Why do sliders have different size grommets (related to "A first look at a no pull cypres save")

[3mpire 0]

In the A first look at a no pull cypres save thread davelepka said:

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Let's face it, there is no requirement to pull your slider down past your toggles. If a jumper is going to adopt the practice, they need to be experienced and aware enough to do it properly (before unstowing the brakes) and still maintain the same margin of safety as someone who is not pulling their slider down.

Talking about this incident with other jumpers, we speculated as to whether the diameter of the grommet on the slider in the incident was a contributing factor.

I'm not in the habit of pulling my slider past the toggle stows, but it would seem that larger grommets would present less of a snag hazard or would be easier to clear.

The question I have is: why do sliders have different size grommets? Is there a reason why some are larger than others (does it affect opening, line wear, etc.)? If a smaller diameter grommet increases the risk of a stuck toggle, is there some kind of benefit to the smaller grommet that outweighs the risk?

[gowlerk 2,253]

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why do sliders have different size grommets?

They don't. At least not commonly on modern canopies. I'm sure there are exceptions for RDS systems and such, but almost all sliders come with size #8 grommets. The newer stainless ones have a slightly smaller inside diameter, but they are basically the same as the brass ones for size.

Different types of risers can be easier or more difficult to get past grommets. Some are not possible. A lot of people don't want their slider to ever go below the links. Which is the safest way to go. When you pull your slider down you are creating possibilities for several different problems. More than I am aware of probably.

Ken

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[3mpire 0]

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At least not commonly on modern canopies.

I guess that is where my knowledge of gear history is limited--I believe brass grommets are larger than stainless, but I don't know when brass stopped being used.

Is there a reason why the #8 is the standard?

[gowlerk 2,253]

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Is there a reason why the #8 is the standard?

Probably because it works well and is cost effective for tooling. Canopy makers intend for the slider to stay at the links like most people want. Those of us who pull it down are not following the recommended procedure. If they used larger ones they would come down past the links when it is not wanted. Making brake toggles fly off and inducing other problems that I haven't thought of yet. Even if you do want to pull it down, you will want to be able to decide when. You don't want the quickly descending slider to continue past the links until you are ready for it.

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[3mpire 0]

It makes a lot of sense that the slider should stop at the links during deployment rather than being forced down the riser and past the stowed toggles. I hadn't thought of it that way--thanks

[wmw999 2,545]

Sliders started when canopies either had old-style L-links, or metal links -- there weren't any soft links. The grommet size was dictated, most likely, by the size (large) of the lines in use at that time, and was chosen from what was reasonably easily available. Risers were all the wide kind. The thought of the slider coming down over the risers hadn't occurred to anyone (of course, most people weren't concerned about "parasitic line drag" either ).

Stainless is harder than brass, and it doesn't discolor the lines. It's a far more recent innovation.

I have a feeling that #8 grommets work well enough that no one feels any particular need to change it.

Wendy P.

There is nothing more dangerous than breaking a basic safety rule and getting away with it. It removes fear of the consequences and builds false confidence. (tbrown)

[sundevil777 102]

Paraflite used much smaller grommets for their SwiftPlus reserves. I don't know if any of their other canopies did the same.

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

[3mpire 0]

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Risers were all the wide kind. The thought of the slider coming down over the risers hadn't occurred to anyone

It hadn't occurred to me that the larger grommet would have coincided with larger risers but that seems very logical. Same behavior (slider stopping at links) just different size/scale.

[gowlerk 2,253]

A quick incomplete history, bearing in mind that I am not Dan Poynter, and although I'm an old guy, I only started jumping in '92.

When sliders were invented, ram air canopies became much more practical. Early sliders used various rings in the corners and many different configurations. Enough about that.

For many years the combination of #8 brass grommets, risers made of type 7 webbing, and #5 rapide links where the norm. The grommets had a nasty habit of slamming into the links and becoming damaged, which would lead to line damage from rough edges. So slider bumpers were added to protect the grommets.

Then, at roughly the same time things started evolving. Canopy makers introduced stainless steel grommets which are very hard to damage and create sharp edges. As well light spectra lines started to replace much thicker and less easily damaged Dacron lines. And canopies went faster. People wanted less drag and smaller type 17 risers along with skinny lines helped with this. Then with smaller size 3 and 3.5 links and thin risers you could pull the slider past all your controls and tuck it away behind your head. (Carefully) This stopped the annoying noise and parasitic drag of the ZP slider flapping in the breezed caused be the speed of the new rocket ship canopies.

Then came popular new soft links. No more grommet damage. And now people who did not want to deal with stowing the slider had the problem of having the slider come down and interfering with the toggles. This problem is solved with slink hats, which are essentially slider bumpers all over again, but for a different purpose.


Ken

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[councilman24 37]

#8 brass rolled rim spur washer is the biggest grommet generally available. Anything bigger that I've found are different in design.

The stainless grommets are more expensive and require a press to install. They can't be installed by hand.

So stainless is not standard. It's usually an option. I believe the stainless grommets uses are also the biggest available. But I can't find my link to the source.

Until type 17 1 inch risers were offered pulling the slider down was not an option. There were several designs of split sliders that could be released in to two halves to accomplish the same thing.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[3mpire 0]

Thanks for the summary, it's really interesting to me how there are cycles where certain designs/techniques come and go and then come back again when it comes to gear.

I wasn't familiar with slink hats, but I like the idea. I did have a brisk opening sometime last season where the slider came down pretty quick and dislodged one of my toggles.

The toggle did wedge in the grommet, however, so it wasn't a full toggle fire. It was enough to put me into a lazy turn, but no biggie. I easily cleared the toggle from the grommet and released the other toggle without incident.

Since all I do is collapse my slider and never pull it down, maybe slink hats would be something I should ask my rigger about. Seems having something like that in place would nearly eliminate the risk of having a toggle stuck in a slider, which was the cause of the incident in the original thread.

It might also have the added bonus of helping to keep my slink tabs from working their way out, which they have a habit of doing.

[3mpire 0]

How about tandem rigs? I seem to recall seeing a grommet on a tandem slider that looked to be much wider, though to be honest I've never really closely inspected a tandem rig to see exactly how big the risers/grommets are in comparison to most sport rigs.

Is it possible for a slider on a tandem rig to go past the links or is the riser large enough to prevent it (or a stopper perhaps?)

[skytribe 17]

I don't believe that any of the tandem system manufacturer build canopies which are intended to stow the slider behind the jumper and therefore they probably should not be setup to allow this to happen. So would probably have some form of bumper/stop.

That being said soft links do provide some advantages and SOME tandem system / parachutes allow slinks to be installed. These are different from the normal sport versions (I believe they use a stronger line in there manufacture).

http://parachutistonline.com/safety_training/ask_a_rigger/soft-links-regular-links

http://www.square1.com/manufacturers/square1/p870.asp


The grommets may look bigger because we are so used to seeing spectra,vectran or HMA lines.

[3mpire 0]

On that first link I noted at the end that you can tack your slink's locking tab in place -- I think that's what I need. What is the risk of having the tab exposed? Increased wear or risk of outright slink failure?

[gowlerk 2,253]

You can have a line snag the tab if it gets outside. The slink will take a set after a few jumps. You need to "train" it to take a set that keeps it inside. If it develops a set that is wrong you may need to push it back in and then use super tack to close the webbing and trap it there until it takes a new set. Do not sew the tab. Ask your rigger if need be.

Every package of PD main Slinks comes with a set of hats. You can probably ask your rigger for some of those as well. They usually have some spares because a lot of people don't use them. But you need to remove and reinstall the Slinks to install the hats.


Go here, near the top you will find Slink instructions. And lots of other cool stuff to read.

http://www.performancedesigns.com/support.asp?filter=sport

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[skytribe 17]

Its normally rotated so that the ring/tab is inside the hidden within the riser. For most manufacturers, it is not required to tack it down.

In fact I'm looking at the PD slink instructions which make no reference to tacking down. Simply states "Tuck tab away"

That said, with the slink being approved under a TSO C23d. The installation should be done in accordance with manufacturer's instructions. Whether container, parachute or slink. The PD instructions do not then require it to be tacked and I may have reservations about doing some of these modifications without manufacturer explicitly stating this.

Precision wrap-it links and Flight Concepts Cinch links also do not mention tacking them.

Aerodyne do specifically detail tacking in the icon manual but and installation instructions.

The interesting statement for aerodyne is
"The Aerodyne reserve soft link, commercial part number C148510000 and technical part number P1487-01 has been tested and received a TSO C23d approval as a separate component. Consequently appropriately licensed parachute technicians can legally assemble the Aerodyne reserve soft link in combination with other TSO-ed parachute components."

So my view would be that as a separate TSO'd component you definitely do what manufacturers state. If they say tack it you do it. If they don't you don't or contact the manufacturer to determine if this is acceptable.

As to the potential problems, if it comes out then it can potentially snag something and I suppose could get more wear which could lead to a failure. Although I think this is unlikely.

Is it rotating and coming out ?. If it has, have you rotated it back in and it occurred again. If its not coming out then I would question whether you need it.

The fact that its not stated by the manufacturers in there installation instructions is probably a good indication that tacking is not required.

[gowlerk 2,253]

I didn't say to tack it. I said "do not sew the tab" What you can do is to apply some tacking to the riser to keep it closed and the tab trapped. It is not normally required, but if you have made the mistake of allowing the Slink to take a set that keeps the tab outside this is one way of helping it to take a different set.

Only Reserve Slinks are approved under any TSO, not main ones. And yes, if it is not coming out there is no problem. However that's not what he is asking about. He is asking about what to do about some that are.

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It might also have the added bonus of helping to keep my slink tabs from working their way out, which they have a habit of doing.

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[riggerrob 643]

sundevil777

Paraflite used much smaller grommets for their SwiftPlus reserves. I don't know if any of their other canopies did the same.

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Yes.
Para-Flite used aluminum #5 grommets on their (5-cell) Swift reserves.
I cannot remember seeing grommets that small on a Para-Flite main???
I vaguely remember seeing #5 grommets on a square main made by National, but National did not build very many square canopies and they quit before ZP fabric became fashionable.

[riggerrob 643]

I hand-tack all soft links, from every manufacturer.
This helps prevent a repeat of Koji's accident.
The hand-tack also backs up the lark's head knot to prevent the soft link from releasing.

[riggerrob 643]

3mpire

On that first link I noted at the end that you can tack your slink's locking tab in place -- I think that's what I need. What is the risk of having the tab exposed? Increased wear or risk of outright slink failure?

...................................................................................

Two soft links have failed in the USA.
The first failure occurred shortly after soft-links hit the American market, during the last 1990s. It was blamed on a brass slider grommet that had a sharp edge. The slider grommet had been damaged by hitting a metal link too many times. When they installed soft-links, they did not bother to inspect the brass slider grommets and ignored a rough edge that eventually cut the tab off the soft-link.

Koji's accident occurred a decade - or so - later. Koji did a thousand or so jumps on a main canopy, without inspecting it. A frayed soft-link failed when he was too low to deploy his reserve.

[Deyan 36]

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On that first link I noted at the end that you can tack your slink's locking tab in place -- I think that's what I need. What is the risk of having the tab exposed? Increased wear or risk of outright slink failure?

This or worse

http://www.youtube.com/watch?v=2sAr8PiJiVI

"My belief is that once the doctor whacks you on the butt, all guarantees are off" Jerry Baumchen

[councilman24 37]

They had aluminum grommets on the toggles that came with them but the swift plus has #5 nickle, (at least the one in I'm packing right now.) I don't remember the 5 cells but I have one some where.

There is a number 10 brass grommet that might have been used. I haven't done much with tandems so don't remember.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[BeteNoire 0]

riggerrob

Two soft links have failed in the USA.

How does that compare with the record of steel links?

[theonlyski 8]

Something else worth noting:

I had a difficult time pulling my slider down past my toggles because the way UPT has their excess brake line stowed on the front of the rear risers, the little bit of Vectran line going around the side of the risers was enough to make it more difficult to pull the grommets over it.

I got tired of it, removed the excess stow loops from the front of the risers and put them on the rear of the risers, it's much easier to pull the slider down now, and it doesn't wear the line nearly as much as it did for the 'other side of the riser' stowing. I had to replace the Vectran lower portion from all of the wear, I replaced them with Dacron and haven't had any wear at all since.

"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

[riggerrob 643]

councilman24

They had aluminum grommets on the toggles that came with them but the swift plus has #5 nickle, (at least the one in I'm packing right now.) I don't remember the 5 cells ...

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There were #5 aluminum grommets on the slider of the last Swift 5-cell that I packed. It was sewn by Parachute industries of South Africa.