Your rope is the key to safe vertical movement. Here's what they're made from and how to choose one.
Climbing equipment- ropes/rope bags
Each component of your climbing equipment makes up your combined safety matrix to keep you alive in the vertical, and your rope is its primary component. With a rope you can make use of all the protection tools, such as nuts, slings and cams. Without a rope these would be totally useless. With a rope you can safely climb up the biggest and steepest pieces of rock and ice on the planet, and with a rope you can descend back down them as well. Your rope is the key to safe vertical movement.
Climbing ropes feature a complex sheath and core design, and high quality nylon
How do ropes work?
Climbing ropes feature a complex sheath and core design, and high quality nylon. For safety, a rope works by elongation, absorbing the falling climber's bodyweight (impact force) and allowing the protection to catch them gradually. If the rope had no stretch (static rope) just the climber and their protection would have to absorb the loading - which could be catastrophic. Impact force decreases with reduced rope diameters (i.e. thinner ropes are more stretchy), but thicker ropes can absorb more falls due to the larger amount of material in their construction. This is why thick, single ropes are used in situations were a large number of falls will be taken. For example, 10mm ropes are favoured by sports climbers and slimmer, twin 'half' ropes are favoured for trad climbing, where falls will be rarer and protection may not be as reliable - requiring a softer 'catch'.
Buying a rope
Although modern ropes are always supplied with a huge list of technical data attached (sheath slippage, impact force and fall rating, etc.) all ropes bought in Europe pass must CE regulations - meaning all ropes are made to a high standard and can be trusted. Saying that though, there is a vast difference between a cheap rope and a good quality rope.
The true value of a rope lies in its construction and the quality of the nylons used. Cheaper ropes are generally manufactured from cheaper nylons and generally constructed in a more simple manner on less-complex machines. Such construction can result in a rope that kinks and handles poorly. The sheath can quickly lose its integrity, causing the rope to grow fatter and allow dirt to enter the core. The sheath of a rope takes a real battering; running over rough stone, being dropped into the sea, and ground into the dirt will clumsy feet - so this aspect of a rope is vitally important.
The appearance of the sheath is also often the only way to judge the rope's strength. The cheaper nylons are also less resistant to abrasion, causing the rope to fur up - with the result that the rope absorbs more moisture and dirt. These ropes are satisfactory for single pitch climbing, but for multi-pitch climbing they can be both a nightmare to use and a potential hazard. A dry treated rope increases the rope abrasion resistance and helps keep dirt out. Such ropes are vital if you plan to use them for winter or alpine climbing.
Rope Diameter
Climbing ropes: quite necessary, really...
Twin rope (7.5mm to 8mm) - These slim ropes are classed as twin ropes, as they are used double and require both strands to be clipped into each karabiner to form one rope. This system is incredibly light, low bulk and allows full-length abseils to be made.
Half rope (8.1mm to 9mm) - This is the most popular rope system in the UK. Two ropes are used, with each rope being clipped singly into protection. This allows the leader to limit the rope and improve safety by using two ropes instead of one. Full-length abseils are also possible. Half ropes are recommended for both single and multi pitch trad climbing.
Single rope (9.1mm to 11mm) - Simple and lightweight when using thinner diameter single ropes, this system is popular for easy routes, sport climbing or in high wear situations (instruction, guiding, big walls, indoors).
Rope bags
Use a rope bag or tarp to keep your rope clean and dry. Storing a rope uncoiled helps to reduce kinking.