RiggerLee

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RiggerLee last won the day on May 5 2019

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  1. None of that surprises me. I've thought about similar things my self. Toyed with the possibility of building base harnesses from ultra light weight spectra webbing. Never went forward but it would have to have been sewed with essentially a bunch of bar tacks. Sewing like that has been the norm forever in other industries like the climbing industry. If you look at there harnesses every thing is sewn with a but load of zigzag on some big pattern tracker. There is no question that this can be done but there are some trade offs. One reason the flexion held together so well was the rings allowing every thing to aline in shear. So with propper design it can be every bit as strong. In fact I think I can make an argument for it better distributing the load across all the fingers of the webbing and better transfering the load through the joint. But... Although it's a smaller needle it's punching that needle through that fabric a lot. It's a known wear issue. Climbing harnesses are considered disposable. They do not and are not expected to last a long time. Think about how old some of our rigs are. That kind of stitching tends to be subject to abrasion. The stitches tend to lie on the surface. Rubbing against rock can abrade them cutting the stitches across large areas of the pattern. I've seen the same thing with roofing harnesses. These things quickly fell apart. A four point sewn lengthwise in a thick loosely woven webbing sinks down into it. It's kind of self protecting. We built a set of roofing harnesses for one of the local skydivers that owned a roofing company. The Gestapo, I'm sorry I ment OSHA, had show up at his site and busted him for not having harnesses for any of his Mexicans. We built skydiver grade harnesses on our seven class. I think there legality may have been questionable. There is probable some kind of certification for fall protection harnesses. They were the the only ones he ever had that held up. All the commercial ones fell apart litterally. They were the only ones his workers would actually use. I find the trade offs in these questions to be fascinating. Lee
  2. Never did the staple thing. At least not for harnesses. I have used e thread mainly for really heavy stuff to avoid the thickness that glue could add. I was maxing out the lift on my seven class. I actually have a lighter walking foot with more lift that I can baist it with. One advantage of hot glue is actually at the other end of the spectrum. When you're sewing some thing light. I'll use the example of a riser end. Let's say you're sewing a riser of type 8. It's structural. You want it to be strong so sewing it on a harness machine would be the obvious thing to do right? Problem is that even though it's a webbing and very much structural it's still soft and light. Sewing some thing like that on a seven class is very problematic. It's hard to keep from shrinking it and causing point loading. There are a lot of solutions. Sew it some other way, like with a boat load of zigzag. Fold the webbing under again so you have three layers and a little more meat and stiffness to it. That's kind of an extreme example but it holds true in all which patterns. If the stitching is contracting it and can not elongate with the webbing under load then ether the stitches them selves break or they cause point loads in the webbing where the webbing will fail. One thing I will say for glue. It can make the layup stiffer and the the sewing more forgiving. That should not be discounted. Not to mention the fact that it is by far the easiest way to get the layup accurate, even, flat etc and to hold it that way all through the process. I was there in that big general meeting, a fly on the wall, lessening to the biggest players in the industry, like Mills, talk about this. Trying to move to clamps was a huge pain for them. They were optimistic that if they could get a set up that worked that production would pick back up. In theory it would save steps glueing. But most of all they just desperately wanted to keep there contracts. Lee
  3. How much do you actually need? If you need rolls you almost have to find some one local. I don't know any one there other then heathcoat. I might just call up a manufacturer. I used to do crw with Red at flight concepts in Atlanta GA. Really nice guy. He would probably roll off a few cells worth of fabric and sell it to me in an envelope or a small box. I hate folded fabric. You know if you could send hi. The drawings in a format that he could early use he would probably cut the whole canopy for you on his computerized table. Custom colors on fabric. You know is straight. I'd pay for that. And that would break down into a box small enough to ship across the water. Lee
  4. It's been a few years but I think that is the $100 machine. Must have been a 7. Just drop feed. That thing was small but a beast. We got a lot of work out of that little machine. Never knew the model. The plate was missing. Lee
  5. No direct experience with that machine. But I've often thought that a 7 class was a bit overboard for 5 cord. There are probable machines out there that could handle 5 cord. Make sure you check the lift. Base jumping harnesses are not that thick. You might be able to find a smaller machine that would have the lift that you need and could see through with 5 cord. I can't remember the model. But we had this really old singer. That we got out of a guys barn for $100. We just called it the $100 machine. He was using it to repair really heavy horse tack. Harnesses and shit for the horses. He was sewing with a heavy cord. No markings on the spool. Probably a dacron but it was damn near 5 cord. Single needle simple dropfeed. Looked like a miniature version of a 7-33. That was actually a really great machine. I wonder how small of a needle would carry 5 cord? If you didn't go bigger then you had to that would make it easier to punch the needle through on a smaller machine. Lee
  6. I'll expand on that with some caviots. Perfectly good model but like most models it breaks down when you try to extend it into the range where the systems behavior becomes nonlinear. That kevlar thread is actually stronger then the nylon tec 500. Sew loops at both ends of a peace of kevlar webbing one with the stronger kevlar and the other with nylon. Pull. The kevlar will break first every time. The nylon junction is stronger not by a little bit but by quite a lot. So on places that are protected and not subject to aerodynamic heating we use nylon where we can. The little bit of give in the nylon let's it share the stress more evenly over the stitch pattern. As you try to get more strength, more stitches, in a joint there is a point of diminishing returns where when you pull on it only part of the stitch pattern bears the load. So the pattern breaks progressively from one end to the other. This relates to the elastisticy on the webbing. It is exaggerated if there is a discrepancy between layers of webbing. Say there are three layers and you are pulling on the top layer. The bottom two layers are stiffer then the top layer. When the top layer stretches it loads the first part of the pattern those stitches break first. Some one once told me that a reinforcing, like a tape on a canopy, should have an elastic coefficient a certain percentage of the substrate to avoid point loads and shear forces between the two. In the same since the stitch pattern must have the ability to stretch and deform to match the material being joined. That is why it's advantageous for the stitching to be as far as possible angled relative to the load. Notice that most of the stitches in a 3 or 4 point are angled. When you pull on it the highest load points are at the corners where the side stiches are straight. This is actually less then ideal. In fact the straighter the stitches the higher the load at the points.. So there is kind of a minimum angle that you would like to maintain in the pattern. Therefore there is a limit as to how long you can make a three or four point or the number of points you want in a pattern. So if you want a larger longer pattern it can be better to dubbel or triple the pattern. Imagine two three points end to end. Now imagine the stitches continuing rather the turning where the points meet. Basically the pattern bounces back and forth from side to side of the webbing like a big zigzag. Think of the dot in the old pong game. Try drawing it you will have an over sew when you get back to your starting point to move to the next half of the pattern. You'll wind up with the same amount of over sew as you would have in an equivalent pattern. But a multipattern can be better then one long four point. The maximum length of the pattern tends to depend on the stiffness of the webbing. The most extreme example of shortening and widening the pattern would be to sew it in a diamond pattern like to sew the four point sideways on the webbing and I've seen this in some heavy load applications on nylon. They actually sewed it back and forth from side to side in a big square block. It defenintly let the nylon stretch but a don't favor this because I think you would tend to snap the webbing at the end of the pattern. But I have seen it done. Most extreme example I've run into. An early project I was given was to test seam designs for a prospective canopy. So I had to figure out a way to load seams to destruction in f111 and zp. Trickier then it sounds. Wanted to load a decently wide area. Clamps didn't work. When the fabric stretched under load the fabric it self would tear under shear at the sides of the clamps. Ultimately I wound up sewing leaves of wide webbing to the fabric to pull on. It was an interesting stitch pattern. Boxes, 3 points, 4 points won't work. Any thing with a straight corner would cause the same shear as a clamp and tear the fabric before the seam. It needed a smoother transition to the unloaded fabric. I wound up with a two point with the points in the middle of the pattern not at the edges let the fabric avoid that sudden shear load. I don't like to think about how many of those test articles I had to sew up. Lee
  7. I'll expand on that with some caviots. Perfectly good model but like most models it breaks down when you try to extend it into the range where the systems behavior becomes nonlinear. That kevlar thread is actually stronger then the nylon tec 500. Sew loops at both ends of a peace of kevlar webbing one with the stronger kevlar and the other with nylon. Pull. The kevlar will break first every time. The nylon junction is stronger not by a little bit but by quite a lot. So on places that are protected and not subject to aerodynamic heating we use nylon where we can. The little bit of give in the nylon let's it share the stress more evenly over the stitch pattern. As you try to get more strength, more stitches, in a joint there is a point of diminishing returns where when you pull on it only part of the stitch pattern bears the load. So the pattern breaks progressively from one end to the other. This relates to the elastisticy on the webbing. It is exaggerated if there is a discrepancy between layers of webbing. Say there are three layers and you are pulling on the top layer. The bottom two layers are stiffer then the top layer. When the top layer stretches it loads the first part of the pattern those stitches break first. Some one once told me that a reinforcing, like a tape on a canopy, should have an elastic coefficient a certain percentage of the substrate to avoid point loads and shear forces between the two. In the same since the stitch pattern must have the ability to stretch and deform to match the material being joined. That is why it's advantageous for the stitching to be as far as possible angled relative to the load. Notice that most of the stitches in a 3 or 4 point are angled. When you pull on it the highest load points are at the corners where the side stiches are straight. This is actually less then ideal. In fact the straighter the stitches the higher the load at the points.. So there is kind of a minimum angle that you would like to maintain in the pattern. Therefore there is a limit as to how long you can make a three or four point or the number of points you want in a pattern. So if you want a larger longer pattern it can be better to dubbel or triple the pattern. Imagine two three points end to end. Now imagine the stitches continuing rather the turning where the points meet. Basically the pattern bounces back and forth from side to side of the webbing like a big zigzag. Think of the dot in the old pong game. Try drawing it you will have an over sew when you get back to your starting point to move to the next half of the pattern. You'll wind up with the same amount of over sew as you would have in an equivalent pattern. But a multipattern can be better then one long four point. The maximum length of the pattern tends to depend on the stiffness of the webbing. The most extreme example of shortening and widening the pattern would be to sew it in a diamond pattern like to sew the four point sideways on the webbing and I've seen this in some heavy load applications on nylon. They actually sewed it back and forth from side to side in a big square block. It defenintly let the nylon stretch but a don't favor this because I think you would tend to snap the webbing at the end of the pattern. But I have seen it done. Most extreme example I've run into. An early project I was given was to test seam designs for a prospective canopy. So I had to figure out a way to load seams to destruction in f111 and zp. Trickier then it sounds. Wanted to load a decently wide area. Clamps didn't work. When the fabric stretched under load the fabric it self would tear under shear at the sides of the clamps. Ultimately I wound up sewing leaves of wide webbing to the fabric to pull on. It was an interesting stitch pattern. Boxes, 3 points, 4 points won't work. Any thing with a straight corner would cause the same shear as a clamp and tear the fabric before the seam. It needed a smoother transition to the unloaded fabric. I wound up with a two point with the points in the middle of the pattern not at the edges let the fabric avoid that sudden shear load. I don't like to think about how many of those test articles I had to sew up. Lee
  8. That's cool I'd never seen that on a pilot rig. I thought I was a radical when I ran a horizontal below the leg junction on a harness. That harness didn't have a container attached to it. It was worn under clothing and that lower band made it feel very comfortable and secure with out a back pad. The container was a separate jansport looking backpack. It also had no hardware on the leg or chest strap. You wiggled too it from the top. Lee
  9. That's cool I'd never seen that on a pilot rig. I thought I was a radical when I ran a horizontal below the leg junction on a harness. That harness didn't have a container attached to it. It was worn under clothing and that lower band made it feel very comfortable and secure with out a back pad. The container was a separate jansport looking backpack. It also had no hardware on the leg or chest strap. You wiggled too it from the top. Lee
  10. It's hard to tell from the above picture but I might consider running the horizontal/leg strap through the center of the mlw as opposed to running the mlw through the center of the leg strap. In theory ether would work but in practice I've seen the two outer layers of the leg peal outwards and down breaking the stiches one by one. By putting the leg on the inside with the tension on the upper mlw I think you force the stitching on ether side into shear. I didn't do this on my rigs because I had stagger in them and I wanted to wrap the leg around the mlw in case it failed. This added redundancy but it did not make it stronger. It made it weaker. If you are going with a continuous leg strap like this I would samwich the leg inside the mlw. You might even think about spreading the leg strap in a v from the hardware to the back pad. Gives you a bit more room for sticking in that joint and makes for a thinner transition at the end of the over lap which is generally to the good in the strength of a junction. Don't be afraid to sew half an inch above and bellow the leg strap but glue that section. Glue helps to stiffen the webbing and makes it easier to sew the ends of the four point with less shrinkage and stress at those points. Don't run the tension higher then you need to to get a good centered stich in the thickest hardest part of the joint. I don't know what's happening up inside your back pad but I'd put a U'd three point by your leg hard wear. On a separate matter. Looking at weight of webbing and weaves and dissimilar webbing vs thread in stich patterns. Interesting things I've seen. Been doing a lot of work with heavy kevlar webbing. Stuff in the 20,000+ range. Kevlar does not stretch very much. There are interesting things that happen with elastic coeff icents and stich patterns. There is something to be said for the ability to stretch and sort of distribute the load across the junction. To maximize the strength you have to have the ability for something to give whether it's in the weave, the thread or the material itself to allow all the stitches to share the load. And it won't be even but I mean as close as you can. Some day I want to do a more organized study but there are relationships between stitch density thread strength thread elasticity length of joint and elasticity of the webbing. We've done some destructive testing of our risers line attachments etc. The kevlar has has allowed/ required us to go to some rather long stitch patterns to get the strengths we need. It's interesting to see how the patterns break. The kevlar is so stiff that we can break just a few stitches at a time pulling it in the hydroloc tester. I think nylon would just go kapow like a rubber band. As an example were ever possible we have been going with a heavy Tec 500 nylon cord rather then a stronger kevlar in our patterns because that little bit of stretch allows for the load to be better shared across those long joints. I don't think I could use that long of a joint with nylon webbing. I think the stretch of the webbing would mean that only part of the joint would be loaded and you would fail the first part of the stitch pattern before the rest. But with the heavy kevlar and the nylon thread we just kept going longer and the failure point just kept going up. It's been interesting trying to get the most out of these materials. Lee
  11. In regards to the racer. Part of the reason he had to do this was that he was using a single layer type 13 mlw. If he had just layed one on top of the other and sewed them together it would never hold. By samwiching it like that with the extra piece running an inch higher you change the failure mode. Now when you pull on that top corner the leg strap webbing is supported by the stitch on both sides. When you try to pull the leg out of the mlw each stitch is supporting the leg on both sides where it passes into the mlw. Looking at other designs. The early vector ones had stagger. They plugged the leg strap into the mlw between the two layers. At some point they started wrapping the webbing of the leg strap around the inner layer of type eight. The sticking of the four point ran down bellow the junction far enough that if the joint failed that loop would probably save them. Javelin looped both around the mlw so that it slipped on. I've seen the stitching fail but because they had some harness stitching in the leg strap, just a box, no one fell out. And the tightening on the leg is not that bad. The National pilot rigs don't even sew that joint. They leave it a slot that the mlw can slide through so it's "adjustable". Some people have spread out the leg strap in a V to get more area in the joint that they are sewing. And yes you can angle it down at a bit of an angle to try to get a more natural loading with out so much of a stress concentration at the top. You can also get creative. Example. John Stanford with the prestige container. I worked for him for a while. That's where I learned most of what I know. He ran the diagonals on his back from one shoulder junction diagonally to the opposite hip to the leg strap back across the lower back to the opposite hip to the leg strap back up diagonally across the back to the opposite shoulder. One big long piece. The leg strap junction instead of being at a 90 degree angle was about 60 degrees and the webbing was spread out. The mlw went between the two layers. He sewed it with a boxed three point. All the stitches of the three point were within the box. If you over stepped it that stitch tended to pop. He found that in drop testing. A lot of the original military harnesses were built with variations of that kind of diagonal harness. Another example was the... Eos container. It had an interesting harness design with an angled joint if I remember correctly. I think I only ever saw one of them and it's been a while. Lee
  12. Perfectly good canopies. Open well. Land well. But they do come in two different versions. If you get the chance to jump if you might note on the card whether it is a "r" or "l" varrent. Lee
  13. I'm with you 100% but I can sew straight and I don't have much of an esthetic since. Taking the time to change thread is a pain. Manufacturers are obsessed with the appearance of there rigs. And matching the thread hides a host of sins in there less then perfect sewing. They have chosen over and over again that looking cool is far more important to them then functionality. Lee
  14. At one of the pia meetings before the symposium where all of the mil contractors and government purcurment people get together to bitch at each other this was one of the topics of conversation. I'd did indeed come from a joint not being sewn. Not a heat issue. All the contractors were trying to come up with mechanical jigs and clamps to hold every thing straight during sewing. There was a lot of suppressed grousing under all the "please please can I keep my government contract?" Underneath all the ass kissing was the universal sentiment that hot glue was better faster easier and more accurate. There was a faint hope that the speed would pick back up if they could ever get the clamps to work and not slip but that arranging the peaces and getting them clamped straight even and on the mark was... Challenging. For small production glue is so much easier and has a proven track record. As a rigger I could get behind the idea of contrasting thread but I don't see it flying estheticly. Also it makes less then perfect sewing blatantly obvious and I don't see manufacturers volunteering to produce unsightly rigs. Lee