Accessory cord as pull cord?

Anybody use 6mm or 7mm accessory cord as a pull cord in the alpine for double rope raps? Pros/cons? What about 5mm?
I know that many people use double ropes, but I am trying to avoid spending too much money at the moment.

I have 6 mm pull cord, which I've stopped using in favor or twins. The downside of a pull cord is if the fat rope gets stuck and all you have to ascend back to the stuck rope is your pull cord, well, you're climbing on 6 mm cord! You could double it, if you have enough, but you have a reduced safety margin if you have to reascend to unstick your climbing rope.

Also, 6 mm can be hard on the hands, if the pulling is even slightly hard. I wouldn't even consider a 5 mm, as it will even be more painful for pulling!

I have/use a 60 meter 5 mm tag line. It is useful in certain circumstances. The main use is hauling a light day pack on steep/difficult multipitch lines. It works quite well for this. It is also functional for occaisional use as a pull line, but I don't like to use it for this very often, due to the reasons mentioned above. If your main like gets stuck, you are hosed. I wouldn't reccomend it as a go-to option for multiple double rope raps.

Leather belay gloves are neccesary for pulling on a thin line; it is hard on bare hands. With gloves it is fine.

Check out the Esprit Alpine escape rope.  6.5mm. Burly sheeth.  And you don’t just need to use it as a pull cord.  You can pull the fat rope as the esprit rope is so stiff and burly there is enough friction while rapping.  There should be a few other threads talking for about this rope if you do some googling.

It’s a really common rope to use in Patagonia.

I tried 5mm as a pull cord.  But it felt too hard to get a good enough grip to make much significant progress.  If you do 5mm, bring gloves.

Recommend getting a static pull cord (a bit longer than your dynamic lead rope).  A dynamic pull cord stretches so much that it can be hard to get going if there's modest friction up there.  Retailers that service canyoneers usually carry static.

Note:  I am not recommending this over dropping coin for doubles or twins.

I think there is a ton of info under "Tag Line".  I have used a 7mm static line for ages. Using twin or half ropes makes sense if you're doing a lot of multi-pitch / wandering routes and need to do double rope rappels, I just never fancied them.

I always let my partner descend first with a backup knot tied at the anchor to prevent slippage, and then descend with the knot set up to pull the fat rope.  I know that there is going to be some slippage, but I would rather have the climbing rope at the next belay than the tag line. A static line is much less likely to get stuck due to the non-stretchy nature than the dynamic rope. Just make sure to undue the backup before you go down or you will be climbing back up the rope.

My 2 cents.

Normally a pull-down cord (5 to 8 mm) is used to pull down the thicker climbing rope as it's less likely that the knot pulls through the anchor; I've used what Buck Rio said many times for the reasons he stated. ..one improvement is that when the 1st climber gets to the lower station (or ground) he/she can tie the end of pull down cord to either the next anchor or himself (with slack in the system), then if "catastrophic slippage" starts there's a back-up to prevent the catastrophe.

One of the "cons" is the smaller the diameter the more "tangles" you get rapping (especially if the stations are those dam single-ring-hangers set far apart). If the first person raps single-strand on the main rope (tied off to the anchor) while the tail rope/pull-down-cords (attached to the rappeller)  is played out from above by the 2nd, there's less chance to tangle than if it's thrown.  

If youre goin for cheap, it works great. I use a 5.5mil 200' pull cord. Even use it to rap with by itself in the mountains from time to time. Its cheap, packs very small, lightweight.

Twins are better, overall. 

Seems you could pull on a small line with a HMS beaner using a clove or munter to grab rope?

Any benefit to having a single line vs mutiple shorter lines that you could tie together when needed? You are not rappelling on this line so no knots to pass.

To reduce tangles wonder if you could tie on your sections as you descend if terrain will eat your ropes, or curse the idea as you blow past your tag line end.

FYI i have zero XP with pulling with a rap lines, looking into what to get myself.

In certain situations I've used 2.5mm dyneema hollowbraid as a pull cord. Haven't done it with a 60m rappel but works well for clean ~30m rappels, paired with a 6mm rope like the Petzl rad/pur line, edelred rap line, etc. As mentioned above, I use a munter or clove on a biner as a handle to pull it down. 

Obviously it's not my go-to, it's niche is an objective where you don't need a rope for upwards progression but do need to rappel - for me that's scrambly traverses but I've seen people use the same setup for rappelling into ski lines as well.

Ryan Fenton wrote:

Seems you could pull on a small line with a HMS beaner using a clove or munter to grab rope?

Any benefit to having a single line vs mutiple shorter lines that you could tie together when needed? You are not rappelling on this line so no knots to pass.

To reduce tangles wonder if you could tie on your sections as you descend if terrain will eat your ropes, or curse the idea as you blow past your tag line end.

FYI i have zero XP with pulling with a rap lines, looking into what to get myself.

I've considered this with 12m (10m plus knots) sections. If only one rap out of four needs a 70m, just bring a section and your 60m. Same goes for if an 80m saves you a rap or two. 

I've ended up just opting for the appropriate length of rope. You might carry a bit more weight and pull more rope up at each belay (and some raps), but the benefits of always having a full-strength rope are great. 

Fewer tangles, faster rap setups, less likely to have stuck or coreshot ropes, easier pulls, more options when shit hits the fan.