Fixed Length Closing Loop

[ChrisD 0]

This is a question:

Does your new container use a fixed length closing loop and why?

Another one:

If you change your main to one that is off the manufacturers sizing chart, what effect does this have on the main closing loop?



Many manufacturers have posted the maximium main pin force required to extract the pin, UPT, for their V3's post's it as a maximum of 12 lbs of force. This is usually measured in the line of orientation that the pin is already in, mostly from left to right considering that most BOC pockets pull from the right side....(not fair to lefties if ya ask me.)

Anyways the min force required is a hot topic. There are lots of skydivers that are under the belief that the more force required to pull the main pin the better! Now with some containers this is asking for trouble, esp if the bridal has to pull across an edge in an unstable deployment, the forces generated by even the smallest seam or sew edge can easily cause a PC in tow condition.

This then leaves many in a quandary and has created the false belief that the more tension the better...

A past repost of this topic:

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=2486560;search_string=closing%20loop%20length;#2486560

If in fact your new container has been sized for a fixed length closing loop, based upon the fact that it is of a certain size and meant to be used ONLY and I mean only with listed sized mains of a particular size,...you are off the charts so to speak by using a main that is either too small or too large compared with the manufacturers design of that container.

This stereotype is in fact so strong regarding less 'ng main pin force by length'in your closing loop, I can't wait for the factorie's response....

Your knowledge level and experience matter if you answer this one. I am not particurly comfortable with this question with begginers or anyone who is not really gear happy.

But considering the fact that skydiving is a gear dependent activity and I see large numbers of individuals that want to leave gear issues to the sole domain of "rigger's" and thus compromise their own safety as compared with learning how their gear actually works, here goes....

C

Yes this is splitten hairs and in a sense I'm askin for a decision between the risks of too tight a pin as compared with too loose a closing loop. It is my position that too many closing loops are too tight and that there is a benifite to loosening your closing loop. But yes you need to know how loose and that is the question isn't it?

If anyone want's to post their own containers min pin force or the manufacturers reccommondations specific flap adjustment procedures many or perhaps some of you will hopefully develop a deeper understanding of this issue. Making unsupported statements or referencing pictures that may or not be relevant is not the same as understanding the reasons why gear is the way it is. Differing manufacturers have differing ideas about their particular gear, we get into trouble by making broad stereotypes regarding closing loops across every brand that is out there...



Here is one example of the main closing loop being of fixed length:

http://www.sunpath.com/resources/Main-Closing-Loop-Length.pdf

This is from the manufacturer....


You might also want to dig up the 2010 piece from Parachutist...

But what do I know, "I only have one tandem jump."

[gowlerk 2,266]

  Quote

Does your new container use a fixed length closing loop and why?

I'm not sure what you mean by a fixed length closing loop. They are all fixed by the placement of the knot, until someone ties a new knot. Closing loops are expendable items that need to be replaced often, and at the first sign of any damage at all. Which means that length will usually get changed at least somewhat every time the loop is changed. Is there some new type of loop that I just don't know about yet?


As far as the risks of a too tight versus a too loose tension on the main pin goes, I'll just say this. Too loose can and has caused premature deployments with all the potential consequences up to and including the loss of aircraft and multiple lives. Too tight could potentially cause a p/c in tow. I know which one I'd prefer to deal with.

I have personally never seen a main pin too tight. I've seen many too loose. Try to keep this all in perspective.

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

[pchapman 279]

To clarify, ChrisD is talking about rigs where

(a) there's a specific recommended length in the manual (eg, Vector III)

and/or

(b) the loop is anchored at the bottom flap so has limited ability to change in length to accommodate different canopies

I for example have a Vector II which in contrast anchors the loop on a small tab the reserve pack tray. Depending on the canopies I put in it on a given day, the loop can be 1 1/2" long or 5" long. That's the kind of rig I personally like. (Although obviously a Vector II is behind the times in other ways, and there are better and worse ways to anchor loops up by the reserve tray.).

ChrisD:
Usually the big fight in skydiving is to get main closing loops that aren't too loose. I haven't generally seen the issue of loops that are too tight, but you are welcome to take a look at that situation...

[gowlerk 2,266]

Thanks, now I get it. That setup leads to loose pins if the canopy bulk is not enough. I think they went with it to lessen the risk of lines snagging on loose grommets. Another design compromise and another compatibility issue.

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

[gowlerk 2,266]

  Quote

Here is one example of the main closing loop being of fixed length:

http://www.sunpath.com/...sing-Loop-Length.pdf

This is from the manufacturer....

I would note that these instructions are a "recommendation" only and assume that sizing is also following recommendations. This type of closing loop is mounted to the bottom of the reserve tray and can easily be longer if a larger canopy is fitted.

I interpret this more as an instruction to use appropriate sized canopies. Not as an indication of what pin extraction force should be.

The only time I've seen P/C in tow arise from a pin that would not extract was caused by a lever effect due to the geometry of the pin, the bridle and a stiffener. No reasonable amount of force, including a sharp pull on the ground after the reserve ride would budge the pin. Although several people looked at it and could see nothing wrong. (Including SDAZ's safety officer) I have never heard of a mal caused by a short closing loop.

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

[Southern_Man 0]

  gowlerk

I have personally never seen a main pin too tight. I've seen many too loose. Try to keep this all in perspective.

Yes, I work as a packer. Usually when a jumper is complaining that the loop is too tight I can pull 2" of closing loop through the last grommet (by using good technique, not by just horsing it closed).

"What if there were no hypothetical questions?"

[GLIDEANGLE 1]

Regarding closing loops that are too short/too tight:

Yes, it is probably uncommon... but doing CReW with sub-terminal openings I have had closing loop too tight which resulted in LONG openings. This was because I had switched main canopies and the CReW canopy packed bigger (no D-bag).

The choices we make have consequences, for us & for others!

[sundevil777 102]

  Quote

I think they went with it to lessen the risk of lines snagging on loose grommets.

Since such snagging incidents happened, at least some (all?) rig mfgs have taken the easy step of covering the grommet with material to eliminate that problem completely. It doesn't take moving the loop anchor position to remove that hazard. Older rigs that are still vulnerable to this could be easily modified I would think.

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

[ChrisD 0]

  gowlerk

I interpret this more as an instruction to use appropriate sized canopies. Not as an indication of what pin extraction force should be.

Thank you for this.

You put in a downsized canopy, and now the main loop force feels "light." So someone shortens the loop as much as possible. You’re not really compressing the container as much as stretching the loop to its max! The individuals pulled so hard that the loop actually pulled thru...

In the other example the loop was so short, the side flaps clearly were pushing against the top flap closing protector, the user was hitting with their fist to get the flap to close, or get it flusher, this was causing unusual wear on the side flaps and the top cover. To the point small indentations and some minor fraying were taking place. Yes, I wish I took a picture. But I was traveling. The small indentations, if the bridal did anything other than a normal stable pull, now faced the prospect of having to slide thru the top cover. Normally the top cover would just open or move out of the way, but with the indentations and small groves in it because over time the side flaps now had matching indentations, the force to open the top flap was greatly increased! All you have to do to duplicate this is just pull your PC from the left side to see this effect.

So after seeing this, I now notice every V3 and Micron from a distance as well as more than a few Icons, you can clearly see the side flaps pressing on the top cover, or how the top cover doesn't fully seat into its slot, because it is clearly bowed, from about ten feet away!

The individuals, the few that I questioned, clearly didn't have a clue, and all mentioned main loop tension as the "important" factor...They were clearly unaware of the manufacturer’s instructions, and in Sun path’s case these instructions are on the front page of their respective container manuals. Clearly the message regarding having a particular size container and a matching particular size main aren’t getting the attention it deserves.

There are more than a few of us that use large knots on our closing loops, we can debate this till the cows come home, under normal circumstances I will always recommend others to use a washer, but if I'm going to make a large knot now I have to look out for overzealous packers that like to use enormous forces, enough to pull a large knot thru a small grommet, which is what my Micron is fitted with. Literally we have all seen others pack with those tools, and frequently use their feet against the container and both arms. So you can see if someone willy nilly shortens my or anyone’s loop without understanding what they are really doing????? Again the loop is fully hitting flaps and isn’t compressing anything! Literally the loop tension is increased because it is being stretched between two fixed points!

The 2010 Parachutist article mentions this, but the large numbers of individuals shortening their loops to the point that the top flap can’t fully close because the side flaps hit is because so many believe that more tension on the knot is the way to go...


As far as the worry about pin tension being too light, caution is always a great idea, but how much is too light? And how do the vast majority of individuals judge this tension? It's not like we have main bags just falling out of the container on a regular basis just because? Do a simple test like sitting sideways in a PAC it don't matter if the pin force is 20 lbs or 2 lbs, you can't tell when your container has hit something or not! And the strange belief that somehow the pin is going to fall out by itself just isn't based upon any facts. Most of these rigs in question have everything fully covered.

But this is a main closing loop tension discussion considering the large numbers of individuals that are making decisions without any factual basis! People are judging the closing loop tension without reading the manuals. And in the case of these fixed loop rigs they are in fact doing things that have consequences. In a sense the tension is determined by the proper canopy. These loops are not adjustable. Main loop tension is a function of design and the correct canopy. Some manufacturers in order to get this point across are sewing the sizing chart into their rigs!

So when I see individuals ignoring the obvious in favor to do what they “think” is the right tension because they have always done it “that” way I get concerned! Especially when a number of riggers I have met haven’t a clue regarding the cover and flaps hitting, the lack of continuing education is quite disturbing considering this issue has been around well before Nick wrote the article in 2010.

But what do I know, "I only have one tandem jump."

[ChrisD 0]

  Southern_Man

***
I have personally never seen a main pin too tight. I've seen many too loose. Try to keep this all in perspective.

Yes, I work as a packer. Usually when a jumper is complaining that the loop is too tight I can pull 2" of closing loop through the last grommet (by using good technique, not by just horsing it closed).


If your speaking about a properly tensioned V3, especially the larger ones, yes you can easily pull a lot more loop thru. But if your not aware of the relationship between the cover top and the side flaps....then it's your opinion how tight is tight or not. And this is the crux of what I'm try ing to point out. Now if you, in the case of just one manufacturer, and basically that's all folks, just one manufacturer has posted the min tension recommended, want to quantify your reasoning somehow....then you might see how the stereotypical attitude of tighter is better than just making the statement "I've seen many too loose." What exactly do you look for when a pin is too loose? I mean if you were to stand up with the rig on and by gravity the pin falls out, I would consider that to be too loose, but short of that how does one make this call?

Thanks for your comments, you did illustrate that being able to pull cord is not related to tension or proper function.
C

But what do I know, "I only have one tandem jump."

[pchapman 279]

That post clearly stated the issue you saw, about main side flaps being pulled in so far that they wear on and restrict the movement of upwards-folding pin cover flaps.

I'm curious whether others have seen the problem much too.

You mentioned Icons in addition to Vector III's. I see in the Icon manual they call for 4 to 6 daN of force, which they don't translate into Imperial, but which is 9 to 13.5 lbs -- Just as a comparison to what others call for.

The Icon though uses a reserve tray mounted loop, and the manual says nothing about not lining up the container grommets. So I'd guess that for an Icon, if the side flaps are rubbing on or interfering with the pin cover flap, that's more a problem with the design, than misuse by the user.

But the Vector III is a different case, as it is designed to be used with grommets not lining up. I can't recall, are there any other rigs like that?

Even in the manual, showing a good pack job, the side flaps do touch the main pin cover flap, as seen in the photo here. So a little bit of wear is possible, and any over-shortening of the loop will certainly cause more contact.

[inline v3-pin-cover-in-manual.jpg]

[ChrisD 0]

You worry me sometimes,....
You can also see that the picture shows a minor bow in the cover flap as well. So much for pictures, perhaps they will make a change?

Ditto your thoughts on the Icon. And considering the Reflex past issues the whole subject of offset grommets sounds like a good idea, which is why I suspect the UPT people incorporated this into their design. Which is my concern regarding something a manufacturer does, that the user "undoes."

Here is the 2010 article :

http://parachutistonline.com/safety_training/ask_a_rigger/closing-loop-length

What concerns me, on a number of different levels, is the reference to the instructions that indicate the "loop needs to be adjusted so that the flaps align properly."

Too much and the cover can bind, too little and you might make a number of people concerned that their isn't enough tension on the loop because it's not what they are used too. Put in a un-recommended main, and now your a test pilot...your stretching the loop not the container.

So is having offset grommets a good idea? I think it is. It increases the reliability of the container, right up until you run into individuals that have missed the requisite knowledge and do their own thing....

I think the V3 is the only one at the moment that this feature is that obvious.

I just don't want to see any incidents caused by packers that are trying like heck to get the grommets to line up on a micron because that's the way its always been done....

And as always this whole flap issue, reserve as well as main, as you have pointed out in the past is a touchy one considering reserve deployment speed.

Once again it's this effort to get users to understand their gear at a level that they have hereto been unaware of that increases safety for everyone.
C

Thanks man....

But what do I know, "I only have one tandem jump."