Thread: Rope construction/material
04-04-2005, 04:21 PM #1
- Join Date
- Dec 2004
What is the feed back on ropes made with nylon over nylon, nylon over polyester, polyester over nylon, and polyester over polyester?
We've had more slipage with nylon prusiks on poly rope and I kinda like that to reduce the dynamic shock on the load. We currently use all nylon ropes and prusiks. We are starting to test new ropes in a homemade drop test tower at our FD. So far from what I've seen and read I think we are looking at going towards a nylon prusik on poly over nylon rope. I like the poly ropes because they seem to have alittle more abrasion resistance. What are you thoughts? I don't want to waste money or make any life safety mistakes. Thanks.
04-04-2005, 09:57 PM #2
- Join Date
- Jul 2001
The success of a tandem prussik belay is largly dependant on the compatibility of the prussik and the rope it will grab on. The only way to know for sure is to test it. Typically if you buy your accessory cord from the same manufacturer as your rope, they will be compatible. Don't be shy about asking the manufacturer. Don't waste your time with the dealer selling the product. I have found that I get the best info straight from the manufacturer and they are more than willing to help.
I would caution against trying to allow more slippage with the prussiks. The force with a 1 meter fall on 3 meters of rope is acceptable(BCCTR belay competence drop). This drop represents a rescue load at the edge transition when the mainline fails. This is when the rope is shortest and the risk of a fall is present. It is typically around 5kn per person (1124lbsf) which is more than reasonable. If the prussiks tend to slip on the rope, I would be testing a variety of worst case scenarios to ensure the system will still be safe. Slippage=heat and too much will melt through your cord.
We are also going to a poly over nylon construction(Petzl Vector). We are using nylon accessory cord and it grabs very well on the rope. The Vector retains its shape really well which gives the prussik a consistent surface to grab.Sometimes, in order to make an operation idiot proof, you must remove the idiot!
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