Rope Impact Forces

All else being equal, will a rope with a lower UIAA impact force generate less force on the top piece of protection in a standard fall?

Yes

About 7

Jim Bouldin wrote: Yes

Thanks, Jim. Would a difference of 1-1.5 kn have any effect on your decision if choosing between two single ropes, assuming that the rope will be used for trad climbing a lot?

I'm contemplating the same question.  I am thinking of getting the new edelrid protect pro whose impact force is 10.3 to replace a mammut serenity whose impact force is 9.7.  The advantage of the edelrid rope would be greater resistance to cutting.  I think I will give the edelrid rope a try when they become available. 

9.7kN is 94% of 10.3kN

Those numbers are from 80kg dropped with a 1.77FF, which probably isn't like your falls. You weigh differently, with a different FF, with a different geometry, through biners, rubbing against rock, and with a belay device that might slip (that itself can have a big impact) with a person that might move.

Makes that 6% difference feel like noise.

I don't have any supporting evidence, just feelings. Guess I'm not contributing much other than feelings.

-- Trapped inside.

climber pat wrote: I'm contemplating the same question.  I am thinking of getting the new edelrid protect pro whose impact force is 10.3 to replace a mammut serenity whose impact force is 9.7.  The advantage of the edelrid rope would be greater resistance to cutting.  I think I will give the edelrid rope a try when they become available. 

Yeah, with that Edelrid rope you’re gaining some safety margin through cut resistance, but it seems as if that’s coming at the expense of impact force on your gear. I’m wondering if the difference in impact force between ropes could ultimately make the difference in a piece blowing or not. 

Also, Pat, I’m seeing 9.9 kn for the Edelrid Swift Protect Pro Dry as a single rope. However, compared to the Mammut Infinity (8.4 kn) or the Beal Joker (8.2 kn), that seems significant.

Don't place/fall on shit gear. That is my advice.

Connor Dobson wrote: Don't place/fall on shit gear. That is my advice.

In my opinion, that’s an impractical mentality that will actually be more likely to get you injured if you’re serious about trad climbing. I think the more realistic approach is to accept 1. That you won’t always be able to get a bomber piece exactly where you want to and 2. That you can’t always guarantee not falling. Then, in light of those facts, try to maximize your chances when you do find yourself in a less-than-ideal situation. 

Connor Dobson wrote: Don't place/fall on shit gear. That is my advice.

Addendum:

• Don't place shit
• Don't fall on shit
• Don't shit on gear
• Don't place shit on gear
• Don't place gear on shit

That is my advice.

High impact force means high impact on that sharp edge.

Low impact force means low impact on that sharp edge.

Joel M wrote: 

• ... I’m wondering if the difference in impact force between ropes could ultimately make the difference in a piece blowing or not. 

I would not worry too much about the spec'd impact force on the rope.  A good belayer and soft catch will do more to keep the impact force low and keep gear from ripping.  Lots of pure trad climbers have not caught a fall in years and will give a really harsh catch.  My advice would be to take lots of falls sport climbing with your trad partner so they get good at catching falls.  And don't fall above bad trad gear :).

Joel M wrote:

In my opinion, that’s an impractical mentality that will actually be more likely to get you injured if you’re serious about trad climbing. I think the more realistic approach is to accept 1. That you won’t always be able to get a bomber piece exactly where you want to and 2. That you can’t always guarantee not falling. Then, in light of those facts, try to maximize your chances when you do find yourself in a less-than-ideal situation.

I am not talking about bomber vs. adequate. I'm taking about if you are worried that your rope is the difference between a piece blowing or not (Your belayer will have a bigger impact than the rope) you probably should not be falling on that piece of gear.

Good belayer with high impact force rope always has a higher impact than a good belayer with a low impact force rope. 

I see what you guys are saying about a soft catch from the belayer being an important role in the force generated on the top piece. However, there will often be situations (every multipitch climb) in which the belayer will only be able to give a very limited “soft” catch due to them being anchored in. 

Joel you clearly have your mind made up so why even post this thread? 

Joel M wrote:

Yeah, with that Edelrid rope you’re gaining some safety margin through cut resistance, but it seems as if that’s coming at the expense of impact force on your gear. I’m wondering if the difference in impact force between ropes could ultimately make the difference in a piece blowing or not. 

That's the trade off.  I rarely place  mental pro but do climb routes that have the occasional sharp edge so the trade makes sense to me.

Joel M wrote: Also, Pat, I’m seeing 9.9 kn for the Edelrid Swift Protect Pro Dry as a single rope. However, compared to the Mammut Infinity (8.4 kn) or the Beal Joker (8.2 kn), that seems significant.

I got the 10.3 number from rei.  Rei lists 8.8 single 6.6 half 10.3 twin and i would typically use the rope as a single  so i should have used the 8.8 number in my previous post.   the serenity which is my current rope is 8.1 single 6.3 half 9.7 twin.

So the 8.4 number and 8.2 for your 2 ropes should be compared to 8.8.  

I could not find info on edelrid's web site and the rope is not the actually available anywhere so perhaps its not really available and the specs are guesses.

I have an edelrid 9.6 rope and it is pretty harsh feeling relative to any other rope i have fallen on.   It is also rare to have a fall that generates worst case impact forces so i am not too worried about the increased impact force for my use. 

As far as I remember, the UIAA impact force number is what you would expect to get on the very first fall on a rope. Who knows how quickly this number deteriorates on any subsequent falls. As someone else said above, a 6% difference really means nothing and if one rope deteriorates quicker than the other, there's no telling which rope is better after the first fall.

Patrik wrote:if one rope deteriorates quicker than the other, there's no telling which rope is better after the first fall.

That’s a good point. Unfortunately (as far as I can tell) that data doesn’t seem to be readily available for climbing ropes.