The art and science of flying a ram-air skydiving canopy is something like a poetic marionette show: where the puppet, working with the forces of the wind, becomes her own puppeteer.

The strings that connect her to the power overhead are some of the most vital -- and overlooked -- parts of the system. Here's what you need to know.

The Same Old Tired Line

It’s a sad fact: all skydiving canopies eventually wear out. The fabric, however, usually lasts much longer than the lines. For a lineset, the “countdown clock” to line retirement can be as short as a few dozen jumps or extend almost to 1,000. The time it takes for a lineset to wear out is predicated on a number of factors, the most key of which is the type of material the line is built from. In this article, you’ll learn about the different line types – and the factors influencing line wear that you, as the skydiver, can control.

The rule of thumb regarding parachuting equipment is to see a rigger for any component that appears more than 10% worn.

Line types are generally known by their brand names, as they use trademarked materials that were specially lab-developed to handle high-stress environments like skydiving. Predictably, different materials have different benefits and drawbacks. When originally selecting a canopy, you’ll want to choose the material with a profile that matches your needs.

Dacron®

Dacron® is the trademark for a DuPont-manufactured continuous filament yarn called a “condensation polymer.” Dacron® is made from a combination of ethylene glycol and terephthalic acid. The combination results in a fiber with high tensile strength, high resistance to abrasion, high resistance to stretching out in both wet and dry environments and good resistance to chemical degradation. As well as skydiving lines, Dacron® is used to make clothing textiles, high-pressure firehoses, and thread.

Dacron®’s inherent ability to stretch and spring back into shape is an excellent match for skydiving applications: the material absorbs some of the opening shocks, then returns to form. Dacron® line lengths stay essentially the same until they break, so don’t wait for the telltale signs of deformation in your flight performance before you replace them.

How to Know When Your Dacron® Lines Need Replacing

Snowy-white Dacron® lines have one easy wear indicator: color. When your lines start to look visibly dirty and grayed, feel rough when you slide your fingers along them, it’s time to go see the rigger. Check the area at the connector links with special care, as when you see wear there it’s definitely time for a re-line. The material isn't the commonest material for skydiving canopy lines, and it's generally found more often on older canopies, skydiving student canopies, canopies for camera flyers and other jumpers who may want the extra forgiveness the "springy" line provides.

Spectra®

Spectra®, trademarked by the Honeywell company, is a high-strength, oriented-strand gel spun into thread by an industrial spinneret. Spectra® is strong enough to be comparable to high-strength steel. The lightweight material’s resistance to cutting, as well as its general toughness, has led to its use in a long list of applications: ripstop luggage fabric, storm sheathing, bowstrings, commercial fishing nets, yacht rigging, water rescue lines, spear gun ropes, military armor and space tethers used by NASA.

As well as skydiving parachute lines, Spectra® is used to make the suspension lines for paragliders and speedwings. Generally snow-white for skydiving applications, Spectra® appears in a rainbow of line colors under the latter two ram-air airfoils.