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Sterling Duetto 8.4 - Dual rated or only half rope?
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I purchased a pair of Sterling Duetto Dry XP 8.4 ropes a while back, and at the time they were advertised only as half ropes. The symbol on the rope ends indicates this as well. However, I was considering selling this pair in search of a double or triple certified rope, and noticed that on the Sterling website (link below) the Duetto is listed as being "certified to half and twin". https://sterlingrope.com/store/climb/ropes/dynamic/half-and-twin/duetto-84-mm Does anyone happen to know whether this rope is dual certified? And if so, is this an updated certification due to additional testing that wasn't performed previously, or do I have rope from an antiquated lot that is still only rated as a half rope? I reached out to the company, but am still waiting to hear back. If anyone happens to know about this, I'd appreciate your help! |
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Hey Elliot, how old are the ropes? I bought a similar set a couple years ago and they both had the dual half/twin mark on them. I think it is just a matter of testing in order to be a twin or a half rope. The standards for each are a little different. For example, the maximum allowed impact force for a certified twin rope (two ropes clipped) is 12kN, compared to 8kN for a half rope |
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Ask sterling. My guess is they changed something to meet the requirements. |
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Buck - That's interesting... The lot numbers on my ropes indicate that they were both made in 2019. Pat - I sent a message to Sterling. I'll post an update here when they respond. |
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I thought all half ropes could be used as twins but not all twins could be used as half ropes. I believe it's just a matter of applying for and passing the certification. Do you think the rope magically knows it's being used as a half or twin? Or does a triple rated rope know when it's being used as a half, twin or single and it changes it's characteristics accordingly? |
wivanoff wrote: Using non twin rated half ropes as twins could result in impact force being too high. |
wivanoff wrote: The only certification that gets a pass is any single can be used as a half because it is basically the same test with less weight. As Climber Pat stated, a twin rope has to be tested as a pair without exceeding the impact force limits. No, the rope doesn’t “know” how it’s being used but a half rope is rated to a lower standard than a single (less weight), because there is a second rope there as a backup. A “fat” single rope couldn’t pass the twin test but the triple rated ropes are built to have low enough impact force that they do pass. |
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https://stephdavis.co/blog/straight-from-the-mammoths-mouth-half-ropes-are-not-twins/#comment-19226 "most of the half ropes on the market will pass the test for both half and twin ropes, and this is common enough that it is assumed. All of Mammuts half ropes will also pass the twin rope test" - Dave Furman Discussion on clipping both half ropes to the same piece as if they were twins: |
wivanoff wrote: All of these mammut ropes are marked with both symbols. |
climber pat wrote: So, what changed? Are they manufactured differently or could they always be used as half and twin but not officially certified? I've been using my Genesis 5.5 half ropes as both for years.
I believe that when the load comes on both half ropes together as twins, the impact force is increased to a calculated maximum of 1.4 times the impact force on one strand - which is consistent with the impact force of a "single" rated rope. Actual tests end up being lower than the calculated 140%. https://www.mountainproject.com/forum/topic/106947682/half-rope-for-the-gym#ForumMessage-106947946 |
wivanoff wrote: I have no idea what changed. There are many factors effecting the performance of a rope. My mammut phoenix rope is dual certified with both symbols. (This rope is old enough that it has been replaces with a newer model) The 1/2 rope impact force is 5.8 KN and the twin rope impact force is 9.5 KN which corresponds to a 1.64X increase in impact force. Using that number for the sterling rope which has a 6.5 KN 1/2 rope impact force you would get a 10.6 KN impact force is used a a twin which is still below the maximum of 12KN. So I would guess something else goes wrong with the test; or possibly sterling just did not want to pay for the extra certification.  I see that the Sterling Duetto 8.4 for sale a REI is a 1/2 hope with an impact force of 6.5 KN. REI Sterling rope. The currently produced sterling rope current Duetto 8.4 is rated twin/double with an impact for of 6.2KN half 9.3KN double. So something changed. (A 1.5X increase in impact force). |
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To anyone interested in the follow up: I just received an email from Sterling’s customer service department stating that nothing has changed about the construction of the rope, and confirming that the pair marked only as half ropes are dual certified as half and twin. |
Elliot Weiss wrote: Thank you. Not surprised at all. Especially since it's been common practice to occasionally clip both ropes to the same piece when leading DRT. Sometimes in the same carabiner, sometimes separated with a draw. |
