and not by some imaginary numbers out of your as* like how some of the climbers are using these days.

TIME FOR PULLING NUMBERS OUT OF MY ASS........

So everything is climbing is based upon matching the ultimate strength of your rope. Ropes are assumed to have a breaking strength of 30kN.
Tie a knot in it and you are down to 20 kN.

Try more like 9.3 kN for a "typical" climbing rope....

Well how about 22 kN? That's a nice round imaginary number that often gets batted around. Where does that come from?

Ropes are assumed to have a breaking strength of 30kN.
.

USNavy,

You will notice I said ASSUMED to have a breaking strength of 30 kN.

This assumption is accepted for all strength calculation of systems, anchors and general rigging.
For simplicity, this "Magic Number" is the same for low stretch and high stretch ropes.

The very abilities we find desirable in climbing ropes make testing predictions incredibly complex. A new rope out of the bag will be virtually unbreakable as it will just continue to stretch more and more.

I have personally witnessed a VERY old rope, with multiple core shots lift a 10000 load (after stretching to about 140% of its length.

The only way in a testing environment is to subject the rope to continued cyclic loading, in which repeated stresses are applied to the point where the elastic properties of the rope are reduced, and the long fibers are fatigued.

This is the method in which I have discovered all the testing thus far, if you find others, I would like to read them.

Again, my background is rigging, not testing methods, so hopefully I haven't botched up too much, but you can certainly understand where I am coming from.

It is somewhat accepted that all ropes will have a ASSUMED strength of 30 kN.
Simple physics would explain why bolts would approach this number, harnesses would be rated to half of that, and why I would have answered the OP in the fashion I did. In fact if you analyze most practiced methods, you will see that all systems we have been taught to use meet this 30kN(-30% for knots) strength.

USNavy,

You will notice I said ASSUMED to have a breaking strength of 30 kN.

This assumption is accepted for all strength calculation of systems, anchors and general rigging.
For simplicity, this "Magic Number" is the same for low stretch and high stretch ropes.

The very abilities we find desirable in climbing ropes make testing predictions incredibly complex. A new rope out of the bag will be virtually unbreakable as it will just continue to stretch more and more.

I have personally witnessed a VERY old rope, with multiple core shots lift a 10000 load (after stretching to about 140% of its length.

The only way in a testing environment is to subject the rope to continued cyclic loading, in which repeated stresses are applied to the point where the elastic properties of the rope are reduced, and the long fibers are fatigued.

This is the method in which I have discovered all the testing thus far, if you find others, I would like to read them.

Yes I know what you’re saying. You’re implying that the breaking strength of a rope under dynamic conditions is 30 kN. I am saying the static breaking strength is much less. That’s all. Was that old rope that held 10,000 lbs. an unmodified dynamic climbing rope 11 mm or less in diameter? Was the load being held by a single strand?

He just did. Did you follow the link? BD tested 4 rope samples with in a static pull test, and they found that they all failed at around 2200–2300 lbf, about 10 kN. How do you reconcile that test with your claim that ropes have an "assumed" strength of 3 times that figure.

Jay

What I am trying to say, is static breaking strengths are an inaccurate method for measuring high stretch ropes.
For example this is what I would expect to see in a test of breaking strength (although as mentioned, I am a rigger, not a tester)

Phase 1 - rope stretches and machine maxes at 5000 lbs.
Phase 2, machinery reset for further pull, DURING WHICH the load is reduced to 1500 lbs as the rope stretches
Phase 3 - rope stretches to machine maximum at 5000 lbs
Phasse 4 - Machine reset and load again reduces to 2600 lbs as rope stretches
Phase 5 - machine stretches, rope fails at 2700 lbs.

(Again these numbers are totally made up, but this is my understanding of how ropes are broken, and explains why static testing does not represent rope strength during use. Ropes are designed to reduce forces, and by that nature, testing ropes eliminates any represeantation of actual use.

...For trad gear I would pretty much always use at least 3 peaces. There are however occasions, ie where there are large tree’s, boulders or bolts to use, where the anchors are clearly so good that two or even one is OK, on the other hand there have been times when I have used 6 or seven peaces of gear to build an anchor.

What I am trying to say, is static breaking strengths are an inaccurate method for measuring high stretch ropes.
For example this is what I would expect to see in a test of breaking strength (although as mentioned, I am a rigger, not a tester)

Phase 1 - rope stretches and machine maxes at 5000 lbs.
Phase 2, machinery reset for further pull, DURING WHICH the load is reduced to 1500 lbs as the rope stretches
Phase 3 - rope stretches to machine maximum at 5000 lbs
Phasse 4 - Machine reset and load again reduces to 2600 lbs as rope stretches
Phase 5 - machine stretches, rope fails at 2700 lbs.

(Again these numbers are totally made up, but this is my understanding of how ropes are broken, and explains why static testing does not represent rope strength during use. Ropes are designed to reduce forces, and by that nature, testing ropes eliminates any represeantation of actual use.

Dynamic ropes are tested for a maximum impact force which is far below 30kN. As long as they can stretch far enough to dissipate the energy of the fall they will have a tension that is not much above that impact force.

Now that we're not really addressing the question could somebody who always uses three pieces make a justification why two is not adequate if they're bomber?