Snow protection

A Firnanker or snow anchors ( in some designs also Firnhaken ) is a device that is used in mountaineering for the production of a fixed point especially in steep firn. It consists essentially of a metal anchorage and a cable, is secured at its end.

Construction

Firnanker (eg aluminum), usually made of light metal. For soft snow wide airfoil- like angled plates (about 200 grams ), used with large area. Their holding power is, however, often regarded as insufficient.

For harder, more solid firn using T- or V profiles, more rarely, U- profiles that can be taken with the hammer or ice pick very stable and deep by ice. Such models are also referred to as Firnhaken. They are usually about 60 to 80 inches long and 300 to 400 grams. In order to increase the holding power, they are sometimes equipped with barbs that make it difficult to slide out. The disadvantage of such devices for removal must be ausgepickelt again, falls here less important, since they are mainly used for anchoring the fixed ropes expedition mountaineering.

After fixing the steel cable ( cable in the center of the armature ) is made between top clip (cable at the upper end ) and mid clip. The top clip attachment here has the advantage of easy mounting, because the cable must not be buried in the snow. Secure, however, is the mid - clip design, since in this case a uniform force distribution occurs and pulling the anchor out of the snow is likely in case of stress. On the contrary, a mid- clip Firnanker is drawn even deeper into the snow when loaded with proper attachment.

Use

Firnanker can be used both as a stand as well as an intermediate backup.

Compared with a T armature Firnanker often have the advantage of a substantial time savings, additionally there will be no ice ax is required elsewhere, buried. The holding forces of Firnankers can with optimal attachment are those of a T- bolt. Compared to the plug pimples, a vertically driven into the snow ice tool, the Firnanker due to its larger surface to far greater holding forces.

A Firnanker must be created specifically for a particular load direction. The right driven into the snow ( as low as possible, the right angle) is essential so that the armature can hold under load. If the angle is too large, that is close to 90 ° relative to the snow surface, the anchor can be pulled upwards at a slight angle to the loading point is located not low enough, and the anchor can be pulled out downward. Mostly an angle of about 65 ° is recommended. This results in mid- clip anchors and a sufficiently long cable a resultant force that drives the anchor deeper into the snow.

As with all other fixed points in snow and firn reliability by stress to the body weight ( sitting or standing on the device) can be increased because so slipping out is also prevented. Also, by setting in a recess or step and solidifying of the snow, the holding force can be improved.