Bogley

[Jaxx]

Tom's story got me thinking about a question I have had for a while. What is the best way to set up a guided rappel? You have two anchors. How do you get the guided line tight enough that it won't sag. How can you use one rope for both the guide and the rap line?

[jwurst]

Use a simple 3:1 haul system to tension the guide line. It doesn't necessarily have to be super tight, just enough so that the rappeller avoids whatever obstacle you are bypassing.

Single rope? If you mean using two halves of a single rope as separate guide and rappel lines then you need to put in a block at the top anchor for the last person down to still allow the rope to be pulled. In a normal situation where the guide line isn't super tight then the block would be on the guide side. If you had enough tension you wouldn't need a block at all. For it to need to be on the rappel side you'd need to have enough tension to actually raise the rappeller against all of the friction in the system. If that is happening then your guided rappel might be turning into a tyrolean. Make sure that top anchor is strong because there is a lot of force involved.

If you mean rappelling on the guide line--you can't--too much tension. You can use an ascending system to descend the line. If the purpose is only to skip going into a keeper pothole then as an alternative to a guided rappel you might be able to rig a pendulum at the bottom--anchor the rope at the bottom but don't put tension on it. Rappel down even with the exit and then use the tail of the rope to pull yourself over to the anchor. This only works if the rappel is quite a bit longer than the pendulum distance.

[SLCmntjunkie]

I'm smiling right now because I know the answers to your questions thanks to some training and practice some other canyoneers were kind enough to give me last week. I didn't read the story yet, so I don't know the context and I'm certainly not an expert, but I'll give it a shot.

You could use one rope if you isolated each strand, setting a block at each anchor, one on the rappel side and one on the guide rope side. You can tension the rope by setting up a mechanical advantage using a z-rig or other techniques.

[SLCmntjunkie]

I guess I wasn't fast enough

[Jaxx]

ok. That is kinof what I had pictured. I think this weekend I am going to set something up in my garage. I hadn't thought of the pendulum deal. Thanks for the info guys.

[ratagonia]

Jaxx wrote: ok. That is kinof what I had pictured. I think this weekend I am going to set something up in my garage. I hadn't thought of the pendulum deal. Thanks for the info guys.

mmmmm. be careful out there. Here's the warnings:

1. Anchors need to be GOOD. Expect to put 3 to 4X bodyweight on the anchors.

2. Usually, the guideline does not need to be exceptionally tight. Careful adjustment of the tightness will keep the loads on the anchors reasonable.

3. After the first person, usually best to tighten the guide line once.

4. MUST use a static line for the guide side. CAN use a dynamic line for the rappel line. The more static the guide line, the less tight it needs to be.

5. To tighten, can do various things. Rarely is mechanical advantage actually required.

6. Without a block, it does not really work. Try it, you won't like it.

here's the cheesy quick diagram:

[oldno7]

Jaxx wrote: Tom's story got me thinking about a question I have had for a while. What is the best way to set up a guided rappel? You have two anchors. How do you get the guided line tight enough that it won't sag. How can you use one rope for both the guide and the rap line?

Are you sure you want to learn this over the internet.
Lots of options,top tension,bottom tension,retrievable,etc.
A retrievable uses the same criteria as pulling a rappel(need double the rap length in rope)
Lots of options as far as angle,friction,etc. I top tension with just body weight, some may need mech advantage. You can use "meat in a pinch as an anchor.(and so on and so on) :rockon:

[ratagonia]

oldno7 wrote: Are you sure you want to learn this over the internet.
Lots of options,top tension,bottom tension,retrievable,etc.
A retrievable uses the same criteria as pulling a rappel(need double the rap length in rope)
Lots of options as far as angle,friction,etc. I top tension with just body weight, some may need mech advantage. You can use "meat in a pinch as an anchor.(and so on and so on) :rockon:

And then, there's the "Throw to the guided rappel" - one of my favorites...

T

[Jaxx]

I set up a guided rappel of of the hitches of my two cars, here is the rundown: I used one static 8mm imlay rope. blocked off one side. The other side I tied a butterfly about 18 inches away from the "anchor" in the guided rap side of the rope. I hooked a biner with a pulley on the butterfly knot. I put that side through a pulley on the hitch back to the pulley on the butterfly. Tightened nicely so I upped the anty and put the rope just through the biner on the hitche and back up to the butterfly and tied a double half hitch behind the butterfly to keep the line tight. It worked very well and only would take about 3 minutes to set up in the canyon once the gear was out of the pack. Since I did it on the hitches of course I couldn't rappel of of them. I do have anchors in my garage ceiling but I was worried about ripping them out. I took a bunch of pics but I can't find the cord for the camera !@#$@#

The question I had was about the bolts for the anchor. How much pressure is on these with that type of setup. I was a little worried about tightening the guide side too tight or with the weight of a rappeler on the other side of the line the pressure would be too much. I guess theres only one way to find out!

Another question. What is the best way to tie off the rope once you get it tight?
I don't mind asking questions or getting answers online because I try it out before I'm in a canyon. Seems reasonable.

[rcwild]

Jaxx wrote: The question I had was about the bolts for the anchor. How much pressure is on these with that type of setup. I was a little worried about tightening the guide side too tight or with the weight of a rappeler on the other side of the line the pressure would be too much. I guess theres only one way to find out!

Another question. What is the best way to tie off the rope once you get it tight? I don't mind asking questions or getting answers online because I try it out before I'm in a canyon. Seems reasonable.

You will find the math here:

http://www.canyoneering.net/forums/showthread.php?t=644

Be extremely careful. Some of the advice given in this thread will get you in trouble. Even if you do try things in your garage first, there are a number of variables that cannot be replicated until you are in a real situation. The answer to your question about the best way to tie off is "It depends ..." In this case on how you rigged the tightening system. If there is something in your tightening system that is releasable, you have more options with the tie-off. If your tightening system is not releasable, your tie-off should be.

[Bo_Beck]

rcwild wrote: Jaxx wrote: The question I had was about the bolts for the anchor. How much pressure is on these with that type of setup. I was a little worried about tightening the guide side too tight or with the weight of a rappeler on the other side of the line the pressure would be too much. I guess theres only one way to find out!

Another question. What is the best way to tie off the rope once you get it tight? I don't mind asking questions or getting answers online because I try it out before I'm in a canyon. Seems reasonable.

You will find the math here:

http://www.canyoneering.net/forums/showthread.php?t=644

Be extremely careful. Some of the advice given in this thread will get you in trouble. Even if you do try things in your garage first, there are a number of variables that cannot be replicated until you are in a real situation. The answer to your question about the best way to tie off is "It depends ..." In this case on how you rigged the tightening system. If there is something in your tightening system that is releasable, you have more options with the tie-off. If your tightening system is not releasable, your tie-off should be.

We use a "guiding line" periodically during rescue. As a rule what I've been taught is that a guiding line should not be pre-tensioned at all unless necessary to clear an object. Once the person has started down whether by rapelling or being lowered, ideally he (or she) should be in contact with the wall or ground the entire time during descent. The guiding line may be tensioned or detensioned during the descent to insure that the person is never at a critical distance from from what ever it is that they are trying to avoid. If there might be failure of the system this minimizes that chance of serious injury (such as slamming back into the cliff face while suspended 20' out). Just my thoughts on the matter.

[rcwild]

Bo_Beck wrote: We use a "guiding line" periodically during rescue. As a rule what I've been taught is that a guiding line should not be pre-tensioned at all unless necessary to clear an object. Once the person has started down whether by rapelling or being lowered, ideally he (or she) should be in contact with the wall or ground the entire time during descent. The guiding line may be tensioned or detensioned during the descent to insure that the person is never at a critical distance from from what ever it is that they are trying to avoid. If there might be failure of the system this minimizes that chance of serious injury (such as slamming back into the cliff face while suspended 20' out). Just my thoughts on the matter.

What we call a guided rappel in recreational canyoneering is similar to what I learned in rope rescue courses called a telfer. Telfer has much less force on it than the highlines you are using in Zion, but enough that setting them up should never be taken lightly.

Bo, have you looked at the math in the above referenced thread on the ACA forums? Pretty easy to hit load multipliers in the 800-900% range and HIGHER!

Have fun. Be safe.

[Bo_Beck]

rcwild wrote: Bo_Beck wrote: We use a "guiding line" periodically during rescue. As a rule what I've been taught is that a guiding line should not be pre-tensioned at all unless necessary to clear an object. Once the person has started down whether by rapelling or being lowered, ideally he (or she) should be in contact with the wall or ground the entire time during descent. The guiding line may be tensioned or detensioned during the descent to insure that the person is never at a critical distance from from what ever it is that they are trying to avoid. If there might be failure of the system this minimizes that chance of serious injury (such as slamming back into the cliff face while suspended 20' out). Just my thoughts on the matter.

What we call a guided rappel in recreational canyoneering is similar to what I learned in rope rescue courses called a telfer. Telfer has much less force on it than the highlines you are using in Zion, but enough that setting them up should never be taken lightly.

Bo, have you looked at the math in the above referenced thread on the ACA forums? Pretty easy to hit load multipliers in the 800-900% range and HIGHER!

Have fun. Be safe.

Yes Rich, I did look at the test figures that Sonny posted. The one thing that isn't addressed, but that Tom mentioned, is that the tests were done using a dyno, but failed to suggest at which point the forces were highest (only one of the variables). I did notice that Sonny mentioned that the angle was 30 deg. or so though. It is true that the tighter the line, the greater the forces that can be expected. The forces are generally going to be highest somewhat around midspan, depending on the angle of the rope. I just worry that with some of the rickity anchors that are found in some of the canyons, that someone may turn a guiding line into a Highline by accident and be involved in catostrophic failure. I tend to believe that if the anchors are questionable, then build them up, or use a skate block and hope that it will keep you dry!

[rcwild]

Bo_Beck wrote: Yes Rich, I did look at the test figures that Sonny posted. The one thing that isn't addressed, but that Tom mentioned, is that the tests were done using a dyno, but failed to suggest at which point the forces were highest (only one of the variables). I did notice that Sonny mentioned that the angle was 30 deg. or so though. It is true that the tighter the line, the greater the forces that can be expected. The forces are generally going to be highest somewhat around midspan, depending on the angle of the rope. I just worry that with some of the rickity anchors that are found in some of the canyons, that someone may turn a guiding line into a Highline by accident and be involved in catostrophic failure. I tend to believe that if the anchors are questionable, then build them up, or use a skate block and hope that it will keep you dry!

Wasn't referring to Sonny's post. Look farther into the thread for the calculations provided by Hubert Shen (barleywino). His calculations reflect the amount of tension/slack in the rope and show forces at various distances between anchor points.

I share your concerns about the risks. This is another system that people think is cool so they want to use it more often than necessary. Primary reason for rigging a guided rappel is to avoid a dangerous hydraulic in a Class C canyon. The risk presented by the hydraulic outweighs the risks of rigging a guided rappel. Anchors in Class C canyons should by necessity be stronger than normal anyway. Using a guided rappel just to avoid a bit of cold water is a bit silly, especially in Colorado Plateau sandstone canyons where the rock quality and anchors are often suspect.

[Bo_Beck]

rcwild wrote: Bo_Beck wrote: Yes Rich, I did look at the test figures that Sonny posted. The one thing that isn't addressed, but that Tom mentioned, is that the tests were done using a dyno, but failed to suggest at which point the forces were highest (only one of the variables). I did notice that Sonny mentioned that the angle was 30 deg. or so though. It is true that the tighter the line, the greater the forces that can be expected. The forces are generally going to be highest somewhat around midspan, depending on the angle of the rope. I just worry that with some of the rickity anchors that are found in some of the canyons, that someone may turn a guiding line into a Highline by accident and be involved in catostrophic failure. I tend to believe that if the anchors are questionable, then build them up, or use a skate block and hope that it will keep you dry!

Wasn't referring to Sonny's post. Look farther into the thread for the calculations provided by Hubert Shen (barleywino). His calculations reflect the amount of tension/slack in the rope and show forces at various distances between anchor points.

I share your concerns about the risks. This is another system that people think is cool so they want to use it more often than necessary. Primary reason for rigging a guided rappel is to avoid a dangerous hydraulic in a Class C canyon. The risk presented by the hydraulic outweighs the risks of rigging a guided rappel. Anchors in Class C canyons should by necessity be stronger than normal anyway. Using a guided rappel just to avoid a bit of cold water is a bit silly, especially in Colorado Plateau sandstone canyons where the rock quality and anchors are often suspect.

Pretty cool calculations for sure. Really what the figures are telling me is that the "Guided Rappel" is transitioning from basically a "Tag Line" to a "High Line". I understand the concept of using a "Guided Rappel" for class 3 canyons and avoiding hydraulics and see the balance between the risks. I just have some concern of the use of these systems without understanding the physics. I would think that someone trying a guiding line for the first time, it would be prudent to install a single prusik at the "anchored end" with a "belly" to the anchor point. At least this way if they use a MA and don't know how tight the rope is, the prusik will act as a clutch and reduce peak force. A single prusik "8mm" on an 11mm rope will slip at between 3-5KN. If using a 9mm rope then a 6mm prusik will do the trick. In Telephone Canyon last weekend I didn't have Kip tension the Guided Rappel until my feet were at the water. He had no problem getting me up high enough to descend the angle to the shore. It reduced the amount of effort he extended until it was necessary to get me over the obstacle. I don't see the need to be suspended out away from the vertical wall until it is necessary. FWIW