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Tech Tip: Question Polyester rope performance on tyroleans/guided rappels?

Discussion in 'Tech Tips and Gear' started by Tricam, Sep 6, 2020.

  1. Tricam

    Tricam

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    For those that have done both, do you find a noticeable difference in sag between static polyester and nylon ropes on tensioned lines, or is this negligible in practice?

    I have no experience with polyester ropes yet, but popular ones are advertised as <1% elongation, while static nylon ropes are around 3%. I need quite a bit of mechanical advantage to tension a tyrolean by myself with static nylon ropes, so I'm wondering if this is any easier with polyester ropes. I'm guessing the difference is minimal, but I'm wondering what others experiences have been.
  2. Bootboy

    Bootboy Atwood Gear

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    A bit to unpack here.

    Generally speaking, polyester static ropes are much more static than nylon, noticeably so with any kind of dynamic loading, even just mild bouncing.

    Nylon is used when building some “reserve” safety into a rope because of its ability to absorb shock loads.

    Even if poly and nylon “static” ropes have nearly equal static elongation figures, those are typically given for a load value that is a small fraction of the rope’s ultimate strength. 300lbs is a typical load at which an elongation rating is given.

    As you increase the load, approaching and up to the rope’s ultimate strength, the elongation values will markedly diverge. Nylon rope will stretch much, much more.

    Even the most static nylon ropes will exhibit more creep when set up in and application like a tyrolian.

    Polyester tends to be cheaper as well. So there’s a plus.

    Hope this helps.
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  3. hank moon

    hank moon kinetically bulbous

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    Tricam likes this.
  4. Tricam

    Tricam

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    @Bootboy thanks for the insight! I had been wondering about this after watching some videos of what I assume were polyester ropes being adequately tensioned for guided rappels without using mechanical advantage. I assume there were other factors at play, but it didn't match my experience when tensioning "static" nylon ropes. This setup really highlights the differences in materials, it seems.

    @hank moon Thanks for the info on creep - I didn't realize that was a technical term, nor the different types. Interesting stuff!
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