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ymcaclimbing
Jul 13, 2003, 3:42 AM
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Registered: Jul 11, 2003
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I understand you can not use spectra cord in friction knots because of low melting points. How is dyneema different? Can it be used in friction knot applications? In the Falcon publication of Advanced Rock Climbing, Long and Luebben (sp?) show the use of Dyneema (or spectra possibly) in friction knot applications in their rescue scenarios. I hope this is a good question.
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brutusofwyde
Jul 13, 2003, 3:55 PM
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Registered: Nov 3, 2002
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In reply to: I understand you can not use spectra cord in friction knots because of low melting points.
For self-rescue, I would rather use spectra cord than hang there and die, or have my partner hang there and die. I would use Spectra, Dyneema, Technora, whatever was at hand. Low melting point is not an issue unless my friction knot slips. For this reason I consider my cordelettes to be part of my self rescue equipment. Ditto Spectra slings. I simply use more wraps in the friction knot to get them to hold. But PLEASE: I am not advising anyone that this advice regarding Spectra is safe or responsible. Beware of misinformation on the Web.
That being said, I carry two perlon prussiks and 3 "free" (not part of the anchor systems) lockers under normal circumstances -- what I need to escape a belay and ascend to a partner -- one locker holds the prussiks, one my chalk bag, the third my cleaning tool.
Climbing is dangerous. you could DIE.
Brutus
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apollodorus
Jul 13, 2003, 6:39 PM
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Registered: Feb 18, 2002
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Spectra and Dyneema are the same thing, just different trademark names. They're not nylon. They're polyethylene, which is in the same plastics family as Teflon (polyolefins). Basically, spectra and dyneema are the same plastic used for garbage bags, except that its been stretched to align the long polymer molecules in the direction of the fiber. It retains the same low melting point as regular polyethylene, and at temperatures lower than the melting point will rapidly lose its high-tech strength.
The problem isn't just low melting point, but also low friction. You can use it for friction knots, but you need to double the number of turns you use in the prusik or klemheist knot. Even then, the stuff tends to slip.
Another thing is that sunlight and other sources of UV attack polyethylene faster than nylon. So, expect spectra and dyneem slings and cords to become weaker faster.
Stick with nylon/perlon for friction knots.
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brutusofwyde
Jul 13, 2003, 8:14 PM
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Registered: Nov 3, 2002
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So is spectra affected by DEET?
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