Fixed point (alpinism)
In mountaineering and sport climbing , a fixed point (also a securing point ) is a reliable fastening point for securing , to which a sling , an express set or a snap hook can be attached. Fixed points are required for intermediate securing and for setting up stands . Particularly reliable anchor points are required for standing areas and when abseiling , as failure here would have particularly serious consequences. In these cases, the backup is usually made using several ( redundant ) fixed points at the same time .
Many established routes in the rock have prepared anchor points in the form of bolts . However, fixed points often have to be attached by the climber himself using the appropriate material . Such fixed points are thereby usually from pre-anodic set and the Nachsteigenden removed.
Fixed points when rock climbing
Fixed securing points
Fixed securing points are permanently attached to the rock (often by the developer of the route) and remain there. That is why they are as weatherproof as possible.
"Glued" bolts are currently the most reliable safety means. "Gluing" means the use of two-component mortar or quick-setting cement. Special adhesive hooks, the so-called Bühler hooks and AV safety hooks , can also be used as a fully-fledged stand, which means that the use of an additional fixed point may be dispensed with. Redundancy through a second fixed point is always recommended, however. In the case of Bühler hooks installed in rock, the breaking load value in the radial load direction is 30 to 60 kN .
Non-glued bolts are also widespread. These do not offer the security of the adhesive hooks, but - with a few exceptions - are among the most reliable securing devices. Normal hooks are driven into crevices by the climber themselves and usually remain there. However, hooks that have already been inserted must always be checked for strength before use. Today mountaineers and climbers hardly ever use normal hooks; these have been largely replaced by bolts or mobile securing devices such as clamping devices and clamping wedges (see below ).
In modern sport climbing , most routes are secured with bolts at short intervals. The resulting increased safety is one of the main reasons why climbing has developed into a trend sport. Fixed fixed points are given in route descriptions and climbing guides and drawn in with symbols in graphical route representations, so-called topos . Bolts are symbolized with a capital "X", stands with a double large "XX" and normal hooks with a small "p". The fixed points can be from 2 to 50 meters apart, i.e. up to a whole rope length . Routes that offer no or only a few fixed securing points for intermediate securing are referred to as "alpine secured".
In general, heavily traveled difficult routes are better secured than easier ones. In routes with a very high degree of difficulty, fixed safety points are almost exclusively possible, as the compact rock structure often does not offer the possibility of setting up additional fixed points. Long climbing routes, in which there are no securing points and none can be attached, are called "moral" because the climber has to take a high risk there.
Fixed points to be set up by yourself
On the one hand, natural fixed points such as hourglasses , trees or rock heads are used. Using a sling at the appropriate length in this case a fixed point can be set up for rock heads this is called Köpfelschlinge .
In addition, knot loops , clamping wedges and clamping devices (for example friends ) are in use today. The latter are known as active securing devices, as they change their shape when loaded and thus counteract tearing out. How secure a fixed point made in this way depends on the rock structure, the material used and the experience and skills of the person installing it.
Wedges or loops may only be loaded in one direction - usually sensible for a downward fall - otherwise the noose will be stripped off or the wedge will be pulled out of the crack. If a stand used to secure the lead climber is then to be used to secure the lead climber, the stand must be converted when using such fixed points (bracing downwards against falling upwards). Another possibility to create an almost fully-fledged fixed point even when using these securing means is to set up two fixed points at a certain distance above one another, whereby the lower one can be loaded upwards and the upper one downwards, and these can be braced together. It should be noted, however, that even with such tensioning of the fixed points, no lateral forces may occur.
Fixed points in snow and ice
When setting up fixed points in the ice, assessing the nature of the ice is of crucial importance. Ice screws are mostly used in solid ice, two of them are usually used for standing areas. With good ice these are used “in series”, that is, the second ice screw is only loaded if the first one fails. In bad ice, the bound triangle of forces is used, which distributes the forces evenly between the two ice screws. Another possibility to set up a fixed point in the ice is an ice hourglass .
In snow or firn , a T-anchor is used as a fixed point, i.e. an elongated object buried in the snow perpendicular to the direction of pull, for example an ice ax or backpack . Firn anchors , elongated metal angles that are rammed into the firn, are used less often.
Compensation anchoring
| angle | Load per point |
|---|---|
| 15 ° | 50% |
| 30 ° | 52% |
| 45 ° | 54% |
| 60 ° | 58% |
| 90 ° | 71% |
| (120 °) | (100%) |
To increase security, fixed points are often set up twice with a triangle of forces . To do this, two or more securing points are connected with a sling and a central carabiner is attached. This achieves:
- Load balancing : the load is distributed over two securing points
- Redundancy : if one backup point fails, there is another one
When balancing the load, it is crucial that the angle between the belt loops on the central carabiner is as small as possible (more pointed than an equilateral triangle).
For redundancy it is crucial that one strand of the sling is twisted to one eye before the central carabiner is attached so that the carabiner continues to hang in the sling even after a securing point has failed.
Forces at the belay point
| Fall | force |
|---|---|
| with dynamic backup | 400 daN |
| with static securing | 600 - 800 daN |
| tested standard fall load | 1200 daN |
| greatest possible fall load | approx. 1600 daN |
The forces that act on a single belay point depend on the climber's weight, the height of the fall, the fall factor , the elasticity of the rope , the friction losses in the dynamic rope belay system and in the intermediate belay systems and the friction between rope and rock.
The table on the right shows the forces that occur in the event of a fall.
literature
- Pepi Stückl, Georg Sojer: Mountaineering: Textbook for all types of mountaineering . Bruckmann, Munich 1996, ISBN 3-7654-2859-0 .
- Chris Semmel: 15: 2. Adhesive hook against expansion anchor . In: German Alpine Club / Austrian Alpine Club / Swiss Alpine Club (Hrsg.): Mountain climbing . No. 2 . Innsbruck 2006, p. 24–29 ( online [PDF; 1.8 MB ; accessed on March 16, 2008]).
- Walter Würtl: construction site stand . In: German Alpine Club / Austrian Alpine Club / Swiss Alpine Club (Hrsg.): Mountain climbing . No. 2 . Innsbruck 2003, p. 50–57 ( online [PDF; 22 kB ; accessed on March 16, 2008]).
Individual evidence
- ↑ Know-how on the mountain. Essential information on equipment, planning and rope technology. Retrieved March 18, 2020 .
- ↑ a b Info script bolts. In: IG climbing. Retrieved March 18, 2020 .
- ↑ Jürg von Känel: For drilling and rehabilitation of placements routes. Retrieved March 18, 2020 .
- ↑ Training documents of the Bavarian Mountain Rescue Service (PDF; 1.1 MB)