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Comments sought on natural anchor design 31-Jul-2012 At 9:56:37 AM uwhp510

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On 31/07/2012 pmonks wrote:
>On 29/07/2012 muki wrote:
>A slump may not be dangerous, but how about a 50cm fall? A 1m fall?
>A 3m fall?

Don't forget that fall factors work for top-rope falls as well, except that they are usually WAY lower than for lead falls. It makes absolutely no sense to talk about the length of fall that is acceptable, without talking about the amount of rope you've got out. The moral of the story is that you can fall as far as you like on your static rope, provided you make sure that your fall factor is low enough.

Given that dynamic ropes, plus all the other gear that we use... (maybe not mini-traxions though but grigris for sure)... are made to deal with at least one factor 2 fall, and assuming you've got a reasonably low stretch static (3% extension under body weight, ie 3 times as stiff as a normal dynamic rope) you could fall 3m, provided you've got 3 x 1.5m = 4.5m of rope above you, and generate roughly same force as your 3m factor 2 fall on a dynamic rope. I think that we can all agree that if you're falling 3m when solo top roping, you're doing it wrong, but if you really want to fall 3m, then put your anchors more than 4.5m above or back from the top of the route and you'll be (mostly) fine.

Now say you've got a super stiff polyester rope, with only 1% stretch under body-weight (ie 10 times as stiff as a dynamic rope). Then you can fall 3m, provided you've got 10 x 1.5m = 15m of rope above you. Not ideal, but probably not likely to lead to imminent death, provided you manage your system well.