Author Topic: Knotty but not Gruesome (VLL's)  (Read 2325 times)


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Knotty but not Gruesome (VLL's)
« on: January 13, 2007, 08:30:20 PM »
VLL = “Vertical Life Line”

This is a nice way to get out of the other thread of similar topic that some found offensive.  Vertical ropes can also be used to save lives -- and that is my business.  These are the ropes you see window washers dangling from after their scaffold or platform collapses and the TV crews show up.  The objectives are the opposite of a hanging.  You want to prevent impact with the ground, you want to minimize the fall arresting loads, you want to apply those loads to the body safely so no one gets hurt, and you want to make sure the rigging holds together.  Since knots used for VLL's have been a source of controversy in this business, I see it as a valid topic of conversation here.  Rigging tends to be similar to that used by rock climbers, but in this industry you try to make it more “fool proof,” not requiring as much skill on the part of the user as you would expect from a rock climber on the face of a mountain.

Anyway, if anyone wants to pursue the topic further, or if you have specific questions, then let me know and I’ll post more.  If we pursue it far enough, answers to all the questions posted in the other thread will be understood.  Engineers who design VLL’s use all the same materials and processes as for the other purpose, but generally make opposite decisions concerning which material to use and how to rig it.

Possible points of discussion:

Material selection
Impulse and Momentum/Energy Calculations
Knots verses eye splices and carabineers
Different ropes do better with different knots
Rope Grabs
Anchor Points
Energy Absorption
Harness Connection

Paul Kruse