No Sew Fingertraps

[NovaTTT 1]

A discussion in a different group has me thinking about no sew fingertraps (NSF), particularly when used for attaching toggles.

I haven't had any problems related to NSF attached toggles - the minor nuisance in undoing them is the only difficulty I've experienced.

What is your experience?

Nova

"Even in a world where perfection is unattainable, there's still a difference between excellence and mediocrity." Gary73

[pchapman 261]

I have ended up only mostly using no-sew finger traps only for myself, unless it is in some nearly-unseen place (eg, kill line inside a pilot chute).

They're just not very common or well recognized, especially by non-riggers, so I worry that they can be misinterpreted. ("OMG, the stitching is missing!") A toggle attached using a standard PD style knot, or a brake line that uses a bartack, that's easily understood as 'normal' technique.

[GoldBug 0]

What's the worse that could happen if they pulled loose in flight?

[riggerrob 558]

I have used the NS finger-trapping technique to replace dozens of lower control lines.
It is as strong as an old-school, bar-tacked finger-trap and lasts hundreds of jumps.

From my perspective, it is mainly about being too lazy to walk over to the sewing machine. If I have spare time, I might put a cosmetic stitch through the finger-trap.

The most amusing reactions are from skydivers who get upset about bar-tacks that are not "factory perfect!"
Hah!
Hah!
Do they understand how little stitching contributes to the strength of a finger-trapped joint?
How many of them realize that a bar-tack is just a fancy zig-zag stitch?

In most finger-trapped joints, the stitching only stabilizes line length until the outer line is loaded/tensioned.

[Remster 24]

GoldBug

What's the worse that could happen if they pulled loose in flight?

Do you understand what the not-sewn technique is?

Remster

[GoldBug 0]

Remster

***What's the worse that could happen if they pulled loose in flight?

Do you understand what the not-sewn technique is?

Yes, a joint that is only secure when under tension, and lines are not always under tension, hence they can pull apart...

I wonder why all the manufacturers stitch their fingertrap joints?

Not to worry though!

Let's make sure people understand that you're using the technique shown in the link below to secure the fingertrap so that it can't slide out. This method effectively uses the loose end of the line to stitch itself in place. Some people might think just slipping one end through the hollow core is sufficient. We've already had people die from brake toggles pulling loose from hard turns or flares, and we don't need more of that happening.

Link: http://www.sidsrigging.com/articles/stitchless_fingertrap.htm

[pchapman 261]

Your post is confusing GoldBug.

Everyone in this thread is indeed talking about the "no-sew fingertrap", which is the one where the line wraps through itself to lock the fingertrap in place. And your post also talks about the very same thing, while also acting as if aghast at people on the thread might allow basic finger traps (with no other protection) to work loose.

A no-sew fingertrap is not the same as a plain finger trap, that is not sewn. All of us riggers here already know that. (Even if there might be confusion for others.)

[Hooknswoop 19]

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Yes, a joint that is only secure when under tension, and lines are not always under tension, hence they can pull apart...

Wrong.

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I wonder why all the manufacturers stitch their fingertrap joints?

Wrong.

You clearly do not understand what a new-sew finger trap is.

Derek V

[dan43 0]

I've only used the no sew finger trap on lower brake lines so far.

I'd like to hear opinion on whether this is a good method on all line types though?

Spectra is pretty easy to work with for example. But, Vectran, particularly the heavier types 750 etc I found difficult to feed through on itself and wondered if there was any damage done to the line? None that I could observe, no broken strands or anything, but it isn't a very pliable line type..

[lyosha 46]

riggerrob

Do they understand how little stitching contributes to the strength of a finger-trapped joint? How many of them realize that a bar-tack is just a fancy zig-zag stitch?

While I've heard that multiple times, I've begun to question it since I started rock climbing and, looking over my harness, it's being held together by a small number of those "fancy zig zag" stitches, and with no fingertrapping. Made me think that maybe they do contribute something.

[riggerrob 558]

Two different materials: braided suspension line versus woven webbing.
To understand braided suspension line, try to picture the outer sheath of kernmantle rope (minus the straight inner strands).
When we fingertrap braided suspension lines, the outer braid tightens around the inner braid, producing a join as strong as the original line. Sewing only holds the two pieces of line in alignment until they are loaded. Finger-trapped joints cannot slip once loaded.
This "no-sew finger-trapping" technique includes passing the bitter end through the other two lines at 90 degrees, looping all the fibres together in what vaguely resembles a parks-head knot. This extra step prevents the finger-trapped joint from slipping.
A "no-sew finger-trapped" joint is also as strong as the original suspension line.

OTOH Harness webbing l cannot be finger-trapped, so all harness joints are sewn. Harness joints depend 100 percent on stitching to hold them together.
I have only seen a few finger-trapped joints in tubular webbing, but tubular webbing is rarely used in parachute harnesses.

Traditionally, harnesses were straight-stitched with heavy cord (5 or 6) borrowed from saddle-makers or sail-makers (5 stitches per inch) while newer harnesses are zig-zag stitched (dozens of stitches per inch) with lighter thread (E thread).
Bar-tacks are just a fancy version of zig-zag stitches. Electronic sewing machines allow climbing harness manufacturers to use sew exotic curved, crescent-shaped, etc. bar-tacks that avoid point-loading on corners.

[lyosha 46]

I completely agree.

My point was more that people in the skydiving community like to think that the bartak is there as little more than decoration, but I feel does add to the system.

[ChickenSwitch 0]

I understand the concept but after following the provided link but am a little confused as to how this is accomplished on a steering line that is already attached to a canopy. In the instructions, you finger trap the toggle attachment loop as you normally would. It goes on to say...

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With the tool through the lines, take the other end of the line (the end farthest from the loop that you just made) and insert it into the tip of the tool

Again, the "other end" is attached to the tail of the canopy via cascades. Rob, you are saying that it is done by...

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passing the bitter end through the other two lines at 90 degrees

Isn't the bitter end hidden inside of the standing part after you make the loop? Seems like you could pull the bight of the loop back through the two lines at 90 degrees. Am I missing something or is that how this is done?

[riggerrob 558]

To replace a steering line: start at the top.
Loop the top end of the line through the line attachment tape. Leave the (raw cut) end hanging 6 inches below the tail. Fingertrap (parallel to long axis of line) 4 or 5 inches into the long part of the line.

Grab the bottom (raw cut) end of the line and pass it through (90 degrees) both inner and outer lines just below the loop. Massage flat.
Repeat the (90 degree fingertrap) process an inch or 2 farther down.

This can be done with a hollow fid (knitting needle with internal threads) but I find it much easier with a wire.
A Cypres needle also works well with thinner lines.

[OzzieDave 1]

Perhaps I understand it wrong but i have been using no sew finger traps for a few years for a few things with no issues. The way I figure it a standard 42pt bar tack with 8lb thread will take ~336lb to brake whereas a NSF would take the strength of the line to fail (in my case 750lb HMA). Easy to undo and re-set my brakes and I don't need any tools other than a fid

[pchapman 261]

I see a few issues and questions about no-sew fingertraps, a couple of which have been brought up in recent posts. No-sew's get used but there's little good information written about them as far as I see.


1) Pulling the line through the core from the loop end vs. the other end farthest from the loop - does it matter?

The original 2003 Jump Shack article, and the Sid's Rigging one, both mention pulling through the end of the line you're not working on. But as ChickenSwitch pointed out here, that's sometimes already attached to something.

I just pull the fingertrapped end through itself in that case. It's stiffer and bulkier and you may be working with only an inch of eye past the pull-through point, but it can be done.

Is this not equivalent to the other way?
Isn't it topologically the same, just with the twist pointing the other direction along the line?

I see the JumpShack manual mentions attaching toggles with a no-sew, so there one is pulling just the short piece of toggle eye through. It seems acceptable to them.


2) Pulling through once, vs. adding a 2nd pull through an inch back.

The Jumpshack article mentions doing a 2nd pull-through for security, but isn't highly clear on why.

They write:
"It can also be used successfully to attach brake toggles. In this application though we recommend that the process be done twice, with the running end being pulled through the outer sheath and the core a second time, about 1” below the first insertion point. "

But, aha, in their manual they mention doing it the 2nd time, "to assure engagement of the core line."

RiggerRob also just mentioned repeating an inch or two lower down.

How important do riggers find this method of having a 2nd pull-through?


3) It has been alleged that the weave of a line opens up too much over time if using around a brake eye?

I saw a rigger mention that in a discussion on the facebook site RiggingForDummies. I can kind of see that happening from personal experience with 750 Vectran brake lines of my own but didn't see that a show stopper. Still, a bartack next to a brake eye loop has the advantage of stiffening the area for when trying to stuff a toggle through, and has the number of perforations between the line threads to really hold everything in place with nothing easily pulled free.


4) Paul Fries' alternative no-sew loop

There's an alternative no-sew loop out there in a pdf document by Paul Fries. He doesn't claim to have invented the method. One starts but doesn't complete a pull-through before making any fingertrap, then starts another, which the bight of the first goes through, and then does a fingertrap with the bitter end. You have to see it to understand it. I haven't tried to work out the topology of the knotting of that one.

I have the pdf but haven't checked where it might be on the web.

Anyone use that method?


5) No-sew for full line attachment of canopies?

It is said Jump Shack did no-sew for line attachments for entire canopies but later went back to standard methods. One tale was that the no sew junctions might take too much wear from the slider and fail earlier.

To what degree is there any truth to any of that? Or what is JumpShack's real history with no-sew in a production situation?

That being said, I have no info suggesting the no-sew is inherently weak, indeed the line will supposedly break in the non-fingertrapped area, says JumpShack. So whether the joint efficiency is one percentage or another, or stronger or weaker than a conventional knot, the loss is still in the doubled up finger trap area. (E.g, a knot efficiency might be 75%, but 2*75% is still 150% of the original line strength.)

[jumpsracer 5]

Jump Shack did indeed produce the initial run of FireBolt main canopies with a no stich fingertrap. I know, I used to own one.

[pchapman 261]

To add to the list of interesting no-sew applications, I should also mention that Jerry Baumchen made a design for main soft links. They use the double no-sew traps to secure each end, and are of the 3-times-around soft link. Easy to make!

[JerryBaumchen 1,046]

Hi Peter,

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They use the double no-sew traps to secure each end

In building them, you will run the bitter end through & also the 'eye' thru to secure or 'lock' them. 'How-to' for both methods are clearly shown in the instructions.

Jerry Baumchen

[GoldBug 0]

pchapman

Your post is confusing GoldBug.

Everyone in this thread is indeed talking about the "no-sew fingertrap", which is the one where the line wraps through itself to lock the fingertrap in place. And your post also talks about the very same thing, while also acting as if aghast at people on the thread might allow basic finger traps (with no other protection) to work loose.

A no-sew fingertrap is not the same as a plain finger trap, that is not sewn. All of us riggers here already know that. (Even if there might be confusion for others.)

Right. And while the riggers may all know it, I'm just trying to make sure that the new guys here don't get confused about this discussion and think that it's safe to make fingertrap joints without any sewing or other means of securing the trapped line. That is all... Thanks!

[jerolim 7]

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4) Paul Fries' alternative no-sew loop

There's an alternative no-sew loop out there in a pdf document by Paul Fries. He doesn't claim to have invented the method. One starts but doesn't complete a pull-through before making any fingertrap, then starts another, which the bight of the first goes through, and then does a fingertrap with the bitter end. You have to see it to understand it. I haven't tried to work out the topology of the knotting of that one.

I have the pdf but haven't checked where it might be on the web.

Anyone use that method?

Tell us more about this method, please,..
Few pictures would be great.

[pchapman 261]

Attached are his instructions put together in one document. I think he once posted a series of photos on dz, something like that, but I don't recall.

Note that it is an unverified technique -- He reverse engineered it from some canopy he found, possibly something from Europe and thought he'd share it. So although it looks clever, one would want to play with it and test it out. If it is any better or worse that a standard double no-sew fingertrap, I don't know.

[BrianM 1]

pchapman

4) Paul Fries' alternative no-sew loop

There's an alternative no-sew loop out there in a pdf document by Paul Fries. He doesn't claim to have invented the method. One starts but doesn't complete a pull-through before making any fingertrap, then starts another, which the bight of the first goes through, and then does a fingertrap with the bitter end. You have to see it to understand it. I haven't tried to work out the topology of the knotting of that one.

I have the pdf but haven't checked where it might be on the web.

Anyone use that method?

I've used it in the past to attach toggles, it has worked very well. I don't use it anymore, because now that I've acquired sewing machines and the skills to use them, I find it quicker and easier to just bartack them.

"It's amazing what you can learn while you're not talking." - Skydivesg

[Unstable 8]

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Jump Shack did indeed produce the initial run of FireBolt main canopies with a no stich fingertrap. I know, I used to own one.

Yup, If I recall correctly, they stopped because of irregular stretch patterns on the lineset with the entire lineset done via that manner. Someone closer to the issue may jump in.

I use them all the time on lower brake lines.

=========Shaun ==========

[hackish 8]

If anyone wants the low-down direct from Nancy at JumpShack I can point her at this thread or ask her in person on Monday. I've used the no-sews a few times but I find people are more comfortable with a bartack they can see. It's rare that lines break anyway so I don't think it matters if you use the no-sew method or tack it. As i recall parachute labs tested their method to failure and determined it was quite strong.

-Michael