? (3:1 integrated with a 2:1).
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Postby Carl Amundson » Oct 10, 2007 9:17 am

You are correct sir.
My concern is how much friction will this haul system generate.

I want to try small pulleys at various points to lessen the overall friction of the system.
As stated above, this is all about testing the most efficient systems for small party/ minimal equipment rescues.
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Postby Tim White » Oct 10, 2007 9:38 am

:hairpull: A lot of friction. Especially in these area (not to mention the lip).

Image
Last edited by Tim White on Oct 10, 2007 9:44 am, edited 2 times in total.
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Postby GypsumWolf » Oct 10, 2007 9:39 am

junkman wrote:You are correct sir.
My concern is how much friction will this haul system generate.

I want to try small pulleys at various points to lessen the overall friction of the system.
As stated above, this is all about testing the most efficient systems for small party/ minimal equipment rescues.


Attaching pulleys where they have carabiners would generate less friction giving you more of a full "t". IMO.
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Postby Carl Amundson » Oct 10, 2007 9:47 am

Tim White wrote::hairpull: A lot of friction. Especially in these area (not to mention the lip).

Image


True, but which placement would be best?
I can only ever on count the single pulley I always carry.

I'm thinking that in this scenario, a pulley at the patient would be best.
Also, instead of using a Garda knot using a Beckmann knot as the progress capture.
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Postby fuzzy-hair-man » Oct 10, 2007 7:00 pm

junkman wrote:Also, instead of using a Garda knot using a Beckmann knot as the progress capture.


Why not take the ascender or ascenders off another member of your group? and use these as your progress capture? a Tibloc also works as a progress capture device *(I carry one as a spare ascender)

* see http://en.petzl.com/ProduitsServices/B01%20TIB%20B01500%20020799.pdf
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Postby NZcaver » Oct 10, 2007 8:30 pm

fuzzy-hair-man wrote:Why not take the ascender or ascenders off another member of your group and use these as your progress capture? a Tibloc also works as a progress capture device (I carry one as a spare ascender)

:exactly: Using tooth-cam ascenders in haul systems like this is often common practice outside the US for companion-rescue (small party) and full call-out responses alike.

Forget the Garda Hitch (in that application). The friction it introduces into the system is exponential. :shock: And I think a Bachmann Hitch would just be a waste of a carabiner - I doubt you would find the resets that much easier than with a regular 3-wrap Prusik. For your PCD and haul cam, use mechanicals scavenged from climbing systems, mini-mechanicals like the Tibloc, or Prusiks.

Pulleys are nice. If you carry a little pulley, and your caving buddies each carry a little pulley.... get the picture? Now three of you have pulleys to construct a 2:1, 3:1, 4:1, 6:1, 8:1 - whatever most appropriately fits the need. Some pulley substitutes (besides just a carabiner) include the lower bollard on your Stop descender or bobbin, a bar on your rack, or even 2 carabiners side-by-side for a larger bend radius (although this means a larger friction surface, too!) I'm thinking if you only had one real pulley available, you'd probably want to place it wherever the rope does the most travel. Perhaps the closest change of direction point to the person hauling?

Sure building a simple 4:1 or 5:1 from scratch like MessedUpMike suggested would certainly be nice and straightforward, especially if you're responding to a rescue with your whole team and a swag of gear. But what if you're responding to something that just happened in front of you? You only have 1 rope (which is already loaded with a static body weight) and the SRT gear you're wearing plus your cowstail. I do believe this is the kind of situation Junkman meant when he said, "Many of these techniques lend themselves very well to minimal equipment/small party rescues."

Also, with the same minimal gear/time/people, think about options for a counterbalance system. Weigh up the pros and cons of having a person who is effectively "captured" in the system (hanging on rope), but is now able to use their full body weight to apply several times the force of a regular haul by hand.

Here's a couple more Petzl goodies:

Rescue an uninjured climber from a crevasse (Similar to earlier diagrams in this thread.)

Haul system simulator/calculator :kewl: :kewl:
(Click on the type of pulley system you want to see, then click on any device in the diagram to change it to something else and see the resulting force required by the person hauling.)
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Postby fuzzy-hair-man » Oct 10, 2007 9:48 pm

NZcaver wrote: Some pulley substitutes (besides just a carabiner) include the lower bollard on your Stop descender or bobbin...


The lower bollard on a Stop can be used as a pulley and progress capture device. (Petzl documentation shows it threaded around both bollards but I'm not sure what this achieves other than adding more fricton :? )

Image

however a couple issues to be aware of obviously the friction increases because it's not a pulley so the load on anchors increases as well, and the Stop AFAIK not hugely strong and it may be relatively easy to get to the loads where it is above the maximum load rating.

Life On A Line had something to say about it.....

Life On a Line has quite a bit about building hauling rigs and it seems quite complete. It is a UK cave rescue publication so some of what it does may not be the same as the US. I think there is a second edition somewhere now. (I can't find the first edition on the web at the moment)

here tis: http://www.lifeonaline.com/
The first edition was a good read so I guess the 2nd edition will be good as well

PS: I think the guy who wrote it used to be on here (LOAL) but I haven't seen him around for quite a while.
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Postby MessedUpMike » Oct 11, 2007 5:48 pm

The first edition is no longer on the web. The new addition of life on a line is, but it's a pay as you go purchase. I'll probably end up getting it anyway sooner than later.

Is it possible that the pulleys are deleted from the initial rigs because they are for ice rescue? I don't know anything about ice climbing, but I can easily imagine ice and possibly snow jamming up a pulley guided system
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Postby NZcaver » Oct 11, 2007 6:05 pm

fuzzy-hair-man wrote:The lower bollard on a Stop can be used as a pulley and progress capture device. (Petzl documentation shows it threaded around both bollards but I'm not sure what this achieves other than adding more fricton :? )

however a couple issues to be aware of obviously the friction increases because it's not a pulley so the load on anchors increases as well, and the Stop AFAIK not hugely strong and it may be relatively easy to get to the loads where it is above the maximum load rating.

When I mentioned using the lower bollard as a pulley substitute, I meant just the lower bollard - no upper bollard, no progress capture function.

Now I've also seen that Petzl Stop 3:1 diagram you showed, and I recall I tried it out one time. However I've never seen anybody rig it for practical use - anyone? It sure looks like it would introduce a lot of friction and inefficiency into the system, but I guess some people may find it useful in a pinch.

Regarding your comment about the Stop not being hugely strong - the figures are obviously much lower than regular pulley ratings, but I'm not really seeing that as critical in this improvised/occasional use/single person load application. I also understand that more friction in the system means a potentially higher load on anchors and other components, but if you're only using the lower bollard it can't be any worse than using just a carabiner in place of a pulley can it?

The current technical notice for the Stop gives a maximum safe working load of 250kg, and a "normal" working load range of 30-150kg. But it also talks about the descender "beginning slippage" on 11mm rope at 5kN, and showing approximately 10mm of slippage after sustaining an 8kN shock load. The weak point in the descender is obviously the crimp point between the bollards, so one had to assume that the lower bollard used as a pulley substitute by itself can handle at least that force (probably many times as much) with no issues.

Life On a Line has quite a bit about building hauling rigs and it seems quite complete.


I have version one of LOAL in PDF (issue 1.3, 2002/03). A great reference!
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