"Tubular Retainer Band Failures" PIA advisory (for tube stow style elastics)

[pchapman 279]

I got the PIA email so thought it should be mentioned here:

There a new bulletin on testing retaining bands that are made of natural latex rubber tubing glued shut.

That sounds like Tube Stoes (old name) or Tube Stows (new name).

Technically it is an "Informational Advisory" from the PIA, not a mandatory bulletin or anything from any manufacturer.


https://www.pia.com/images/rocketlauncher/PDF/SERVICE_BULLETINS/TubularRetainerBands8-3-18.pdf

Noteworthy:

Quote

Numerous reports of failed TRBs from worldwide sources indicate that both newly manufactured TRBs as well as older stock are failing at the glued overlap and other locations along the tubing.

Recent independent testing has shown that natural rubber latex (NRL) tubing is adversely affected by UV light, ozone, excessive heat and age. As a result of this testing, at least one company has initiated a 2-year product shelf life and ships their TRBs in sealed UV resistant packaging with DOM clearly marked to help ensure consistent performance.

The test to be done is to pull to at least 25 lbs (12kg) for 5 seconds, and pull to 9 to 12 inches elongation depending on stow size. The test isn't technically intended for ones you have in use, as they say to not make parachute rigging use of any that are tested.

My comments:

Not included in the advisory would be elastics like Silibands & Silirings that appear are moulded with no seam, and are also not natural latex rubber but are silicone based.

I would guess that in practice people using stows will probably just adopt a less destructive and formatl procedure and give the stows a good yank and double check that they are not all abraded and close to failure.

I do notice that older tube stows change colour to a darker brownish colour as they age. Storing spare ones in cool conditions away from light seems better. Regular elastics also degrade over time, but if well stored can be in pretty good shape for many years.

How much to trust old stows is a bit more up in the air now. The whole point of using stows rather than regular elastics is that their life may be 100+ jumps rather than a just a few, especially when doing the stows at the mouth of the bag.

[sundevil777 102]

The glued junction doesn't get any real stress if you just install them to be at the base of the larkshead. It has always seemed obvious to install them that way. Glue is actually not needed at all, as I have made my own in years past from silicon tubing.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[pchapman 279]

Good points. The friction in the lark's head should reduce the stress on the joint, and I also placed the joint in that area when using Stoes. Someone did once publish on the web his method of building the stows at home.

[sundevil777 102]

Quote

Someone did once publish on the web his method of building the stows at home.

I have made many of my own tube stows from the bulk silicone tubing I used to be able to find in the fishing section of sporting goods stores.

Use a pair of needlenose pliers to turn one end over about 5mm. Insert the closed pliers into the other end and open the pliers to expand the tubing. Now take a pair of hemostats to grab the turned over end of the tubing and insert it into the opened end. Carefully slide the tubing off the pliers and you're done. No need to glue anything.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[Westerly 61]

Or you could just use rubber bands like most people. The tube stows always worried me a bit because they are much stronger than a rubber band. It's pretty well known a good PC can easily break a rubber band, but a tube stow is less clear. It seems like a tube stow could increase your chances of a bag lock if one bight of line were to wrap inside another.

[sundevil777 102]

Quote

Or you could just use rubber bands like most people.

Yes, that is a possibility, or perhaps most people don't appreciate the benefits of a locking stow that is so much less likely to break, and they have fallen for the prevention of bag lock story.

John Sherman didn't trust a couple rubber bands when designing the speed bag, he made every band a locking stow. This is for a good reason - individual bands are unreliable. The bands have to withstand the most force right at the time it is most important, during the acceleration of the bag out of the tray. I do not trust traditional rubber bands for that.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[tripp9r 2]

sundevil777

The glued junction doesn't get any real stress if you just install them to be at the base of the larkshead. It has always seemed obvious to install them that way. Glue is actually not needed at all, as I have made my own in years past from silicon tubing.

And thats the way theyre supposed to be installed... Thats written in evry manual u get with those tube stows.
Just one more time of "rtfm".

For me its like saying that a ur cutaway handle might malfunction if u dont route the the teflon cable through the housings.

[pchapman 279]

Westerly

It seems like a tube stow could increase your chances of a bag lock if one bight of line were to wrap inside another.

That has been a common concern.
I figure the issue is minimized if using tube stows only for the mouth of the bag, where the 2, 3, or 4 stows tend to be well separated -- not like the rest of the stows lined up side to side.

Also, I'd rather have a bag lock than explosive opening.
Of course maintaining one's stows is important, but if they break every few jumps (eg double wrapped mouth stows with elastics in some cases), then the maintenance hassle is less if using something that breaks less often.

[koppel 4]

pchapman

Also, I'd rather have a bag lock than explosive opening.

the damaged discs in my neck agree with you

I like my canopy...


...it lets me down.

[sundevil777 102]

Quote

Also, I'd rather have a bag lock than explosive opening.
Of course maintaining one's stows is important, but if they break every few jumps (eg double wrapped mouth stows with elastics in some cases), then the maintenance hassle is less if using something that breaks less often.

Quite right.

If rubber bands on the critical locking stows are breaking every few jumps, then it seems likely that occasionally they are breaking before line stretch. They could even be breaking while in the container. After installing a new rubber band, it all too often will show cracks when stretched for the first use.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[flyhi 24]

Quote

if you just install them to be at the base of the larkshead

What are you calling the base of the lark's head knot? Is it the red box portion?


Thanks and sorry about the pic. Was in a hurry before my boss came in.

Shit happens. And it usually happens because of physics.

[Westerly 61]

sundevil777

Quote

Also, I'd rather have a bag lock than explosive opening.
Of course maintaining one's stows is important, but if they break every few jumps (eg double wrapped mouth stows with elastics in some cases), then the maintenance hassle is less if using something that breaks less often.

Quite right.

If rubber bands on the critical locking stows are breaking every few jumps, then it seems likely that occasionally they are breaking before line stretch.

Not necessarily. It depends on why they are failing. For example, awhile back I was puzzled as to why I would put on a brand new rubber band, double stow it, and the come down with two broken, new rubber bands. I found out that when I was double wrapping the bands occasionally I would turn the bag to put between my legs and I would put a twist in the band in the wrong direction. In other words, I'd put a clockwise twist in the band to stow the lines, then a counterclockwise twist as I turned the bag to put between my legs. The end result was a knot in the band that made the stow impossible to release and the PC would have to break the band to get the stow off. Once I figured out what the issue was I corrected it and I havent had problems with failed bands since then. Because I was using rubber bands, I dident even notice the issue. The parachute opened just as fast as normal. However, if I was using tube stowes and I did that, I may have had a bag lock (not that anyone double wraps tube stows).

[sundevil777 102]

flyhi

Quote

if you just install them to be at the base of the larkshead

What are you calling the base of the lark's head knot? Is it the red box portion?

Thanks and sorry about the pic. Was in a hurry before my boss came in.

Yes, correct.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[sundevil777 102]

Quote

I found out that when I was double wrapping the bands occasionally I would turn the bag to put between my legs and I would put a twist in the band in the wrong direction. In other words, I'd put a clockwise twist in the band to stow the lines, then a counterclockwise twist as I turned the bag to put between my legs. The end result was a knot in the band that made the stow impossible to release and the PC would have to break the band to get the stow off.

I would like to understand, but can't from that description.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[Westerly 61]

sundevil777

Quote

I found out that when I was double wrapping the bands occasionally I would turn the bag to put between my legs and I would put a twist in the band in the wrong direction. In other words, I'd put a clockwise twist in the band to stow the lines, then a counterclockwise twist as I turned the bag to put between my legs. The end result was a knot in the band that made the stow impossible to release and the PC would have to break the band to get the stow off.

I would like to understand, but can't from that description.

Start by single stowing the band. Then instead of grabbing the band and wrapping it around a second time, your grabbing the band, twisting it 180 degrees, and then wrapping it a second time which creates a knot in the band. In my case, I was not twisting the band 180 degrees, I was spinning the bag 180 degrees, but the end result is the same.

[sundevil777 102]

Westerly

***

Quote

I found out that when I was double wrapping the bands occasionally I would turn the bag to put between my legs and I would put a twist in the band in the wrong direction. In other words, I'd put a clockwise twist in the band to stow the lines, then a counterclockwise twist as I turned the bag to put between my legs. The end result was a knot in the band that made the stow impossible to release and the PC would have to break the band to get the stow off.

I would like to understand, but can't from that description.

Start by single stowing the band. Then instead of grabbing the band and wrapping it around a second time, your grabbing the band, twisting it 180 degrees, and then wrapping it a second time which creates a knot in the band. In my case, I was not twisting the band 180 degrees, I was spinning the bag 180 degrees, but the end result is the same.

The "grabbing the band, twisting it 180 deg, and then..." part isn't unusual, if after twisting the band, which causes you to have a "loop"you then pass over the line bite.

I think the problem you've described is in how I see some people wrap the band around a line bite (byte?) as if the band were loose at one end and you needed to wrap the loose end around the lines twice. I noticed this a while back, some young jumper wrapping the band around the bite (as if wrapping a piece of tape around the line bite). It had never occurred to me to do it this way. Instead I've always placed the loop of the band over the bite of the line, then twisted the band 180 deg to make a new loop that again gets placed over the bite of the line. There is no "knot" that results if this is done, but the other way of wrapping the band around the bite definitely seems faster.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[gowlerk 2,190]

Bight, it’s a nautical rope term.

[sundevil777 102]

gowlerk

Bight, it’s a nautical rope term.

One must do one's bights right, especially if they're tight.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[Elpnor 5]

Anyone ever double wrap the large silirings for the locking stows? I've never had one in my hand and have no idea the length or the elasticity of one. But I do like my locking stows to be solid. Regular large rubber bands seem to fray and break too easily.

[tripp9r 2]

No need to... Just use smaller ones for the locking stows.

[Veis 29]

We made and sold about 3000 tubular rubber shows per season, cheap (about $ 5 installation kit) - and carefully waited for feedback. There were few reviews, one of them: 250 jumps were made, not a single break of the stow. I think the experiment was successful...

[sfzombie13 324]

On 8/7/2018 at 12:09 PM, sundevil777 said:

I have made many of my own tube stows from the bulk silicone tubing I used to be able to find in the fishing section of sporting goods stores.

i tried that last year and they didn't work.  wrong kind of tubing.  do you know the name of the tubing that you used or if it even has a name?  i have tried three different kinds, and they all seem to use the wrong kind.  on the plus side i now have a stock of tubing if i can find a use for it.

[Veis 29]

1 hour ago, sfzombie13 said:

i tried that last year and they didn't work.  wrong kind of tubing.  do you know the name of the tubing that you used or if it even has a name?  i have tried three different kinds, and they all seem to use the wrong kind.  on the plus side i now have a stock of tubing if i can find a use for it.

3-6мм from China. It stretches perfectly, the main is a reasonable causticness of the glue, so as not to damage the material deeply

[pchapman 279]

On 8/9/2018 at 3:29 PM, Westerly said:

Not necessarily. It depends on why they are failing. For example, awhile back I was puzzled as to why I would put on a brand new rubber band, double stow it, and the come down with two broken, new rubber bands. I found out that when I was double wrapping the bands occasionally I would turn the bag to put between my legs and I would put a twist in the band in the wrong direction.

Since this 2018 thread was revived:
It is interesting to consider the "two ways to double stow" issue that sundevil777  brought up after Westerly's observations.

To recap, there's the "wrap around twice like wrapping it with tape" , and there's "make a single stow, stretch the elastic, make a half twist to create a new 2nd loop, and put that over the line bight". One sees the first method, for example, in one PD tips youtube video.

I confirmed that both methods are equivalent topologically in the sense that the final result can be changed from one to the other while the elastic is in place on the lines. If you try it, you can look down at the line bight in its double stow, and move one loop of the elastic over a little and be back to the first instead of the 2nd configuration. Like sundevil said, there's technically no actual knot created. But the 'twist 180' method does seem a more secure or little more grabby, as there's more rubber band overlapping other parts of the rubber band.

Whether there's any significant effect on line deployment in practice, who knows. So far I'm not worried about  which method I use. I also tend to do the twist 180 method. Which one does will depend on what one is used to , but perhaps also likely on how tight the elastics are when trying to wrap the bights. The simple wrapping method works better for me if there's a lot of stretch in the elastic relative to the position of the lines needing to be stowed.

As for Westerly's elastic breakage issue:      I may not be imagining correctly what Westerly did. I'm not sure if he meant putting in the 180 twist, or even adding another 180 on top of that, which does change things and make it impossible to simply slide the elastics around once in place on the line bight, to change to the other configurations. That might in effect be 'tighter' and put more stress on the elastic when the bight gets yanked out of it.

[sfzombie13 324]

21 hours ago, Veis said:

3-6мм from China.

i can't seem to find tubing that feels like a real tube stow.  the tubing i have is different.  i have yet to try the ones i made but another jumper did last year and they didn't work.