in the AMGA and PCIA we learn that one anchor point perfectly sutible, as long as it is BOMBER....but the main thing to remember is the stability (moving master point side to side, by climbing off route) of the master point; with a single point anchor it is very difficult to achive stability.
when using a bottom managed TR site (beley from bottom not top) the worst case senario is a 20kn impact force on the anchor system. So follow the impact force up the system your using, and if everything can handle that load your good to go!
1inch mil spec webbing(courdory) has a breaking strength ~4000lbs, 1inch climb spec (smooth) has a breaking strength ~5000lbs
Remember LOOP stength is stronger then tensil strength, if possible make a big loop, NO GIRTH HITCHES.
Pad the edges and you should be fine.....if availible use static cord, or static cordelettes
Anchor Point Question
It is actually in the Big South Fork. It is not the least bit sketchy or chossy. Going to the red is always a superior choice, I agree. I love going to the red, but the BSF is very close. The route is actually a recognized trad route. It makes for good practice when I don't have the time to make the trip to the red. From my observations there the BSF could equal or outstrip the red for available rock if it were ever developed to it's full potential.KD wrote:the whole thing sounds sketchy/chossy if its in the louisville area. For the same amount of trouble i'd go to the red and get on some real routes with real anchors.
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225lbs person falling 10ft....Slow beley, fast climber....We've all seen it with gumby beleys! Climber climbs to fast and the beleyer cant keep up, ~5ft of slack infront of him and ~5ft of slack at the beleyer side.....But remember thats the WORST CASE, and the beleyer is anchored....It happens, trust me
"climb, fall, send, go home"
From the research I've done, I can't seem to figure out a way for me to generate any more than about 12kn, and that's with a fall factor of 2, and I weigh 215 pounds. Fall factors on Toprope really can't get to 2. I can't remember if I was looking at force on the rope, or force on the gear though, I suppose the force on the anchor would be 2x the impact force felt by the rope.
Gaar, I would have to differ with you on the being able to generate 20kn on a toprope bottom belay system. Even if the person weighs 300lbs there is no way to generate this much force. The highest fall factor that you can have in a toprope system is really FF 0.9999. This could only be achieved if some one had taken up the first 5 feet of slack and then not taken any more and the climber climbed to the top and fell at the anchor.
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Karsten, I'm not talking about fall factors, I'm talking about froce!
Here's the sloppy math. A 225 lb person falls 10 ft which = 2250lbs on the climber side. This force has to be counteracted by an equal and opposite force on the belayer side (10 kN). The force on the anchor would theoretically be 4450 lbs (20 kN). We know that the carabiners at the turn around point absorb some force (30-50%). If we used 50% that would be in our favor so let's use 30% (not in our favor). Using the new number we get 10 kN going in to the turn around point but only 8 kN gets transmitted to the belayer so you get 20 kN on the anchor. We also know that the climbers knot will tighten absorbing some energy, their harness will stretch, their body will goosh, the anchor carabiners will stretch, the belayers harness will stretch, belay carabiner will stretch, the belay device will slip a little (as long as it's a plate type device) so it's hard to even get to 20 kN.
Now you might say why build to 20 kN? Here's my arguement. There are so many variables that why not just use a bigger number to build in a safety margin. Let me use an example that might illustrate my point. So let's say you have a 300lb client, it's a short cliff (not much rope in the system, shorter spring), since they are a big client you decide that a plate device might be hard to stop a fall with so you use a GriGri (static belay), and you use a low stretch rope cause they are sooo big. If they fall you could end up with a bigger force.
Here's the sloppy math. A 225 lb person falls 10 ft which = 2250lbs on the climber side. This force has to be counteracted by an equal and opposite force on the belayer side (10 kN). The force on the anchor would theoretically be 4450 lbs (20 kN). We know that the carabiners at the turn around point absorb some force (30-50%). If we used 50% that would be in our favor so let's use 30% (not in our favor). Using the new number we get 10 kN going in to the turn around point but only 8 kN gets transmitted to the belayer so you get 20 kN on the anchor. We also know that the climbers knot will tighten absorbing some energy, their harness will stretch, their body will goosh, the anchor carabiners will stretch, the belayers harness will stretch, belay carabiner will stretch, the belay device will slip a little (as long as it's a plate type device) so it's hard to even get to 20 kN.
Now you might say why build to 20 kN? Here's my arguement. There are so many variables that why not just use a bigger number to build in a safety margin. Let me use an example that might illustrate my point. So let's say you have a 300lb client, it's a short cliff (not much rope in the system, shorter spring), since they are a big client you decide that a plate device might be hard to stop a fall with so you use a GriGri (static belay), and you use a low stretch rope cause they are sooo big. If they fall you could end up with a bigger force.
"climb, fall, send, go home"