Originally Posted by
ratagonia
Are you an engineer?
THIS engineer (mechanical engineering, B.S., 1982) thinks engineering is about UNDERSTANDING systems. I have the advantage of having seen 1000's of broken biners in my time at Black Diamond, and having seen the FEA of carabiners under development. There are critical locations on carabiners that you should have concern about compromising, but the basket, where the rope runs, is not one of them. I don't have too much concern about rope grooves from rappelling, and also use the "1/3 rule".
However, I have also seen a carabiner cut half way through on a 100' rappel, when conditions were perfectly bad. Matter of fact, that was two carabiners under an ATC, and both carabiners were chewed pretty good. If I had only one biner, would it have cut all the way through?
A good reason to use FAT carabiners like the Petzl Attache carabiner. And check it after every rappel.
Tom