Ta Prusik or not ta Prusik?
Posted by: fatelmo on Jun-10-13 8:10 AM (EST) Category: Other Gear
-- Last Updated: Jun-10-13 12:44 PM EST --
Dat be de questoon! Wetter it be noobler in de mind ta use a mechanical ascender such as a climbing ascender on a Z-drag setup or ta use de standard prusik.
General consensus amongst me river rescue crowd be... dun't ever use a ascender.
Wat be yer take on dat matter?
Alas poor Andy_S... ah' knowed him, Horatio.
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- Ta Prusik or not ta Prusik? - fatelmo - Jun-10-13 8:10 AM
Posted by: mintjulep on Jun-10-13 8:42 AM (EST)
Faster and easier.
Need to make sure you get the direction right though.
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Posted by: thebob.com on Jun-10-13 9:08 AM (EST)
Several reasons I can think of for NOT using a mechanical ascender:
1. Ascenders are expensive.
2. Ascenders were not designed to be used in rigging haul systems for retreiving pinned canoes.
3. Ascenders take up more space, and are heavier than a couple of prusik loops.
4.During the haul; if the rope breaks below where the ascender/prusik is attached to the haul rope, and "fly back" occurs........which had you rather get hit with, a prusik, or an ascender. Yes, I know there are ways to weight the rope to stop/slowdown flyback.
5. If the ascender has teeth on it that grab the haul rope; after a while they will start to damage the sheath of the haul rope, especially if the ascender starts slipping.
6. A prusik that breaks can more easily be replaced than a broken ascender.
7. Ascenders have working parts; prusiks don't.
P.S. Anyone who is considering using a haul system to retrieve a canoe should learn how to do the Steve Thomas "rope trick" before they learn how to set up a Z drag, or some other haul system. May negate the necessity of setting up a haul system in some circumstances.
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Or even better|
Posted by: mintjulep on Jun-10-13 9:34 AM (EST)
Anchor one end of the rope AND THE PULLEY to the pinned boat.
No Prusik, ascender or whatever required.
Does not triple the load on the rope the way a Prusik using Z-drag does.
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Posted by: thebob.com on Jun-10-13 9:39 AM (EST)
Where on the boat are you going to anchor the rope?
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Posted by: mintjulep on Jun-10-13 9:50 AM (EST)
Same place you'd anchor the rope anyway.
Tug-eye, grab handle, hard point (real creaking kayaks), thwart (weak, but sometimes the only thing you can reach)
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Posted by: thebob.com on Jun-10-13 1:12 PM (EST)
If you could thread a haul rope thru a tugeye, that might just be a decent anchor point?
The stress of a haul system on a badly jammed canoe will often snap wooden grab handles & wooden thwarts like toothpicks. Have seen built in grab handles; as incorporated into the decking of Old Town & Mad River canoes used as anchor points. Have seen it work on occasion(light jams); have also seen complete decks ripped off the gunwales of canoes, and part of the gunwales destroyed to boot. Have also seen aluminum thwarts & seats ripped out of Grumman, Alumacraft, and Osagian canoes when they were used for anchor points.
All depends on the situation.
One option: multiple, snug wraps of the haul line around the canoe as anchor to the canoe.
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prussiks vs. ascenders|
Posted by: willowleaf on Jun-10-13 9:55 AM (EST)
I haven't used them with boats, but back in my relative youth my outing club used mechanical ascenders (and prussiks) for alpine mountaineering and vertical caving. We learned to set up z-drags in glacier crevasse rescue and mountain evacuation practice. I also worked at the time selling gear in the local independent wilderness outfitter store where we salespeople got vendor training in the dos and don'ts of various pieces of gear. General consensus was that safest mechanical ascenders to use on muddy, wet or icey ropes were Gibbs. Mountaineers at the time typically used jumars since they were easier to handle with gloves on, but after some high-profile accidents due to failure many that I knew switched to the Gibbs.
I think concerns about rope wear are overstated -- it's one thing to be worried about sheath wear with a climbing rope that has to take thousands of pounds of dynamic force load in a leader fall. The stress that would be placed by even the heaviest canoe on a rope is minimal (unless you are dropping it in a free fall off a cliff). If one is using competent cordage (not hardware store clothesline) the effect of the cams in a mechanical ascender would be negligible. BTW, Gibbs don't have teeth like other ascenders do, so they are less damaging anyway.
I always found prussiks to be a PITA -- the only benefit to them is they are more portable than a mechanical ascender and could be used for other purposes on a trip.
Gibbs ascenders are amazing little devices. I once climbed a 230' free dropped rope (under a highway bridge) using two of them on a chest and foot strap harness and helped with rescue evacuations where we used them to manage descent with a Stokes litter. I used to always carry one with me on any wilderness trip.
But, surprisingly, it seems like rescue pros are going back to prussiks for some use. To wit, an article on prussiks vs. Gibbs on an "adventure rope gear" site:
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Boat haul system|
Posted by: thebob.com on Jun-10-13 10:38 AM (EST)
-- Last Updated: Jun-10-13 12:29 PM EST --
The Adventure Rope Gear article should be a must read for anyone thinking about using either ascenders or prusiks for boat retrieval/haul systems.
I'd guesstimate that about 999 out of every 1,000 paddlers won't have to worry about it much. The vast majority of paddlers don't know how to rig a Z drag, and certainly not other more complicated haul systems. And besides, they don't carry the equipment necessary to do so; even if they did know how.
Pretty sure that nobody whose arm or leg is trapped between a canoe and a boulder, in a class 3 rapid, is going to argue with you regarding your choice of a prusik, or a Gibbs ascender. :^) Especially if they have no gear that will facilitate your hauling the canoe off of them. Try to imagine hearing, "If you're gonna use a pruski/Gibbs; I don't want your help"!
I readily accept the results of testing by CMC, and their recommendations; I acknowledge them as professionals.
That means I will change nothing about how I rig a haul system; I'll stick to using using prusiks.
I am an ex vertical caver, and have received professional training in high angle rescue.
Have used jumar, and gibbs ascenders, as well as prusiks on my personal climbing systems. Used all 3 on haul sytems I rigged for 2 of the 3 real rescues that I led. One victim had a broken back, received in a fall(no belay/free climbing) onto a boulder.
I think it is a mistake to totally rule out the use of any piece of equipment. No doubt some equipment is better than others at specific functions/tasks. Oh the other hand; you need to be able to adapt to the situation, and to use what equipment you have available.
There is a difference between adaptation, and ignorance. I was called once by a highway patolman, seeking assistance in removing a "wanna be" caver from the bottom of a 45 foot deep vertical pit. When I inquired about what attempts he & 3 volunteer firemen had made to extricate the wannabe; he infomed me their attempt to use a fence stretcher has failed......miserably. He later stated, "I am never, for the rest of my life, going into another cave"! He was no where to be found when we exited the cave with the wannabe.
P.S. I'd much rather be using jumars or gibbs ascenders on a rope climb than prusiks!
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Posted by: Steve_in_Idaho on Jun-10-13 12:21 PM (EST)
If the stress on the rope is minimal - why is the retrieval system even needed (rhetorical question). I find it hard to believe that a falling human body generates more stress on a rope than a swamped & pinned canoe. Besides - aren't we talking about completely different rope construction? (forgive me - my climbing days are almost 40 years gone)
(no dog in the "ascender or knot" fight)
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Posted by: thebob.com on Jun-10-13 12:52 PM (EST)
-- Last Updated: Jun-10-13 1:18 PM EST --
And now, we progress to the dynamic vs static rope issue, and all the nuances of that subject.
The sun is shining here, the temp. is great; I'm retired, and my opinion means squat.
I have decided that a road trip on one of my bikes, or in my Mustang take precedence; I am outa here!
P.S. Add on shore anchor points, possible need for multiple on shore anchor points, using correct angle of pull, possible use of vector pull, 10 little boy scouts, piggyback rigs, upstream warning to other paddlers, downstream retrievel of boats/gear etc to the agenda.
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canoe vs. climber|
Posted by: willowleaf on Jun-10-13 4:58 PM (EST)
You're right, Steve, different ropes for climbing (mountaineering and rock climbing ropes have to stretch under abrupt dynamic load to absorb the fall shock or they would seriously harm the falling human), but caving ropes are static, non-stretch lines like Bluewater (if you tried to ascend a deep cave on a climbing rope you would be climbing until Christmas before your weight pulled out all the stretc.) And ropes used to ferry line or lower a canoe on portage would be non-stretch as well. A 200# climber falling 50' puts WAY more acute stress on a rope running through a protection point than even a loaded canoe pinned by a high volume stream would. To expand what I said before, the only way to come close to a human leader fall stress would be throwing an 80 lb canoe loaded with 120 lbs of gear off off a 100 foot cliff and arresting its fall at 50' tied to a single point. The continuous force of a pinned boat is not an abrupt dynamic shock to the rope. A hard leader fall of an average sized person puts an immediate force of over a ton on the rope and any protection equipment. This is why climbing carabiners and other gear are rated at 3000 lbs and up.
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Posted by: kelvin1 on Jun-11-13 9:19 AM (EST)
It's the water pressure on the surface area of the canoe that creates the load on the rope. A 17ftx3ft canoe pinned submerged on edge against a strainer in a 4.5mph current will require a force of over a ton to pull it against the current.
This example doesn't use an unusually strong current as it would still be possible to paddle against it and as the force is velocity squared a doubling of velocity would quadruple the force. It makes me glad I'm a kayaker with the much smaller surface area and less chance of pinning.
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Posted by: Andy_Szymczak on Jun-10-13 9:59 AM (EST)
Did I die and nobody told me?
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Posted by: booztalkin on Jun-10-13 7:42 PM (EST)
Well I've used a Prusik and never laid eyes on an ascender, other than in a catalog. I trust a prusik and it is a neat looking knot.
I understand the function of the ascender and it seems like it would work okay. However, I'm thinking an ascender doesn't have a very big bite on the rope, z-drag may be subjected to multiple times the force of a person on a rope, and there may be potential to damage rope with an ascender.
This is all conjecture on my part. I only responded so Id get to type prusik and say it is a neat looking not. Prusik, prusik. Believe it because you read it on the internet!
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Prusik, prusik; who's got the prusik|
Posted by: thebob.com on Jun-10-13 8:24 PM (EST)
I agree with your assessment of the neatness of "prusik".
Read more about the prusik, it's use, and limitations.
Whitewater Rescue Manual(New Techniques for Canoeists, Kayakers, and Rafters).
By Charles Walbridge, and Wayne Sundmacher Sr.
Ragged Mountain Press
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Posted by: kelvin1 on Jun-11-13 6:58 AM (EST)
In my experience in whitewater recoveris prussiks are used to attach carabiners or pulleys to the rope rather than as a one way sliding loop.
My personal sequence would be to try a direct pull, if unsuccessful anchor the rope and try a vector pull, if still unsuccessful use a prussik to add a pig rig.
There is an excellent analysis of the forces involved at http://chung.ayjscience.ca/phy4561/Physics%20JA/Force-River%20rescue.pdf
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Posted by: willowleaf on Jun-11-13 10:25 AM (EST)
I freely admit my aversion to prussiks is probably rooted in having had to extract myself from an overhung crevasse in the Canadian Rockies using prussik foot loops sliding on a rescue line. Halfway up I was so exhausted and pissed off that I was only half joking when I asked my belayers to just cut the rope. Prussiks are great until you have to move them.
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Prusik.. not just for climbing/zdrags|
Posted by: sloopsailor on Jun-11-13 11:01 AM (EST)
I use a prusik loops all the time in my job. We needed to secure a piece from moving on tight walk wire(yes walking a tight rope). Rig the tight rope (10 ton tension up hill cable). We needed a temporary piece so the actor could mount the line. Slipped the mount under the wire, held it in place with a prusik so it couldn't slip. The Circus people were very interested in how well it worked.
When camping, I ran a cable 80' or so over the top of the campsite. Used prusik loops to position the tarp where I wanted it over the cable.
Rigging safety on fly lines in the theater, holding adjustable counter weight bags. Used one to help clear a jammed line on a sailboat winch. It gave us another purchase point to relieve the pressure so we could unwrap the jammed winch. A great knot to use!
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I thought you meant Prosit ! |
Posted by: seadart on Jun-11-13 5:29 PM (EST)
Which is the same as skål.
Always polite to prosit.
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Posted by: haresfur on Jun-12-13 6:19 AM (EST)
Whatever you use, practice with it. If you are thinking about using something else, practice with it.
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Posted by: TommyC1 on Jun-12-13 6:53 AM (EST)
I'm learning some things here!
Thanks to all.
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Posted by: Mattt on Jun-12-13 9:15 AM (EST)
prusic knots for me, and a Bachman knot at the anchor. to act as a one way ratchet so that the prusics can be reset/moved down the rope as needed - the Bachman holds the taut rope you've just pulled the slack out of, so you can move the prusics out again and reset for a second pull - most likely you will only be able to set up the Z for a short pull, unless you have a lot of rope to work with. if you are not using a static/rescue line, you'll be doing a lot of pulling to get the slack out, and you can lose the mechanical advantage of the Z, so you may need to reset
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Posted by: jimyaker on Jun-12-13 5:58 PM (EST)
Another vote for a Prusik in the Z-Drag scenario for any type of haul line. With the right size and type of lines, it would likely take somewhere between 1000 to 2000 lbs of force on the Prusik for it to slide or fail. The ascender will start tearing into the rope at some point and could cause a catastrophic failure.
As with anything, do your research, get the gear you think you need, and then go learn to use it to see what happens when you put a few hundred lbs of force on a rope and whatever device you chose. Much better to get the experience on dry land than trying to learn what does and doesn't work at the river's edge.
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