auto-block on rappel

sorry for the noob question but I am confused and I want to get it correct.....

In ALL the photos I can find of an auto-block used in a rappel they all show the know tied on a single rope. My question is can I back up a rap (safely) with an auto-block on a double rope. My understanding of physics says yes... but the instructions all seem to seem to show it on single rope

thanks for your input and advice

Jim

yes

Yep, works better when your autoblock is a smaller diameter than rope. Go try it out a foot or two above deck to see for yourself!

Thanks for the input and resource... My intent is to use 6mm cord on 10.2mm dyno rope. I just wanted some sort of conformation before I go test and trust my concepts. Just because it "seems" to work at 3' does not make you want to trust it at 30' unless you have outside information to back up your understanding.

Thanks again.

Jim

6mm should work fine on doubled rope. It'll help if the 6mm if soft (rather than stiff).

jim202000 wrote:sorry for the noob question but I am confused and I want to get it correct..... In ALL the photos I can find of an auto-block used in a rappel they all show the know tied on a single rope. My question is can I back up a rap (safely) with an auto-block on a double rope. My understanding of physics says yes... but the instructions all seem to seem to show it on single rope thanks for your input and advice Jim

I typically use a shoulder length nylon sling. Do not use dynama, it is too slick to grab the rope properly and has a lower melting point. If you want something else, Sterling makes a pre-sewn 13.5" cord. Check the link below.

Sterling Auto Block

worleybird wrote:I typically use a shoulder length nylon sling. Do not use dynama, it is too slick to grab the rope properly. If you want something else, Sterling makes a pre-sewn 13.5" cord. Check the link below. sterlingrope.com/c/climbing…

Bill Kirby wrote: You can use a dyneema sling if you tie a Khemheist hitch. I would only use it if it's the only thing left but it works.

Call it good if you are using any number of friction hitches as a back up. Don't climb like it is 1987, use a back up! The added benefit of an auto block include ease of use (simple principle of wrapping a single cord around a double rope setup), easy to verify it's been attached to the system right. Have fun.