Is it safe to use the Petzl Zig Zag in an SRT setup with the Rope Wrench? What is the breaking strength of the Petzl Zig Zag and the Zag Wrench Tether? What forces are exerted on a rope and climber in different kinds of tree climbing accidents? How much force can the human body withstand? Watch this video and hopefully the tests and analyses shown here will help you make your own decisions.

Thanks to Kevin Bingham (https://www.singingtreedetroit.com) for providing the Rope Wrench used in the pull tests and to Richard Mumford (http://climbinginnovations.com) for performing the pull tests.

Results of the 7 stress tests shown in this video:

1. Zag Wrench Tether setup (SRT) on Blue Moon rope. ZZ slipped at 1237 pounds
2. Zig Zag in pure SRT setup on Blue Moon. ZZ slipped at 604 pounds
3. Zag Wrench Tether (SRT) setup on Marlow Vega rope. ZZ slipped at 1349 pounds
4. Zig Zag in standard DRT setup on Marlow Vega. ZZ skipped at 1496
5. Zag Wrench Tether (SRT) setup on Marlow Vega rope with alpine butterfly stopper knot. Rope broke at 4995 pounds
6. Zig Zag in standard DRT setup on Blue Moon with alpine butterfly stopper knot. Zig Zag broke apart at 4663 pounds
7. Straight pull test of the Zag Wrench Tether. Tether broke at 5505 pounds

Credits, References, and More information:

1. You can download the Zag Wrench Tether design file or find information on how to buy a Zag Wrench Tether at: https://www.tree-minded.com/p/tether....
2. The original video showing the Zag Wrench Tether is at:    • Zag Wrench Tether  
3. More on fall factor from Wikipedia: https://en.wikipedia.org/wiki/Fall_fa...
4. Richard Goldstone’s paper on deriving and explaining the impact force equation. Contact me for a copy or download the paper for free at: http://www.rockclimbing.com/cgi-bin/f...
5. Blue moon rope modulus: http://www.yalecordage.com/custom-and...
6. 67 page paper titled Survivable Impact Forces on Human Body by Harry Crawford. Contact me for a copy of download the paper for free at: http://www.hse.gov.uk/research/hsl_pd...
7. Pendulum equation derivation:    • Horizontal Pendulum & Tension as a Ce...  
8. More on John Stapp    • John Paul Stapp and Sonic Wind No.1  
9. Another video about John Stapp:    • MANNED ROCKET SLED RUN  
10. Petzl ZigZag certification explanation: https://www.petzl.com/US/en/Professio...
11. Changes made between the 2013 and 2014 ZZ as a result of the recall: https://www.petzl.com/security/profes...
12. Johnny Pro's crane swing video:    • Crane Swing  
13. Results of side impact testing on the Zig Zag: https://www.petzl.com/US/en/Professio...