Checking stitching strength

[wingnut]

Does anyone have a simple test method for checking how well your sewing is going to hold? I'm considering Making my own climbing aiders and would like to test them somehow just for peace of mind. I'll be using 138 thread and will sew in a boxed w pattern instead of using a boxed X pattern on the overlap.

 

[Trav2525]

If you go down a couple threads to the Frankenstein saddle post #6. You should be able to figure your breaking strength with the formula. That's what I used and of course tested at ground level also.

Sent from my SM-G960U1 using Tapatalk

 

[bj139]

Most people just calculate as mentioned in this thread.
https://saddlehunter.com/community/index.php?threads/sewing-resources-and-information.6100/
I was going to try to pick up the back end of my truck with the trailer hitch and a 4 foot jack using my DIY saddle but I haven't had the urge to try it yet.

 

[Bango Skank]

Can make two exactly the same and send one off for break testing. Arbsession and I think TreeStuff do it. Probably a few others.

If I ever run across a nice price on a Rock Exotica enforcer, I’ll make my own break testing doohickey, maybe with an old log splitter.

 

[drew13]

I calculate it using the aforementioned calc but I have also tested a sample up to 1000 pounds using my big game scale and come along. I know 1000 lbs is not my target strength but it’s as high as my scale goes! My calcs say the sewing in my main loop should hold 7500 pounds.

 

[wingnut]

Thanks for the direction to look. I know it can get very technical to see how strong the stitching really is and calculating static and dynamic loads is way deeper than I want to go.

 

[bj139]

Thanks for the direction to look. I know it can get very technical to see how strong the stitching really is and calculating static and dynamic loads is way deeper than I want to go.

Make sure you back stitch over the beginning and the end of your stitches. That is where it is most likely to come undone.

 

[wingnut]

I can't remember the source but they did rip tests on different sewing patterns to see which was stronger. They concluded that rows of stitching running lengthwise on the material held better than rows running width wise, like a series of bar tacks. Most straps you see use the boxed X pattern on the overlap but that only gives you two rows of stitching running lengthwise. I plan to sew a double boxed X by running a row from the lower corner of the box to the center of the top then down to the other lower corner. Back up the side and repeat, top corner to center bottom then up to the other top corner. Twice around the box and call it good. XX

 

[bj139]

Sailrite says there is no clear stitching pattern winner. Based on this I usually just sew enough lines across the strap.

How to Sew Webbing Loops

Learn what the strongest stitch patterns are for sewing webbing loops and how to sew webbing for load bearing applications using a handy formula.

www.sailrite.com

 

[raisins]

I can't remember the source but they did rip tests on different sewing patterns to see which was stronger. They concluded that rows of stitching running lengthwise on the material held better than rows running width wise, like a series of bar tacks. Most straps you see use the boxed X pattern on the overlap but that only gives you two rows of stitching running lengthwise. I plan to sew a double boxed X by running a row from the lower corner of the box to the center of the top then down to the other lower corner. Back up the side and repeat, top corner to center bottom then up to the other top corner. Twice around the box and call it good. XX

I read something similar, maybe same source (no reference though). They said that after the first row started to give that the rest kind of peeled off like tape.

 

[drew13]

Here's a good thread to resurrect from 2019:

DIY sewn webbing strength

I have an industrial machine. I’m using T90 mil spec thread, 4000lb breaking strength mil spec 1” tubular webbing. Following direction of On Rope: North American Vertical Rope Techniques for stitching patterns and specs. Here are a couple videos of lifting some motors with what I made. You...

saddlehunter.com

 

[Fl Canopy Stalker]

I calculate it using the aforementioned calc but I have also tested a sample up to 1000 pounds using my big game scale and come along. I know 1000 lbs is not my target strength but it’s as high as my scale goes! My calcs say the sewing in my main loop should hold 7500 pounds.

Is that break strength or working load limit?

 

[Fl Canopy Stalker]

Sailrite says there is no clear stitching pattern winner. Based on this I usually just sew enough lines across the strap.

How to Sew Webbing Loops

Learn what the strongest stitch patterns are for sewing webbing loops and how to sew webbing for load bearing applications using a handy formula.

www.sailrite.com

They also say their sewing machine sews quality stitches through thick webbing. I found out that wasn’t true. I tightened the top tension still loopy on the bottom, loosened the bobbin tension as far as it would go, a little tighter and better but still not good equal tension. Adjusted the tensioner spring to shorten its travel, and played with different pressure foot settings... needless to say the Juki does a much much better job and I’m left with not many positives about sailrite.

 

[drew13]

Is that break strength or working load limit?

The calc is for break strength.

 

[wingnut]

I stand corrected when I said bar tacks were not as strong as a double boxed, x pattern. In the Sailrite video the bar tacks were the strongest of the patterns tested on the 1" tubular webbing. I have an older Machine without reverse so Its hard for me to make bar tacks, of the other 2 patterns that I can do the w which is roughly what I'm sewing is stronger than the boxed x. This is the same video I looked at when trying to decide which was stronger.

 

[Fl Canopy Stalker]

The calc is for break strength.

Yea I know it is tensile strength x number of stitches per inch x 1.5 for lock stitch configuration (aka basket figure) then take that number and divide it into the breaking strength you want and that’ll give you the number of stitched inches you need. And that is the generally accepted formula.
Other factors come into play such as age of the material, the weakening factor of passes in the webbing and most importantly is thread tensioning. These are reasons they suggest sewing an extra 25-50 percent of your calculation. If your thread is too tight on the top and loose and the bottom or vice versa, you lose stitch strength because part of the strength is from friction of the webbing against itself.
it is worth mentioning that if he is only making the webbing as an aider, then all he technically needs is around 900 lbs of break strength because his intended use is static and should not be subject to shock load nor is it life supporting if he is roped to the tree. Most tree stands we’ve all used are rated to 300 lbs because they build them to around 900- 1000 lbs break strength. If I’m not mistaken the testing done to certify one is a 3 minute pull down test at 600 lbs. at the end of the test there can be no broken welds, bends or signs of structural integrity /damage. Even the straps are that hold them up are less than 3000 lbs (typically). But I could be misinformed?