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.
I 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.
- 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.