Prussik loops, haul lines and z-drags

[yarnellboat]

Speaking of safety on the river...

Anyone try a z-drag lately?

It seems that throw-rope fashion is to go with thinner and thinner ropes. So, as the haul lines get smaller, the differential between the haul line and the sliding Prussik is less, so the Prussiks are less likely to work well.

Anyone else come across this? Anyone have a solution?

PY.

[dccjon]

The new tech cords on the market work well for prussik use provided you use the proper knots. 5mm diameter and 5K mbs is likely stronger than most throwlines out there. Thin enough diameter to work with most throwlines also. Price is a bit more than standard prussik cord.

[Mattt]

Do more wraps with the prussic. The less the difference in diameter, the more wraps you need.

Normally for a rappel, with double ropes, I'd use only two wraps. With single line, I'd go 3, and if its wet from rain, I'd go four. The smaller the difference indiameter between the prussic and the rope, the more wraps you need. I have older materai for prussics - it is less slick than the stuff they seem to sell nowadays. 5 or 6mm is strong enough as a loop.

Haven't practiced a Z pulley in years - guess I should see if I remember how someday.

[yarnellboat]

Thanks,

I'm re-assessing and re-organizing some of my gear and the way I carry it. I'll look into some thinner tech cord.

For those who aren't sure how the stuff in your kits works together, and if you haven't practiced in a while, it's always a good idea to get together with your partners and go through it now & again!

Newer throw ropes are pretty thin & slick.

Cheers, PY.

[esprit]

Hi Patrick,

Despite throwbags getting smaller and smaller..... we are still recommending 8.5mm to 9mm high quality rope for throwbags. We have found that this diameter is easy to throw, catch, stuff... can be used for basic swimmer rescues as well as hauling systems, lowering systems, raising systems.... with 8.5... to 9mm we use 6mm prussiks.

Jim

Esprit/rescue3northeast

[yarnellboat]

Thanks Jim, I agree with you. I still use my big rope, and I know my prussiks work with my rope.

However, any throw rope in the group could be used as a haul line, you also need to know whether your prussiks will work with other peoples' throw ropes!

Better to know ahead of time than to be mid-rescue and have to think/discuss whether you should try additional wraps on the prussik!

Cheers, PY.

p.s. I think I know the answer to this, but for sake of public sharing - do webbing loops work as prussiks? I assume their use is only as anchors.

[esprit]

Well.... perhaps.... unfortunately I have seen a lot of ropes that are appropriate for swinging a swimmer into shore used in hauling systems that the smaller, weaker, stretchier ropes really were never designed to be used for.

Regardless.... I would suggest any hauling system (3:1 for example) be finished with a change of direction so that the pullers are out of the "impact zone" in the event something lets go.

Typically using cord 1/3 smaller than the base rope at 3 wraps is best ratio.

Webbing can be used as a camming device but size and space make cord a better choice.

jim

[yarnellboat]

Good point on knowing your ropes...

Many throw ropes out there are the small (6-7mm) poly ropes for swimmer rescue, with breaking strength of 800-1100lbs, and are not cool for mechanical hauling.

The big poly ropes (9.5 - 10mm), with a strength of 1800-1900lbs, are better, but still iffy for hauling?

Spectrx and other high-tensile water ropes in the large size (9.5mm) are best for thickness and strength, and are approved for rescue, with min. breaking strengths over 3,000lbs.

Normal static cord at 5mm is not recommended for prussiks, 7mm is minimum recommended with 2200lbs breaking strength. The 5mm tech cord has 5,000lbs. Make sure you grab the right 5mm cord!

I believe most caribiners and slings of 20mm nylon webbing (18-25kN) would be approaching 5,000lbs.

Our prussiks and especially throw ropes are typically our weak link, so we'd better know what we got - I'll be putting a closer eyeball to the gear of my paddling partners, and I'll be giving a nudge to those who don't carry 'biners and pulleys and who only have the 6.5mm poly rope!!

PY.

[Jan_dettmer]

Pat,

I prefer the combo of a small Spectrx rope on me all the time (I use the NW belt) and a rescue rope of Spectrx.

Thin ropes can certainly work, but you have to know how and practice.
As an alternative to the prussik you can also use a klemheist, than works with slings.

Using slings, it is important to remember that Dynema can and will melt if it slips, so that is not appropriate for klemheist knots.

I carry:
70' 1/4" spectrx rope
70' 3/8" spectrx rope
2 metal pulleys
4 locking biners
2 120cm thin dynema slings
3 prussik slings (1 for progress capture, 2 for the z-drag itself)

I always carry this on me in my life jacket. The system works with both ropes. SO even if I loose my boat I have a stipped down version still on me (minus the thicker rope). The kit also has enough gear for the odd rappels etc.
The system works well but I do practice and I also climb quite a bit which really helps in being familiar with all the knots and gear...

Happy adventure paddling, Jan

[yarnellboat]

Thanks for the info Jan,

I have no concerns about the thinner (1/4"), static Spectrx ropes at 3700lbs tensile strength. But I will get thinner tech cord for prussiks.

It's the 1/4" stretchy poly ropes at 800lbs tensile strength that might be a concern, especially if used with knots or tight bends.

With a number of "similar" products out there in different shapes, lengths, colours, diameters and materials, I'll bet there's lots of groups on the rivers who carry thin, poly throw ropes and think that they're covered. Maybe they are, 800lbs sounds like a lot - I have no idea what kind of force is required of "a typical" z-drag - but I'd prefer to err with a beefier setup.

I'd suggest that we/the industry should more clearly differentiate and label the difference between a "throw rope" and a "rescue rope", just so people know what they're buying or carrying.

Cheers, Pat.

[Jan_dettmer]

yeah, I agree. I see lots people with poly ropes which is only good for bagging.
What really hurts you is the stretch, not the break strength.

I suggest you get a 3/8 rope for rescue and have the other one on you for bagging all the time.

Getting real thin prussiks, make sure they cannot melt when they slip.
(you want nylon). Just playing around with a log once, we melted straight through a dynema sling that was used in a klemheist.
I am not sure what this can do to the core of a prussik but there is a lot of heat when something slips under a large load with lots of friction...

Cheers, Jan

[esprit]

A recent incident in Utah has lead to us modifying our hauling instruction. We now instruct everyone to finish their haul system with a change in direction at their anchor. That way the pullers are out of the "impact zone" if something were to fail.

Although not perfect... at least if there is some inappropriate equipment in the system.... nothing flies back and injures the haulers.

jim