ANSI Standards Regarding Rope - Stretch?

lxskllr

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I was idly looking over wesspur's rope catalog, and noticed this in one of the descriptions(emphasis added)...

Arborist Climbing Ropes are required to have a minimum breaking strength of 5,400 lb (24 kN) when new, and should be no smaller than 1/2” (12.7mm) unless the employee has been trained in the use of smaller line (down to 7/16” / 11mm), and the line's working elongation should not exceed 7% at 540 lb load.

What is the thinking behind limiting stretch? Annoyance aside, I'd think stretchier lines would be safer within reason. A rubber band bouncing you around probably wouldn't be good. Any thoughts? Even better, are there ANSI whitepapers that get into the selection process/debate over the various specs?
 
And what is the training for sub 1/2" lines?
im guessing it goes back to tautline hitch days where rope diameter mattered allot more
I use 11/11.8mm as a climb line normally and find no difference is safety/handling from a 13mm line, except none of my "modern" lightweight thin 24/48 strand lines will work with a blakes or tautline good enough to be safe

although I have no real clue, just guessing here
 
I've never seen that diameter verbage before either. I thought the just frowned upon smaller than 7/16". My take on the stretch guideline is that it separates work positioning from fall arrest.
 
Stretch vs load info is hard to come by. Here's some extraneous reading

I'd love to see the data and graph from Two Full Burger where this is based from:

Our Tachyon excels due to:
  • Low stretch at low loads for less bounce while climbing
  • High stretch at high loads thus minimizing the shock effect in the event of a fall
 
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