alexey 6 #1 December 3, 2004 Is it posible to make the same strength joint with E thread(with more spi)? If yes - why use 5 cord - it is simpleir to make all harness with one size cord... Sorry for bad English...Lexa Quote Share this post Link to post Share on other sites
mjosparky 4 #2 December 3, 2004 QuoteIs it posible to make the same strength joint with E thread(with more spi)? If yes - why use 5 cord - it is simpleir to make all harness with one size cord... Sorry for bad English... With 5 cord it takes about 25 inches of stitching (at 6 spi) in Type VII webbing to make the joint match the strength of the webbing. With E thread it would take around 66 inches of stitching (at 9 spi) to do the same thing. That would make a 4 point joint go from around 4 in. to over 8 in. in length. I hope this helps. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
darkwing 5 #3 December 3, 2004 there are other issues that relate to joint strength than just the thread strength. First, shear and peel are quite different regimes in terms of failure mechanisms. In peeling for example, the load is concentrated at the peel junction, and any thread more than about 1 stitch away from there doesn't contribute to the strength. Also, Friction between the fabric (or tape or webbing) layers is a player, and it is related to thread tension, as well as stitch density. -- Jeff My Skydiving History Quote Share this post Link to post Share on other sites
sdctlc 0 #4 December 3, 2004 To add in just pure strength terms, "E" has a Tensile strength of about 8.5 lbs. "5" has a tensile strength of 40lbs Scott C."He who Hesitates Shall Inherit the Earth!" Quote Share this post Link to post Share on other sites
alexey 6 #5 December 3, 2004 Quote That would make a 4 point joint go from around 4 in. to over 8 in. in length. Can you make more points in stitch parrern - i.e. - 5-6 points cross stitch? Or, you can use zigzag? Sorry for bad English...Lexa Quote Share this post Link to post Share on other sites
FrogNog 1 #6 December 4, 2004 Darkwing's reply was that certain loading types would attack the stitches almost individually (or in a line-section). You can see that for these loading types, weaker thread, even with more overall stitches, would fail earlier. -=-=-=-=- Pull. Quote Share this post Link to post Share on other sites
mjosparky 4 #7 December 4, 2004 QuoteDarkwing's reply was that certain loading types would attack the stitches almost individually (or in a line-section). You can see that for these loading types, weaker thread, even with more overall stitches, would fail earlier. Where the load is a "peel" to the joint you would use a confluence rap. This is where you wrap the two pieces of say Type VII with Type XII and then stitch it. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
parafredo 0 #8 December 4, 2004 I think there is a weird idea is going on...Simply NO,NO,NO.Use the right tread for the right job.Do not even think about changing or redesigning harnesses work.Hoping that harness will not be tested somewhere,if so,we might see this news tread on (skydiving incidents forum...) Quote Share this post Link to post Share on other sites
alexey 6 #9 December 4, 2004 I dont want to do it - I just asking - why not? (If you CAN do the same streght some how)Lexa Quote Share this post Link to post Share on other sites
jsconn 0 #10 December 4, 2004 While working at the loft at Skydive City, a girl from Canada came in with a rig resized for her using E thread. She had put 40 jumps on it at her home DZ and nothing had happened. The four of us that saw it, including the manufacturer, almost fainted when we saw it. Using the above example, the harness was 'strong' enough but I wouldn't put my dog in something like that. Jody Conn Aerodyne ResearchJody Quote Share this post Link to post Share on other sites
riggerrob 643 #11 December 4, 2004 Circa 1990, Rigging Innovations drop-tested the Flexon harness to TSO C23C standards. The Flexon was the first ringed harness and most of the joints were bar-tacked with E thread. The bar-tacks were a special pattern about 2 inches long with hundreds of stitches. If I remember correctly, only the thick (5 layers) shoulder joint was sewn with 5 cord. Bar-tacked Flexon harnesses held together well, too bad the machines didn't. After a couple of years pounding through thick webbing, R.I.'s bar-tack machines started wearing out, so they reverted to the old Class 7 machine and now sew most of their harness joints with 5 cord. In conclusion, R.I. proved that you can bar-tack a harness together with E thread, you just need very expensive, complicated bar-tack machines that wear out quickly. How ever, that is largely theoretical as field repairs should be done as close copies of factory stitch patterns and most factory harness stitching is done with 5 cord. Quote Share this post Link to post Share on other sites
masterrig 1 #12 December 4, 2004 A few years ago, I had a 'Sweet Hog' come into my shop fir I&R. During the course of my inspection, I found where the leg-straps had been damaged and 'repaired'. The rigger who did the 'work', simply cut the leg-strap in half, over-laid the webbing about 6" and sewed it in some wavy-gravy type stitch pattern with 'FF' thread. Then, slid the padding back over the repair. I sent the harness-container to the manufacturer. They in turn, sent it to Relative Workshop who pulled the leg-straps to destruction. Both leg-straps failed at about 1200-lbs.! Not cool. Chuck Quote Share this post Link to post Share on other sites
alexey 6 #13 December 4, 2004 Thanks for your info... The last question - if you need (somewhy...) to make it with E thread - you have to make 66 inches of stitching (actually less, if you use type 8 webbing) Can you make 5 or 6 or 7 (whatever its need to be) points cross stitch - its simplier to sewn thick materials with straight stitch? P.S. Pure theoretic, just for info - how far can you gj from Pointer :) Sorry for bad EnglishLexa Quote Share this post Link to post Share on other sites
