Double Wrap Stow Bands

Q:

 

Should I Double Wrap My Stow Bands?

A:The latest company line from canopy manufacturer Performance Designs is, “Keep calm and double stow!” The company has even produced pull-up cords that promote the idea. Larry Liebler, tour rep for Icarus Canopies, agrees: “Double stowing your lines is nothing new, and we’ve all been preaching it for years. It’s the low-hanging-fruit prevention for all sorts of opening problems.”

Getting here is a journey that started with everyone wrapping each bight of lines with the common 3/8-inch-wide by 2-inch-diameter by 1/16-inch-thick (10mm x 50mm x 1.6mm) natural rubber bands available from most equipment dealers. These medium bands seemed to work fine, but back then, lines were fatter, more elastic and more numerous.

As lines became smaller and made of new materials that don’t stretch to absorb much opening shock, people began double wrapping their stow bands to prevent the bights from coming out too early in the deployment sequence. Many experts warned against the double wrap, saying it caused knots, line twists and possibly bag locks. Smaller “micro-line bands” the same width and thickness but only 1½ inch or 1¼ inch (38 or 32mm) in diameter came into existence. Also came the pricier, longer-lasting Tube Stoes (designed like a snake eating its tail) in several sizes, which some jumpers still prefer. Additionally, solid, round cross-section bands that promised a longer life and came in designer shapes and colors came on the market but didn’t remain on the scene very long.

A lot of packers got tired of breaking micro-line rubber bands, the extra effort required to re-install the little-bitty things and separating their fingernails from their cuticles after packing with them all day. So they went back to double stowing with the medium bands. However, many jumpers still suspected the practice. Some compromised by single wrapping the first two to four locking stows but double wrapping everything else.

A few years back, some factory reps answering questions on the boogie circuit simply advised jumpers to stick to an idea that’s remained relatively constant throughout this whole debate: Stow your lines so that they require eight to 12 pounds (3.5 to 5.5 kg) of force to extract from each bight, no matter how you get there. That left room for interpretation.

The New Gospel of Double-Stow
Now, we seem to have come full circle (well, two full circles: medium rubber bands, double wrapped). Why?

First, hard openings—killer hard openings—have gotten everyone’s attention. Double wrapping (or “double stowing,” as many call it) is certainly better at keeping the lines in place than single wrapping. It’s clear that if the lines get out early, anything goes. There’s video floating around of canopies escaping from the corners of their deployment bags with the noses beginning to inflate before all the lines have paid out.

Second, it’s about prioritizing malfunctions. PD professes that it can’t confirm that double stowing has ever caused a bag lock. Yes, there have been bag locks, but no one has confirmed that they were the result of double stowing. Also, some jumpers feel that overzealous stowing, especially in combination with other factors, can get the bag spinning into unrecoverable line twists. But jumpers can cut away a bag-locked or line-twisted canopy and follow up with a reserve pull. A serious hard opening is another beast altogether.

Third, it’s about data. Over the past decade or more, line stows have been the subject of testing, testing and more testing. Results with double stowing using medium rubber bands show better openings across the board, and the malfunctions aren’t appearing as many thought they would. Rusty Vest of Performance Designs says, “We’ve been doing the double wrap with properly fitting bags in our [research and development] department for 10 to 15 years now. In addition, all of the engineering and marketing personnel who jump outside of work have been doing the same. That is a lot of jumps with not a single problem.”

This testing has led to a better understanding of the mechanics of double stowing. As the pilot chute yanks the bag from the container, the lines pull downward on the elastic stows, elongating them. The lines can more easily escape an elongated single wrap. The second wrap cinches the lines and helps keep them contained no matter how long the elastic bands stretch. Each bight remains stowed until its turn to deploy.

Exceptions and Alternatives
When asked about semi-stowless bags, canopy manufacturers demur. Rightly so. Container manufacturers who offer the option to free-snake the lines into a pouch all have their own ideas about how to best do that. They use tuck tabs, magnets, locking stows with elastic bands and combinations of these methods. Some work better than others, and results can vary with how full the deployment bag is stuffed. Canopy manufacturers have no control over any of this.

Another point to consider is compatibility. Vest says it concerns him to see an overstuffed deployment bag packed using locking stow bands that span long distances to reach the grommets. That condition can make it impractical to double-stow. A good rule of thumb here is that you should be able to pull the grommet into contact with the base of the rubber band, even if an inch or so (two to three cm) shows after you finish making the stow. Otherwise, it might be time to consult a rigger about your container-canopy combination or just tune up your packing to get more of the canopy’s bulk to the sides of the bag.

None of this is to say that jumpers can’t continue to swear by what has been working for them all along. However, keep in mind that changing something in your system (a pilot chute, a main or reserve) or switching jumpsuits or disciplines can make a difference in your openings... and all of a sudden... wham! So, what you are doing now may be fine, but the heavy research points to double stowing with medium rubber bands. The adventurous are free to experiment.

If you have any questions, call the manufacturer of your canopy and get it from the most reliable source. It’s in both your best interest and the manufacturer’s to get that company’s canopies to open as smoothly and reliably as designed.

ASKARIGGER201507-1
Two commonly found sizes—medium and micro—of Keener-brand natural rubber bands.
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Double wrapping cinches each bight of lines until it’s time to let go.
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The need to overstretch the closing stows could be due to packing technique. These two photos depict different pack jobs on the same rig.

 

—Kevin Gibson | D-6943 and FAA Master Rigger
Rahlmo’s Rigging in Orange, Virginia

Comments

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Corey Miller
Wed, 09/02/2015 - 09:00

This is a very good article with some very relavent information. I would just like to encourage people to still change out bands that are too stretched out. When bands get stretched to their limit they will break; if they break at the wrong time they could cause a rapid deployment (although I cannot cite and incident where this was a causal factor). Bottom line, double stowing is great, but I don't recommend doing it just to keep from changing worn out bands.

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