Primitive tension testing results.

Recently I saw someone rigging a “primitive” slackline with five carabiners (one on the static end, and four for the tension system). The “elegant friction lock” method I use was also not being employed. Basically this is as far as you can get from how I setup my primitive systems and still be considered the same thing. After tight they would wrap the line several times about the tree (while holding it tight) and then tie it off to keep it tight.

Then a few days later I met someone else who was also using this five-biner-method, and they asked if it was not more efficient than my preferred 3 carabiner method. I didn’t think so, but couldn’t say for sure. Well, now I can.

_MG_0834I headed to Golden Gardens today and setup the dynamometer on a 40-foot line. First up was the five-biner-method, where the line goes back and forth 4 times between 4 carabiners (two on the line locker, and two on the anchor). Using a carabiner as a handle, I pulled a maximum of 336lbs, which quickly loosened up to 256lbs as the line stretched after I tied it off (without friction lock).

Next up was my traditional “z” style (3 carabiners for the tensioning system) primitive with the friction lock. I was able to pull 436lbs, which loosened to 374 over the next five minutes. After five minutes I got on the line and bounced for a bit. When I got off the line had loosened to 294lbs.

Last I added my double-pulley multiplier and pulled the line to a crispy 826lbs, which loosened to 740lbs over the next few minutes. I hopped on the line and bounced hard, seeing peak numbers around 1100lbs. Getting off the line, it then had stretched to 630lbs of tension. This number slowly rose and then capped around 650lbs. Again I bounced, seeing peak numbers around 1050lbs. After getting off this time the line read 610. It slowly tightened up to 620lbs.

Conclusions:

  • 3 carabiner tensioning system is the most efficient “primitive”
  • 1 person can put roughly ~2-2.5x bodyweight tension into a slackline, using the primitive method
  • Primitive + double pulley and cordalette = ~5x bodyweight
  • Lines loosen over time simply sitting with no one on them, and loosen even more with use.

3 Comments

  1. georges says:

    Hey,

    thanks for all the info!
    I have recently seen (on slacklinemontreal.com) that you can increase your primitive set up mechanical advantage to 15:1 by adding 2 biners to the set up (still using the ‘elegant friction lock’)
    What’s your opinion on that?

    Thanks a bunch

    Georges

    It works. Although I like to use 2 extra single pulleys rather than biners (less friction). See here.

  2. nick says:

    Thanks for the videos and all the great information. I only use two biners for my tensioning system. I go from the linelocker up through the anchor biner, down through the linelock biner, then up through the anchor biner again but tucked underneath to achieve a friction lock, then back down and under for another friction lock on the linelock biner. Would I have more m/a by putting another biner in my system? Thank you

    EDIT: Yes, you would. 3 carabiners in the tension system is the ideal configuration.

  3. Eli says:

    From a physics / practical standpoint, why is a 3 carabiner system better than 5? Ignoring the results for a second, you would think it would be easier to pull the 5′er setup than the 3 since they work kind of like pulleys. I started slacklining by reading the tutorials on this site and ended up using 4 on the tensioning system (one on the static end) just because I could then pull the line the other direction. What are your thoughts?

    EDIT: The carabiners introduce a significant amount of friction into the system. At some point the added mechanical advantage cannot overcome the added friction. Not sure what you mean by 4 on the tensioning system (with one on the static end). To me having 4 in the tensioning system means you would have 2 on the line locker and 2 on the static (tree) side. Is that the configuration you mean? As noted in the article, the ideal configuration is 2 on the tree side and one on the line locker.

Leave a Comment (for questions please email Adam directly)

 

— required *

— required *