Absorbing shock with your leash

[yogabeachslacker]

it's also worth noting that a shorter line will undergo more stress from a whipper than a longer line. this is because there is less line in the system to stretch and absorb the shock. As a thought experiment, imagine falling off a line with a huge leash, say 20 feet or so. would you rather fall on a 20 foot line that's going to stretch maybe 4 feet (all these numbers are just thrown out there by the way) in order to absorb your shock, or a 100 foot line that would stretch 20 feet under the same amount of tension? I wouldn't park my car under the short line.

Anyone who climbs will see the parallels with rope falls. the more you fall, the higher your kn, which is offset by the higher amount of rope in the system which leads to more stretch and shock absorption. My point isn't that longer highlines are safer, there are a lot of other variables, but that you shouldn't assume that short ones are either.

[goterps]

I think you mean a greater stress difference... Some of these longlines probably have more tension without a person on it than the shorter highlines will have during a whipper. And the really short highlines are fine if you just give them less tension.

[yogabeachslacker]

well, more testing surely needs to be done, and I could definitely be off, but my concern is more about the anchors than the webbing itself. it's my understanding (or ungrounded belief if you prefer) that even on a super long highline, with high overall tension, the force of the whip will be far more dissipated than on a shorter line with less tension. Maybe I shouldn't have made such a broad claim, but my real point was only that short does not equal safe.

[still-slackin-thru]

Quote:

...I wouldn't park my car under the short line...



I think it is more important for any leash shock absorbsion system to protect the highliner, not the highline. With the materials available today a properly rigged and anchored highline should never break.

[yogabeachslacker]

first off, I was just trying to say that under greater forces, it's possible that a short line could fare worse. if, for instance a line were being rigged with cams, then I think the anchors become more of a concern, and I think it's important for us to build a better understanding of how the forces may change with the length of the line. Maybe I shouldn't have tried to make any definitive statements without data, so instead, let me just say, without additional data, why not leave the backup on?

[still-slackin-thru]

I think those assumptions are true, but also have no way to prove them.
I assume (OK - know) a short line has less "standing tension" than a longer line
I assume a leash fall would "shockload" the webbing and anchors more (as a percentage??) on a short line than a long line (for the same reason a leadfall is harder on the rope and anchors when less rope has been fed out).
I have always assumed if a whipper is taken very close to the anchor it will shockload that anchor far more than usual (ie if the whipper is taken farther from that anchor and more towards the middle).
I also assume a whipper taken close to the end of a longer highline (where the highline is darn static combined with the greater standing tension) would really suck! (potentially very hard on your body).
I also assume a whipper taken on a thick static amsteel line would suck!!

It's easy to subject a piece of hardware or webbing to a hydraulic break test device to measure its true break strength. Its much harder to measure how much force hardware or webbing will REALLY be subjected to in various real world highline situations

[yogabeachslacker]

well, if someone had a dyno, couldn't they just rig a line with that, then subject themselves to a series of whippers near the anchor and towards the middle, and have someone else observe the spike in the dyno? I've never used one or even seen one in person so I don't know. Surely someone has a little brother or something they can donate as a whip dummy for our very scientific cause...

Anyways, it's not critical that I know these things, I'm mostly just curious. We'll always need more data, there will always be more variables, and hopefully more ideas will continue to arise from this confusing juncture of theory and observation.