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wilcox

spectre with dacron lines - softer openings?

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I've heard that the difference in opening shock force between canopies with spectra / dacron lines is up to 300% on hard openings.

Spectre is known to open soft, would it still be a noticeable difference if I change to dacron lines? Anyone compared dacron and spectra spectres?

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I did about 200 jumps on my Spectre 135 (bought 2nd hand) which was lined with microline.

The openings used to go something like this: snivel, snivel, snivel, snivel... pop!

Not a big deal, but not perfect either.

Earlier this year I had the canopy re-lined with dacron. The openings have improved as I no longer seem to get the "pop" at the end. It seems to take about the same altitude to open.

I should say though, that I'm comparing an out of trim, microlined Spectre with an in-trim dacron lined Spectre so this may not be the most useful comparison!

All in all, I'm very happy with my decision to re-line the canopy with dacron. I have noticed no loss of performance from doing so and it only increased my pack volume a little. Dacron lines work fine with normal sized slinks too.

There were some helpful posts on this thread when I asked the question myself.

hth!

Vicki

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Before I downsized I used to fly a Spectre 190 with Mico lines and it was a pretty soft opening but quite comfortable. I didn't have any really long snivles and it never rocked me on opening. My wife flys a Spectre 150 with Dacron lines and has very long snivles! She bought the canopy from a camera flyer who wanted the soft opening canopy with the bigger line set so that his camera woudln't hurt his neck on opening. She has consistant 1,000 foot snivles and has even reached her hard deck by the time she was in the saddle. This caused her to reach for her cutaway handle once or twice but luckily she didn't have to use it. Overall she loves the soft openings but she found that she has to pull a few feet higher to get her open at the altitude that she is comfortable at. Unless you have a reason for very slow opening (camera flying), I would suggest micro lines on the Spectre.

Kevin
FALLATIO #13
PELT HEAD #20

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Unless you have a reason for very slow opening (camera flying), I would suggest micro lines on the Spectre.



Interesting - I've had no such problems with my 135.

My experience is that a Spectre with either type of line uses up about the same amount of altitude on opening but the openings just feel a bit softer and smoother with dacron.

Vicki

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You probably have a better comparison than I do just because you used the same canopy with two different line sets. I'm comparing two different canopies, a 190 and 150 which might have different openings just based on the size difference. We did have the same wing loading on the two canopies at 1:1
FALLATIO #13
PELT HEAD #20

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I have both my 2 Spectre 120's lined with Dacron 525 on them; one I had relined from the original microline. I also relined a previous Sabre 120 of mine from microline to Dacron 525 (and had no issues selling it on when the time came)

I much prefer the dacron lined canopy's openings. Even softer than a routine Spectre opening, which is soft already. But I couldn't say there's a 300% difference!

Dacron has many advantages
- outlasts microline for wear and tear
- will not get out of trim like microline does
- absorbs more of the opening shock, making the openings nicer for you and the canopy

The slight disadvantage is your canopy packs up slightly bigger. Reckon on adding an inch to your closing loop versus the micro-lined canopy.

There will also be some extra parasitic drag from the bulkier lines but as I jump Spectres for my own longevity and not for screaming swoops, I'm not the kind of jumper who can notice or care about that.

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What the lines are made of has nothing to do with how the canopy opens. What you are dealing with is “felt” snatch force and opening shock.

Dacron lines have some elasticity (elongation) where spectra has almost none. The Dacron lines absorb some of the opening forces that spectra transfers directly to the jumper and the canopy.

Sparky
My idea of a fair fight is clubbing baby seals

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I've heard that the difference in opening shock force between canopies with spectra / dacron lines is up to 300% on hard openings.



Dacron will affect the opening in 2 ways:

First, your slider will come down the lines a bit slower, because Dacron is less slippery than Spectra.

Second, Dacron will stretch and absorb a lot of opening shock, while Spectra will transfer most of the load directly to the jumper.

What you refer to is the second. You will probably notice more of the first effect on normal openings and more of the second on hard ones (where slider didn't do its job properly). The second may be a real life-saver in case of a severe linedump etc. It is the reason all BASE canopies use Daron lines.

bsbd!

Yuri.

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What the lines are made of has nothing to do with how the canopy opens.



Sorry Sparky, But I will have to totally disagree with that.

The type of line has a lot to do with the opening. The dacron will "grip" the slider grommets more than the Spectra line material. Size of the material has a lot to do with it also.

MEL
Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

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What the lines are made of has nothing to do with how the canopy opens.



Sorry Sparky, But I will have to totally disagree with that.

The type of line has a lot to do with the opening. The dacron will "grip" the slider grommets more than the Spectra line material. Size of the material has a lot to do with it also.

MEL



Mark,

You are right, but most skydivers do not have access to equipment that can measure the difference.

Sparky
My idea of a fair fight is clubbing baby seals

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Unless you have a reason for very slow opening (camera flying), I would suggest micro lines on the Spectre.



There's more than one slider size available for the Spectre. Sounds like you have a large slider at present, ideal for cameraman. PD should be able to supply you with a smaller slider to speed up your openings. Then you still have a free choice of microline or dacron, whichever suits you best.

I have a smaller slider and my openings are about 600ft every time.

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Dacron lines have some elasticity (elongation) where spectra has almost none



Actually, elasticity of dacron during an opening is not the same as elongation. Elasticity is the temporary "stretch" of the fiber as it is loaded (like a rubber band has); elongation is a permanent lengthening over time. Some fibers have lots of elasticity with no tendency to elongate, and visa versa.

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I know of several people who switched to dacron lines on their canopies after having neck surgery including my girlfriend who is a rigger and AFF instructor. All of them pretty much agree that the dacron lines absorb a great deal of the opening shock and provides substantially softer openings.

A great person to talk to about this is Tony Hathaway. If I remember correctly, Tony has over 5000 jumps on Spectres. A few years ago he switched to dacron to help protect his neck from damage. Tony usually jumps with quite a bit of camera gear on his head. He swears by the dacron. He has thousand of jumps with and without the dacron and will gladly tell everyone that the dacron makes a huge difference. He is on DZ.com, so if you want more info, ask him.
Time flies like an arrow....fruit flies like a banana

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Here is what BILL BOOTH has said on dropzone.com about DACRON LINES. Great source of info!:

"My tests show up to a 300% increase in opening shock felt by the jumper using Spectra vs. Dacron suspension lines. It is not always that much different. It depends on how quickly the force is applied...and canopy makers have done a good job of designing canopies that open slowly enough to allow the routine use of Spectra. However, when a rare hard (quick) opening happens, Spectra lines will definitely make it hurt more."

"Tandem canopies are public transportation. Little old ladies and parapelgics jump tandem. Dacron lines give lower opening shocks. It's that simple. This might not matter much on a "normal" opening, but if someone make a small mistake packing which results in a super fast opening, the Dacron lines could save somebody's grandmothers life. I know Dacron is bulkier, but I've seen no evidence that Dacron lined canopies have more malfunctions. In fact, I believe the opposite may be true."

"Anyone who doubts that suspension line stretch is a factor in reducing the opening shock felt by a jumper, should make a bungee jump...only replace the normal stretchy bungee cord with a stainless steel cable. What's going to happen when you hit the end of that steel cable? Your leg is going to be torn off, that's what. Now remember, Spectra line stretches about as much a steel cable."

"If you are not using Dacron lines, they would help. They stretch a little, and also slow the slider down due to surface friction. Spectra (micro) line does not. If you are already using Dacron lines, and still having hard openings, get a canopy that opens slower."

"The best way to avoid injuries from that occasional super hard opening (as well as the hard openings themselves), is not to jump no-stretch lines. Ask yourself, "Do I really need the (slight) advantages no-stretch lines offer?" If not, get Dacron. Your body will thank you, because even if you are not ever seriously injured on any single jump, each even slightly hard opening on no-stretch lines is damaging your body...and it all adds up."

"Spectra (micro line), Vectran, Kevlar, and HMA are "no-stretch" lines. They do not "absorb" opening shock the way Dacron does. This means that the same "hard" opening can hurt you a lot more. It's like doing a bungee jump with steel cable. The same force is applied...but a hell of a lot more shock is felt by the jumper. All the opening shock caused broken harnesses (two PDF tandem harnesses recently broke), injuries (a guy just broke both femurs), and fatalities (4 in the last two years that I know of) have all been on "no-stretch" line canopies, and could probably been prevented if Dacron line had been used. No stretch line is used because it is thinner, lighter, and has less drag than the same strength Dacron. While this is an "advantage" in a high speed swoop, it has no place in tandem. 85 year old grandmothers jump tandem. They, and many other tandem students, need the softest opening shock possible. This is why we only use Dacron line on our tandem products. Not to mention that our tandem equipment was NOT drop tested with no-stretch lined canopies.
I don't care if you have 1,000 jumps on a particular canopy with no-stretch lines with no problems. Ever canopy opens hard eventually. When that happens, I want some "bungee cord" between that canopy and the tandem passenger."

"One thing is for sure, if you jump "no-stretch" lines, especially Spectra (because it's so slippery, and reduces slider drag) your chance of being injured or killed by a hard opening shock is much greater than if you jump Dacron line, which stretches just enough to absorb some of that shock before it hits you."

"Spectra (or micro-line) is strong and tiny, so it reduces both pack volume and drag , which means you get a smaller rig and a faster canopy. Unfortunately, It has a couple of "design characteristics" (this is manufacturer talk for "problems") It is very slippery (less friction to slow the slider), and stretches less than stainless steel. This is why it hurt people and broke so many mini risers when it was first introduced. Now, I must say that the canopy manufacturers did a wonderful job handling these "characteristics" by designing new canopies that opened much slower than their predecessors. However, the fact still remains, that if you do have a rare fast opening on a microlined canopy, Spectra (or Vectran) will transmit that force to you (and your rig) much, much faster, resulting in an opening shock up to 300% higher than if you have Dacron lines. (It's sort of like doing a bungee jump with a stainless steel cable. At the bottom of your fall, your body applies the same force to the steel cable as it would to a rubber bungee cord, but because steel doesn't stretch, your legs tears off.)."

"Reinforced type-17 webbing risers rarely break. They have a new breaking strength of around 3,500 lbs. This is not that much less than type-8 risers breaking strength of 4,000 lbs. The real difference is whether you have mini rings or large rings...and the difference here is in cutaway forces, not breaking strength. While properly designed mini-ring risers can easily release even a 250 lb. jumper in a 3 or 4 "G" spin, the problem is that it is harder to manufacture mini-ring risers correctly. What causes any riser to break is usually a combination of a heavy jumper, a hard opening canopy, and no stretch (Spectra, Vectran, or HTML) line. Broken risers on Dacron lined canopies are very rare indeed."

"Single rear riser break is very rare. Risers usually break where they go around the large harness ring. It is obvious that since the "reinforcement" in type 17 risers is below the confluence, it does nothing to prevent this kind of damage. When this riser broke, it "released" a lot of energy, thus preventing much more serious injury of the jumper. Which is a good thing. The only way I know of to prevent "killer" opening shocks, is not to jump Spectra (Microline) or Vectran. They don't stretch at all, and therefore do nothing to help absorb the energy of a really hard opening. As long as we insist on jumping non-stretch lines, incidents like this are bound to happen. (Canopies with Dacron lines can still open hard, but much less shock is actually felt by the jumper.)."

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Also Skydive Radio show #7; there's a bit where someone (Joe Jennings?) spends some time heaping praise on his Dacron lineset for reducing opening shock when jumping camera.
--
"I'll tell you how all skydivers are judged, . They are judged by the laws of physics." - kkeenan

"You jump out, pull the string and either live or die. What's there to be good at?

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Unfortunately, all the "micro-lines" are also "micro-stretch". Specrtra is the worst, because it is also slippery (less slider friction). The harness is made of Nylon, which is even more stretchy than Dacron, so it does stretch a little to absorb opening shock. Trouble is, the harness is thick and not very long, so it doesn't have very much stretch to offer. Although nobody thinks about it, longer (Nylon) risers can also help absorb opening shock. However, risers are really short nowadays so that people can reach up and pull down their sliders. Also, I think hardware that slips a little can help.

Try this: Fall down on a solid concrete floor. Now fall down on the same floor with a 1" gym mat on it. You are applying the same force, but I'm willing to bet that the bare concrete floor hurts more. Now do that same test 1,000 times (as in a thousand jumps) and tell me you still want to jump micro line.

One more good reason to avoid "micro lines". When lines entangle with grommets and flaps, they're always "micro lines". The thickness of Dacron lines keeps them from getting stuck under things.

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