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Quagmirian

Base rig project

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Paging Riggerlee, paging Riggerlee...

I posted this on Basejumper just before it got taken down and now it looks like there's no backup.

Last year I made a canopy for *ahem* "low altitude skydiving" and my friend was impressed and asked me to make him a base canopy. So I scaled it up, added 2 more vents and gave it Dacron lines. Since he would be doing the first jump on it he asked if he could name it. The result was Aya. He jumped it out in France this September

First jump video

Since then, he's done about a dozen jumps on it and asked for some modifications like a flatter trim and larger crossports, and a shallower brake setting.

I've been given the patterns to a Darkside container and I've been making good progress making a pair, but it's slow because I've never really done that much container work, and there are elements of the design that I'm struggling with. I'm also not equipped to build containers. I'm probably going to throw the first one in the bin and count it as experience.

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7 hours ago, Quagmirian said:

Paging Riggerlee, paging Riggerlee...

I posted this on Basejumper just before it got taken down and now it looks like there's no backup.

Last year I made a canopy for *ahem* "low altitude skydiving" and my friend was impressed and asked me to make him a base canopy. So I scaled it up, added 2 more vents and gave it Dacron lines. Since he would be doing the first jump on it he asked if he could name it. The result was Aya. He jumped it out in France this September

First jump video

Since then, he's done about a dozen jumps on it and asked for some modifications like a flatter trim and larger crossports, and a shallower brake setting.

I've been given the patterns to a Darkside container and I've been making good progress making a pair, but it's slow because I've never really done that much container work, and there are elements of the design that I'm struggling with. I'm also not equipped to build containers. I'm probably going to throw the first one in the bin and count it as experience.

249248723_10159769905347841_3397738258224980835_n.jpg

260409228_10159839658162841_613247670108628080_n.jpg

Hi Quag,

Why not take what you have there and do a visit to Thomas Sports Equipment in Bridlington & see what they have to say.  I don't think they build base rigs but they design/build skydiving & PEP containers for themselves & others.

Jerry Baumchen

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Sounds like you have another fun project. I can't see a lot of the rig but it doesn't look bad... If you've got access to a double set up as a binder and a 7 class you should be in decent shape. Honestly just copy what every one else has been doing forever. That's all we did when we started. In many ways it's far easier then a canopy.

 

If your asking for general thoughts you know what kind of can of worms that is. I'll toss out a few.

 

Do you need three rings? Landing near water etc? If you skip them it makes it easier and lighter. 

 

Lighter is good. Depending on where you plan to jump it it could be several hours of hiking up hill for 3 to 180 sec of freefall. You might ask your self some questions like how much padding do you need in those leg straps? Do those flaps really need to be dubble layer? Why would you need hip rings? Etc.

 

Pin rigs have become the norm but there are some real advantages to Velcro. I don't know what your plans are but pin rigs are more figgity and less forgiving in design and packing.

 

Actual issues people have had...

 

There have been some flap/pin/bridle issues in the past. There was a big long thread on basejumper about some pin hesitations seen at perion. Turned into a long discussion on flap design, pin clearance, pin orientation, bridle piercing, etc. If it still exist it would be worth finding.

 

There was an incident of a failure of the upper harness junction. It was a peeling issue. Bottom line is that back side loading is better. That's the best way I can phrase it. Example. Look at a skydiving rig. Main three ring back side, no peeling, good. Reserve risers, front side loading, bad. But reserves have always been built that way. They don't put my.p after jump on them. Base openings can be brisk. Body orientations can be more whippy. And skydiving rigs have the main three ring there to kind of act as a loop. Bottom line, we blew up that harness. Another big thread. Some people started using a slink design but I still favor an L bar. 

 

Looks like you have a continuous harness with no stagger. That's fine but I would encourage you to include redundant stitching. The hip junction takes a lot of tork. I've seen it tear.assume all stitching in the hip joint will fail. I've seen it happen. The only reason the guy did not fall out was that there was some redundant harness stitching in the leg strap by the buckle. 

How big of a pc pocket do you want? Just about have to make a choice. Large or small. Long delay or short delay

Need more pics but looks good for a first try.

 

Lee

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I've given up on the first attempt and started a fresh one, going well. If I had all the machines and tools I need, I could do it in 2 days easily. For reference, these are the harness junctions I am copying. I would have thought that just one confluence wrap would be enough for the peeling issue, but the Darkside designer has gone for two. As for the legstrap junction, it doesn't really matter if it fails, you just get a leg injury on opening that's all. All the other details I'm just copying straight.

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1 hour ago, Quagmirian said:

I've given up on the first attempt and started a fresh one, going well. If I had all the machines and tools I need, I could do it in 2 days easily. For reference, these are the harness junctions I am copying. I would have thought that just one confluence wrap would be enough for the peeling issue, but the Darkside designer has gone for two. As for the legstrap junction, it doesn't really matter if it fails, you just get a leg injury on opening that's all. All the other details I'm just copying straight.

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Hi Quag,

I would suggest that you Start-Stop the stitch pattern here or double up the stitching here:

1762714415_Quagjpg.JPG.1389a28a48f159d8154dff924f37bc7a.JPG

That is where the highest point of loading at that joint is.

Jerry Baumchen

 

 

 

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20 minutes ago, Quagmirian said:

What about rotating the webbing so it doesn't meet at right angles? I assume this could also be solved with a hip ring, but that just introduces more weight and failure points.

Hi Quag,

Re:  What about rotating the webbing so it doesn't meet at right angles?

It is almost impossible to form this joint so that all the stitches load equally.  People are simply too different in stature.  A ring does allow all of the stitching to be loaded equally.  'All of the stitching' means the stitching in each portion of the hip joint, not all stitch patterns.

Al MacDonald of Flying High in Canada, a number of years ago, did some comparative testing of hip joints with & without rings.  The ringed hip joint was substantially stronger.

Jerry Baumchen

PS)  If it were me, and not using a ring, I would rotate the stitching 90*, so that the stitch pattern is in line with the horizontal back strap.

quag-1.jpg.4b0b0395581023e26556893e872267c2.jpg

PPS)  Shoot me an email & we can discuss this more; and in more detail.

Edited by JerryBaumchen
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Agreeing with what riggerlee and Gerry Baumchen said ... but may I add a bit more?

Many years ago, John Sherman found that a short WMW stitch pattern like yours was not the best. Sherman was using Type 13 to make his SST Racer harnesses, but found that sometimes a stitch would break at the corner, so he added an extra piece of webbing to the back-side and sewed a 4 inch WMW stitch pattern. No more broken stitches because the greatest load was in the middle of the stitch pattern. 

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8 hours ago, riggerrob said:

...but found that sometimes a stitch would break at the corner, so he added an extra piece of webbing to the back-side and sewed a 4 inch WMW stitch pattern...

I'm using two layers of interleaved ty8, so what if I extended the stitch pattern an inch or so up the MLW? Would that take the stress off the corner where the MLW meets the legstrap?

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5 hours ago, Quagmirian said:

I'm using two layers of interleaved ty8, so what if I extended the stitch pattern an inch or so up the MLW? Would that take the stress off the corner where the MLW meets the legstrap?

Hi Quag,

I can tell you what Rob is talking about.

1.  Cut a piece of T-8 at 6" ( 150 mm ) long

2.  Turn both ends under 1" ( 25 mm ) - you now have a piece 4" ( 100 mm ) long

3.  Place over your hip junction on the underside of the MLW but centered on the hip junction so that an equal amount of the T-8 is above & below the hip junction

4.  Now sew it with a 4-point stitch pattern for the entire 4" ( 100 mm ) both above & below the actual hip junction - you now have stitching both above & below the hip junction that only connects this piece of T-8 to the MLW

What John Sherman found was that by doing this, some of the load at the actual hip junction would then be supported by this longer piece of T-8 where it is sewn to the MLW.  This allows the T-8 that is above & below the hip junction to carry some of the load; thereby reducing the load that the stitching at the hip junction has to carry.

Do you understand this?  If not, get back to us.

Jerry Baumchen

PS)  When I saw my first SST back in the early 70's I could understand why this extra piece of T-8 was there.  Now, I know.

Here what I worked up.  The black outlines the piece of T-8 & the red is the stitch pattern.

quag-3.jpg.14e6cc3b1bc51b4f2f8e433156c5472e.jpg

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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

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90 degrees is not the perfect angle for upper leg straps (ULS) to meet the main lift web (MLW) and lower leg strap (LLS). The angle changes with loading as the leg straps try to equalize the load ... meaning that they both share half the load. This puts the greatest load on the top, forward stitch. That is why Vectors and Talons double the stitching along the forward edge of the hip joint.

"Ved" leg strap junctions (e.g. Softie pilot emergency parachute) end up more like 60 degrees a part.

70 degrees is the angle between the upper leg strap (with hardware) and the (longer) lower leg strap on the Voodoo Curv hip joint. The Curv also has hip rings which allow the lower leg strap to self-adjust its alignment with the MLW.

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Yes riggerlee,

Adding the extra layer of webbing halves or thirds the shear stress on any individual stitch. The more layers of webbing, the lower the shear stress at any given joint.

2 layers of webbing put 100 percent (1/1) of the shear on a stitch, because there is only one shear face.

3 layers of webbing put 50 percent (1/2) ...

4 layers of webbing 33 percent (1/3) ...

5 layers of webbing 25 percent (1/4) ...

6 layers of webbing 20 percent (1/5)...

etc.

Ultimately the number of layers of webbing is limited by your sewing machine. The higher the presser foot can lift, the more layers you can sew at one time.

Also consider that Mike Johnston (sp?) told me that when he tested harnesses made of multiple layers of Type 8 webbing, they were slightly stronger because Type 8 stretches a bit more than stronger, thicker webbings (e.g. Type 7).

Edited by riggerrob

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2 hours ago, riggerrob said:

90 degrees is not the perfect angle for upper leg straps (ULS) to meet the main lift web (MLW) and lower leg strap (LLS). The angle changes with loading as the leg straps try to equalize the load ... meaning that they both share half the load. This puts the greatest load on the top, forward stitch. That is why Vectors and Talons double the stitching along the forward edge of the hip joint.

"Ved" leg strap junctions (e.g. Softie pilot emergency parachute) end up more like 60 degrees a part.

70 degrees is the angle between the upper leg strap (with hardware) and the (longer) lower leg strap on the Voodoo Curv hip joint. The Curv also has hip rings which allow the lower leg strap to self-adjust its alignment with the MLW.

Hi Rob,

Re:  90 degrees is not the perfect angle for upper leg straps (ULS) to meet the main lift web (MLW) and lower leg strap (LLS).

I agree.  Here is a photo from Paraphernalia's/Softie website:

softie.jpg.bf05be3feb8002cbc5bd9a492029ee34.jpg

IMO this is a nicely splayed webbing at the hip joint.

I'm not sure why Quag wants to do it like this; I'm sure he has his reasons:

quag.jpg.1a7ab352a059a418eefdbaaaac7ad23c.jpg

Jerry Baumchen

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I'm doing it that way because it's like that on the harness I'm copying. It only has 4 jumps on it but that's proof enough for me that it works. I'll double up the stitching on inside corner and just hope that the second layer of type 8 is enough to stop the first layer peeling upwards off the legstrap.

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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

Edited by RiggerLee
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I have nothing to contribute to this discussion from a technical standpoint.

But I want to comment that it's absolutely amazing to see folks with decades of experience in this sort of thing freely contributing and sharing to help the 'new guy' get it right.

This is basically 'doctorate level' harness design and construction stuff.
Both theory and practical.
Way, way, waaaaaaay beyond my skill/experience.

But the fact that Jerry, Lee & Rob are willing to help at the level they are is REALLY cool. 

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+1 for joe's comments.

I was reminded of the "Rocky" movie by the Word Association thread.

I see Quag a bit like Rocky.
The "i'm going to build my own canopy" was like the Quag I movie.
This "i'm going to build my own container" is the Quag II movie. "Yo Lee, I did it!"

Fun to follow along at home.

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The way I'm stacking the layers is leg strap on the bottom, followed by a MLW layer, then the other legstrap layer, then finally the second MLW layer on the top. That's the way it is on the one I'm copying.

I do read everything that's written here but I often just go away and think about for a while rather than reply immediately. One of the reasons why I put this on a public forum is that when I was starting out, there was precious little in the way of reference material, and this way it's all available for others who want to read about these things.

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Whether you stagger the hip joint is determined by whether your backpad is longer or shorter than your Main lift web.

Small skydiving rigs tend to have staggered hip joints because the container (think 100 square foot canopies) is shorter than the MLW.

OTOH pilot emergency parachutes tend to be longer than MLWs. PEPs range in (back-pad length from 60 to 100 cm (40 inches), so sometimes, they work better with horizontal back-straps sewn BELOW the upper leg strap (see PEPs made by Flying High Manufacturing in Canada). Sewing the HZ below the ULS reduces the risk of the wearer falling out of the harness buttocks first. 

Also consider that most skydiving and BASE containers bottom out at belt level, while PEPs need to extend down to the seat bottom to relieve the load on the pilot's shoulders.

Edited by riggerrob
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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

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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

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1 hour ago, RiggerLee said:

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

Hi Lee,

Re:  I thought I was a radical when I ran a horizontal below the leg junction on a harness.

It has been a number of years ago, but I read & saw photo where Sunpath did this for one of their Jav rigs that they built for a VERY short member of the Golden Knights.

I don't have the photo, or I would post it.

Jerry Baumchen

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