What Are Slings?
Slings, Known in the USA as Webbing, are one of the most versatile and useful things in your climbing rack. They are basically a loop of extremely strong tape. They are made from either Dyneema or Nylon.
Dyneema Slings vs Nylon Slings
Dyneema Slings, sometimes called Spectra slings, are made from Polyethylene. They are rated normally at 22kn which is approximately 2.2 tons of force so they are very strong. In fact Dyneema has a strength to weight ratio higher than steel.
Nylon slings are made from polyamide. They are generally rated around the same strength of 22kn but it is heavier.
Dyneema Slings are almost completely static so they pretty much don’t stretch at all, this is both good and bad as we will explore later in the article. Whereas Nylon slings have just a little stretch in them, not so much that you would notice much if you pulled on both ends but when you put a force on it, the difference is apparent.
Dyneema Slings also have a significantly higher resistance to cutting(more durable on sharp rocks), and lower water absorption (important in winter and british weather), making it an ideal material for slings and quickdraws. It is also less venerable to ultra-violet rays and chemical attack than nylon.
So Why Use Nylon?
Nylon slings have a much higher melting point than Dyneema with Nylon being 245 degrees C and Dyneema being a mere 110 degrees C. This is important when you think about the uses of the sling. For instance if you were abseiling off a Dyneema sling then the heat generated by pulling the rope back through could be enough to cut through it(so don’t do that!). Also by tying a knot in it can weaken it because if you were fall on it then the heat generated by the knot tightening could break the sling. And another thing is that because Nylon is slightly stretchy, it can absorb impacts better so if you were to fall on it you would generate less force on you and your anchors, and have less chance of breaking.
This last Paragraph has basically been a summary of a report published by DMM which displays all these findings and explains why it happens, you can view the full report here http://dmmclimbing.com/knowledge/how-to-break-nylon-dyneema-slings/
So which should I use?
That is a decision you should make for yourself depending on what you are using the slings for. Using the information above you should be able to make an informed decision, basically though the question you need to ask is will you be creating lots of friction (i.e. heat) on the sling that could damage a Dyneema sling. If not then Dyneema is generally a good option.
Sizing
A quick note about buying slings is the difference in the way people describe the sling. A lot of climbers still refer to the size of slings in ‘old money’ so 4ft, 8ft and 16ft slings which is the length of the actual sling all the way round. More recently though slings are measured, for one in centre metres and also they measure the closed length of the sling. So a 4ft sling in old money is a 60cm sling in new money. This can be confusing if you are used to one way of describing slings, I know I have been caught out buying the wrong size slings online!
Any other things?
You can also get what are commonly referred to as ‘daisy chains’ , these are slings that are sewn every couple of inches so that you can clip into any part of it to effectively make the sling longer or shorter without having to tie knots or anything. Very useful on stances.
I nice fact is that you will notice on most slings that it is sewn together with about 8 or 9 bands of thread, in actual fact, you only need one or two of these bands to be as strong but because it looks stronger with more bands, its sells better!
If you have any questions or comments, let us know in the comments…
You should check manufacturers guidelines for strengths and important facts before using any product, this is only intended as a guide.