Just looking for input on rapping with an 8 mil. static and a 10.2 dynamic. I got the skinny cord for this purpose but so far haven't tried it out. Is rapping like this jacked?

Jeremy, that's the rig I use and have found it to work quite well. I use a standard overhand knot to tie them together, leaving plenty of tail. The 8 mil also works well for hauling in most applications.

That's the setup I use a lot (well, a 9.9 and an 8mm) but I use a triple fisherman's and tighten the S$#@ out of it before rapping down. I put the fat rope through the anchor and pull thin. If anything crazy happens and the thin line is cut or whatever, the fat line's knot is usually to big to fit through the links, rings, chain, or whatever and I'd just finish the rap on a single line. I wouldn't be able to retrieve my rope, but that's hard to do when you are dead as well, so I guess I still do it that way and find it better. Only disadvantage is having to pull the thin line to get it all down. It is harder than pulling a fatter rope.

Put the knot on the skinny rope side of the rap anchor. More friction on the 10.2 side, will cause you to end up with uneven tails....having the knot jam into anchor prevents this (tie knots to be safe). I run a similar rig.....works great, except when my partners bitch about having to rap on an 8 Mil static......(though they never bitch when trailing it!)

1. Aside from the hauling application, what is the need for the static line? Are you carrying it just to rap on? If that is the case, I'd suggest a 200' retrieval cord (very thin and light, fits in a fanny pack that your second can carry).
2. I know you're not supposed to use a Reverso or B52 in locking mode with two hugely different diameters. Does this same type of warning apply to rapping? Does the larger rope take most of the friction?

If you thread the thin rope, and pull the fat one, the knot will creep downward amazingly fast (because the static line doesn't stretch as much)! I did this recently and the knot was just flying down, and I kept stopping and having my partner pull it back up. Anyway this is the reason to thread it the other way around.

But do not use this setup if your rap anchor is just a sling (probably bad in general anyway), because the knot will be able to jump over to the other side if it isn't getting jammed in a rap ring, and the creep could also cut a nylon sling.

I don't use the EDK ...

One knot to consider using to tie a skinny and fat rope together is the double (or even triple) sheet bend.

http://www.iland.net/~jbritton/sheetbend.htm

Scroll down that page to see the double sheet bend. Note the skinny rope is the one that gets wrapped around twice; the fatter one is the bight, coming in from the left of the picture. Wrapping the smaller cord three times is good for a really big diameter difference or slick static.

Maybe some folks have thoughts about whether this knot is too bulky and would tend to cause problems pulling the rap. But in my experience its a safe way to join a skinny/fat rope combo.

I also use this setup a lot. Tagging an 8mm line has advantages over a 6mm or 7mm "retrieval line".

Number one is that those skinny lines are a pain to deal with when its windy and always seem to get snarled. They are a great solution for "just in case" scenarios, but if you know you are going to have to rap the descent, bring the 8mm.

Second, you can rap/jug on a single strand 8mm. It's sometimes a little scarey because of edges, but if you get in a storm and have to get down NOW, you can tie your lead rope and tagline together and loose 400' of vertical muy pronto.

The biggest reason for me to not routinely use a retrieval line is that if you get a stuck rope (which eventually you will) all you have to work with is that 6mm cord. For that reason, I generally thread my raps so that when I pull I am pulling the lead rope (the oppossite of Tony - I'm usually more worried about stuck ropes than getting the chop). Yes, this means that the knot has a tendency to drift down from the anchor because the thicker lead rope has more friction. Keep an eye on the ends of your ropes so you don't come up short on the tagline. I know some people cut their tags a little longer to compensate for this. On newer, slicker ropes you may need to use a "feeding" motion versus just letting the rope slide to keep things running evenly.

I use an EDK for more or less equal diameter ropes, but not for joining an 8mm tagline to a 9/10mm leadrope. I think Moyer did some testing - looks like someone posted the link above. My knot of choice is usually a Figure Eight Bend (not the Flat Figure Eight tied in the same manner as an EDK, which is a very dangerous knot) backed up with Double Overhands. Tie the eight in the lead rope, and follow through with the tagline. It's a bulky knot, but by dressing it so that it is compact as possible it very seldom hangs up. I don't see any real advantage to using a sheet bend for rappelling. It's a little more finicky, and after you add back up knots it's also more bulky.

On multi pitch routes, my partner and I have used a 9.4 and 7 mil. Works well, the rappel can be a bit fast so I use a guide atc and 2 locking biners for more friction. I believe we used the figure 8 follow through to join the ropes of different diameters. Drawback is that knot has a tendency to catch as you pull your ropes. Any other suggestions for the safest knot to use with different diameter ropes?

Safest knot? Or most efficient knot for rapping? -- if you want the safest knot it's not gonna be the most efficient knot to work with.

I'm using the flat overhand which I think Mike had already pointed out, which can be backed up with an overhand in one strand to keep the main knot from rolling out. I used to use the double fishermans, but I've switched to the flat overhand.

It's a scary sensation to be rapping using a skinny static rope and a fat dynamic rope when the knot is sliding down. You get the feeling the ends are getting so uneven you are going to go off the end, but I don't think this is true. What's happening is that the dynamic rope is stretching, and the knot is moving to compensate. The lower ends of the two ropes are still together!

It is when the knot is on the "correct" side that the ends become uneven! Because then the dynamic stretches but the knot stays in the same place, so by the time you reach the end the dynamic rope is longer (assuming the two ropes are the same length when unweighted).

Tell me the problems with the following.

Lately, I have been trailing a thin line, putting the thick line through the anchor, tie them together with a big knot, a knot and carabiner, or connect them with a locking carabiner, then I just rap down the thicker line on my Grigri. The knot can't pull through the anchor, I get a safe, easy rap. Pulling the thin line can be a pain, but it has been worth it. I don't have to deal with rapping with a skinny and thick in my rap device. Etc., etc. I see lots of benefits (auto lock rap being one of them) and few drawbacks.

Tell me why I am lucky to be alive or something...

John, that's how I've been taught to rap a single strand with a gri-gri or munter. So I'd say, ok.

You're lucky to be alive, or something...don't know why, because I said so.

I have been using a ~10mm dynamic climbing rope and a 6mm static line to rappel for several years. I tie them together so that they do not actually share a knot- slippage should be a huge concern. First I tie a figure-8 on a bight and then tie a re-woven figure 8 with the other cord so that the 2 loops that are formed are connected. This eliminates all worries of rope diameter disparity related knot slippage.

The thin cord gets tangled very easily, so i started stacking it in a small stuff sack. I typically use a reverso and thread both cords through the device just to keep both ends in reach when i finish rappeling.

I have also used the thin cord alone to rappel after soloing. This requires gloves and a friction knot and is actually kind of slow, but it feels like nothing when you are climbing.

This is what I use to join rappel ropes:

Avery,

I checked out the link you posted above. Looks like the overhand knot rolled at 1,230 lbs when "well dressed and pretensioned". For me, that seems like a more than adequate margin of error for the forces involved in any possible rappelling scenario.

In my experience, I prefer the overhand bend for one reason: its lower profile that is less likely than a more bulky knot (e.g., fig-8, double or triple fishermans) to become snagged upon retrieval. To summarize what others have mentioned,

• thread the thicker rope through the anchor (i.e., set-up to pull the skinny rope upon retrieval) to minimize the knot from creeping

• dress the knot well and pretension all 4 strands

• leave plenty of tail

• don't use on two ropes of DRASTICALLY different diameter. For ME, a 10mm lead line and an 8mm tag line is acceptable.

For tying knots together of relatively equal diameters, I favor the EDK, as it leads to fewer stuck knots while pulling. I forgo that advantage when rapping with ropes of very unequal diameters (like my 7 mm static and 10 mm dynamic) because the EDK isn't well suited for this. What I tie is a figure-8 loop in one rope and another figure-8 loop with the second rope around the first. This will never become untied accidentally. John