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Sewn eye and thread strength

lukepighetti

Member
Joined
Sep 22, 2016
Messages
57
I tested the included speedy stitcher thread to 35 lbf breaking strength. Then I sewed up an eye with 60 stitches, doubled thread. The stitching should fail around 2200 lbf with a 75° stitch angle. The Bluewater 7mm accessory cord is rated for 2,300 lbf.

Does anyone have a rope test rig we can try it on?
 

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Wow! I can make sewn eyes with my speedy stitcher? That's awesome!

I did this with the thread and a regular blunt tip leatherworking needle. I wish I could find someone with a test rig so I could see if my math brings me anywhere close to real-world performance!
 
I tested the included speedy stitcher thread to 35 lbf breaking strength. Then I sewed up an eye with 60 stitches, doubled thread. The stitching should fail around 2200 lbf with a 75° stitch angle. The Bluewater 7mm accessory cord is rated for 2,300 lbf.

Does anyone have a rope test rig we can try it on?
Wow! I can make sewn eyes with my speedy stitcher? That's awesome!
I would be very careful with this guys. I was reading a few threads on this topic on an arborist site, and some very experienced climbers were very very wary of doing this on their own. I know there is not much information to go on with that, but just reading that was a sign for me.
 
Yep. I completely agree. In all honesty, splicing is probably waaaaay better for DIY. I considered not posting this at all, to be honest.
 
Well I know it's with a machine, but at the end of the day it's just a needle and thread. Put enough stitches in it and It will hold.
 
Saddle stitching can only be done by hand and it fails more gracefully and is theoretically stronger than machine lock stitch.

I haven't been able to find any engineering standards around load-bearing sewing. From what I can tell, manufacturers design, test, implement quality standards, and ship.

Here's a neat video of one being sewn. It appears to have 300 stitches and I'm not sure what the rating of the rope and thread is.


Does anyone have access to a dynamometer and load cell? I'd love to send you some speedy stitcher sewn eyes with a failure load prediction.
 
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Put enough stitches in it and It will hold.

I wonder if there is a fine line or a thick line between not enough and too much. Is it possible to damage the rope or in most of our case webbing with too many stitches? In other words, do you punch enough holes in the webbing that you are relying on only the thread?

Don't know, not suggesting you are recommending that here either. Just something I've thought about.
 
I know. I really wish I had access to a dynamometer and load cell. We could answer all of these questions in a weekend.

But maybe no-one posts anything online because they don't want to give people the idea that they can sew their own life and safety gear... and then die because of it.
 
Very true. I'm confident splicing Amsteel for life support, but sewing ropes seems a bridge too far.
 
Yes, I have heard concerns about the speedy stitcher's sharp edged needles cutting webbing and reducing the strength. Man I wish I had access to a load cell.
 
I've been using a hand sewn eye in my climbing rope for about a year now. I didn't do any official test but I did use myself(235lbs) and a portly gentleman(410lbs) bouce testing using foot stirup prusics at the same time. It still looks pretty good. I'll take a pic to share. But the main thing was I stiched the X patern to hold the eye then went back like in the video to stich protective stiching.
14729138_10209652157854458_5301207930226339863_n.jpg
 
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I should add this is completely pointless now that I know how to spice doublebraid.
 
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