Spectra ripcords and pin force

[gowlerk 2,216]

I'm having trouble with getting a legal measurement of pin force with the UPT bungee type spectra ripcord. When I scale it by hooking it to the marine eye pin it measures 8 lbs. When I hook the scale to the handle and stretch the bungee till it moves the pin it's 30 lbs. All because of the friction inside the housing I suppose. I'm not liking Spectra ripcords at all. But that's what UPT is pushing on everyone unless otherwise specified. Does anyone else besides Bill Booth like these? Do they ship them in Sigmas too?

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[skydiverek 63]

Yes, on Sigmas too.

[pchapman 279]

Thanks for bringing this up.

I haven't collected and data on this sort of thing, but did notice the pull force went up on a rig I intalled a Spectra ripcord on. Even just having one of those thick, squarish reserve pins seems to make the pull force high for a given apparent tightness of the reserve loop. (The Vector pin designs have varied in design over the years)

Then combining those factors with the tightness expected of rigs now, it makes for slightly awkward pull forces.

One sometimes gets that on other rigs too, where the pull force does seem to be just sort of a still legal 22.00 lbs, "at least I thought the pin moved a teensy bit at that point, or at least it should will be a realistic 22 lbs after sitting 24 hours but I have to hand this rig back soon .... or maybe it will be 22 if I walk in place on the reserve for a few minutes and test right afterwards ... and I used the same loop length as the rig has always had".

That being said, one sometimes does build an overly-ambitious tight loop that is a struggle to close (on any rig), giving a high pull force that suggests one might as well just go back and put a slightly longer loop in, for the benefit of everyone in the long term.

I've found Wings can also have a bit of a pull force issue because so much of the cable is dragging not metal on metal but dragging on fabric as it goes around the shoulder.

[Unstable 9]

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I'm having trouble with getting a legal measurement of pin force with the UPT bungee type spectra ripcord. When I scale it by hooking it to the marine eye pin it measures 8 lbs. When I hook the scale to the handle and stretch the bungee till it moves the pin it's 30 lbs. All because of the friction inside the housing I suppose. I'm not liking Spectra ripcords at all. But that's what UPT is pushing on everyone unless otherwise specified. Does anyone else besides Bill Booth like these? Do they ship them in Sigmas too?

I repacked a VIII with a spectra ripcord a few days ago, and I did measure the pull force from the handle, pulling straight down away from the housing (there was no bend in the cable

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coming out of the housing) and I measured right at 19 pounds. I can review my logs and see what the measurements from others have been.

You do have a good point - the biggest question I have regarding the Spectra Ripcords is what will they look like after 20 years of use? We know how the traditional ripcord assemblies look after that length in the sky, but only time will tell.

=========Shaun ==========

[Unstable 9]

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That being said, one sometimes does build an overly-ambitious tight loop that is a struggle to close (on any rig), giving a high pull force that suggests one might as well just go back and put a slightly longer loop in, for the benefit of everyone in the long term.

interesting point! I measure all pull forces for each rig I pack, and I really haven't seen a strong correlation between the effort required to close the rig and the measured pull force. I don't use a ratchet assembly to close a rig, just the packing paddle and bar, and even rigs with significant effort still stay in the 17-20 pound sweet spot. I have that measurement for every rig I have ever packed (~900), It may be a fun exercise to go plot it out by rig manufacturer, although I do not record the closing loop length in my logbook (and without more info, that wouldn't be incredibly useful).

=========Shaun ==========

[RiggerLee 61]

I wonder if the housing was rough on the inside? Housings look all smooth and shiny on the out side. The truth is that they are just bent coiled sheet metal. All the sharp edges are turned inwards. Depending on how they are made I've heard concerns about sharp edges on the inside of the spiral. If you think about it a steal cable is pretty hard and smooth and stiff. It will just kind of ride over that sharp edge. Maybe even polish it down. On the other hand a spectra line, which is supposed to have a very low friction, is soft. A sharp edge would dig into it and scrape, and drag, and eventually tear. So all this shit about spectra being slick and smooth and an easier pull, it really does have a lower coefficient of friction, may be a lot of bull shit when it tries to ride over a rough surface like the in side of a poorly made housing. Make me wonder what might happen over time with that particular rig. This my be a sign of a bigger problem.

If that rigs still around, just for shits and grins you might take a nice peace of spectra, uncoated if you have it, Put the rig on some one to get a good curve, and saw the line back and forth through the housing. See how it wears in comparison to another rig. I wonder if you will see and fraying with a little effort. Or I wonder if you could push a patch of some thing through their, Some thing really snaggy... I good example is not coming to mind but some thing with a lot of loos looped fibers that would catch on any rough spots. Even if you had to make it by cutting some fibers in a patch of F-111 to create runs.

Lee

Lee
lee@velocitysportswear.com
www.velocitysportswear.com

[pchapman 279]

Unstable

I measure all pull forces for each rig I pack, and I really haven't seen a strong correlation between the effort required to close the rig and the measured pull force.

To briefly expand on what I wrote, I agree that the correlation can be weak. On some rigs the geometry does seem to be particularly favourable, so even when it took a lot of work to close the last flap, the pin starts sliding at 17 lbs. I do use a torquing device however, where it is a matter of feel as to what is still reasonable vs. a ridiculous amount of pressure. The torquing device does allow for packing tighter, easier... but shouldn't be used as a crutch for poor technique and not "working" the pack job better early on, and then just using force to get the pin in the last flap...

[erdnarob 1]

I have a Vector 3 with a Skyhook and Spectra ripcord. I know what you mean about the "square" pin increasing the sliding force. I always check the minimum pin sliding force using a memory scale attached to the ripcord handle. For doing so, you put your foot on the rig where your shoulder goes in order to "round up" the spectra line housing while you apply force on the scale. When doing this on a conventional steel cable ripcord, a friend of mine is holding in place the special tool from ParaGear which limits the move of the pin (see the picture of such a device I made from stainless steel). In other word you try to reproduce the normal configuration. Even though that tool doesn't work for Spectra line ripcord, a friend can "hold" the top of the pin while scaling to prevent a complete extraction. You can also apply some silicone on the grommet and pin. Even at 22 lbs, there is no problem to pull the ripcord even using one hand,

Learn from others mistakes, you will never live long enough to make them all.

[mxk 1]

It's been almost 180 days since I first assembled my V3. Fortunately, I met Greg Raw at the Skydive Orange boogie a couple of weeks ago, who offered to give me some packing tips. He took my pack job apart, replaced the loop, and closed the container. The pull force at the handle of my original pack job was 24 lbs with the seal still attached. My loop was a bit too long at 5 1/8", which was one of the things I wanted his help with. He closed the container with a loop measuring 4 5/8".

I still needed to inspect everything, so I opened the reserve again this weekend. Pull force at the pin was 10.5 lbs (average peak value of 4 measurements with a digital force gauge). Pull force at the handle - 33.7 lbs without the seal. That's 23.2 lbs difference between the handle and the pin

My Spectra ripcord is labeled 2012-01, so not affected by the PSB. I'll be replacing it anyway with the updated version, though I'm not sure that it will make much difference.

[Alexg3265 0]

Check to see if it's one of the affected rigs. Upt issued a service bull item about the spectra ripcord a having too high of pull forces. Too much polyurethane coating I guess and they need to be replaced by December 2015 or they're not airworthy. I don't have a link but I think it's all the 2014's?

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