Finger Trap Technique

[Lowpuller]

I posted this on my build thread but thought I would put here as well.

 

[rharshberger]

I posted this on my build thread but thought I would put here as well.

[video=youtube_share;h8QE8dTEi64]https://youtu.be/h8QE8dTEi64[/video]

Very clean, I have seen this done with paracord.

 

[Lowpuller]

I am parachute rigger that's where I learned the technique.

 

[Woody's Workshop]

Would there be any bonus to a double loop in the swivel like a fly fishing knot?

 

[scsager]

Very nice!!

I want to see the next step - I would like to see how you do the two rows of stitching.

 

[K'Tesh]

Nice Video!

I'll 2nd Scott's motion (or a nice photo of it).

 

[GregGleason]

Nice Video!

I'll 2nd Scott's motion (or a nice photo of it).

Ditto!

Greg

 

[Lowpuller]

I use a single needle machine and this little guide.

 

[watheyak]

Thanks for sharing the video!

I do this on all my recovery harnesses. With no stitching. Stitching is not needed for strength, believe it or not. I put a lot of effort trying to get this method to fail, it just doesn't happen.

 

[manixFan]

I've also been using the 'finger trap' technique for many years with all sizes of Kevlar. Since I don't stitch mine down (I like to be able to undo the connection) I use a much longer portion of trapped cord, about 2x-3x shown in the video. Even on large 50lb+ rockets it has never failed.

Once you get the hang of it I find it does not take very much time and I eliminated the need for quick links. None of the three rockets I flew at BALLS used quicklinks - all were connected using loops made using the finger-trap method. The cord packs a lot neater and area for packing and weight is reduced.

Nice video, thanks for sharing it.


Tony

 

[Lowpuller]

Thank you for the comment.

If you leave the stitching out, over time the tensioning and untensioning of the finger trap will allow it to loosen up and eventually slip out. Granted it takes many occurrences but eventually it will happen. Try it on the bench sometime, my guess is that it will fail in 10 attempts or less.

Another factor that comes into play is the length of the tail, the longer the tail, the less likely the failure.

Having said all that I believe the likelihood of yours failing are slim to none, but why take the chance. My only regret was not using Kevlar thread, but it was crazy expensive on eBay.

 

[rharshberger]

Thank you for the comment.

If you leave the stitching out, over time the tensioning and untensioning of the finger trap will allow it to loosen up and eventually slip out. Granted it takes many occurrences but eventually it will happen. Try it on the bench sometime, my guess is that it will fail in 10 attempts or less.

Another factor that comes into play is the length of the tail, the longer the tail, the less likely the failure.

Having said all that I believe the likelihood of yours failing are slim to none, but why take the chance. My only regret was not using Kevlar thread, but it was crazy expensive on eBay.

Check out The Thread Exchange, they have kevlar threads at decent prices.

 

[Lowpuller]

WOW! Thank you, the thread exchange is actually less than 5 minutes from where I work but I had ever heard about it.

 

[rharshberger]

WOW! Thank you, the thread exchange is actually less than 5 minutes from where I work but I had ever heard about it.

They have excellent service via their online sales, but I cannot speak for onsite sales.

 

[Lowpuller]

I'll let you know!

 

[manixFan]

Thank you for the comment.

If you leave the stitching out, over time the tensioning and untensioning of the finger trap will allow it to loosen up and eventually slip out. Granted it takes many occurrences but eventually it will happen. Try it on the bench sometime, my guess is that it will fail in 10 attempts or less.

Another factor that comes into play is the length of the tail, the longer the tail, the less likely the failure.

Having said all that I believe the likelihood of yours failing are slim to none, but why take the chance. My only regret was not using Kevlar thread, but it was crazy expensive on eBay.

I often undo and then redo my loops as I don't use quick-links. So I need the ability to be able to undo the loops. But I dress them before every flight.

I do agree that if you don't secure the loop it can come undone over time. Either stitch it as you do or make sure to dress the loop every time you fly. BTW, after seeing your trick I've tried it with very small cord using solid core copper wire and it works great. Beats my old way of doing it hands down.


Tony

 

[soopirV]

This is definitely getting filed away for future use...thanks for sharing!

 

[ksaves2]

I gotta make me one of those wire loop pullers!!!! Dang that's slick. Thanks. Kurt Savegnago

 

[EddieJ710]

I am parachute rigger that's where I learned the technique.

It's cool to see fellow riggers involved in rocketry.

 

[Lowpuller]

Cool, we probably met along the way, 2000+jumps, AFFI, SLI, PRO, Senior Rigger, working on Master. I learned the technique from Dave DeWolf.

 

[burkefj]

One of my contractors did something similar for making loops in a wire rigging that helped support/stiffen my deck roof members....

Frank

 

[cwbullet]

I corrected the video post. It should work for you now - subscribed.

 

[RocketFeller]

I've done this for years on my crab pot lines. It works great with hollow polypropylene rope.

 

[RocketFeller]

Anyone tried this with tubular nylon? Seems like the tight weave might make it difficult.

 

[caveduck]

The other way to do this is with a "fid" tool that will let you thread the free end of the line back thru the braid an arbitrary distance (standard practice in the sailing world). With that method you're not limited by the length of the wire loop. Warner Recebaren showed me these a while back. They have to be the right diameter so you need a set; they're kind of expensive to buy pre-made but you can easily make them from knitting needles in just about any size.

Larger Kevlar braid will definitely loosen if you don't either stitch it or make a really long splice.

A wire loop tool may be needed for some kinds of kevlar braid that are so dense/tight that it's hard to work a fid through it.

You can buy a nice set of really small fids here: https://www.ebay.com/itm/Fid-splici...ash=item3b006db712:g:xRcAAOSwhcNad5Yr&vxp=mtr