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BlindBrick

Super Bulletproof Soft Links

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I know that regular soft links are supposed to be able to take anything we can dish out. OTOH, this past weekend I learned that in under twenty jumps I have managed to knock my new canopy's lines out of trim by over an inch and a quarter on the left C's and D's.

What I am wondeirng is if the kind of stresses that would affect trim that drastically, that early, would comprimise a standard Spectra softlink? If so, is there a stronger line type that would be better suited to the demands I am putting on the setup?

I ask because I am worried about the possibility of metal fatigue or stripping the barrell on the Rapide minilinks I am currently using on my main.

-Blind
"If you end up in an alligator's jaws, naked, you probably did something to deserve it."

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What type of lines does your main have? 20 jumps should not make a 1.25" difference. Something is wrong.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Reserve/tandem slinks from PD are stronger than regular main slinks, but that is not your biggest problem.

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1. Did you check the trim when you got the canopy? Really, did you? I know few riggers doit on brand new canopies.

2. The vast majority of Spectra line shrinkage happens within the first 100 jumps.

3. If you are so worry about the slinks get the PD approved ones for reserves and tandems.
Memento Audere Semper

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Hey brick,

I'm 250, and have 1000+ jumps on each of two sets of mini risers with slinks. they won't break. Mini links will also hold up fine if you put them on correctly. There is no reason to be scared of slinks or mini links because of your size, IF they are installed properly.

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1. Did you check the trim when you got the canopy? Really, did you? I know few riggers do it on brand new canopies.



No I didn't. I just made sure all the fingertraps were sewn and that the seams on the canopy looked good. I will freely admit that this was a downsizing for me and that it could have been a bit out of trim new because for the first few jumps I put on it, I was mostly in the "OMG, this thing is fast" phase and didn't notice a lot else about the flight characteristics. However, in the last 10 or so jumps, I have been intentionally studying the flight characteristics of the canopy. During that time, I can tell you that the turn has gotten worse. When I first noticed it, it was a very slight drift only noticable on final. Now, it's to the point that it is turning somewhere between 20-30 degrees per second(estimated by focusing on a fixed object and letting the canopy fly).

I know that line is not supposed to shrink that fast, but I am pushing the envelope hard enough that I'm not sure that conventional wisdom is entirely accurate.

Which brings me back to the links. I'm not sure how to calculate peak stress on the links. I know my total exit mass is ~150 kg and thanks to a trio of freefall computers, I know I decel from 74 m/s to 4 m/s. Video of a couple of my openings shows pretty much insta'canopy. I haven't had the chance to run the video through a machine with a timer that measures down to the hundreth of a second, but I would estiamte that from canopy extraction to full inflation is no longer than 2-2.5 seconds. Now I know that in an ideal situation, the force is spread evenly between the four risers which I would think would divide peak force by 4. Assuming that( and F=ma), I am getting an ~peak force of 1300 n which is ~290 lbs per link.

Does that sound right?

-blind
"If you end up in an alligator's jaws, naked, you probably did something to deserve it."

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Video of a couple of my openings shows pretty much insta'canopy.



Actually there have been arguments made that Slinks (for main canopies) maybe should be designed to break at lower threshold because as they are right now they'll take more stress than metal links. So if enough force were put forth to break a slink, your body would be damaged badly. In case of such a horrendous opening, it'd likely be better for the slink to break, cutaway the damaged main & then deploy the reserve.

In other words I wouldn't worry about the slinks if you're handling the hard openings & willing to jump again :)

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PD Slinks or Maillon Rapide metal links will out last risers or suspension lines.
But I doubt if that is your biggest problem.

"Insta canopy" sounds more like line dump.
How tight are the rubber bands around your suspension lines?
Are you 100 percent sure that your slider is still hard-up against the underside of the canopy?

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"Insta canopy" sounds more like line dump.
How tight are the rubber bands around your suspension lines?
Are you 100 percent sure that your slider is still hard-up against the underside of the canopy?



I am using tandem bands, double stowed on my locking stows. And I am positively anal about my slider. I check it four different times. First time is when I clover leaf it(which is myt last step before rolling the tail), second time is just before I begin S folding, third time is after the S-fold and one final time after I've got the canopy in the bag.

-Blind
"If you end up in an alligator's jaws, naked, you probably did something to deserve it."

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I am using tandem bands, double stowed on my locking stows.



If your main fits your container, that seems excessive and dangerous due to the (in my mind) greater extration force needed to pull the lines from the rubber bands (leading to a bag lock).

What's the thinking behind that?
--
drop zone (drop'zone) n. An incestuous sesspool of broken people. -- Attributed to a whuffo girlfriend.

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>>" I haven't had the chance to run the video through a machine with a timer that measures down to the hundreth of a second" ...



If you have a frame skip-forward button, try it. Try the frame skip forward button. Usually every press of the skip-forward button is 1/30th second. Add them all up, and presto!

(Make sure that 30 presses of skip forward equals 1 second though. Most playback systems do. Some systems only need 15 pressses, others 24, and others 60.)

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Guarantee you it's not line-dump...bag dump maybe, but not line dump. Lots of folks (myself included) have been jumping without friction on the lines for quite a while. Lines only need to be stowed such that they don't get tangled.

BUT...you do need to be to line stretch before the canopy gets out of the bag or it will hurt. The earlier the canopy gets out of the bag during the deployment, the faster the opening time.

Line dump vs. bag dump...some folks think it's just semantics...let me assure you, it's not!


"...and once you had tasted flight, you will walk the earth with your eyes turned skyward.
For there you have been, and there you long to return..."

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Blindbrink,
Do you have Spectra? (which is an option on the Safire 2)
Is is very possible that the lines have shrunk out of tolerance in twenty jumps if the jumps were with fast, hard openings. It really depends on how fast and hard.

Let' say the heat generated during a normal deployment is 100 degrees...if the heat genereated during your openings is five times the normal heat index (500 degrees) the shrinkage could be equal to as much as 100 jumps.

The heat generated during a fast opening compared to a normal opening can cause the lines to shink as if they had many, many jumps on them.
Spectra can look like new and not be in tolerance.

We need to look at that canopy of yours.

MEL
Skyworks Parachute Service
"The Icarus Service Center"
Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

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Blindbrink,
Do you have Spectra? (which is an option on the Safire 2)
Is is very possible that the lines have shrunk out of tolerance in twenty jumps if the jumps were with fast, hard openings. It really depends on how fast and hard.



I will freely admit that I have /zero/ experience with Vectran. The lines look like Spectra to me, but since everyone was saying that it was Vectran, I just assumed that I had made an inexperienced rigger's mistake and misidentified the line.

After reading your post, I broke out my materials ID guide and the one example of Vectran I have is a this dun colored line that is thinner and rounder than Spectra. If that's the only form that Vectran comes in, then I definately have Spectra lines.

As for openings: The first sixteen or so jumps were all high speed openings with deployment speeds varying between 155 and 175 mph, but with the majority in the 165 mph range. The last six or seven jumps have been sub-terminal hop and pops with an average deployment speed of about 75 mph. Two or three of the openings have been the softest openigns I've ever experienced, most have been rough enough that whenever I see the "Openings as soft as falling into pillows" adline, I think "Damn, I really should buy the Icarus marketing team new pillows." and a few have been bad enough that I actually contemplated landing downwind, miles off-field just so I wouldn't have to move and therefore be able to just hang in the harness.

And yes Mel, I am planning on sending it back to you for evaluation. The only problem is that I am having to wait until I find a suitable spare canopy as I have to make a certain number of jumps before Sept. in order to qualify for a coaches course, and going without a canopy for more than one weekend would be cutting it very, very close.

-Blind
"If you end up in an alligator's jaws, naked, you probably did something to deserve it."

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The first sixteen or so jumps were all high speed openings with deployment speeds varying between 155 and 175 mph, but with the majority in the 165 mph range.



I am not at all familiar with the Safire2 but opening at speeds above 150/160 mph is going to be brutal. How much do you weigh out the door?

Sparky
My idea of a fair fight is clubbing baby seals

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The first sixteen or so jumps were all high speed openings with deployment speeds varying between 155 and 175 mph, but with the majority in the 165 mph range.



I am not at all familiar with the Safire2 but opening at speeds above 150/160 mph is going to be brutal. How much do you weigh out the door?

Sparky



Not exactly sure, but 325-330 is probably close enough for government work.

I know the key here is to slow down. I am going out of state tomorrow to pick up a custom suit. It's a very generously cut freefly suit made of two layers of heavy fabric, and sporting large zp wings and gills to further slow down fall rate. I'm hoping that will work because if that doesn't, then I am looking at having to break early and deploying some type of drouge.



-Blind
"If you end up in an alligator's jaws, naked, you probably did something to deserve it."

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