Semi-Stowless Bag

Q:

 

What is a semi-stowless main bag?

A:A semi-stowless main bag is just what its name suggests: a deployment bag for your main canopy that uses only two or three rubber bands as locking stows but doesn’t use additional bands for stowing the remaining suspension line. Jumpers who have this type of bag fold the additional line neatly into a pouch that closes up against the bottom of the bag. During deployment, the unstowed line extracts from the pouch until it reaches full line stretch, then the locking-stow bands pull free and allow the main bag to slip off of the canopy.

Semi-stowless main bags have now been around for more than 10 years and are starting to gain in popularity. Almost every container manufacturer now offers a version of the bag. If you are worried that 10 years of use in the field is not enough time to test a deployment bag, fear not: Manufacturers have used the same type of system for reserve freebags for more than 30 years.

Even after 10 years of success, some still incorrectly claim that semi-stowless bags create “line dump,” a situation that leads to explosive openings when all the lines “dump” from the bag at one time. Semi-stowless bags don’t create line dump, which is really an incorrect term for what is actually “bag strip,” a situation that occurs when sloppy packing leads to all of the line stows—including the locking stows that hold the bag on the canopy—releasing simultaneously at the beginning of the deployment sequence.

In cases of bag strip, as the pilot chute lifts the bagged main canopy out of the pack tray, some or all of the line stows release simultaneously, and the main bag comes off of the canopy while the suspension lines are still slack. The canopy is now free to begin to spread out and push the slider down the lines. The result is a canopy that opens instantly while the suspension lines are still slack because the slider can no longer do its job of slowing the opening. The semi-stowless bag is not immune to this type of deployment, but as long as the locking stows are the correct length and the rubber bands hold them in place during deployment, the main bag will stay in place around the main canopy until the suspension lines fully extract from the pocket. Once the suspension line pulls out of the locking stows on the bag, the bag comes off the canopy and the canopy begins to inflate with the slider still in the correct place, which slows down the main canopy’s inflation.

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On a semi-stowless bag, the suspension lines pack up in a pouch at the bottom of the deployment bag.
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Sloppy packing may have led to this developing case of bag strip (on a traditional deployment bag).

Additionally, semi-stowless bags may reduce the chance of an off-heading opening. Traditional bags hold the main portion of the lines with rubber bands that release one stow at a time from opposite sides of the bag, which can cause the bag to rotate on deployment. Semi-stowless bags release the lines symmetrically from the center of the bag, which minimizes the chance the bag will rotate.

Semi-stowless bags have won the test of time, proving to be both reliable and durable over many thousands of jumps in all sorts of conditions. If you are tired of constantly changing broken rubber bands and are looking for help with on-heading and soft openings, a semi-stowless deployment bag might be just what you are looking for.

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

Comments

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Alvaro
Wed, 05/20/2015 - 10:03

Hi, thanks for the explanation. Definetly I´ll go for this system on my next gear. I just have a doubt, the difference between stowless and semi-stowless is just the number of rubber bands? So the stowless has no rubber bands? any advantages?

I´m about to buy a gear but can not choose between stowless or the semi.

Thanks.
Cheers,
Alvaro.

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