UKC

Does anybody here have experience simulclimbing with skinny ropes? I normally use a kong duck (a toothless clamp device like an ascender) to protect against my second falling when simulclimbing, but normally climb with an 8.4mm rope or fatter. I just bought a pair of 7.8mm twin/half ropes for alpine use, and am wondering whether or not I need to devise a new system, and what other people are doing for simulclimbing on skinny ropes. 

Two things in particular I'm worried about are (1) the rope just sliding through the device when the second falls (device doesn't engage) and (2) on the other end of the spectrum the device engaging too well and either shredding not just the sheath but the core too (if it's toothed) or pinching the rope so hard it outright cuts it (if it's a non-toothed device).

Any thoughts/experiences that might shed some light on the options for skinny ropes?

Main problem you'll have is that a Duck, a microtraxion, CT rollNlock, or seemingly any other device around are only rated down to 8mm. I discovered at a non-ideal time last summer that even 0.2mm can make a big difference when it comes to rope clamps - I tried to use a Ropeman 1 (10-13mm) on a 9.8mm rope in a pinch and it essentially did nothing.

A toothed device may get you the extra 0.2mm leeway you need. I do a fair bit of caving using toothed ascenders and whilst it's a different set up I'm yet to see anything more than a bit of fluff from falling onto them.

Why the RollnLock is only rated to 8mm I´ve no idea since it´s also designed for use with tape. It has the advantage it takes two strands of 7.8mm rope no problem, I´ve top-rope soloed with it like this (though normally I use a Shunt).

Interesting. I have jummared many an 8.5mm rope on one.