Ascender instead of prussik?

As an old timer, back in the day, we did not back up our raps. As I look at adding this extra layer of security, I was wondering if possible/any advantages to using an ascender instead of a prussik? Or is that just nonsense? It still seems to me a prussik knot will keep catching.

ascenders do not work in this fashion, keep using a prussik.

Alex Drew wrote:

ascenders do not work in this fashion

Actually they do--I've rappelled with Jumar ascenders many, many times, using them to also get back up (banding birds).  Petzl ascenders have more of a tendency to lock up, and aren't recommended--dunno about BD.  For rappelling backup, they are unecessary, heavy and bulky, and a prussik is a much better option.  Done properly, you shouldn't have any trouble keeping it from locking up on you.

Use an autoblock instead of a prusik if you feel that a prusik is catching too much. Very easy to undo a wrap if necessary.

Since most raps are done with two strands it would be tough to back up a rappel with an ascender.  Ascenders are heavy and bulky and if you had to stop suddenly the sharp teeth wouldn’t be great for the sheath.  Just do an auto block. 

Thanks for quick replies - just watched a few videos on autoblocks - looks simple enough!

Just put a Sterling Hollow Block on my Christmas List!

If your ascender grabs the rope during your rappel, good luck unweighting that shit without a second ascender, foot loops, etc.

Stick with prusiks or auto-blocks. If you absolutely want a mechanical backup, use the Petzl Shunt. It releases when you pull down on the lever.

For decades I almost never used a backup on rappel and then one day realized it was just stupid. Now I always use an autoblock.

Autoblock is the way to go - it is trivial to setup and you can use any sling or cord that is handy.

Extending the rappel device off the harness makes the setup work much better.  Another reason to keep a PAS on the harness ... ;-)

The Petzl Shunt is advertised as being suitable for this purpose. It's a non-toothed device, works on single or double ropes, and states that it can be used as a rap backup. (I don't own a shunt, but when shopping for ascenders, noticed those unique characteristics listed.)

Andrew Krajnik wrote:

The Petzl Shunt is advertised as being suitable for this purpose. It's a non-toothed device, works on single or double ropes, and states that it can be used as a rap backup. (I don't own a shunt, but when shopping for ascenders, noticed those unique characteristics listed.)

Sure, my brother uses one all the time. Like most Brits I also use one for top-rope soloing, it´s even known as "Shunting" in the UK. 

Matias Francis wrote:

Use an autoblock instead of a prusik if you feel that a prusik is catching too much.

My prusik has never locked up, and I hang on my prusik backup _often_ while developing new routes.

If it ever did lock up, I would just raise one leg, wrap the free lower end of the rope around my foot two or three times, and stand up on that foot -- thus take the weight off the prusik knot.

If all else fails, I carry a little knife (because stuck backup knot is not the only thing that can go wrong on rappel -- or while climbing).

Ken