The skinny on slings

I find myself in the market to replace a half-dozen or so sewn slings. I already have on my rack a few of the:

- Mammut Contact 8mm Dyeema
- Edelweiss 7mm Dyeema
- BD 10mm Dynex (threads seem to pull easily)

I see that these competitive slings are also available:

- Mammut Contact 6mm (!) Dyeema (also has a more compact bar tack by nesting the ends)
- Wild Country 10mm Dyeema

They all have a rated strength of 22kN. By far, the WC and Edelweiss are the cheapest.

So, here's my question:

Has anyone seen a (destructive) comparison of these, with respect to failure -- due to knots, sharp edge, bearing area (biner manufacturers always make a point to provide this), etc?

I'm curious how each of these behave for the above categories, and if at some point, too-small is an issue for reasons other than 'rated strength'. They're a great weight, space, CF savings... but when getting down to 10 -> 8 -> 7 -> 6 mm, are we losing anything outside of rated strength?

You save a few grams going from 10 -> 8mm, but it's nothing like the savings going from nylon -> 10mm.

Cheers,
Avery

BD has some compairisons of their 10mm Dynex and Mammut 8mm dyneema, specifically in girth hitched situations here bdel.com/scene/beta/qc_kp_a…. BTW Mammut stop producing their 6mm slings because they felt wore too quickly/ were not up to Mammut standards. I read someones hypothesis that dyneema slings would increase a biners real world strength because its thin size would promote a more even lengthwise loading than a larger nylon sling. I could see this being a factor in a tripled sling ( Yos. quickdraw) on a small wiregate but doubt it has much of an effect. Especially not between 8mm and 10mm.

Seeing some of the other tests showing dynex looses much of it's strength when older I now put my slings in more of a disposable catagory like my rope. I prefer the 8mm Mammut Dyneema to others on the market but replaced all of mine this year after about 4 years of use.

I"ve had 4 friends die in the last 2 years so I'm changing my "light is right" approach.
In my opinion the entire industry is getting lighter, not stronger. This is fine with some items, but not slings and ropes. Why? Cus it doesn't really matter how strong it is straight off the rack, it matters how strong it is after two months of use, some sunscreen, sand and dirt rubbed into it, and plenty of abrasion. I am personally switching back to the thicker stuff. Honestly, just how heavy is it... whats the difference? A sip of water before the climb is gona be the same weight as the difference in the 7mm vs the 10mm.
Go with thehavier stuff.. and for that matter, use a heavier rope for everything but sport climbing and ice climbing.

SOmeone is going to say "They are lighter, but they are rated to same strenght". NO, they are not. They are rated when they are tested, brand new... but a lot of different things are done to your gear that they do not do before they test them... a little extra material might help you out after that.

Thats my 2 cents...

Kevin and Sam,

Thanks for the responses.

Kevin, that page has some very useful info, and has me leaning away from the skinniest of skinny slings.

The one piece of missing info is a comparison of strength loss due to various knots in the skinny and traditional slings. That would be really nice to see, if anyone has any beta or links on the topic.

Sam, I'm very sorry to hear about the recent losses of your friends.

I agree that the lightest is not 'rightest', especially for things like soft goods. I *completely* agree with you about the rated strength of slings not having much validity after you've worn them from lots of use, pulled some fibers here and there, had them at very high altitude for a month in the sun, and then fall on them frozen with a knot in the sling. Your argument has always been the foundation of mine, when it comes to suggesting why these soft goods have to be so much stronger than the pro.

One of my unstated questions -- that the BD page did answer -- is that the actual pull strength of the nylon was about 30% greater than the rated strength, versus the skinnier slings which were only about 10% stronger than the rating. That's kind of what I suspected. I'm sure the majority of climbers would look at the rating on both slings and call them the same strength.

I decided to buy some of the WC 10mm dyeema slings, instead of the thinner ones (which were also more $). IMO, one of the real advantages of the thinner slings is cutting down on the bulk/CF factor that you have hanging off you when you climb. That being said, I always have a couple traditional nylon runners along on my climb... I think that variety is important for a certain set of situations, including friction knots.