Sabre 1 120 reline

[masterrigger1 2]

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Do you know what was changed between early and later versions of the Sabre 2 that make a difference?

I know that they removed the type IV on the leading edge of the load bearing ribs in the center and had a couple of revisions; i.e. P01, P02, P03,...


MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[masterrigger1 2]

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I have long had a suspicion that the 3" tape that sliders are outlined with may be a culprit. If both the front and rear of the slider have a 3" border fold under it could leave a much smaller hourglass shape to do the job.

I could see that being a variable or issue especially with the heavier, thicker tape.

MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[masterrigger1 2]

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is technora just a fancy word for hma,

No, it is not just a fancy name.

Technora is the trade name of the original fiber that was produced by Teijin Fibers in Japan. It is a High Modulus Aramid.

We started using this about late 2000 as the first lines especially made for Pro-Swooping Canopies. Chuck Blue and Joe Bennett had the first two line sets ever made strictly for competition. It was a 340lb line..

Other manufacturers started calling it HMA as a marketing tool obviously as not to seem to follow in someone's previous path.

Just to show this, look at the trade name of the other line materials:

Spectra ----Polypropylene
Dacron ----Polyester
Vectran ---Liquid Crystal Polymer
Technora---High Modulus Aramid

Also Technora has a better resistance to wear than Vectran. It problem is that it is UV sensitive. This is why we both coat the natural/Tan fiber and also use the black fiber for UV protection.

MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[masterrigger1 2]

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MEL, I'm surprised to see Spectre on that list. I have Dacron lines on mine and picked it specifically for its opening characteristics. Is it just down to the line choice or are there design aspects as well that put it so high on your list?

I would say it is mainly the line choice. Of course, the canopy design and materials has a lot to do with it also. But again, it boils down to the line.

With a Dacron lined canopy, the dimensions with grown over time, not shrink. This will usually make the canopy snivel more since it is mostly elongating in the center A-B Lines over time. This allows the nose to be more in a positive pitch relative to air flow.

A Spectra lined canopy will shrink at the Lower control lines, the USTs, and the outer lines as these are the lines in heavy contact with the slider during inflation. This is the difference of the line trim that is more prone to hard openings. With Spectra, the canopy can be more in a "cupped" shape.


MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[betzilla 56]

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Do you know what was changed between early and later versions of the Sabre 2 that make a difference?

They also increased the size of the slider on the larger sized Sabre 2's.

[EvilGenius 0]

Hi MEL,

Thanks for posting it's really interesting, I hadn't though about lines from a chemistry POV before.

Since HMA rather than being a specific material can be any of a class of materials "para-aramids" with brand names such as Kevlar®, Twaron®, and Technora®. I wonder if manufacturers are using the same fibers e.g. Technora and just naming things different or if they are using structurally different materials e.g. Kevlar? Maybe it's neither and they are using generic equivalents, if such a thing exists?

Thanks!

Stuff about rope/line materials http://www.animatedknots.com/rope2.php#lcap

[EvilGenius 0]

Slightly more on topic!

I've have about 100 jumps with Vectran lines on my Sabre 2 and a few 100 with Spectra before that. Excluding the weird stuff that happens towards the end of the Spectra line-sets lifetime I haven't really noticed a massive difference in terms of opening.

I chose Vectran simply because it was in stock!

[skytribe 16]

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Long story short, never been an issue, even with small suits and slick jumps.

Isn't that what everyone says until it is an issue. If you changing the line types then your introducing a new variable into the mix.

[RiggerLee 61]

Sorry, I got distracted but I want to get back to this because I think it's important.

You argue that canopies lined with specter will open softer then the same canopy lined with vectran or HMA because spectra has slightly more stretch in it's weave. Then you state that the hardest opening canopies, the ones that have caused the most injuries, are the ones lined with specter.




Post:
Quote:
I don't buy your argument that vectran would open harder then specter do to specter having greater elasticity.

Obviously you have never jumped a canopy with Spectra, lined that same canopy with Vectran and then jumped it.
I have and the difference is what I have previously explained.

Quote:
Specter doesn't have a lot of give to it. It sets and has very little give,

Spectra is easily shown that is has more elasticity to it than Vectran by simply putting a piece of Spectra on a line table, put it under load, make a mark that matches the same spot on the table, and then watch the two mark separate slowly. It will do it every time..

Vectran will not do this...
So my statement stands.

Quote:
I think that whole business is a bit of a myth.

You need to look into it more.
Dacron lined Mantas open just fine. Put Spectra on one and you will soon see the difference, enough to have to install a nose mod on them.

Quote:
Of all the issues with hard openings I just don't think line elongation is a significant factor. And your own evidence points to specter being even less forgiving.

Elongation (or lack of..) is an issue if you have a hard opening would you not agree??
Most people would think so.




First, I want to talk about the energy absorbed in the elongation.

The kinetic energy stored in the jumper is 1/2MV^2, Half the Mass times the velocity squared. 190 lb jumper(convert mass to slugs), 176 ft/sec, gives you 91,389 ft*lb of energy. To absorb that energy you have to do Work on the system over and above the force of gravity. Work is Force times Distance lbf*dis. In theory over a 700 ft opening it would only take 130.5 lb of force over and above the force of gravity, that would assume a constant load. The reality is not that nice with a higher peak and a bell curve dependent on all the vagueries of drag and the characteristics of the opening.

Now let's talk about what happens when some thing stretches. The lines are a good example but there are other parts of the system with as much or more stretch, compression, or absorption in them. The mass is moving 176 ft/sec. A load is applied by the canopy. When the lines or some thing else stretch they limit the force applied to the mass. The force seen by the mass is dependent on their elongation curve. The mass will see only that force as the elongation occurs and then once the "spring", that's what we're really talking about, saturates, reaches the limit of it's elongation, then all the force will be transferred to the system. So the mass is moving. It has a certain kinetic energy. While the lines stretch it experiences a limited load restricting the peak force. Over this distance a certain amount of kinetic energy is absorbed out of the system based on the capacity of the spring, force over distance to the saturation of the spring. Then the rest of the opening proceeds normally. Let's say the peak force of the opening of the canopy is reduced in relation to the remaining kinetic energy or you could think about it in terms of the opening occurring at the new lower velocity based on the energy absorbed by the spring, the lines. But from that point on the lines can do nothing to mitigate the peak load of the opening. They are as stretched as they can go, the spring is totally saturated, there is no more "give" in the system.

Sounds, great. Stretchy lines. This is what we've been saying for years. But let's put this in perspective. Energy absorbed by the lines. The weave of the lines has some spring to it. once the weave elongates and the line is set there is not much change. The fiber it self has a much higher modulus, spring to it. So the curve goes way up with very little elongation. So when you build a line set you have to stretch the line to get that spring out of the weave and get a good consistent measurement on length. Let's say you put 20 lb on it and got 1 inch of stretch out of the line. Honestly I never really paid attention to the stretch. I never started measuring things till I had them loaded. 20 lbf over 1 inch is 1.667 ft*lb of kinetic energy per line times 12, 19.92 ft@lbs absorbed out of the 91,389 ft*lbs of energy in the system. That's assuming that it takes 20 lbf to stretch the line all the way along that distance. Not the case. If it were linear more like a spring then it would be half that. In reality it's probable some thing in between with a bump at the front and then a curve going up. Let's say it's a 9 cell with 12 main lines. Ten cascaded supention lines and two break lines. But even in the most generous scenario it's only absorbing 0.0219% of the energy of the system. Beyond the elongation of the weave you could talk about the modulus of elasticity of the polyethylene. I haven't bothered to look it up and you would have to talk about area and how the load is distributed. The loads are much higher but the length of elongation is much shorter. There just isn't enough change in length to absorb a lot of energy and you'll quickly reach beyond the peak loads of the opening trying to stretch it by inches much less feet. Let's say the peak is 5 G's For 190 exit weight the peak load is 950 lb. Once all the set is taken out of the weave how much more stretch do you think you will get out of 12 fully set lines with only 950 lbf on them. Take that line with 20 lb load on it, fully set, and add another 80. Let's say you got another inch out of it. over the whole line set you're talking another 79 ft*lbf out of the system that's another 0.0864% So in the best scenario I can come up with for specter lines it looks like they would absorb just over 0.1% of the energy of the opening before they saturated.

Some body check my math. It's been a while. Now if you leave a polyethylene line under load for a while it will stretch. Like leave a twenty pound weight hanging from a peace of it for a week. That's actually creep that happens slowly over time, think days. It's a product of the molecule. You may not see that in HMA or vectran. That has nothing to do with what happen in the opening. It isn't even applicable over the life span of the canopy. Note that that line shrink from the heat more then they stretch in creep.

Tired of typing. I'll try and get in to the other factors later.

Lee

Lee
[email protected]
www.velocitysportswear.com

[masterrigger1 2]

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Sorry, I got distracted but I want to get back to this because I think it's important.

Obviously so do I.

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You argue that canopies lined with specter will open softer then the same canopy lined with vectran or HMA because spectra has slightly more stretch in it's weave. Then you state that the hardest opening canopies, the ones that have caused the most injuries, are the ones lined with specter.

No I am saying that if given the same magnitude of a severe hard opening, Spectra has more give to it than Vectran or Technora.

I am also saying that the canopy lined with Spectra has a great chance of developing a hard opening to begin with.

Two entirely different statements.

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But from that point on the lines can do nothing to mitigate the peak load of the opening. They are as stretched as they can go, the spring is totally saturated, there is no more "give" in the system.

Well, did you calculate the elastic and plastic values of each material??
Remember that even steel has number with Young's Modulus.
These are needed finish your equation.

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Now if you leave a polyethylene line under load for a while it will stretch. Like leave a twenty pound weight hanging from a peace of it for a week. That's actually creep that happens slowly over time, think days.

I am not talking about leaving a line under load for days; it is seconds.

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Like leave a twenty pound weight hanging from a peace of it for a week. That's actually creep that happens slowly over time, think days.

That definition would be incorrect as it is not days to take creep out of line material.

Creep is defined in the Braid trade as the amount of dimensional line change from a unloaded specimen to a loaded one. What makes "creep" to begin with is the "looseness" of the bundles to one another.
When these bundles finally come together, this is the end of "creep" in the specimen.

JFFI, line starts out as fiber, spun into carriers, then into bundles, and lastly into the finished product.


MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[pchapman 261]

Ok, so RiggerLee makes the point that the energy absorbed in stretchier lines is going to be miniscule compared to the total amount of energy dissipated during the opening process.

Or one might say that if the canopy inflation takes a few hundred feet and a couple seconds, having an extra inch of line stretch or springiness isn't going to make a difference.

So I'll agree that for that aspect of the opening process, line type won't make a huge difference.

Where I suggest line stretch can make a difference is smoothing out all the little shocks and changes in acceleration that can happen given that a canopy doesn't open in some ideal smooth fashion. The G load on the jumper doesn't smoothly curve up to say 4g and smoothly reduce again.

The big question is, to what extent does line stretch actually make a difference for that sort of thing? That's what's hard to quantify.

So the jumper may need to get to a few g of deceleration for a few seconds, ramping up somewhat gradually to avoid a sudden jolt. But during that deceleration time, as the canopy is buffeting and fighting to open up -- as one sees in slow motion videos -- to what degree do stretchier lines reduce the shock load on the jumper?

That's where it may be nice to have a little give in the lines; better to have Dacron than lines made of steel cables.

That doesn't change whether the canopy snaps open or snivels, but for a given style of opening, the type of line can moderate sudden shocks during the process.

The analogy can be debated, but I'd say it's a bit like braking a bicycle on a cobblestone street. You're still going to need 50 ft or whatever to come to a stop, depending on the design of your brakes. But how you feel during the process will depend on whether it's a traditional bike with no suspension and skinny tires, or a mountain bike with suspension and fatter tires, to absorb the shocks along the way.

Summarizing the situation, we still have the various factors involved in how hard an opening feels. This isn't necessarily exhaustive:

1. Canopy design.
(Those smaller aspect ratio ZP canopies like Spectres and Triathlons do seem to be over-represented among rogue openings? Although as has sort of been noted, a rogue opening on a 90 ft sq canopy could easier on you and not get discussed on dz.com, compared to the same bad opening on a 180 sq ft canopy with twice the drag area.)

1a. Going out of trim
(Spectra canopies near end of line life, the cupping effect of lines shortening.)

2. Slider size and drag
(Plenty of cases of slider size being increased by the factory compared to a canopy's original slider size)

3. Line friction on the slider
(Clearly Spectra is slippery and can allow the slider to shoot down the lines sooner and more quickly.)

4. Line stretch effect on overall opening energy absorption
(A miniscule amount, RiggerLee argued.)

5. Line stretch effect on shock loads superimposed on the overall opening G loads
(The aspect I wanted to mention.)

So I'm kind of thinking -- and I don't have anything like the experience MEL has -- that if a canopy is well behaved in general, having a more or less stretchy line isn't going to make a huge difference. But if it is prone to snappy behaviour during the opening, a stretchier line may be useful. We're still debating that tradeoff -- like slick but stretchier Spectra vs. HMA/Vectran/etc. on a Sabre 1.

[RiggerLee 61]

Creep:

In materials science, creep (sometimes called cold flow) is the tendency of a solid material to move slowly or deform permanently under the influence of mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and generally increases as they near their melting point.

The rate of deformation is a function of the material properties, exposure time, exposure temperature and the applied structural load. Depending on the magnitude of the applied stress and its duration, the deformation may become so large that a component can no longer perform its function — for example creep of a turbine blade will cause the blade to contact the casing, resulting in the failure of the blade. Creep is usually of concern to engineers and metallurgists when evaluating components that operate under high stresses or high temperatures. Creep is a deformation mechanism that may or may not constitute a failure mode. For example, moderate creep in concrete is sometimes welcomed because it relieves tensile stresses that might otherwise lead to cracking.

Unlike brittle fracture, creep deformation does not occur suddenly upon the application of stress. Instead, strain accumulates as a result of long-term stress. Therefore, creep is a "time-dependent" deformation.

https://en.wikipedia.org/wiki/Creep_(deformation)


Speaking of polyethylene:

Mechanical properties[edit]
Polyethylene is of low strength, hardness and rigidity, but has a high ductility and impact strength as well as low friction. It shows strong creep under persistent force, which can be reduced by addition of short fibers. It feels waxy when touched.

More specifically this is what we are talking about:

https://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene

They have yield strengths as high as 2.4 GPa (350,000 psi)

So there is the yield but still looking for the elastic modulus. I may just have to call up CSR and get the curve.

Sorry, got to go shoot guns.

Lee

Lee
[email protected]
www.velocitysportswear.com

[RiggerLee 61]

Places where it makes more deference. Sorry had to go shoot some Tannerite.

If you think about the canopy as it is accelerated to line stretch. Let's start with the old rounds. Booth used to say that a canopy took, or should take, about .7 sec to reach line stretch. I seem to recall that he was quoting a military study of malfunction rates. The sweet spot was around .7 sec. I'm guessing they were using C-9 or some thing like that. Call the lines 28 ft. Let's say it weighs 12 lb.s? I'm just fudging numbers. Let's assume the acceleration is constant. 28 in .7 would be 40 ft/sec but it's doing it from a dead start so let's say 80 ft/sec when it hits line stretch. Kinetic energy is 1,192 ft*lb energy. The lines on a C-9 are way stretchier then any modern line. It really is measured in ft. and It's a better spring it doesn't hit a wall in it's elongation like specter. Let's make up some more numbers. Say it takes a 30 lb to max out the line with 24 inches of travel. Let's assume it's linear. so 30*24/2*28 28 lines. I get 10,080 ft/lb of energy that could be absorbed in the line set of a C-9 which is more then enough to smooth out the sharp spike of the snatch force when the canopy hits line stretch and even to ease some of the opening. But it's still only like 11% of the total kinetic energy of the opening. But please note that with 28 ft of acceleration the spike in the load as the canopy hit's line stretch on a C-9 can be the highest peak in the load curve. Especially when the deployment is high speed with high extraction forces.

A sky diving canopy isn't as bad in the since that it doesn't have as far to accelerate before it hit's line stretch. Most PC's don't have as much drag as an old MA-1 so there is less force over that distance. It doesn't build up as much energy. It also weighs a bit less on average. Still there is a bit of a sharp pop when the bag hits line stretch and the canopy comes to a stop. Watch in a video as the jumper is jerked up right past a sit as the canopy hits line stretch. Our lines just don't have near as much stretch to absorb that sharp yank as the type 3 line on an old round.

Still looking for the modulus.

Lee

Lee
[email protected]
www.velocitysportswear.com

[RiggerLee 61]

I talked to a girl at CSR and she said that they would send me the strain curve for some of their line. I'll probable get a call back from one of the techs asking, "What the f@%k?"

In the mean time I'll present my arguments for other factors affecting the opening of canopies.

All of the hard opening incidents and accidents that I can recall have been on specter lines. I don't think the difference in elongation of the weave or the modulus of elasticity plays a significant part one way or the other. I'll list some things that I think do affect the statistics.

Over our history there are just far more canopies lined with specter than other lines. There have simply been more jumps on made on specter line.

Specter was the favored line when ZP arrived on the market. There were a lot of incidents in this time period as the first generation of ZP canopies came on the market, several of which had less then forgiving opening characteristics.

At this same time when we made the transition from dacron to specter people were still coming to terms with the importance of tight line stows and staging. People were still using large rubber bands and do you remember when they used to say, "Don't double wrap your stows, you'll get bag lock!" "It will make your bag spin and you'll have line twist!" "Don't make your stows longer then an inch, they could get over each other if the loop is too big and cause a bag lock and you'll die!" Even with the same tightness, bands just don't hold specter lines near as well as dacron. So we had hard opening canopies and line dump issues. in this time period when almost every thing was being lined with specter.

The Triathlon got a bad rep. It's a seven cell and they started out trying to put 500 lb specter on most of their canopies. They flew great but they had very little line bulk. I think this made them more prone to line dump when people did not stow their lines tight enough. Even double wrapping the stows still tended to be lose with so little line in the stows.

A lot of larger canopies got a bad rap as hard openers. There were some real reasons. Limited number of slider sizes putting the larger canopies at the small end. The fact that big boys bought these canopies. Tight jump suits were becoming popular even for big boys. Used to be the fat guy bought a balloon, or at least a loose cotton, jump suit. No more. Falling fast was all the thing. Heavier weight, higher PC snatch force, With higher snatch more prone to line dump. Higher weight and higher speeds meant higher energy in the system to begin with. And the higher speeds directly affected the openings of the canopy it self even if the staging was good.

Big boys bought triathlons and large sabers and later specters because they wanted a nice canopy, mellow but with performance. People in the highest risk categories generally didn't buy the smallest high performance canopies. Fat guys with a paunch generally don't want to try to run out the landings of a small velocity or VX. So the canopies highest on your list are simply the kinds of canopies that the people at the highest risk of line dump or just hard openings jumped.

They are also some of the most popular canopies with some of the highest jump numbers on them. Way more sabers, triathlons, and spectors have been sold then the supper hot... fill in the name of the top dog swooping canopy right now.

Got to go.

Lee

Lee
[email protected]
www.velocitysportswear.com

[masterrigger1 2]

Quote

In materials science, creep (sometimes called cold flow) is the tendency of a solid material to move slowly or deform permanently under the influence of mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and generally increases as they near their melting point.

The rate of deformation is a function of the material properties, exposure time, exposure temperature and the applied structural load. Depending on the magnitude of the applied stress and its duration, the deformation may become so large that a component can no longer perform its function — for example creep of a turbine blade will cause the blade to contact the casing, resulting in the failure of the blade. Creep is usually of concern to engineers and metallurgists when evaluating components that operate under high stresses or high temperatures. Creep is a deformation mechanism that may or may not constitute a failure mode. For example, moderate creep in concrete is sometimes welcomed because it relieves tensile stresses that might otherwise lead to cracking.

Unlike brittle fracture, creep deformation does not occur suddenly upon the application of stress. Instead, strain accumulates as a result of long-term stress. Therefore, creep is a "time-dependent" deformation.

This definition of creep applies only to the elastic/ plastic stage of materials and not to the textile definition which I was speaking.

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I may just have to call up CSR and get the curve.

I have literally hundreds of these on file.

MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[masterrigger1 2]

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Big boys bought triathlons and large sabers and later specters because they wanted a nice canopy, mellow but with performance. People in the highest risk categories generally didn't buy the smallest high performance canopies. Fat guys with a paunch generally don't want to try to run out the landings of a small velocity or VX. So the canopies highest on your list are simply the kinds of canopies that the people at the highest risk of line dump or just hard openings jumped.

While I don't have time to reply to all of your points (have to go to work)

The above is truly mythical.
Some of the incidents included heavier jumpers, but the majority were "fit" jumpers that were well with desirable weight loading.
It would be easy to just say that it was a fat problem; it is not.


MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[RiggerLee 61]

Don't tease us. Let's see a couple of strain curves for 825 and equiv HMA.
Show us from the elongation from 0 to 100 lb for a line for say a 12 inch section. Integrate from say 0 to 80 lb's X by the line length X by 12 and let's see exactly how many foot pounds energy is absorbed by the line set.

Don't make me go down stares and bust out the load cell.

Lee

Lee
[email protected]
www.velocitysportswear.com

[RiggerLee 61]

Now We're just playing semantics. What you are calling creep is what I called set in the elongation of the weave. The true definition above is a real term in material science. And you will see it in the polymers of line. I refereed to if as you seemed to be talking about leaving line under load on a cutting table for a prolonged period of time. That would be called creep under the above definition. Regardless of what you call it it's really irrelevant to openings which are much shorter events. So the fact that a peace of specter will "stretch", what you really mean is creep, over a prolonged time period doesn't matter. And HMA being less prone to creep is just a product of the molecule and is again irrelevant to opening. There's no way around the fact that you really can't get above a fraction of a percent of the total kinetic energy of the opening.

Lee

Lee
[email protected]
www.velocitysportswear.com

[masterrigger1 2]

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Don't tease us. Let's see a couple of strain curves for 825 and equiv HMA.

First, there is not a real 825lb Spectra out there. It is 725lb.

Second, I am at a Nuclear site trying to get a reactor ready to go back on line.

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Don't make me go down stares and bust out the load cell.

Pleased do and let's see how your's compares to CSR's own data sheet.

MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[masterrigger1 2]

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What you are calling creep is what I called set in the elongation of the weave. The true definition above is a real term in material science.

The true definition is whatever you believe it to be.
The definition as it relates to braid is exactly what I said it was. It is a term used often.

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Regardless of what you call it it's really irrelevant to openings which are much shorter events. So the fact that a peace of specter will "stretch",

I beg to differ and live results says differently.

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what you really mean is creep, over a prolonged time period doesn't matter

No, it is not what I really mean.
I have been in non-destructive testing of materials probably longer than most people on here including you just so you know (36 years). It has a lot of parallels to this issue.

MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[RiggerLee 61]

I'll ask Phil about it. We were set up to do some weld test for the new friction stir used on the new tanks a while ago. The recorder should be all set up but life is pretty busy pushing through the next hold down test.

I don't know if we can measure that light of a load. We normally use a 20k load cell and I question how good the data will be at such a low range. Maybe I can talk him into doing some test towards cascading the lines on the canopy. I've been pushing for it. Now that we seem to have the opening whipped maybe we'll get around to that. I might be able to justify it in that regard but right now every one is pretty strapped for time.

Lee

Lee
[email protected]
www.velocitysportswear.com

[gb1 2]

Well Flipwithit, look what you have done. You are not a beginner like many on this forum. You have asked a simple question and now have the "big guns" on this forum threatening to pull out test cells and risk another 3 mile island incident. Just ask the wing suit guys in your area what they think. Jump some of their gear if you can, and make your own decision. Obviously we are getting no where here. GB1 46yrs in sport

[masterrigger1 2]

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Obviously we are getting no where here. GB1 46yrs in sport

Jt,
I think we got him going in the right direction, so we did get somewhere.

46 years in the sport..damn you getting old! You got me by 5 years (1976)

MEL

Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

[RiggerLee 61]

Haven't talked to Phil. He's busy dealing with a problem with the post processor on the DMU he needs to fix it before we can do the blocks for the ACS. They are a cool small design but complicated to build. In any case the the load cell and every thing is down there but I kind of need him to run it. I think I could mount part of the length sensor of the bottom plate so we wouldn't have the lower clamp hanging on the line, they're heavy. But I don't see getting any thing done soon.

CSR sent me some thing but it's not a strain curve. It's just a list of elongations at breakage for a set of test.

Here are the elongation results from our CSR Style #9512-725 that was manufactured in March 2017:

SPECIFICATIONS TEST RESULTS AVERAGE
ELONGATION @ BREAK (%) <6 5.6 5.5 5.5 5.3 5.6 5.4 5.483

This isn't the curve that you're interested in integrating. And you're only interested in the first part of that up to about 80 lb. This is the final breaking at 800+ lb after it's yealded and finely failed.

At 6% times 20 ft you would in fact stretch the line 14 inches when you broke it at around 800 lb ten times what you would see in an opening. If you were to pull the entire line set to breaking, elongating it 14 inches, assuming 800 lb breaking and a liner stretch. Yah, lot of assumptions, most of that stretch will be at lower loads so smaller area, but, I'm being generous. You would absorb 10% of the opening energy in the stretch of the line. But it would require you to survive 84 G's. In other words long dead. You really only want to know how far it elongates under about 100 lb force per line. Which I still argue is under a percent.

Lee

Lee
[email protected]
www.velocitysportswear.com