P A R A C H U T I N G ' S N E W S M A G A Z I N E
Ask the Editor
Contents of Batch 25:
When should Vectran lines
be replaced?
Looking for information on
a Rawa freefly/camera helmet.
The following questions were submitted by visitors to our
Web site and answered by the editor of Skydiving
magazine. .
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When should Vectran lines be replaced?
Q. What is the typical jump life of a set of Vectran lines? How many jumps before I need to re-line my canopy?
A. There are two main reasons to re-line a canopy: The lines are worn, or they've stretched or shrunk enough to have affected the canopy's trim.
These days Microline (Spectra) is the most popular suspension line for main canopies. It's strong for its diameter and abrasion-resistant. But it's not as "dimensionally stable" as everyone would like; as a canopy accumulates jumps, the length of its Spectra suspension lines usually changes. The lines at the corners of a ram-air canopy sometimes shrink several inches, apparently the result of being heated by the slider zipping down the lines.
While larger and more docile canopies aren't affected very much by minor changes to the lengths of their lines, smaller high-performance canopies often are.
If the opening and flying qualities of a parachute start to deteriorate, one of the first things to check is the length of the lines. Oftentimes restoring the lines to their correct lengths will cure the problem.
Rather than rework the existing set of lines, it's usually more cost-effective to install a new set. Most manufacturers sell line sets for each model and size of canopy they make. Cost is about $200, and that includes installation.
If you're happy with the way your main opens or flies, then your lines don't need any attention - unless they show noticeable wear.
The first line to break on a canopy is usually the one that's been damaged or subjected to higher-than-average wear.
A corner line is often the first to go as a result of the extra wear caused by the slider grommets. Steering lines break early because they are abused by the slider grommets as well as by the guide rings on the risers. A nick on a grommet or guide ring can chew through a line in a very few jumps. A flapping slider combined with inadequate slider stops can also wreak havoc.
Slider grommets aren't the only things that wear out suspension lines. Fine grit particles from the ground work their way into the lines and sever fibers, accelerating wear. Canopy manufacturers say suspension lines wear much faster at arid DZs with sandy soil.
The break itself often occurs near a knot or fingertrap, because knotting and fingertrapping weakens the line. The points the suspension lines attach to the risers are a particularly vulnerable spot.
A jumper doesn't have to be a rigger to inspect her canopy's lines. It takes only a moment to look for broken strands, unusual fuzziness and other anomalies. The steering lines deserve extra attention, as does the riser-line interface. If something looks questionable, ask a rigger.
While Spectra is a pearly white, Vectran has a light tan color. Although it keeps its original length better than Spectra (it's more "dimensionally stable"), it doesn't wear as well. Some high-performance ellipticals use Vectran because these canopies need its superior dimensional stability.
Vectran gets fuzzy much sooner than Microline. This can be alarming to a jumper who hasn't had any experience with Vectran. But moderately fuzzy Vectran keeps much of its strength. But the wear will continue and when too many fibers have turned to fuzz, the line will need to be replaced.
But because Vectran is more dimensionally stable, lines made of it are less likely to need replacement because the canopy has gone out of trim, as does happen with Spectra. But Vectran wears out sooner.
While lines made of 800-pound Spectra might last 1,000 jumps or so on a small canopy that's been well cared for, Vectran lines of approximately the same rated strength might need to replaced after 600 to 800 jumps. (Spectra is also widely available in 500-pound test, but it requires much more maintenance than the stronger stuff.)
There are no absolute numbers because there are too many variables involved. As Rusty Vest, the customer service manager for Performance Designs says, "How many miles do you get out of a set of tires?" Not only does that depend on what type of tires you have, but also where and how you drive, and how well you take care of your car.
As with tire problems, the best way to avoid broken suspension lines is to take care of them and monitor their condition.
A Broken Line Can Be a Big Deal
A broken line was a factor in a fatal accident in mid-July involving an Australian skydiver with nearly 3,000 jumps.
Writing recently in Australian Skydiver Magazine, Ben Nordkamp described the accident this way:
"He had initiated a very low, aggressive front-riser hook turn to land. As he began to flare 'out of the corner' using his toggles, one steering line broke below the brake lock. Although he tried to get onto back risers to complete the flare, he impacted the ground before he was able.
"He was flying a Jedi 120 main canopy at a wing loading of about 1.8 lbs./sq.ft."
Investigators found the canopy had been relined with Vectran 11 months before, and he had logged about 340 jumps on it since then. Of those jumps, more than 100 were made near a beach.
Other jumpers told investigators they had told the skydiver "about the poor state of his steering lines, which appear to have worn rather quickly."
Nordkamp reminded his readers that Vectran wears more quickly than Spectra. "Also, it does not like contact with hook Velcro, so be careful setting your brakes."
The author also pointed out that "operating a parachute near salt and sand dramatic- ally shortens - can halve - the life of many parachute components."
Nordkamp didn't stop there: "Many parachutists get a little too complacent about main parachute maintenance, reasoning that their main is tested during deployment and opening shock, and, if it fails, it can be cut away. (But) one part of most parachutes that is not subject to opening shock are the brake lines below the brake (loop)."
Suppose a steering line breaks at altitude and the canopy is otherwise okay. How about landing it with the rear risers?
It can be done, but it's harder to do correctly than most of us realize. While the "stroke" of a steering line - the distance the toggle must move from full flight to stall - can be several feet long for a typical canopy, it takes only a few inches of pull on the risers to stall the same parachute.
When a jumper tries to land a smaller canopy using the rear risers, he typically pulls the risers down too much and too soon - and thus quickly gets dumped on the ground flat on his back.
It makes sense to practice flaring your canopy with the rear risers up high, before a steering line breaks or becomes knotted-up. You'll see that it takes a delicate pull of only a few inches to slow the canopy down to its stall point.
If you ever do land using a rear-riser flare, it's a better idea to use both risers rather than one riser and one toggle.
Looking for information on a Rawa freefly/camera helmet.
Q. I saw a freefly/camera helmet at the DZ called the Rawa. It might be from Brazil; I can't find anything else about it. Can you help?
A. We asked SKYDIVING'S photography columnist Robbie Culver to answer this one:
I've never heard of the Rawa. I'd strongly recommend sticking with an established manufacturer who you can call and talk to. Even if the camera helmet meets or exceeds your expectations, questions or problems will pop up. My experience has taught me that Sky Systems and Bonehead are the best manufacturers, and they stand behind their products. Stay away from Headhunters; I've found the quality of its helmet and after-sale support are both lacking.
Remember, you're investing in something that you'll be using as a tool, and something that may save your head if you have a hard landing (mine did). It's best to stay with a known supplier and product, even if it costs a little more or doesn't look as cool.
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