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Dyneema ropes?

Discussion in 'Tech Tips and Gear' started by Chasetharp, Feb 15, 2018.

  1. Chasetharp

    Chasetharp

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    Has anyone had any experience or conducted any experiments with dyneema ropes? I have read about the pros and cons of the material and it doesn't seem like the most ideal material for making a rope. This question comes from curiosity rather than a desire to buy a rope made with dyneema, I just haven't had much luck finding information about it. I have read that it's weaker when knotted, harder to untie, and the common knowledge of it being awful when it comes to shock loads but I do know it has positive aspects as well. I also don't know how those negatives relate when only the core is dyneema, but I am happy to hear any information!
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  2. ratagonia

    ratagonia

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    A rope made entirely from a ultra-low-friction, low-melting point fiber? I guess the good news is it would be difficult to generate enough heat to melt it, as you slide quickly towards the ground.

    Dyneema core / Polyester sheath has been around for a long time (BlueWater Canyon Pro), and now is available from Atwood Gear as the Grand Rope. https://atwoodgear.com/ It makes for a good rope. Since I do not make such a rope, perhaps I am a little bit biased agin' it, but I am glad Taylor / Atwood is making it. In particular, a Dyneema core/ Polyester Sheath rope:

    Pros:
    Strength: easy to get plenty of core strength even at a small diameter.
    Weight: the overall rope tends to be quite light in weight.
    Static: the core is very very static, though it does seem to creep (at least, the Bluewater ones did).
    Coreshots: My experience with the BW Canyon Pro was that even when banged up pretty good, they tended to hang in there a long time. Core shots do not grow (as fast as on other ropes).

    Cons:
    Price: Dyneema is an expensive fiber; therefore the ropes tend to be more expensive.
    Creep: When set up in guided rappels, they tend to stretch out more than polyester core ropes, and need to be adjusted more. Odd.
    Sheath slippage: because of the extremely low friction core, they tend to shrink more than other ropes, and you end up with unfilled sheath at the ends. (The Grand Rope might not have this problem). Varies widely from batch to batch. Can be mitigated somewhat by pre-shrinking. Can be a LOT worse and a definite problem when used wet.
    Sheath: in general, the durability of this rope will depend on the durability of the sheath only. Given that the rope is of particularly small diameter, the sheath will tend to get beat up more than a larger diameter rope.
    Fast: It has a small diameter, so careful setting of the device will be required. (a statement that can be made about all rappels, all ropes, all devices).

    Taylor has named it the "Grand Rope" which I think entirely appropriate. When lightness is a major benefit, I will be using the Grand rope.

    Tom
    Last edited: Feb 15, 2018
  3. Bootboy

    Bootboy Atwood Gear

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    Moot points when considering just a core made from Dyneema and a sheath of some other material.

    Ropes of all fiber types are weaker when knotted (in so far as I'm aware), both in terms of dynamic and static loading.

    The reason it may be harder to untie a knot with such a rope would be a function of its diameter, which is made possible by the material's superior tensile strength. Ropes made from 100% Dyneema are actually much more jam resistant, due to Dyneema's exceptionally low coefficient of friction and its staticity.

    Polyester, practically speaking, is not functionally any different in terms of its ability to absorb shock loading.

    If you come from a climbing background, pretty much everything you've heard about Dyneema is in the context of comparing it to Nylon, so most of those points made in that comparison go out the window when we are comparing it to polyester in a very different application instead.

    Tom did a pretty good job of covering the drawbacks of Dyneema in rope construction.
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  4. Rapterman

    Rapterman

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    Good question and replies.
    Some clarifications: Canyoneering and Climbing are two very different sports that use DIFFERENT ROPES.
    Climbing ropes are dynamic (made from nylon), designed to absorb shock from climbing falls. They can also be used for rappelling, but are not ideal for this
    due to excessive elongation and 'bounce' under load. When immersed in water they become heavy, soggy, pains in the booty.
    Canyoneering ropes (at least the ones we favor in the US) are static ropes. They are optimized for rappelling and have low elongation
    and very little 'bounce'. They (mostly) use static (non-stretchy) fibers like polyester, technora, and dyneema. Do not EVER use them for lead climbing.
    Do not EVER shock load them.
    As in :hungover: :hungover: :hungover:
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  5. ratagonia

    ratagonia

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    The "so weak when tied" meme came from when sling webbing started being made from Dyneema. Can't we just make tied slings out of dyneema? The answer is a bit more subtle than "NO", but NO is a good general statement.

    Knots depend on friction. Dyneema lacks friction. Therefore, if you were tying slings out of dyneema, you need to use special knots that are more convoluted than the knots you normally use. Rather than carry around in your head an extra set of special knots, it is better to just go with NO.

    All materials when tied in knots are less strong. We generally characterize this as a percentage of strength: A water knot in 1" tubular has a strength of (made up) about 65% (of the strength if there was no knot), for instance. Some people debate the values of knots based on their "strength", as if the difference between a 78% knot vs. a 74% knot is important. (It is not). But dyneema even using those special dyneema knots is weaker in knots than our usual fibers, as in 50% for dyneema vs. 65-70% for nylon.

    Which comes down to, the climbing industry as a group was smart enough to end up NOT selling dyneema webbing by the foot. And coming up with a good story as to why not. When you come across dyneema webbing in the field rigging an anchor, please remove it. Unreliable.

    Tom
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