opening shock with dacron lines

[wilcox 0]

Has anyone compared opening shocks between a canopy with microlines and the same kind of canopy with dacron lines? Is there a big difference?

[skydiverek 54]

Yes, up to 300% percent.

From Bill Booth:

"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.)."

[rushmc 18]

I bought a new Sabre2 260 with Spectra. I put about 120 jumps on the canopy then I cut off the spectra and put on dacron. Now, I don't think I can say that I noticed a 300% difference but it most definatley took some of the edge off.

I did the conversion after much research.....

"America will never be destroyed from the outside,
if we falter and lose our freedoms,
it will be because we destroyed ourselves."
Abraham Lincoln

[JohnRich 4]

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I cut off the spectra and put on dacron. Now, I don't think I can say that I noticed a 300% difference but it most definatley took some of the edge off.

He didn't say it would make that much difference on normal opening shock - only during "a rare fast opening".

[rushmc 18]

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I cut off the spectra and put on dacron. Now, I don't think I can say that I noticed a 300% difference but it most definatley took some of the edge off.

He didn't say it would make that much difference on normal opening shock - only during "a rare fast opening".

Well , I don't think I want to try and pack and fast opening on purpose. I have had a brisk on but not one like I have had with the spectra. I can still see those stars.......

Just trying to put some perspective on this .....

"America will never be destroyed from the outside,
if we falter and lose our freedoms,
it will be because we destroyed ourselves."
Abraham Lincoln

[Deuce 1]

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Has anyone compared opening shocks between a canopy with microlines and the same kind of canopy with dacron lines? Is there a big difference?

I just relined my Spectres with Dacron. I would say the openings are half-again softer than with the micro lines. I think part of that is that the slider comes down way slower on the Dacron lines.

The lines are barely noticeably larger than the micro. When it was still in the bag, a rigger friend went so far as to say, that I didn't get the dacron.

Anyhow, much softer and very noticeable.

[JohnRich 4]

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I just relined my Spectres with Dacron. I would say the openings are half-again softer than with the micro lines.

Yeah, but you're no longer "cool" for having the latest and greatest high-technology spaghetti lines, and your canopy is going to fly one-tenth of a mile per hour slower. Oh the horror!

[mattjw916 2]

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"cool" for having the latest and greatest high-technology spaghetti lines

I resemble that remark...

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your canopy is going to fly one-tenth of a mile per hour slower. Oh the horror!

Somehow I think the difference is a LOT more than that... but I'm not even going to attempt to introduce any math into this thread.

NSCR-2376, SCR-15080

[mjosparky 3]

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"cool" for having the latest and greatest high-technology spaghetti lines

I resemble that remark...

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your canopy is going to fly one-tenth of a mile per hour slower. Oh the horror!

Somehow I think the difference is a LOT more than that... but I'm not even going to attempt to introduce any math into this thread.

No matter what the difference is, there are only a handful of canopy pilots that can tell the difference and have the ability use it. The rest are going for "cool".

Sparky

My idea of a fair fight is clubbing baby seals

[mattjw916 2]

Negative...

I jump canopies lined with Technora since they are a) abrasion resistant b) dimensionally stable c) smaller pack volume. "Cool" was not a part of my decision-making process, sorry.

The work MEL has done shows that HMA lines have a positive and tangible effect on speeds and swoop distances. And not just for the top 1% of canopy pilots either.

Going from a Safire 175 with Vectran to a Nitron 170 with HMA was a H U G E increase in performance for me with only a 5ft² difference in canopy size. Obviously canopy design plays a big part there, but the lines are part of that equation, and it doesn't take a genius to realize that the same performance would not be possible with bulky Dacron.

NSCR-2376, SCR-15080

[kelpdiver 2]

since Deuce often wear a camera rig, I think he decided to optimize for neck performance. That one is very tangible, even after the swoop is over.

I don't think it takes a genius either to compare the surface area of the front of the body versus the lines. People don't swoop with 7 cells to eliminate two sets of lines.

You might notice the difference going to dacron, but between the various microlines? How many would notice the difference in drag between vectran and hma (or spectra 525)? Isn't the driving desires there over the wear issues?

[skydiverek 54]

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People don't swoop with 7 cells to eliminate two sets of lines.

Yes they do. That's why the Velocity is a 7-cell (or 21 cell if you wish).

[mjosparky 3]

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Going from a Safire 175 with Vectran to a Nitron 170 with HMA was a H U G E increase in performance for me with only a 5ft² difference in canopy size.

How much faster were you going and how much farther was your swoop?
Sparky

My idea of a fair fight is clubbing baby seals

[mattjw916 2]

I would say at _least_ 30% longer under my Nitron all things being equal. I know there is more there too, I just need more practice.

NSCR-2376, SCR-15080

[mattjw916 2]

If my camera setup was as big as Deuce's maybe I'd think about stretchy lines too, but mine is _much_ lighter and _I_ (sorry Deuce ) am much lighter than him too.

NSCR-2376, SCR-15080

[Deuce 1]

Good lord, everybody is lighter than me these days.

But actually I'm much cooler now with the Dacron. More like Greg Gasson, Brent Finley and Tony Hathaway.

I'm training with an advanced 4 way team this year that has a 300+ training jump schedule on top of my regular weekend instruction and video work, and I'm a middle-aged guy. The dacron is just easier over all on the body and the cumulative stress on the bod can be reduced by going dacron.

Where I really notice the difference is in the difference between the A2 tandem canopies and the 384's. A2's open fast, and because of the dang microline on them it does get an instructor's attention at full inflation. Snivelllllllll-WHUMP. The A2 handles great, but I just don't know why they dont have dacron linesets. The 384's open Snivellllllllllllllll-whoooosh.

[mjosparky 3]

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and I'm a middle-aged guy

Baaahaahhaa. ROTFL.

Spakry

My idea of a fair fight is clubbing baby seals

[wilcox 0]

Has anyone collected data: done some jumps with a dacron-lined canopy and written down the opening shock forces and then done the same with a micro-lined canopy of same type, and then noticed how big the difference in opening shock was?

[skydiverek 54]

Yes - that data was published in 1997 or 1998 Skydiving magazine.

[thepollster 0]

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Going from a Safire 175 with Vectran to a Nitron 170 with HMA was a H U G E increase in performance for me with only a 5ft² difference in canopy size.

If I'm not mistaken. Precision measures their canopies differntly than Icarus/PD, so you are dealing with a much larger size difference than you think. Try comparing the Nitron 170 with a Safire2 160 and see if you still think the same.

If I am wrong with the measuring system, I'm sure someone will stand up to tell me

[mattjw916 2]

Actually I already corrected the size of my Safire. It was placarded at 189 which, with the 7% differential, makes it approx a 175.

Current Precision canopies and Icarus canopies are now measured with a comparable method AFAIK now.

NSCR-2376, SCR-15080

[johnny1488 1]

Those are also 2 totally different canopies. The Safire is a mid range 9 cell while the Nitron is a fully elliptical high performance one, which I now see you mentioned.

Until you reach the upper part of the canopies capabilities, I dont think the lines make as huge a difference in overall performance as many people think.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[teason 0]

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Yes, up to 300% percent.

From Bill Booth:

"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.)."

Where does he get that from?

If his statement is true, then an average openning of 3-4 gs would become an average openning of 12-16 gs! And that's an average opening. Let's say it only happens on fast openning that would be in the 8-10 g range. Well that means an opening of 32-40 gs!

Old Bill says some odd things, I think we need some data. He's probably drawing the conclusion that because spectra has an elongation of 3.5% and polyester line has an elongation of 14% (300% more elongation) that it will cause 300% more opening shock. That conclusion is obviously flawed as it doesn't take into account the canopy, the risers or the harness' ability to absorb shock as well.
Can you publish the skydiving article findings?
Do they inclube the amount of shock the line absorb vs. the entire system?

The comment about it having the same stretch as steel, that comment is highly misleading. Spectra line has a weave.

Just a sec....
(runs to table, ties a piece of spectra to a fixed point and marks 194" down the line. Pulls. Line moves 1 1/2 inches).

Well either spectra line does stretch or I'm a superhero.
(I'm totally weak)
I don't think I can stretch steel with only a couple pounds of force.

I would rather be a superb meteor, every atom of me in magnificent glow, than a sleepy and permanent planet.