Reserve closing loop length: measure from where to where?

[skydiverek 54]

Hi,

Quick question without suggesting an answer ;-): if the container manual says the reserve closing loop should be 4 inches long, where is the start and end point for this measurement? In other words: from where to where ?

[erdnarob 1]

Generally the length of the closing loop is measured from the washer to the end of the closing loop. But there is two types of closing loop anchorage at the bottom of the reserve container 1) with only one grommet ie the former WINGS and 2) with two grommets like the new WINGS and most of the rigs. That makes the length from washer to the end quite different.

Learn from others mistakes, you will never live long enough to make them all.

[peter.draper 0]

A well written manual should explain that. The Paratec manuals for my military equipment states from the washer to the tip of the loop. (I think this is usually the assumption, but there is nothing like clarity - especially with parachute equipment)

[riggerrob 558]

Most manuals state a "washer to tip length" for Cypres loops.

A few manuals state "pack tray to end of loop" (aka "installed") length.

A good manual will make it clear which measuring method they are using.

[iowa 0]

''wellwritten manual / good manual'' . where do you find one of those?

Keith

''Always do sober what you said you would do drunk. That will teach you to keep your mouth shut.'' - Ernest Hemingway

[peter.draper 0]

iowa

''wellwritten manual / good manual'' . where do you find one of those?

My Paratec, CPS and Airborne manuals are truly well written (all running to hundreds of pages, but if you can't find the answer to your questions in them you ain't asking the question right ;) )

[hackish 8]

Check out the Vector Manuals. They're pretty good. People don't realize the amount of work it really is to write a good manual. Jeff was the primary force behind it and he did a really good job.

-Michael

[mxk 1]

So what is it for the Vector? The manual says 4 1/2" +/- 1/2" on pages 16 and 30 (paper version) for all container sizes. From the washer or the grommet? I'm having a really hard time packing my V358 with OP-235 (standard fit) for the first time with a 4 1/2" loop measured from the washer.

I would call the Vector manual poor. Some information is missing altogether. Are we not supposed to attach the reserve pilot chute to the bridle...? I guess it's not that important because we're never told to do so or how to do it. We have to refer to a separate document for hesitator bungee installation instructions. Why? Look at the top photo on page 19 (skyhook). Think anyone might find it confusing why the magnified "To Pilot Chute" text is pointing toward the free bag? And then there are the spelling and grammar errors... I think UPT could have done a lot better.

[pchapman 261]

mxk

So what is it for the Vector? The manual says 4 1/2" +/- 1/2"

In my in-expert opinion, I find a lot of the closing loop length recommendations in manuals are optimistic....

Yeah manuals often have problems. Even from big UPT, manuals have often been way behind the times for gear and techniques, and one has to use supplemental documents. But they are getting better. One Vector III manual I have, the 30 MB MAN-004 rev 1 dated 2010, does have the hesitator loop included. I only skimmed it now but don't see a length recommendation. (They're up to rev 4, Jan 2015 now.)

I could go on about manuals. Some companies don't even show you what the current revision is (that includes UPT) on their web page, so you have to download the damn thing every time to know whether you are using the updated version to be fully legal. Idiots.

[erdnarob 1]

The needed length of the reserve closing loop is changing due the air relative humidity. When packing a reserve in a dry air (like in Canada in the early Spring), the volume of both main and reserve increases due to the static electricity forces between reserve folds and main folds then a longer loop is needed to match the increase of volume. The same rig will likely show a bulge on the reserve container due to the pilot chute pressure in July and August when humidity is at maximum. Last year with a reserve packed in the Spring, I had to change the length of the loop twice for that reason. Some rigs with apparent pilot chute crown are more subject to this problem like Wings, Dolphin and Javelin. One can see quite often the pilot chute material shown when the crown has a gap. All these rigs have been packed in the Spring with a pin minimum sliding force test of 18-21 pounds.
Now do you know the length it takes on a closing loop for a double knot ? Here is the Vigil information sheet on the subject.

Learn from others mistakes, you will never live long enough to make them all.

[mxk 1]

Given that a container lock is a possible outcome of an AAD fire with a loop that's too long, you'd think that UPT would spend a bit more effort covering the subject. I finally managed to close my container using a 5 1/8" pre-stretched loop, which is outside the spec. I'll do some testing later this week and then repack everything, but I'm not sure what else I can do to get the loop under 5".

[pchapman 261]

Is loop length even mentioned in more recent manuals? I don't recall seeing it.

It doesn't matter whether the loop is long, it matters whether there's slack in the way it is packed.

(Skimming my packing records most of my Vector III packs seem to be 4 3/8" to 4 7/8" long but with a few lower and a few above 5.0" from the washer)

[mxk 1]

The current manual says 4 1/2 ±1/4" on page 16 and 4 1/2 ±1/2" on pages 30 & 38. I didn't even notice originally that the range is 1/4" in one place and 1/2" in the other . Where this is measured from is never stated, but I guess if you try to measure it from the grommet, you'll find out that it doesn't work.

From your records, which container sizes required a loop of 5" or more? Is there a clear pattern of bigger containers requiring longer loops or are there other factors involved? Do you have any records specifically for a V358 by any chance?

[riggerrob 558]

For Vectors and Talons, I measure 4.5 inches from the Cypres washer.

[indyz 1]

riggerrob

For Vectors and Talons, I measure 4.5 inches from the Cypres washer.

Pre- or post-stretch?

[riggerrob 558]

4.5 inches from the Cypres washer, post-stretch.

[pchapman 261]

mxk

The current manual says 4 1/2 ±1/4" on page 16 and 4 1/2 ±1/2" on pages 30 & 38. I didn't even notice originally that the range is 1/4" in one place and 1/2" in the other .

Yeah you're right. They've had Vector III's since the late 1990s and never put anything in manuals in loop lengths, but sometime between the 2010 and 2015 manuals they added in references to it. And it is silly that they make it sound like a dimension which is not just a suggestion but mandatory, which would be highly unusual for normal rigging practice. (You don't want to have to be explaining something in court, saying, "Yeah, sure the manufacturer says that, but we all know that's B.S. if taken out of context.")

Edit: You asked about specific container sizes. I don't always have that recorded and don't think I'll get into a big analysis tonight. But it looks like the 5.0" or slightly longer loops were usually on student gear with bulky reserves. (Some student gear could have quite sort loops - maybe due to wider containers allowing more spreading of bulk) Having a Skyhook adds another flap etc too but where it actually lies under the PC spring depends on the rig size.

[mxk 1]

riggerrob

4.5 inches from the Cypres washer, post-stretch.

That's another good point. When manuals say "pre-stretched" one can easily understand that to mean "before any stretching" instead of "a loop that has already been stretched." So the poor use of language continues...

By the way, is the reserve anchor plate on the bottom of Vector 3 supposed to have a slight curve to it running the entire length (top to bottom) or is it supposed to be completely flat? I don't use the torque tool, and I doubt that I could have bent it just with my hands, but I haven't noticed it previously.

[riggerrob 558]

Pre-stretched means "stretched before installation" in common usage.

[riggerrob 558]

riggerrob

4.5 inches from the Cypres washer, post-stretch.

I just packed a pair of Micro Sigmas. The old loops were about 5.5 inches long from the Cypres washer.
Regular sized Sigmas can be packed with 4.5 inch loops if you are very careful to push canopy fabric away from the center.

[riggerrob 558]

.... is the reserve anchor plate on the bottom of Vector 3 supposed to have a slight curve to it running the entire length (top to bottom) or is it supposed to be completely flat? ....

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

For decades, the Vector factory installed perfectly flat, aluminum pack tray stiffeners (aka. anchor plate).
I have never seen one bent along the vertical axis (parallel to the spine). Maybe this is something new from the Vector factory??????
It is common to see Vector pack tray stiffeners bent along the lateral axis (shoulder to shoulder) because Vector stiffeners are so long, twice as long as stiffeners in Infinity, Javelin or Talon).
Javelin pack tray stiffeners often get bend (along the vertical axis) by riggers who use more muscle than skill when closing tight Javelins.

OTOH, Vertical bends are factory-standard on Racer pack tray stiffeners, because it helps stiffen the aluminum stiffener and helps maintain the correct spacing between the two ripcord pins. The Racer pack tray stiffener is a vastly simplified version of the pack tray stiffener in a military BA-22 container.

[mxk 1]

Thanks for the information. I checked with UPT and they told me that the plate is supposed to be flat, but minor bends are normal and can be fixed by hand as long the grommets aren't damaged. The uniformity of the bend and the axis is what made me wonder if it came from the factory like that. As you say, if you pull too hard, you would expect the bend to form along the shortest dimension, not the longest one.

I was going to repack everything this weekend anyway, so I'll try to take some photos from both sides of the pack tray before I do anything else to it.

Another thing I found out during my discussion with UPT is that the staging loop was never needed for sport containers, and is only "recommended" for student and tandem rigs. Since this thread has morphed into complaints about the manuals, I'm curious how many other riggers were lead to believe that the loop must be installed with a skyhook rig?

[riggerrob 558]

... Another thing I found out during my discussion with UPT is that the staging loop was never needed for sport containers, and is only "recommended" for student and tandem rigs. ....

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

My theory is that the need for a staging loop is based on the weight of the reserve canopy. How many of you can remember when staging loops were fashionable in Wonderhogs?
Did the round reserves (e.g. Strong 26 foot diameter Lopo) weigh as much as a 250 square foot student reserve?
Has any one weighed a tandem reserve recently?
My theory is that only student and tandem reserve canopies are heavy enough to pull a Collins lanyard and ruin your day.

[nigel99 143]

Picture is worth a thousand words and should make it un-ambiguous
Note that this is for the Sunpath Javelin.

Talking of words creating ambiguity though - I really don't like the inclusion of the word "un-stretched" in the Jav text. Especially when you have the Cypres loop instructions that could cause confusion.

Experienced jumper - someone who has made mistakes more often than I have and lived.

[pchapman 261]

For JAVELINS:

So that jpg, presumably current, shows 2 1/8" (53mm) to 2 1/4" (56mm) unstretched.

Funny, because the manual current in 2012 ("rev 3") says:
"Suggested reserve closing loop after setting and pre
stretching to be 54mm to 57mm. (2 1/8 +/- ¼”)"

The numbers differ, the measurement techniques differ, and the metric conversions are inconsistent and can't all be correct. But who knows, maybe it was all a deliberate change.

(And does everyone really get the loops that short in practice??)