RescueMan wrote:What these tests indicate to me is not so much to avoid girth hitches (though the symmetrical hitches, as I suggested earlier, are superior), but to avoid anything but nylon (or polyesther) in ropes, cordage, and slings.
While I would agree with you for rescue purposes (the origin or this thread) I use my 10mm spectra slings quite often and like them quite a bit. However, I never girth them, and on the very few occassions where I'd had a need to join them I used either 2 carabiners opposite and opposed, or a symmetrical hitch. I've been tempted to use the tech cord for anchor building, but in the end remained with my nylon cordage even though it is bulkier and heavier. I don't think that the spectra/dyneema/dynex/whathaveyou is inherently bad, though I DO think proper usage is key. The stuff certainly isn't "idiot proof". I've used some of the even skinnier slings, mammuts and edelweiss's super skinny ones and they are slick, but I've only used them for specific purposes. I hung from them once at an anchor and untied the rope and I'll tell you, rated to 22kn or not, having your A$$ hanging a couple hundred feet off the deck on what looks like shoestrings made me pucker a little even though there wasn't any chance of them rubbing across a sharp surface or being shock loaded or anything.
Also I think what we are also finding out is that the spectra/dyneema stuff might degrade a little faster than nylon. And for people who are used to dealing with fairly burly (relatively speaking) 9/16, 11/16, and 1 inch webbing, the life span of a 6,8, or 10 mil sling is going to be less. You just can't treat the two materials the same. But this isn't exactly rocket science. Skinnier stuff generally needs to be replaced more quickly no matter what kind of material your dealing with, be it slings or ropes.
This conversation might be a little silly here as I only really use my spectra slings when climbing. Due the nature and quantity of gear I take on a traditional climb, the 10mm slings are what I feel comfortable using given their weight and bulk savings. When vertical caving, however, I'm generally only dealing wtih 11/16" or 1" webbing as I don't have to carry so much. I have used spectra slings for rigging applications before and redirects and felt comforatable with the use there as well though they are few and far between. For the most part, it's nylon.
But you know, when in doubt, nothing comforts quite like nice fat nylon