petzl rack on a loaded rope

[ek]

It's probably easier to accidentally flip the rope off the hyperbar than it is to accidentally unclip a bar.

Yes, this happened to a friend of mine near the bottom of the 186' entrance drop in Sites Cave. Fortunately he was using all four bars, and (after speeding up some from the slack that was created when the rope came off the hyperbar) he spontaneously slowed down to the speed he preferred by bringing his brake hand farther behind him.

[NZcaver]

I hope Hank doesn't shoot me for suggesting this...

Blam! Seriously, I don't know if a latch bar would work there w/o modification or a bit of hassle. Not much room for the frame to flex due to the fixed bars above and below.

Look out! Someone's shooting!!

Good point about the frame not flexing between fixed bars... unless you replace that third bar with a swinging one of course.

[brrrdog]

I would say the rule still applies. An accidentally unclipped bar or not, 3 bars makes the margin for error extremely small. If you truly anticipate the need to rappel on 3 bars, you should get a longer rack. 3 bars is just too risky.

Can you explain the risks Scott? I'm not questioning you, but the more I know about the reason for a rule, the more likely I am to remember it. I suppose one reason is that there is only one bar holding you on. Although it would be pretty tough to accidently bump out the #2 bar, I'm sure it's possible. What else?

And for the record - no I don't anticipate a need to rappel on 3 bars - I'm just learning. So far in practice, I've been perfectly happy with 5 and I still had a lot of spacing to work with.

[Scott McCrea]

In normal conditions, 3 bars does not offer enough friction to control a rappel. Abnormal conditions would be needed to add enough friction to make a 3 bar rappel possible. Something like rope weight on a long rappel, stuck caver below, very dirty rope, something pulling down on the rope. In other words, something is either tensioning the rope or making it less slippery. Should one of these abnormal conditions go away, clean spot on the rope, stuck caver steps on a ledge, etc, 3 bars suddenly provides very little friction. I don't really like relying on outside factors to determine if I have enough friction to avoid a making a crater.

Your Petzl rack is a fine descender and should work well is most situations. Thinking about and even practicing possible scenarios is a great way to expand your knowledge of how these things work.

[brrrdog]

Thanks Scott (and everybody else) for all the info. Now I just need to find a tree so I don't have to go to the climbing gym every time to practice ;).

B

[hank moon]

Hi Y'all

Just for the heck of it, I rapped a few times on 3 bars (Petzl rack) just now. Rough conditions: 10' rap, I weigh ~170#, new rack, slightly used Petzl VECTOR 11mm low-stretch rope. It was difficult to hold my weight with the rope in the "normal" (i.e. down) position, fairly easy with rope redirected 180° around the bottom bar - very easy when redirected through a carabiner clipped into frame above top bar. I also unweighted the rack and shook it vigorously in all directions trying to get the rope to come out. Eventually it did.

So....what? 3 bars *might* be appropriate for an unusual situation (i.e. emergency) but *only* as a last resort. Frankly, it's difficult to imagine a realistic scenario where it would be necessary to rap on 3. I'd rather use a Munter hitch.

[Lava]

I've seen the old first bar/second bar/hyper-bar combo (on a micro-rack) used before, and it was very effective. Of course this was a lightweight guy doing a short sloping drop on thick (11mm) gypsum-encrusted rope

You have got to be talking about Apricot Pit. Yeah, I did the same thing with my micro rack there. Was a little weird, but what with all the chockstones and ledges it wasn't too bad. I did keep my gloved hand smashed over the top of the hyperbar the whole time tho.

[NZcaver]

I've seen the old first bar/second bar/hyper-bar combo (on a micro-rack) used before, and it was very effective. Of course this was a lightweight guy doing a short sloping drop on thick (11mm) gypsum-encrusted rope

You have got to be talking about Apricot Pit. Yeah, I did the same thing with my micro rack there. Was a little weird, but what with all the chockstones and ledges it wasn't too bad. I did keep my gloved hand smashed over the top of the hyperbar the whole time tho.

Same cave - different pit. Actually, several pits.

I was using a Stop, and was having trouble moving at all. I tried a Munter Hitch on one ~40 foot sloping drop, and it cut through a fair chunk of my aluminum carabiner! I found that C-rigging the Stop was the answer for me, and the 2 bar/hyper-bar combo for my friend.

[fuzzy-hair-man]

Just for the heck of it, I rapped a few times on 3 bars (Petzl rack) just now. Rough conditions: 10' rap, I weigh ~170#, new rack, slightly used Petzl VECTOR 11mm low-stretch rope. It was difficult to hold my weight with the rope in the "normal" (i.e. down) position, fairly easy with rope redirected 180° around the bottom bar - very easy when redirected through a carabiner clipped into frame above top bar. I also unweighted the rack and shook it vigorously in all directions trying to get the rope to come out. Eventually it did.

There are diagrams that partly show what (as far as I can tell) Hank was up to in the literature about the RACK on the petzl webite here

The one I'm not too sure about is

fairly easy with rope redirected 180° around the bottom bar

My club uses a rack similar to the Petzl rack, we have recently had a fair few beginners who are very light (think 50 kg or less) and they have a very hard time descending on the clubs slightly stiff but otherwise very servicable ropes.
The first inclination for a beginner when they find they have too much fricton is to start feeding rope (something I have been drumming out of them ) so I consider the situation a dangerous one (beginners descenders and all systems in my opinion should have where possible the instinctive or intuitive action help rather than hinder, and should help form good habits rather than bad ones(feeding)).

Currently, our solution is to train lighter members on racks (the clubs standard descender) then progress them to either a bobbin, stop, or stainless steel rack. When we were trying to find a solution the first suggestion was to drop a bar, so I tried it (in controlled circumstances), I found you are effectively dropping 2 bars if your hip braking position is unchanged, needless to say this was very hard to control the only way I'd consider using it would be with the rope placed up over the top of our U frame racks (ala hyper bar style) it is still hard to control.

I thought I'd add my two cents that for some very light people it may be that they will routinely be looking for less fricton than the rack offers.

Frankly my opinion is to move them on to a more appropriate descender (bobbin or Stop) as we are getting outside the 'working' weight range of the racks we are currently using. The stainless Steel rack whilst an improvement was not a huge improvement and some of the lighter girls were still struggling although no where near as much.

[Princess Butterfly]

Currently, our solution is to train lighter members on racks (the clubs standard descender) then progress them to either a bobbin, stop, or stainless steel rack. When we were trying to find a solution the first suggestion was to drop a bar, so I tried it (in controlled circumstances), I found you are effectively dropping 2 bars if your hip braking position is unchanged, needless to say this was very hard to control the only way I'd consider using it would be with the rope placed up over the top of our U frame racks (ala hyper bar style) it is still hard to control.

If your using a rack and have to pop a bar you may end up with a situation where the rope comes over the bar and to the brake hand where it would only count as half a bar. If this provides too much of a friction change (too little friction) there are several things you can do about it.

Without changing hips you can use your feet to add extra friction. Have your students try wrapping it over one of their feet to provide a little extra friction. The rope can also be wrapped over one foot and under the other provide more friction. If the rope is too heavy for these you can put your heels together and make a V shape and let the rope ride there. Another method would be to push/pull (depending on configuration) the rope through the frame to capture the last bar. These additional control devices can be used to supplement the work of the rack without having to switch hips.