Jack line stiching

[model 10]

I have new jackline webbing and I want to sew a loop on each end. The webbing is 1" polyester with a breaking strength of 4500 lbs. I only have regular polyester thread for the sewing machine. How long and how much stitching should there be for each loop? I know I should cover the stitching for uv protection when I'm done.

[Dennis.G]

Tenara thread has high UV resistance and is what we use on canvas work. Several times the cost of regular poly thread.

[Sun and Moon]

Do some research, but I believe teflon thread is UV resistant. Talk to a sailmaker. Or probably for a few dollars you can get them to sew the loops.

I use a water knot in mine.

[Wotname]

I can't help you directly but I can say I know an engineer who had to proof test stitching on webbing cargo belts and he always said only the first 2 or 3 stitches at end of a longitudinal run carries the load. If they let go, the next few stitches take up the load and so on.

He always suggested in the absence of formal destructive testing that there should be MANY longitudinal rows all starting and stopping in the same transverse line ie, all the same length and nicely in a row. The length of the longitudinal run was not that important but he suggested about twice the width of tape "looked nice".

I have no reason to doubt him, he did this sort testing stuff every day.

[Hydra]

There are some test results in this thread started by estarzinger: http://www.cruisersforum.com/forums/...ts-118009.html

Alain

[model 10]

Originally Posted by Hydra

There are some test results in this thread started by estarzinger: http://www.cruisersforum.com/forums/...ts-118009.html

Alain

It's hard to search those long threads without reading 8 pages of stuff, all interesting of course. Wottie gave me exactly what I was looking for.

[wrwakefield]

Originally Posted by Guy

I have new jackline webbing and I want to sew a loop on each end. The webbing is 1" polyester with a breaking strength of 4500 lbs. I only have regular polyester thread for the sewing machine. How long and how much stitching should there be for each loop? I know I should cover the stitching for uv protection when I'm done.

See: http://www.bethandevans.com/pdf/OnRope.pdf

Cheers!

Bill

[Dennis.G]

Originally Posted by Sun and Moon

Do some research, but I believe teflon thread is UV resistant. Talk to a sailmaker. Or probably for a few dollars you can get them to sew the loops.

I use a water knot in mine.

I would say if planning on just using some regular poly thread that you happen to have on your sewing machine, you would be better off with a water knot. That knot won't fail. Your poly thread can.

BTW a water knot to make a loop at the end of a length of webbing is just making a bight, and then tying the doubled webbing in a simple overhand knot.

[model 10]

Originally Posted by Dennis.G

I would say if planning on just using some regular poly thread that you happen to have on your sewing machine, you would be better off with a water knot. That knot won't fail. Your poly thread can.

BTW a water knot to make a loop at the end of a length of webbing is just making a bight, and then tying the doubled webbing in a simple overhand knot.

Don't use the frown sir. Actually water knots do come loose as proven by mountain climbers so they don't use them. I have been using water knots on the jackline for years and now I want to switch to a shackle and a loop at the end of the webbing. As for poly thread, it is used for all kinds of things and is perfectly suitable. As I said in my op, I will put a sun cover over the sewn portions.

[thinwater]

I worked with Starzinger on that a bit; he was focused on machine sewing, while my testing was on hand sewing. Either way can work. And there are LOTS of ways to do it wrong. We both did lots of them.

a. Make some samples and break test them. If the machine is set wrong, the wrong thread, the wrong pattern, or stitching spread too far you will fail. If you don't read his entire thread, you will not know all the ways to do it wrong. And break testing a smaller number of stitches (say, 10% to 500 pounds) will NOT tell you if you did it right; at high loads the webbing distorts, changing the load distribution.

b. If you are not willing to break test samples, buy tethers. If you are too suborn to buy them, tie a knot and sew the tails down so that they cannot creep. This will be stronger than your stitching. It requires practice and break testing to do better than a knot, IMHO. It will, however, be under strength.

c. Better yet, splice them from Amsteel. Easier to do right the first time.

Practical Sailor published an article on jackline materials last month.

[estarzinger]

The direct answer to the question is bar tacks, with as heavy thread as you or your sewing machine can handle.

" the first 2 or 3 stitches at end of a longitudinal run carries the load."

It is actually the stitches in the first 2" or so that carry the load. So you essentially want to pack as much bar tacking into that area as you can. But it also makes sense to keep stitching for about 6", so that if the first 2" do break you have 3 more 'zipper opportunities' to absorb the shock load and catch it before the whole thing lets go.

The indirect answer is, as thinwater indicated, it is MUCH more difficult to get 4500lb stitched loops than most would think. For the vast majority of DIY, splices and knots are much more reliable.

And the indirect indirect answer is that really jack lines as normally set up are a shitty solution in any case. You can still go over board when attached to them. You can still die when attached to them. Fixed work station tethers are prefered, and short centerline dyneema jacklines if you feel the need for something for moving up and down the deck.

[model 10]

Originally Posted by estarzinger

.
And the indirect indirect answer is that really jack lines as normally set up are a shitty solution in any case. You can still go over board when attached to them. You can still die when attached to them. Fixed work station tethers are prefered, and short centerline dyneema jacklines if you feel the need for something for moving up and down the deck.

Yeah that's probably true but I don't like connecting and disconnecting. I have started using a tether with 2 hooks but I don't like the safety hooks on the ends that you have to press in on one part first before it will open.

[Dennis.G]

Originally Posted by Guy

Don't use the frown sir. Actually water knots do come loose as proven by mountain climbers so they don't use them. I have been using water knots on the jackline for years and now I want to switch to a shackle and a loop at the end of the webbing. As for poly thread, it is used for all kinds of things and is perfectly suitable. As I said in my op, I will put a sun cover over the sewn portions.

OK, you have been putting more thought into this than I had assumed. We have sewn bar tacks on webbing and this is a very clean way of making slings or loops. We still use water knots too, as they are much less trouble to do. I leave a good 4"+ tail on water knots - they can creep a bit if not set well. I have found that when pulled tight (i.e., with body weight applied) when wet with salt water however, they are pretty much set for life (i.e, a bitch to untie). Some hand stitches can be applied to the ends securing them to the standing part for extra safety, but that's something I haven't found needed if knot is well set. BTW lots of climbers use water knots.

I am not sure how your sun cover is to be done, but sounds like a good idea. Regarding UV weakening of poly thread, might look at this: http://www.sailrite.com/PDF/Tenara%2...re%20Chart.pdf

[Dennis.G]

Originally Posted by Guy

...but I don't like the safety hooks on the ends that you have to press in on one part first before it will open.

These double action safety hooks are a very easy to use alternative to locking carabiners. Regular non-locking carabiners or spring hooks are just too risky as can easily come undone if the jack line runs over the outside of the gate, and should not be used on tethers. I think double action hooks are required by some offshore racing rules.

[estarzinger]

For those who dont want to plow thru all the gory detail on load testing on my website . . . I will comment that there is one jackline configuration that makes successful DIY results much more likely. This is to construct the jackline as a 'sling' . . . like this:



This accomplishes two things . . it halves the load on the stitching and it makes the load on the stitching more uniform so that all the stitches carry load rather than just the end ones. Most high load commercial slings are made this way.

It does require twice the length of webbing. But in return you can use lower strength (about half) less specialized webbing. It also requires more sewing.

After all my testing this was how I choose to make jacklines for a friend who ask. And it would be my recommendation to anyone who wanted to do this themselves. Here's how it looks in real life - I added extra (blue) webbing into the end loops also for wear protection:




There is another technique, used my parachute manufacturers, called the 'added insert'. That also spreads the load, using less stitching and less webbing. But it requires more care and knowledge to get it right. It is detailed on my website.

Here is a picture of the para insert loop tested vs a store bought west marine conventional sewn loop. The insert loop (right side with red insert) held and the west loop (left side) stitching broke. The west jackline used both more stitching and heavier thread but is greatly hindered by its inferior 'conventional' design.



Regarding hooks - the ISAF regs say the following:
Warning it is possible for a plain snaphook to disengage from a U bolt if the hook is rotated under load at right-angles to the axis of the Ubolt.
For this reason the use of snaphooks with positive locking devices is strongly recommended.
At least 30% of the crew shall (I have edited here) be provided with dual hook tethers.