In reply to TobyA:
> (In reply to rgold) My point is that the neither the new Reverso or the ATC Guide are slick, not with doubled icelines anyway.
I'm not convinced, but I guess everyone has different experiences. I have friends who use 8mm doubles who find both the Reverso and the BD insufficient for rappelling without doing something to add extra friction. Beal says on the Ice Line specification page, "Select an appropriate belay device for use with thinner diameter ropes," so they obviously think there may be a problem with some belay devices. Then they say "Please note: When a rope is new, the braking effectiveness of belay devices is significantly reduced." Hmmm. One belay device for new ropes, another for older ones?
But the main issues is how the devices will perform in the rare and unexpected cases when the loads are really high. These situations don't happen often, and I think many climbers don't realize that they may have a lot of trouble holding such falls. So when someone says, "I'm not having any problems," I'm not necessarily sure that means all is well.
> The only time I've seen slippage with doubles is when the climber was using a single rope teamed up with a skinnyish half rope, the climber fell onto the thinner rope.
So all those climbers climbing on two "skinnyish" half ropes, which is what is under discussion here, will be having that slipping problem. In other words, you just confirmed my statements.
> I don't read every thread on UKC I guess, but I've read many of them since the end of the 90s and I don't remember reading about these sorts of accidents
An extremely cursory search turned up these two threads:
http://www.ukclimbing.com/forums/t.php?t=385251 (2009)
http://www.ukclimbing.com/forums/t.php?t=413676 (2010)
There are many more references in the logbooks.
> is it really as much of a problem as you seem to be suggesting?
I think that whether you think it is a problem or not depends partially on whether you think the belayer should be able to deal with every possible fall or whether you are willing to give up on the belayer holding the very unlikely but really bad ones without severe burns and possibly loss of control.
> Did you have a bad experience like this?
I have a lot of experience in the sense that I learned to climb in the U.S. at a time when we practiced catching severe leader falls (like fall factor 1.8) with no friction other than a single carabiner. From this I learned how much worse a severe fall is then the kind of "ordinary" fall we are called on to hold most of the time. Almost no one does this kind of practice any more, so most climbers have no idea what a severe fall is like to catch unless and until one happens to them in the field, at which point it is a little late in the day to discover that the belay device has inadequate friction for the task. I'm not convinced the standard belay devices are fully up to the this task with ordinary single ropes, and I'm almost positive those devices will be wanting with an 8mm half rope.