Line Replacement

Q:

 

How do I know when it is time to replace the lines on my main canopy?

A:For skydivers, it seems to be one of the great mysteries of the universe: Who built the pyramids? Why does Stonehenge exist? When do I need to replace my canopy’s lines? Perhaps this article will be able to provide an answer to the latter question.

ASKARIGGER201410-1
Severe wear on Vectran Lines.

Your main canopy should last for 1,500 jumps or more before it is time for retirement, but its lines won’t last nearly that long. So you’ll probably have your canopy relined at some point—maybe even two or three times—before you retire it to car-cover status. Unfortunately, there is no magic number of jumps that determines when it is best to have your main canopy lines replaced. (Lines on canopies jumped in the desert or at the beach tend to wear out sooner than those jumped into grass areas and packed in cleaner environments, for instance). Even so, it is fairly easy to figure out when to replace them as long as you know what to look for. Don’t hesitate to ask for help if your lines don’t look quite right. As with anything equipment-related, the manufacturer and your local rigger can be valuable resources.

ASKARIGGER201410-2
Severe wear on HMA lines.

The type of line installed and the condition of that line are the determining factors for replacement. With each deployment, the slider comes down to your risers with enough speed that the friction between the slider grommets and suspension lines generates heat. This heat causes nylon line such as Spectra and Dacron to shrink. The outside suspension lines and steering lines tend to suffer most from this process, so over time those lines become considerably shorter than lines that attach to the center cells. For Spectra-equipped canopies, it is not unusual for the outside lines and steering lines to shrink five inches or more in just a few hundred jumps. Many jumpers with Spectra-equipped canopies begin to experience unusual openings and slower canopy speeds due to the shortened lines, even though the actual condition of the line seems OK. This happens so gradually that most jumpers never notice the poor opening and flight characteristics developing. However, if you occasionally measure the lines and compare the measurements to the manufacturer’s line-trim chart for that canopy, it will reveal the problem.

ASKARIGGER201410-3
A serrated line.

Regardless of the type of line your canopy uses, you’ll want to inspect your lines regularly. You’ll most likely find the first signs of wear on the outside lines where they attach to the risers and on the lower steering lines just above and below the cat’s eye. The slider grommets tend to abrade the outside line attachment points at the risers, breaking the fibers and making the line thinner. Worn lines appear fuzzy or develop scalloped edges that are easy to see. Once a line is at this point, it is time for replacement, since a worn line will eventually break in two.

Vectran and HMA (high-modulus aramid) lines resist shrinkage well, so inspection may be the only way to determine if they are in need of replacement. However, Vectran and HMA lines have been known to break before showing obvious signs of wear, so jumpers may want to keep track of the number of jumps on each line set and replace them at regular intervals. (Check with the canopy manufacturer for recommendations.)

Spend a few minutes of each jumping day to inspect your lines so you can keep an eye on the wear that is taking place. It will help you catch problems early and may even help you avoid a reserve ride. Besides, you will sleep better at night knowing you have solved one of the world’s greatest mysteries.

—Jim Crouch | D-16979
USPA Director of Safety & Training and FAA Senior Rigger

Comments

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Glen Whitener, D2930
Mon, 02/16/2015 - 23:02

Lines Are important and they almost always work, but a properly trimmed parachute can make the difference of just hitting the pea gravel or stepping on the disk. I was at the Nationals in 1972 and was having trouble with accuracy when the champion of the previous year told me to measure my lines. I did and found that my front lines on my "CLOUD" were stretched about 4". I cut the threads and adjusted the length and taped the lines below the not and I could get the dead centers that I needed to compete. Check your lines!

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