Web Stitch Strength Info

[JohnSawyer]

What I saw when I looked at this was the box x or multiple box x was what was used also. It would not surprise me if the optimum pattern was a function of the webbing material, the structure of the webbing, the tread material, and the size/strength of the treads. Actually, I would expect that.

Think for a minute about the polyester mule tape, or pull tape. It is light weight because there is not much in the way of threads used perpendicular to the webbing. I would not trust sewing loops in this in general but particularly if they were only sewn along the length of the webbing because there is not much there to hold the stitch.

Valid point on the mule tape. I've sewn loops in mule tape, but typically make the sewn-section quite long (3"-4"). I've bar-tacked across the width almost exclusively, and have tried the long-stitches.

I don't have testing equipment, but I did pull the mule tape tight across a 12' horizontal, and hung my 220# from the center without the loop failing. Those loops were all larksheads for hammock-ends, and the larkshead also constricts the two layers of tape, which I assume would add to it's strength...

I have to go re-think my mule tape uses....

John

[Ramblinrev]

My question is very basic. Is there a legitimate reason to dismiss any stitch pattern given the use and forces which we as hammock hangers subject our equipment to? I am not disputing the data. More a case of "so what". Statistics can be wonderful things. But they can also be almost meaningless given their context. If there is no practical reason to require overkill then choose the method that you prefer or meets your skill level.

All the tow straps and load straps I have seen use the box pattern. Yeah you can program macnines to do that pattern all by itself so all you need is a body to push the "on" button, but essentially the same is true for any stitch pattern.

Don't get me wrong, for rescue, life support and dynamic uses there is a good reason to exceed "good enough." But if you don't hang higher than you are willing to fall and you choose your site properly to avoid potential obstacles then Good enough is just that. I've had straps break using the "worst" of the patterns but the have _never_ broken at the stitches. They have always broken because of issues outside of the stitch pattern that was used.

Very few things instill fear like statistics that don't really mean anything in context.

[Youngblood]

Rev... it is important to not do something foolish that derates the webbing strength significantly without realizing it. It is one thing to use a single 3 inch long box x pattern at 10 stitches per inch with 10 lb breaking strength polyester thread to sew a loop in 1500 lb polyester webbing and it is another to use a single 1 inch long box x pattern at 8 stitches per inch with 1 lb breaking strength polyester thread.

Intuitively without knowing all the specifics, I think larger/stronger thread with a box x pattern or multiple box x patterns is best. But with smaller/weaker thread, then several rows of bar tacks or tight zig-zags would be preferred. And some machines have reinforced stitching, or triple stitching, which can be used to make smaller/weaker thread imitate larger/stronger thread.

I keep trying to go back to the basic 'strength of thread times the number of stitches' to get a basic sewing strength for the job at hand. Once you have that then you can deal with the type of stitches to use. Smaller/weaker thread lends itself to bar tacks or tight zig-zags to get a lot of stitches in place while larger/thicker thread can't do that without jamming things up. But you can space out the stitching and don't have to use as many stitches with larger/stronger thread.

[oldgringo]

Rev, I just don't see any reason to degrade the strength of any component unless it's made unavoidable by the end use/design.

[Ramblinrev]

Rev... it is important to not do something foolish that derates the webbing strength significantly without realizing it. It is one thing to use a single 3 inch long box x pattern at 10 stitches per inch with 10 lb breaking strength polyester thread to sew a loop in 1500 lb polyester webbing and it is another to use a single 1 inch long box x pattern at 8 stitches per inch with 1 lb breaking strength polyester thread.

Intuitively without knowing all the specifics, I think larger/stronger thread with a box x pattern or multiple box x patterns is best. But with smaller/weaker thread, then several rows of bar tacks or tight zig-zags would be preferred. And some machines have reinforced stitching, or triple stitching, which can be used to make smaller/weaker thread imitate larger/stronger thread.

I keep trying to go back to the basic 'strength of thread times the number of stitches' to get a basic sewing strength for the job at hand. Once you have that then you can deal with the type of stitches to use. Small/weak thread lends itself to bar tacks or tight zig-zags to get a lot of stitches in place while larger/thicker thread can't do that without jamming things up. But you can space out the stitching and don't have to use as many stitches with larger/stronger thread.

You are absolutely correct, which is kind of my point. Statistics, outside of their context do not always accurately represent the full range of knowledge. Again.. all I am saying is overkill does not always present practical benefits.

I have serious concerns about zig zag bartacks because of the stretch issues. The more threads caught between the zig zag the more stretch will be imparted to the stitching. The zig zag stitch is essential a linear stretch stitch and is not designed for high tension stress. If you can run a straight stitch between two horizontal threads then there is no stress from stretching imparted to the stitchline.

[Youngblood]

I have serious concerns about zig zag bartacks because of the stretch issues. The more threads caught between the zig zag the more stretch will be imparted to the stitching. The zig zag stitch is essential a linear stretch stitch and is not designed for high tension stress. If you can run a straight stitch between two horizontal threads then there is no stress from stretching imparted to the stitchline.

The way had I figured it out was that a tight zig zag could stretch along the stitch line but not orthogonal to that stitch line. Conversely, a straight stitch could stretch orthogonal to the stitch line but not along the stitch line. And a typical zig zag could stretch along the stitch line and orthogonal to the stitch line. All of this stretch is within bounds determined by the stitch spacing. But I think a bar tack works well for sewing loops in webbing when you are using the appropriate thread.

[Busky2]

I made some loops for larkheading (is that a word) and made one a bit longer to test with (non scientific) with a combo of bar tacks (4) in 4 inches with a zig-zag 4 passes. I encircled my 2.5 ton floor jack, placed 4x4 blocks to protect the Mule Tape and pumped it up. It crushed the blocks pretty good and when the jack started to fold up I chickened out and stopped pumping but the Mule Tape did not fail nor did the connection.

[nik.martin]

My question is very basic. Is there a legitimate reason to dismiss any stitch pattern given the use and forces which we as hammock hangers subject our equipment to? I am not disputing the data. More a case of "so what". Statistics can be wonderful things. But they can also be almost meaningless given their context. If there is no practical reason to require overkill then choose the method that you prefer or meets your skill level.

My main point was the "prettiest" stitch isn't the strongest, and that the strongest is the easiest to make, and it is accessible from ANY sewing machine.

[Ramblinrev]

Looks like the recommended "box with an x" is the absolute worst way to sew webbing!

My apologies. I read that line as advocating _against_ the Box - X pattern. In my experience it is more than adequate for anything I have done and so is not the "absolute worst." The fact that other stitches may be stronger is a different issue altogether. Any stitch pattern can be accomplished from any sewing machine given that the zigzag stitch is a relatively recent addition to home machines and is not _required_ for a good pattern..

[xxl_hanger]

I used almost exactly this pattern:
http://diygearsupply.com/wp-content/...rap-lowres.jpg

For my first try a view days ago, I'm very happy! I tried to sew accurate to the millimeter with one seam only. I started to sew loop-sided with straight stitches across the webbing (approx. 8 standard stitches per inch, with Gütermann Tera 40 thread, optimized bobbin thread tension, high upper thread tension and a Schmetz #16 jeans needle - the #16 universal needle would be fine too). Then I changed the direction to vertical mode and made the second horizontal seam at the short tail end. Then again vertical up to the seam start where I made my third horizontal seam parallel to the first one. Then the first diagonal (connection!) seam followed by another horizontal seam. This procedure repeated three times up to the second horizontal seam at the short tail end. Then the hole thing vice versa up to the seam start where I made a last zig-zag horizontal seam (the only one! across the first and third horizontal straight ones - as a lock seam). This way I got a total of ten straight horizontal seams, 8 diagonal ones and one final horizontal zigzag lock seam. So I have 4 boxes with an x and a final zig zag seam - which means my tree straps should hold at least 120%!

I will try to make daylight pictures of my self-made three straps tomorrow. (The picture already shown is my first upload test. I hope I can provide a better picture tomorrow)