Response of Some 3:1 Haul Systems to Excessive Loading THOMAS EVANS, SAR 3

Why Study Haul Systems? Limited by personal study Want more than I can find What I have been trained: Often wrong Test what I have been taught Curiosity How?

The Prusik Clutch Haul system loaded Prusik slips at ~5.3 kn (1200 lbs) Limits load As load increases Prusik slips again Keeps load low ~5.3 kn (12000 lbs)

The Prusik Clutch Does the prusik clutch exist? I have never seen it during prusik testing Does it work the way I was taught? How does it work? How variable is it?

Design: Empiricism Built 3:1 haul systems Two configurations Hauling Resetting Observed properties when loaded Failure Slippage

Materials Rope/cord donated by PMI 8mm cord (nylon) Cut into 41, 48 lengths Alternating along spool Tied with double fisherman s bends All tied by author for consistency

Materials Rope 11.5mm Isostatic (polyester) 11mm Classic Pro EZ (nylon) 11mm Classic Sport Max (nylon) 129 lengths

Methods Inline 3:1 haul system Z-rig Appears most common Broader applicability?

Methods Built in two configurations During a haul During a reset

Methods Slow pull, ~8 /minute Omega LCCA-15K 200 measurements/second Data scaling None needed for reset configuration 3/2 scaling needed for hauling configuration

Methods Hauled on anchor Rope stretch Should not alter results Anchored/ stationary

Results: Box and Whisker Plots Displays descriptive statistics Compare data sets rapidly

Sample Peak Loads (kn) Results: During a Haul 17 Isostatic (N=12) All broke at bowline Classic Pro EZ (N=13) 9 slipped, no breakage 2 knots failed 2 prusiks failed Classic Sport Max (N=11) All slipped, no breakage 16 15 14 13 Isostatic Classic Pro EZ Classic Sport Max

Force (lbs) Force (lbs) Force (lbs) 4000 Results: During a Haul 3500 3000 2500 2000 Prusik slippage All prusiks slipped at least once Range of initial slippage forces Range of future slippage forces 1500 1000 500 0 Sample Isostatic 4000 4000 3500 3500 3000 3000 2500 2500 2000 2000 1500 1500 1000 1000 500 500 0 Sample Classic Sport Max 0 Sample Classic Pro EZ

Results: During a Haul Prusik slippage 4 as expected 32 increasing

Force (lbs) Force (lbs) Force (lbs) 4000 Results: During a Haul 3500 3000 2500 2000 1500 1000 500 0 Sample Isostatic 4000 4000 3500 3500 3000 3000 2500 2500 2000 2000 1500 1500 1000 1000 500 500 0 Sample Classic Sport Max 0 Sample Classic Pro EZ

Sample Peak Load (kn) Results: During a Reset 28 Isostatic (N=16) 11 mantles failed 2 prusiks failed 26 24 22 2 ropes cut 1 slipped, no breakage Classic Pro EZ (N=16) 20 18 1 slipped, no breakage 3 mantles failed 12 prusiks failed 16 14 Classic Sport Max (N=10) 12 3 mantles failed 7 prusiks failed 10 8 Isostatic Classic Pro EZ Classic Sport Max

Results: Broken Rope Two broken rope samples

Force (lbs) Force (lbs) Force (lbs) 4000 Results: During a Reset 3500 3000 2500 2000 Prusik slippage All prusiks slipped at least once Range of initial slippage forces Range of future slippage forces 1500 1000 500 0 Sample Isostatic 4000 4000 3500 3500 3000 3000 2500 2500 2000 2000 1500 1500 1000 1000 500 500 0 Sample Classic Sport Max 0 Sample Classic Pro EZ

Sample Peak Load (kn) Sample Peak Loads (kn) Conclusions 17 16 15 A range of responses 14 No one answer Test your own gear Strengths were not as high as expected Strong enough for SOP s/sog s? 13 28 26 24 22 20 18 16 14 12 10 8 Isostatic Classic Pro EZ Classic Sport Max During a Haul Isostatic Classic Pro EZ Classic Sport Max During a Reset

Force (lbs) Rigging Consequences 4000 If a prusik slips Reduce forces! Obvious 3500 3000 2500 2000 May or may not get another slip Prusik or mantle breaks Rope cut 1500 1000 500 0 Sample Classic Sport Max

Conclusions: Prusik Clutch 4000 It exists Why not observed before? Does not behave as expected Variability! Prusiks slip at higher values Does not keep force low Slows down failures 3500 3000 2500 2000 1500 1000 500 0

What s The Point? When will I generate these forces? Practically rarely occurs Know when getting close Explains how systems are working Variability! Teach the variability! Reduce rigging lore

Acknowledgements CMC provided Laboratory time Laboratory equipment Staff time PMI provided the rope and cord Cedric Smith for running the equipment/time Loui McCurley for facilitating rope and cord donation

Questions?