sandym wrote:Oh, I see what you mean, someone who did not think the whole thing through was trying to abseil a multi-pitch route where the anchors were a “typical rope length” – whatever that is anymore - apart and they either did not bring a tag line or have two ropes and were forced to abseil off one of the protection bolts mid-pitch to reach the next station. Not you I hope?
Not sure why you are expressing yourself in this way, but I don't abseil multipitches. Not my thing. Unless I have to. But this sentence of yours make me believe you are going off-topic.
sandym wrote:I can’t give you route names but I have climbed routes at Tinbeerwah, Kissing Point and Mount Keira which, at the time, had one bolt anchors.
Don't know Keira or Kissing Point. But I know Tinbeerwah. The "single bolt" at the top, is a series of giant ring bolts installed by the army for training purposes. You can safely (I assume) belay or rap from one of them, but you can also equalize from a collection of them. "Almost all bolts at Mt Tinbeerwah are carrot bolts (BRs in the descriptions) so bring plenty of bolt plates. A few climbs have fixed hangers (FHs) or u-bolts. There are large numbered rings along the top of the 'Main Wall' as well as double bolt belays (DBBs) for rapping and belaying." This is from the guide.
sandym wrote: If you assume that, as in your picture, a Fixe or Raumer hangar and ring for a fixed station is correctly installed in solid hard rock (not soft sandstone), loose boulders or any other crap you see. The anchor is rated to 25 kN. Standard abseiler with pack can’t weigh more than 100 kg, and an abseil is only body weight (plus pack weight and clothing). You can’t directly convert to kilograms because a kN is actually a unit of force not weight, but a rough conversion would be 2550 kilograms. The anchor is over-engineered, as is most climbing gear.
Tubular webbing is rated to about 17 to 18 kN, but if you put in knots you reduce the rating by about 30% so tape wrapped around a tree technically holds less force. Gosh, I haven’t even mentioned what a climbing rope is rated to, which is maybe 8ish kN depending on diameter and whether half, single or double.
I don't assume anything and the photo is not mine. Please keep posting info about kN and gear, someone could be interested, but my original post was about redundancy of a single bolt, not gear strength. If I have to rap from the single ring bolt at Mt. Ngungun main cliff, on a 45 degree angle slab, for 7 metres, I have no problem with redundancy (not that I need to set up an abseil for 7m low angle slab), but if I have to use the single ring bolt on Leaning Ridge, with 400m of void below be, then no thanks.
sandym wrote:A single tree is not however, redundant unless you back it up with a cam, nut, horn, flake, other tree, etc, equalised into the system. Simply putting more wraps of tape around a tree does not make the anchor redundant.
With ACIA (Australian Climbing Instructors Association), I set up single tree anchors for training in commercial climbing and abseiling (according to their protocols of anchor assessing). If the tree is big enough I need to add. You may be referring to shrubs, hence saying about backing up a tree with a nut.
sandym wrote:Apparently, you are a climber so you know all this anyway.
Please don't tell people that one single bolt is redundant. As I said, I have already experienced two bolts popping out on me, in either occasion there was no injury and no drama because it happened mid-route. Just because there is a bolt, it doesn't mean is 100% safe (we don't know the hardware, the rock around it and inside, the shock that the drill made on the rock, the installer and his/her experience, etc). And if is not 100% safe then is not good enough, that is the prime principle of setting up or assessing anchors. This is not my personal opinion and believe only, but I'm passing what I have been taught by professional climbing instructors. I suggest you, if you allow me, to speak to someone else to get a second opinion on this matter.
Also, for gbagua, I would be surprised if parks or rescue have installed the bolt and create liability. I know that in many other places of high traffic and big rescue numbers, they have drilled the rock but they are using removable anchors. You can see these holes on Beerwah and Tibrogargan in several places.