UKC

Lowering with a Guide plate

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 GridNorth 20 Aug 2015
Has anyone had issues with this. It appears that there have been cases of the ropes running uncontrollably through the plate when lowering in guide mode. I have tried to emulate this with both the DMM Pivot and Reverso 3 and can't create the problem. If I let go of the krab, used to lever the plate, the rope just locks up as I would expect. There are several videos for doing this safely using prussiks and re- directs etc. which is all well and good but if you do it with a guide plate why do you not need to do the same with a GriGri for example. i.e. if you don't release the lever the rope would run through the device very fast. Seems like the same issue to me.

Black Diamond recommend backing up the system but as far as I can see neither DMM nor Petzl do.

Al
 jon 20 Aug 2015
In reply to GridNorth:

The Magic Plate by NewAlp was the very first of these plates and was/is a great bit of kit - except that once loaded you couldn't release it (other than completely bypassing it). Then the current plates appeared with the facility to release under load. The way I see it is that it's more to rectify that slight hic with the Magic Plate and give the possibility to be ABLE to release under load rather than to provide a feature that you use systematically. I guess some devices are smoother than others in this respect (I don't know as I've binned my Reverso 3 and gone back to the old Magic Plate...) I agree with you completely about lowering someone from a belay using a GriGri (I'm assuming that's what you meant) I've tried it a few times and it's certainly not ideal.
 David Coley 20 Aug 2015
In reply to GridNorth:

Hi, I guess it depends on what you mean by safe, and how much experience of the act you have at the time.

1. when you leaver the thing with a krab it can release fast. How fast depends on the friction (e.g. whether the rope is taking a zig-zag through runners etc.) So the question is has the person tested this in a series of settings.
2. yes, if you let go of the krab it will lock. But will you let go? Letting go is not instinctive, gripping is. This has been found when belaying with a grigri - people grip the climber's rope rather than letting go. They get burnt, climber decks.
3. climbing in a three. This needs people to read the instructions that come with the device. As you lower the second, the third will be unbelayed, so had better be backed up.

Conclusion. If you are lowering, use a back if new to it, possibly not if experienced.
So, what is meant by experienced. One way to think about this is for each activity state what N, F, and C are. Where N is the number of times you think someone should have done the thing to be not get it wrong more than F percent of the time and C is the consequence of getting if wrong. If C high, probably best if F small.
 Hephaestus 20 Aug 2015
In reply to GridNorth:

The only problem I have is getting my (old) reverso to let go of the ropes in the first place. Then just moderate the friction as with a gri-gri.

How do you find the pivot? Think the wear on the reverso is getting pretty bad so looking at replacements.
OP GridNorth 20 Aug 2015
In reply to Hephaestus:

I like it a lot. The ropes seem to run smoother and it is easier to control when lowering a second. It still takes some effort to get that initial release though which is possibly a good thing. I used to use my nut key with the reverso which helps a little.

Al
 andrewmc 20 Aug 2015
In reply to GridNorth:

I tried it from the top of a sports route (brought up my heavier friend, lowered him from the anchor) using a Reverso 3. I was very glad for the backup Italian on my harness! Try it without any additional friction in the system i.e. lowering directly from the anchor, without the rope running over an edge or through additional carabiners. It was very difficult to get it to release at all, so you ended up pulling quite hard, but the difference between 'completely stationary' and 'near-falling' was extremely subtle.
OP GridNorth 20 Aug 2015
In reply to jon:

> I agree with you completely about lowering someone from a belay using a GriGri (I'm assuming that's what you meant) I've tried it a few times and it's certainly not ideal.

But I have never heard of anyone, least of all a professional Instructor advising that the GriGri be backed up with a prussik and as far as I can see the issue is very similar.

Al
 David Coley 20 Aug 2015
In reply to GridNorth:

> But I have never heard of anyone, least of all a professional Instructor advising that the GriGri be backed up with a prussik and as far as I can see the issue is very similar.

> Al

They are very different.
When lowering from a grigri one puts the rope back over the edge of the device. This is what gives control. Lowering from a reverso in guide mode is more like lowering with a grigri with the strands held parallel - very little control.

This is why if you hang a grigri directly from an anchor and lower from it in guide mode you need to run the slack side of the rope up to a redirect. There is a picture here: http://people.bath.ac.uk/dac33/high/6TheBelay.htm#directbelayingwithagrigri
 jon 20 Aug 2015
In reply to GridNorth:

Ah, I hadn't really understood your question before. I'm sure David C can answer it better than I - I like the redirect for the GriGri. I'll get back to painting the stairs.
OP GridNorth 20 Aug 2015
In reply to David Coley:

No I'm talking about a GriGri in it's most commonly used scenario, bottom roping and I'm comparing the principle of operation rather than the specifics. To lower you pull the lever and to stop lowering you release. If you didn't release the lever the rope would fly through the device uncontrollably. I'm suggesting that it is the same principle that applies with the guide plate but no one has suggested backing up the GriGri.

Al
 tehmarks 20 Aug 2015
In reply to GridNorth:

> If you didn't release the lever the rope would fly through the device uncontrollably. I'm suggesting that it is the same principle that applies with the guide plate but no one has suggested backing up the GriGri.

If you didn't release the lever your hand on the dead rope will control the descent! Obviously that's not possible with a direct belay in guide mode, the only thing controlling the descent is the krab or sling that you're using to pull the device into a lowering position.
OP GridNorth 20 Aug 2015
In reply to tehmarks:

That's true, engage brain before posting doh. it's a long time since I used a GriGri.

Al
 jimtitt 20 Aug 2015
In reply to GridNorth:

> No I'm talking about a GriGri in it's most commonly used scenario, bottom roping and I'm comparing the principle of operation rather than the specifics. To lower you pull the lever and to stop lowering you release. If you didn't release the lever the rope would fly through the device uncontrollably. I'm suggesting that it is the same principle that applies with the guide plate but no one has suggested backing up the GriGri.

> Al

The instructions always used to tell you to open the lever completely and control the speed with the brake hand/rope. Nobody does though.
 Mike Nolan 21 Aug 2015
In reply to GridNorth:

Sometimes you will need to thread a sling into the guide plate, clip it back through the anchor and use your body weight to release the guide plate. If you're knocked out, or fall off the ledge whilst doing this, the prussik will bite. With a GriGri, I'd imagine you'd let go of the handle, so this backup isn't necessary.

Sometimes you might be able to get away without using an Italian hitch, but I think this depends on the ropes and plate you're using. Skinny 8mm ropes would be a lot harder to control without an Italian hitch than 10.5mm ropes. When you release a guide plate fully (as you might if you used your body weight to release it), the ropes are essentially just running through a karabiner and very little friction is created by the plate, an Italian hitch would be needed here to give you more control in some circumstances.

 David Coley 21 Aug 2015
In reply to Mike Nolan:

> Sometimes you will need to thread a sling into the guide plate, clip it back through the anchor and use your body weight to release the guide plate. If you're knocked out, or fall off the ledge whilst doing this, the prussik will bite. With a GriGri, I'd imagine you'd let go of the handle, so this backup isn't necessary.

This is I think a key point. If you are releasing such a device using a sling not a krab then for many reasons you might not be able to react fast enough to control the situation. Some people will use a prusik to add safety; I like a munter on my belay loop.

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