Zip line rope selection

Phil

Phil

Carpal tunnel level member
Location
Oak Lawn, IL
I'm sure this has been discussed somewhere here before but I've searched the threads and haven't come up with anything too detailed.

I'm going to put together a recreational zipline and am looking for input on the best rope based on durability basically. After some research I'm leaning towards a kernmantle construction due to strength of core and the cover is basically there to protect the core. I see this as an advantage in regards to possible fuzzing from repeated trolley runs. I do like the poison ivy rope though as it has a lower elasticity that something like sterling HTP or Samson's static kernmantle. I guess I can distill this discussion into a few questions:

1) has anyone noticed fuzzing or cover wear on zipline ropes worthy of it being a noticeable concern?

2) is a thinner 11mm line better than a larger 1/2" line? I've seen some different opinions on this. I'm wondering if there is a benefit to a smaller line other than a lower length to weight ratio.

3). Those with zipline experience, any input on various ropes you've used would be greatly appreciated.

I got a smokin deal on a CMI micro trolley 5.8 which has a recommended rope diameter of 1/2" - 5/8". I could probably use this with an 11mm line as long as the rope doesn't touch any part of the cheek plates.

www.cmi-gear.com

MICROTROLLEY5.8

Stainless steel sieplates, two 1 1/2" stainless steel sheaves, ball bearings and stainless steel axles. Max Speed = 90 ft/sec or 60 MPH MBS Cable/Rope Capacity Size Weight Efficiency 14000lbs 1/2" - 5/8" 5x3in 0.90lbs n/r !WARNING: Riders weight must be supported by a lanyard and supporting...
www.cmi-gear.com
 
I have a 175' zip line and have a 600' in the works. I use 3/8" cable. It seems like the steel cable stretches enough as is, I can't imagine using rope.

If your zip line is going to be 150 or less, try hitting up the local 4x4 groups. Lots of people replace their brand new winch cable with synthetic rope and will give away their steel cable. I've gotten 5 free cables over the years without even really trying.
Some winches have 175' but most are 150'. Some are 5/16" also,
 
Tom Dunlap said:
If I were making a zipline with a nod toward a permanent installation...meaning more than a weekend or so...I'd look at cable. YOu can tension cable...no UV degrade...industry standard...check out ACCT for specs. Be sure to choose trolleys that are designed for cable.
Click to expand...

This will definitely not be permanent. Setup for an afternoon and then pack it up.
 
For temporary zip installs I like a kernmantle construction, 13mm or 1/2" is a good rope diameter. NE Ropes KMIII or Sterling HTP are strong choices. I've never noticed any cover damage to rope from a zipline trolley. For the CMI trolley I ended up bending the side plates out on the back side (where the secondary attachment point is) they were contacting the rope when it ran down the zip.

I set my rope zips so that they can be re-tightened a few times during the time they're used, the line will progressively stretch especially with hearvier adult riders. I use a redirect though a block to a portawrap as the anchor. I put a MA tightener between the block and the porty to make it quick and easy to tighten and re-anchor on the porty.
-AJ
 
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moss said:
For temporary zip installs I like a kernmantle construction, 13mm or 1/2" is a good rope diameter. NE Ropes KMIII or Sterling HTP are strong choices. I've never noticed any cover damage to rope from a zipline trolley. For the CMI trolley I ended up bending the side plates out on the back side (where the secondary attachment point is) they were contacting the rope when it ran down the zip.

I set my rope zips so that they can be re-tightened a few times during the time they're used, the line will progressively stretch especially with hearvier adult riders. I use a redirect though a block to a portawrap as the anchor. I put a MA tightener between the block and the porty to make it quick and easy to tighten and re-anchor on the porty.
-AJ
Click to expand...

It's funny you mention bending out the rear part of the cheek plates on the CMI trolley. I was wondering if that spot would hit the rope in the belly of the run. I was planning the tension as you describe. That just sounds logical.
 
We used to make tyroleans out of Bluewater II static rescue line. That stuff turns into wire cable after a while...
 
Not much to add to the excellent comments, except that I met the Zip Line inventor and canopy researcher, Donald Perry, when attending last year's tree Climbing Rendezvous in Costa Rica. He's evolved the zip line into the Ecotram. Check it out...

 
@climbstihl and I built a temporary controlled zipline a while back. We used his normal 12mm rope (I think It's 16 strand XPe), and the stretch with the rope tensioned by a 3:1 MA system was substantial, about 2-4m in the middle, even at the steep angle of the rope which was about 30-45°. This is of course because our static rope is semi-static in reality in order to comply with PPE regulations.

I was also in a group with a self-proclaimed "survival expert" once, He decided to build a rope bridge across a local river with semi-static Kernmantel rope. Although the rope was under serious tension (3:1 with 4 people tensioning) I was in the water after 3m, and because the river was so shallow at that point my back started scraping actoss the river floor...

So you'd need to have both the entry and exit of the zipline at quite a big height of the ground, but it would work. The runout would be extremely long, which might be potentially dangerous if you dont hit the sweetspot between hitting the anchor tree or the ground and not stopping in the middle of the ride.

Dyneema Kernmantel rope might be an interesting alternative to steel cable, Liros Torpedo rope costs 6€/m here in Germany (2$/foot)
 
Jan_ said:
@climbstihl and I built a temporary controlled zipline a while back. We used his normal 12mm rope (I think It's 16 strand XPe), and the stretch with the rope tensioned by a 3:1 MA system was substantial, about 2-4m in the middle, even at the steep angle of the rope which was about 30-45°. This is of course because our static rope is semi-static in reality in order to comply with PPE regulations.

I was also in a group with a self-proclaimed "survival expert" once, He decided to build a rope bridge across a local river with semi-static Kernmantel rope. Although the rope was under serious tension (3:1 with 4 people tensioning) I was in the water after 3m, and because the river was so shallow at that point my back started scraping actoss the river floor...

So you'd need to have both the entry and exit of the zipline at quite a big height of the ground, but it would work. The runout would be extremely long, which might be potentially dangerous if you dont hit the sweetspot between hitting the anchor tree or the ground and not stopping in the middle of the ride.

Dyneema Kernmantel rope might be an interesting alternative to steel cable, Liros Torpedo rope costs 6€/m here in Germany (2$/foot)
Click to expand...

That is hilarious, as long as your back didn't get too scraped up on the river bottom. Yeah I think any of the ropes we normally use with sufficient rating will do for a temporary zip setup. It takes some time doing the first setup to determine how high to set the starting point (and end point to a lesser degree) to account for stretch characteristics and so you: (A.) don't bottom out during your ride, and (B.) so you don't each the end point at too high a speed. That's why I use a block on a sling above a bollard at the starting point, it's easy to move it up or down when you're doing initial setup. I've been building my end point as a suspension/redirect between two trees and then the anchor is after the redirect low on a single tree (if that makes sense0. The benefit of the the suspended redirect at the end is it's easy to tune the end height or side-to-side positioning of the zip. With all of those variables under control you can fine tune a perfect landing for a range of weight zip riders. I "land" zip riders up in the air. A short rope tether is attached to the trolley with a Grigri on it. The Grigri is set at a comfortable riding position below the trolley. When the rider reaches the end they lower themselves with the Grigri the short distance to the ground. I'll have a facilitator at the end to grab the tail of the tether and coach the rider if they don't have experience operating a Grigri.

Dyneema core cordage is indeed costly, for a say 250' zip line that's getting expensive.
-AJ
 
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Also, neglected to mention.... I test my setup by lowering myself down the zip with a second line and a Rope Runner, any multicender or descent device will do. In that test I can find where the low point in the zip is and can make further adjustments from there to tune the speed and landing point. I'm done with "Oh this should be good, I'll just take a ride and see" ;-)
-AJ
 
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