Rigging: re-belays or big drops?

[owd git]

Big pitches are safer,  by dislodging a wee nib of really painfull cave, as could happen even  with the utmost care, a wait may seem the prefered option. 
especially in a shaft 
O.G.

 

[Pete K]

......When we've been working in JH a lot...........We used the throughbolt on the south wall as it's a better hang, but that is really showing its age now - a nice pair of 'official' resin bolts there would be great, and would possibly then make the other single resin bolt on the north wall a bit more helpful too.

This is actually on the list of DCA jobs. I brought this up a while ago at a meeting but there is a backlog and perhaps not enough installers. It will get done.

 

[Chocolate fireguard]

Big pitches are safer,  by dislodging a wee nib of really painfull cave, as could happen even  with the utmost care, a wait may seem the prefered option. 
especially in a shaft 
O.G.

Ok, I give in. I have read it several times and I haven't started drinking yet.
What does it mean?

 

[bograt]

Big pitches are safer,  by dislodging a wee nib of really painfull cave, as could happen even  with the utmost care, a wait may seem the prefered option. 
especially in a shaft 
O.G.

Ok, I give in. I have read it several times and I haven't started drinking yet.
What does it mean?

 

[zomjon]

I think O.G. Is alluding to the possible falling deads or other debris a caver might inadvertently kick out whilst ascending a tight, loose shaft, such as Snake.

 

[Fulk]

topcat:

topcat:
Quote
Entrance pitch Death Head [it has RB's near the top already, needs more]

There is a re belay lower down.


We were looking for the dev. bolt mentioned in the rigging guide but no one in  party of 6 spotted it!  Used a natural instead, and was surprised that it stayed in place.
Obviously we need to look harder!

Some notes I made after a trip:

. . . then a Y-anchor for the last ca. 30+ m, where we used two pairs of maillon rapides on account of how the rope would lie flat against the rock with just one off each bolt; deviation maybe 15?20 m from floor, hard to spot; remember that it's 2?3 m off to the left on a level with a fairly prominent bedding plane in the rock face.

 

[Simon Wilson]

On a 'big' pitch a rebelay would speed up progression of a large party but on a 'small' pitch it would make progression slower. So it would seem logical that there is a length of pitch in between those two where it does neither. I'm not sure Bar Pot lower pitch comes into the first category. Also, there are already roughly 189 anchors too many in Bat Pot (IMO).

 

[caving_fox]

Anything up to 60m (not ft!) or so should be rigged as a single drop if possible, cave, water and rope rub allowing. More fun to descend and doesn't take that long on ascent. It's about as convenient a rope length as fits in a tackle bag, reduces the rigging faff,and is generally just more enjoyable. IMHO obviously. But leave the big pitches alone!

 

[cap n chris]

Disagree. 20-30m between rebelays makes for good progress of a team.

 

[topcat]

But leave the big pitches alone!

Any re-belays would be optional if they were there to split the pitch rather than to avoid rope rub............

 

[Over the Hill]

My examples above are not good examples and miss the point of my post!  [Just got back from walking the dog and thinking about it]

My poor examples are poor because there are bolts there to use if you so desire.  Like the last pitch of Aquamole: I rig the third deviation as a RB.

What I was really looking at are the shafts that currently can only be done as a big pitch and that 'need' extra bolts.  Which is I think where Simon was coming from too.

Rift/Longkin
bottom of Lost John [drop at the end of Battleaxe Traverse]
Entrance pitch Death Head [it has RB's near the top already, needs more]

I'm at work suffering from brain-fade: there must be dozens.........

Drop at end of Battleaxe has always, even on ladders of old been a choice of a broken decent. Just drop onto the large ledge to break it up. 

 

[Disgusted from Cornwall.]

We tend to double rope big drops and do them in pairs. Don't like stretch? Use a more static rope.

 

[Speleokitty1]

I have typically done longish pitches (80-100m) in one go. Its simpler/quicker to go down without putting in a rebelay and the waiting time for coming back up can be greatly reduced by tandom prusiking.

Not everyone likes to tandom but its no so bad if one person rests while the other prusiks. Just make sure that you have thought about how you are getting off the rope when you have someone else's weight on the rope.

 

[cooleycr]

There is a very informative document at http://www.cavediggers.com/vertical/6DESCENT
there is a table from which I have taken this excerpt

Petzl Stop is best on pitch length <50m
Petzl Rack is best on pitch length 10m to 100m

so if you use a Stop then according to this data it would be advisable to install a rebelay on ANY pitch over 50m, otherwise use a Rack.

I don't think that they are suggesting that your Stop will disintegrate at -51m but should we take that chance?!!?!?!? 

 

[bograt]

Suspect it might be a case of overheating and glazing the rope, or rope weight affecting the brake mechanism.

 

[Fulk]

For some reason I can't access http://www.cavediggers.com/vertical/6DESCENT, so I don't know what their conclusion is based on, but I don't remember having any problems with pitches up to 100 m on a Stop ? provided that the rope has been wetted first.

And should:

'Petzl Stop is best on pitch length <50m
Petzl Rack is best on pitch length 10m to 100m'

be:

'Petzl Stop is best on pitch length <50m
Petzl Rack is best on pitch length 50m to 100m' ?

 

[MarkS]

It should be http://www.cavediggers.com/vertical/6DESCENT.pdf

 

[Chocolate fireguard]

If you get rid of the 6 it works.
And no, it does say "10m to 100m".

I wouldn't use a Stop on a long pitch (actually I don't like them much on any pitch but I sometimes use one instead of a Bobbin to keep in practice).

On a very long pitch I think a rack makes things so much smoother and more restful.

I remember doing a very wet 200+m  pitch (one of the longest in Derbyshire I would think) on a rack which gave a beautifully smooth descent.
Passing the knots was perhaps less easy than it would have been with a Stop.
A friend coming down next on a Stop finally arrived having expended a lot of effort and time on the top half where he had to lift the rope one-handed (200m of very wet rope) to get it to go through the Stop.

 

[Mark Wright]

Part of the testing for a Petzl Stop involves carrying out a continuous descent of 100m with a 150kg load at a rate of 1m/s. It should not get too hot or glaze the rope. If it did it wouldn't pass the test for EN341A.

The article is actually from Al Warilds Vertical book. It also suggests a Stop is best used on ropes as thin as 7mm. It definitely isn't. 7mm and 8mm 'rope' isn't actually regarded as rope but accessory cord. If you carried out some of the other testing required under the same standard on 7mm or 8mm rope, the rope will probably break.

There is absolutely no chance of a Stop disintegrating if you abseil more than 50m.

I've done some really big descents on both Stops and Racks and I prefer a Stop, others prefer Racks. In my experience, loading the second bar of a Rack with 200m of wet rope underneath you is just as hard as loading a Stop in the same situation, assuming the 1st and 3rd bars of the Rack are fixed.

Mark

 

[Chocolate fireguard]

I've done some really big descents on both Stops and Racks and I prefer a Stop, others prefer Racks. In my experience, loading the second bar of a Rack with 200m of wet rope underneath you is just as hard as loading a Stop in the same situation, assuming the 1st and 3rd bars of the Rack are fixed.

Mark

Apologies.
I didn't make it clear that my friend had to lift the rope every time he wanted to make downwards progress at first because squeezing the handle did nothing due to the weight of the rope.