What is a typical elongation of a dynamic climbing rope?

Question

I'm looking into buying a rope for rock climbing, and I know that I need a dynamic rope for lead climbing. However, trying to find information on the elongation percentages of ropes is proving tricky.

Some sources say that an elongation of 6.5% is typical for a dynamic rope, but others put this number at around 30% (with a maximum allowed of 40%). The rope I'm looking at is a 6.5% elongation, and the salesman says it's dynamic. However, some websites reference static ropes at "under 10% elongation" while others say "1-5%".

Can someone help clarify?

Answer 1

You are apparently confusing static and dynamic elongation. You must use rope that is UIAA-101 / EN-892 certified for the task at hand. You will be buying a Single type rope unless you specifically know otherwise.

Quoting Beal Ropes:

Dynamic elongation:
This is the stretch of the rope during the first UIAA test fall. It must be less than 40%.

Static elongation:
Measured under a load of 80kg it must not exceed 10% for single rope, 12% for double rope, and 10% for two strands of twin rope together.

So you see the static elongation must be no more than 10% for a Single climbing rope, yet to meet the impact force requirements the dynamic elongation is going to have to be much higher than that (though it may not exceed 40%).

Impact force

Values required by the Standard:

• Single rope: Impact force lower than 12kN holding the first factor 1.77 fall with a mass of 80kg.
• Double rope: Impact force lower than 8kn holding the first factor 1.77 fall with a mass of 55kg.
• Twin rope: Impact force lower than 12kN holding the first factor 1.77 fall with a mass of 80kg, on two strands.

The impact force printed in the technical notice must not be lower than the poorest result found by the certifying laboratory.

Answer 2

First of all, DO NOT buy a rope or ANYTHING for that matter that you will trust your life to, purely based on what a single salesperson says, or what I say. Find a few experienced climbers (at least 5+ years of experience each), preferably certified guides and ask them their opinions. Now on to your question:

There is ambiguity in this because apparently ropes are labeled by their percent elongation for 'static' and 'dynamic' testing/use, in addition to themselves being called static and dynamic ropes. That is, you can have a rope that is static (meant for top roping, hauling, etc NOT for lead climbing) or dynamic (designed for lead climbing) and any rope from either category can be testing for 'static elongation' and 'dynamic elongation'. i.e. static ropes will have crappy dynamic elongation by definition.

See the petzl nomad for example:

http://www.petzl.com/us/outdoor/verticality/dynamic-ropes/98-nomad

Static and dynamic elongation is precisely defined here:

http://www.rei.com/learn/expert-advice/ropes.html

In other words you should ask the salesman if he is talking about static or dynamic elongation. 10% dynamic elongation is certainly not enough for lead climbing considering the Nomad has 30% dynamic elongation and that is certainly a lead climbing rope.