I am considering purchasing a skinny static rappel line for double rope rappels. I have used 8mm which works, but I like to save weight. How skinny can I go?

Some concerns are rope slicing, sticking, tangling. I have also read about using 8mm plus for hauling which might be a nice feature to have in case I decide to hit up a big wall.

The 8mm line always came up short of the dynamic. Based on the 4.5% static rope stretch my dynamic is rated to I should buy 210' of static. Does this sound right?

Here is a brief survey of stats I put together.

size, weight, strength:

6mm - 3.3 Lb/200' - 6.5 Kn (1529 Lb)
7mm - 4.0 Lb/200' - 9.3 Kn (2091 Lb)
8mm - 5.4 Lb/200' - 14 Kn (3147 Lb) works with ascender
9mm - 7.1 Lb/200' - 19.4Kn (4361 Lb) works with ascender
10.2mm 8.7 Lb/200' - standard dynamic lead line

I use a 6mm that is 75m long for a 70m rope. But, I always feed the larger rope, and only use the small one to pull. That way I can rap only on the larger rope, and I don't have to toss the small rope so I can feed it out as I go to keep the tangles to a minimum.

Thanks Brett.

Maybe I should have titled this thread "Best Skinny Lines On Which To Rap Bolt Long Climbs Into Submission". Might of generated more interest.

I had a 6mm cord that we used as pull cord for a few routes. The same kind that canyoneers use. The only problem is that when you pull a big rope (9 - 10mm+) with a small rope, it can be difficult to pull. After cutting a new 70m climbing rope because of this, I don't use a 6mm pull cord any more.

I now take an 8mm (ice floss) rope as a rap line. It is very compact (fits into the bottom of a bullet pack) and I feel totally comfortable rapping with the 8mm line thru the chains. The ropes always pull really easy, but the knot can migrate away from the chains if you're not careful. We've had really good luck with this system. Used it flawlessly on the Diamond last year. I always put a knot at the end of the ropes to make sure I don't rap off the end.

One thing to keep in mind if you use a 6mm cord to pull is that if your fat rope gets stuck half way through the pulling, you are stuck at the belay with only a 6mm cord.

I prefer to always have a leadable rope in hand.

I've seen people using long sections (50-60m) of regular old utility cord for the trail line. It works great but the sheath is not nearly as durable as a climbing rope's.

They seem to get core shots in 2 seasons in my experience.