What are "deadman" anchors and are they safe?

[rcwild]

A deadman is a buried object (i.e. rock, log) used as an anchor. Holding power depends on four variables: (1) the surface area of the object "projected" towards the line of force, (2) the depth at which the object is buried, (3) the inclination of pull, and (4) the quality/density of soil material.

Here's an example: An object buried three feet, with a 45 degree inclination of pull will hold 950 pounds per square foot of projected surface area.

Sounds good on paper, but these figures are for deadmen anchors in ordinary loamy soil, rarely found in canyons. To get the same holding power in sand, you would need to (a) use an object with a significantly greater projected surface area, (b) bury the object deeper (rarely possible in a canyon since you will likely hit bedrock), and/or (c) engineer a shallower inclination of pull. In any case, the amount of excavation needed to construct a safe deadman anchor would be considerable.

Due to the amount of work involved in construction and the fact that conditions are rarely encountered where one can be constructed properly, seasoned canyoneers only use deadmen anchors as a last resort. Your time will be more wisely spent learning other natural anchor methods.

[rcwild]

Here's an illustration showing the correct way to bury a deadman anchor. The object (X) can be a rock, log, etc. Depth (D) is often limited; you will likely encounter bedrock. The angle (A) that the webbing exits the T-shaped trench is important. The flatter this angle the better.

You may not be able to dig deep enough to install a deadman that will work well on its own. If good-sized rocks are available, consider stacking them on top of your deadman to add additional strength.

NOTE: Deadman anchors are not very common in Class C canyons. The constant flow of water has likely washed away material right down to the bedrock.

[ratagonia]

A deadman is a buried object (i.e. rock, log) used as an anchor. Holding power depends on four variables: (1) the surface area of the object "projected" towards the line of force, (2) the depth at which the object is buried, (3) the inclination of pull, and (4) the quality/density of soil material.
...

Due to the amount of work involved in construction and the fact that conditions are rarely encountered where one can be constructed properly, seasoned canyoneers only use deadmen anchors as a last resort. Your time will be more wisely spent learning other natural anchor methods.

Considering the fairly small forces we generate when doing ordinary rappels, one of the most important factors is the geometry provided, and a second important factor is the weight of the actual object. The point of burying the object is to increase its effective weight.

Advantageous geometery is often found in the canyon environment. A pothole just before the drop may present virtually perfect geometry for absorbing much of the force of the rappel via friction over a rounded edge. In our experiments in sandbags, we even found one pothole that was slightly concave at the lip, that the sandbags with 8 lbs of sand were sufficient to hold a rappel, and could be cleaned ONLY by having 2 people pulling on ropes with all their might, out aways from the drop to get a better angle. In many cases pothole geometry will decrease the load on the "anchor" by anywhere from 5:1 to 20:1. In many cases, just the weight of a 20 lb rock in a pothole provides sufficient (though not necessarily convincing) anchorage for carefully performed rappels.

And, on the other point: deadman and cairn anchors are one of the mainstays in several areas, including the Roost and certain backcountry areas of Escalante. The aspirant backcountry canyoneer's time is better spent learning these techniques than such unreliable oddities as webbing chocks, in my opinion.

Tom

[rcwild]

And, on the other point: deadman and cairn anchors are one of the mainstays in several areas, including the Roost and certain backcountry areas of Escalante. The aspirant backcountry canyoneer's time is better spent learning these techniques than such unreliable oddities as webbing chocks, in my opinion.

If the aspirant canyoneer intends to spend most of his/her time in areas like the Roost and certain backcountry areas of Escalante, where the geometry is ideal for deadman anchors, his/her time would be well spent learning these techniques.

If the aspirant canyoneer intends to spend most of his/her time elsewhere, where the geometry sucks for deadman anchors, but the rock is ideal for knot chocks, his/her time would be better spent learning proper placement of knot chocks than such unreliable oddities as deadman anchors.

If the aspirant canyoneer intends to become a well-rounded canyoneer with skills appropriate to a variety of canyons, he/she should make sure all of these tools are in their tool box.

[rcwild]

Advantageous geometery is often found in the canyon environment. A pothole just before the drop may present virtually perfect geometry for absorbing much of the force of the rappel via friction over a rounded edge. In our experiments in sandbags, we even found one pothole that was slightly concave at the lip, that the sandbags with 8 lbs of sand were sufficient to hold a rappel, and could be cleaned ONLY by having 2 people pulling on ropes with all their might, out aways from the drop to get a better angle. In many cases pothole geometry will decrease the load on the "anchor" by anywhere from 5:1 to 20:1. In many cases, just the weight of a 20 lb rock in a pothole provides sufficient (though not necessarily convincing) anchorage for carefully performed rappels.

Seems like you're stretching the definition of "deadman" a bit. A term like "counter weight anchor" might better suit what you are describing.

[Paul Nelson]

One concern I have with deadman anchors, besides the name, is the issue of litter. A sling around a tree or large rock may survive the next storm, but deadman's may be washed away at the next storm. Thus the sling is now litter down the canyon. In a popular canyon, in 10 years this may become a serious visual impact. I am no fan of unnecessary bolts, but would a properly placed glue-in be a better option than numerous people building deadmans and creating future litter?

Sorry for feeding the fire of the bolting debate.

[ratagonia]

One concern I have with deadman anchors, besides the name, is the issue of litter. A sling around a tree or large rock may survive the next storm, but deadman's may be washed away at the next storm. Thus the sling is now litter down the canyon. In a popular canyon, in 10 years this may become a serious visual impact. I am no fan of unnecessary bolts, but would a properly placed glue-in be a better option than numerous people building deadmans and creating future litter?

Sorry for feeding the fire of the bolting debate.

From an aesthetic viewpoint, yeah.

But has been discussed (cussed, debated, etc.) numerous times, placing a bolt crosses a philosophical line (that SOME people recognize and some people don't) that other forms of litter do not.

I could argue, in popular canyons, that chewed up piece of webbing will be replaced by the next diligent canyoneering team, before it washes away and becomes loose litter. I believe that, about 60%. Otherwise, I believe that if the sling washes away, the first party that notices it will be dissappointed, but they will pick it up and carry it out, and it is no longer litter.

The bolts, on the other hand, will be there quite some time, even after we all wear the *Kloghoofer* canyoneering shoes that absorb impacts from jumps up to 80 feet (100 feet when landing on sand), and that spot is no longer a rappel.

The deadman in the end of Not Mindbender lasted about 2 years before it was so natty people would not use it anymore. I don't know what happened to the sling - I suspect people cut part of it out, but left most of it buried in the sand.

Tom

[rcwild]

I split two posts from this thread (from Canyonette and Ratagonia) that sounded better suited for To Bolt or Not to Bolt (http://www.canyoneering.net/forums/showthread.php?t=777)