This is the second thread about this article, that is because we had an earlier one in which I had made a huge and very significant mistake, and kept trying to reinforce my mistake. The mistake was all my own addition both in the article, and then more dramatically on the thread itself. It was only by going back to Adrian's (now-printed) text that I was able to see my mistake.
We got quite a few replies to that thread and many of them made good points. An especially useful mathematical point was made by jkarran:
If you have a runner at R meters,
climb X meters past it,
and there's an additional Y meters of slack:
Based on the "distance fallen/available rope" equation
FF = (2X + Y)/(R + X + Y)
plug some numbers in and it becomes apparent that you need to be falling past your belayer before increasing Y reduces FF, up to that point increasing Y marginally increasess FF. Not a common scenario in my limited experience.
Since this article is tied to an FAQ, it is important that it contains good information, therefore I had to remove the thread with all my nonsense in it.
Apologies for all who took the trouble to reply (and especially those I made condescending replies to) and rest assurred, the information in the book is correct, is it only this numpty who doesn't know what he is talking about.
In reply to Alan James - UKC: The article still implies a longer fall is better than a shorter fall which is wrong.
When talking about the length of a fall I think of the free fall before the rope tightens. In most cases this should be kept as small as possible, as given by the above equation. I get the impression that the article talks more about the distance fallen whilst the rope and belay are stopping the fall, which should be long to keep the forces on the runner low, however this is a small portion of the overall fall and to say,
"if the only thing you are going to hit when you fall off is fresh air, then you will almost always load your gear less if you take a longer fall and hence you should be safer."
> (In reply to Kane)
> I think you are looking at the old version since that line has been removed. Try refreshing your browser to see the later version.
> Current article views number at the bottom is 417. If you see a number less than this then you may well be looking at an older version.
yeah the view count is only 200. tried refreshing the browser but it stays the same.
Funny thing is that fall factors are rarely crucial but really important when they are. People seem to get away with terrible treatment of their ropes in the lower fall factor region (eg repeated biggish indoor falls around 0.5 with no rope rests in between) where if you logged it cummulatively (as manufacturers say), ropes could be retired in a single session! Also in this area of rope lifetimes, many people worry too much about ropes snapping and too little about losing elasticity.
Generally just repeatedly refreshing tends to do the trick eventually. Holding shift works for some browsers and holding 'control' I think works for others.
Emptying your cache shouldn't touch your log in cookies, just stored pages and images. It might clear them on old browsers but most now have a 'Clear Private Data...' function where you can specify exactly what it is you want to clear. Having said that, you shouldn't need to do it in this case since the key-hold refresh trick should work.
Alan, I think there's still too much emphasis on the 'long falls can be safer' schtick. On the second diagram you say:
'a longer fall of 3m, the fall factor would be only 0.15 - significantly less - and safer' (than a 2m, factor 0.2 fall)
The difference in fall factors here is not at all 'significant', its slight. In reality other factors would become more important as to which is safer. I think you should drop the second diagram and just explain fall factors before trying to introduce the concept that sometimes a longer fall can be safer.
I have to teach this to industrial users most weeks so I have some experience of confusing folk!
Yeah, a .15 is only about 9% less than a .2 (on my Beals).
The reason is that peak force only goes up like the square root of one plus the fall factor, even though the coefficient of it (within the root) is very large, being twice the reciprocal of the fractional extension under body weight (so 1/0.07 for mine - a 7 % stretch), you're only talking between 2 and 8.5 times body weight. According to the linear spring `bounce forever' `independent of length' model which I don't believe anyway.
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