canyon_admin
03-28-2005, 06:31 AM
Posted by Charly Oliver.
Numerous cautions have appeared on this group (mostly from me) regarding the use of light-weight/high strength hybrid ropes for canyoneering. The ropes canyoneers have been drawn to generally use Spectra or Kevlar fibers to increase strength and decrease weight. I have been using the BlueWater Canyon Pro almost exclusively the past two years for this reason.
We all love a lightweight/compact rope. However, people who use these ropes need to be aware of important shortcomings of these high performance fibers.
Spectra/Dyneema
These fibers melt at a relatively low temperature, 147C. Spectra or Dyneema usually make up the core of the rope which is protected by either a nylon or polyester sheath so it is doubtful your scorching hot rap device will melt the rope, but it's probably a good idea to at least be aware of this.
Aramid/Kevlar
Although it resists high temperatures (Kevlar begins to break down around 427C) the fiber does not hold up well to repeated flexing. In fact, its strength is dramatically reduced after relatively few cycles. Kevlar is also very abrasive and when used in the sheath of a rope will wear through aluminum rappel devices more quickly than nylon or polyester.
Very Little Stretch
Neither of these fibers stretch worth a damn. This means they don't absorb shock worth a damn either. Any bouncing or accidental dynamic loading could result in catastrophic anchor failure. Especially, when using some of the less than bomber anchors commonly found in Colorado Plateau canyons.
More Spectra Caveats
I see many canyoneers using a Spectra webbing daisy chain for their personal lanyard. I've seen them rigged both as a climber would (girth hitched to the harness and clipped in short through the appropriate loop) and as a double lanyard (clipped in close to the middle creating a short and long lanyard).
The climbers method is how a daisy chain was designed to be used and should only be statically loaded. This method can be dangerous to fall on. (As when you might need to briefly step above the anchor but then slip). Clipping directly into one of the loops and using the tails as a double lanyard is improper use and potentially very dangerous.
I recently viewed test data that showed catastrophic failure of Spectra fiber daisy chains at <1m drop. Yes, the daisy chain broke and dropped the load. The same test using nylon daisy chains broke some of the loops but did not result in catastrophic failure. Spectra fiber will not stretch to absorb the shock, nylon will.
Spectra and Kevlar fibers have their place but should not be used entirely as a nylon or polyester replacement without thorough understanding of their performance characteristics.
Spectra Core Ropes
I will continue to use my Canyon Pro because it is very compact and light weight. I will however, be very careful not to bounce on it either when starting or during the rappel and will caution all who are with me to do the same.
Kevlar Ropes
Whether used in either the core or sheath, I don't see any real value in using this fiber for canyoneering ropes. Commonly found small diameter "Kevlar" ropes on the market are designed as personal escape lines for fire fighters and are intended to be used only in emergencies and then retired.
Spectra Webbing Daisy Chains
I would encourage everyone out there currently using a Spectra webbing daisy chain as a lanyard to toss it back into your wall climbing gear box and replace it with a nylon web daisy chain or better yet a shock absorbing lanyard like the Petzl Spelegyca or a Purcell Prussic.
Be careful out there.
Charly
Numerous cautions have appeared on this group (mostly from me) regarding the use of light-weight/high strength hybrid ropes for canyoneering. The ropes canyoneers have been drawn to generally use Spectra or Kevlar fibers to increase strength and decrease weight. I have been using the BlueWater Canyon Pro almost exclusively the past two years for this reason.
We all love a lightweight/compact rope. However, people who use these ropes need to be aware of important shortcomings of these high performance fibers.
Spectra/Dyneema
These fibers melt at a relatively low temperature, 147C. Spectra or Dyneema usually make up the core of the rope which is protected by either a nylon or polyester sheath so it is doubtful your scorching hot rap device will melt the rope, but it's probably a good idea to at least be aware of this.
Aramid/Kevlar
Although it resists high temperatures (Kevlar begins to break down around 427C) the fiber does not hold up well to repeated flexing. In fact, its strength is dramatically reduced after relatively few cycles. Kevlar is also very abrasive and when used in the sheath of a rope will wear through aluminum rappel devices more quickly than nylon or polyester.
Very Little Stretch
Neither of these fibers stretch worth a damn. This means they don't absorb shock worth a damn either. Any bouncing or accidental dynamic loading could result in catastrophic anchor failure. Especially, when using some of the less than bomber anchors commonly found in Colorado Plateau canyons.
More Spectra Caveats
I see many canyoneers using a Spectra webbing daisy chain for their personal lanyard. I've seen them rigged both as a climber would (girth hitched to the harness and clipped in short through the appropriate loop) and as a double lanyard (clipped in close to the middle creating a short and long lanyard).
The climbers method is how a daisy chain was designed to be used and should only be statically loaded. This method can be dangerous to fall on. (As when you might need to briefly step above the anchor but then slip). Clipping directly into one of the loops and using the tails as a double lanyard is improper use and potentially very dangerous.
I recently viewed test data that showed catastrophic failure of Spectra fiber daisy chains at <1m drop. Yes, the daisy chain broke and dropped the load. The same test using nylon daisy chains broke some of the loops but did not result in catastrophic failure. Spectra fiber will not stretch to absorb the shock, nylon will.
Spectra and Kevlar fibers have their place but should not be used entirely as a nylon or polyester replacement without thorough understanding of their performance characteristics.
Spectra Core Ropes
I will continue to use my Canyon Pro because it is very compact and light weight. I will however, be very careful not to bounce on it either when starting or during the rappel and will caution all who are with me to do the same.
Kevlar Ropes
Whether used in either the core or sheath, I don't see any real value in using this fiber for canyoneering ropes. Commonly found small diameter "Kevlar" ropes on the market are designed as personal escape lines for fire fighters and are intended to be used only in emergencies and then retired.
Spectra Webbing Daisy Chains
I would encourage everyone out there currently using a Spectra webbing daisy chain as a lanyard to toss it back into your wall climbing gear box and replace it with a nylon web daisy chain or better yet a shock absorbing lanyard like the Petzl Spelegyca or a Purcell Prussic.
Be careful out there.
Charly