Martini

I think I get what you're thinking, that the slider starts with zero velocity/zero heat at the top and builds heat as it travels downward. The first part is somewhat correct but max velocity is not necessarily at the bottom of the lines because the slider may slow down considerably before hitting the risers. Also the slider may reach its max velocity very near the starting point depending on how the canopy opens. As far as stretching goes, all of the stretching should take place in the shrunken areas because those areas are shrunken due to "curling" of the heated fibers. The unaffected fibers are straight and won't significantly stretch. Spectra lines are considered non-stretch just like HMA or Vectran. The problem is that Spectra isn't non-shrink like those fibers. Sometimes you eat the bear..............

Well Dave, if that's what you heard then it's only because that's what you wanted to hear. Right... Do you have something useful to say or just want to stir the pot? Sometimes you eat the bear..............

Ian, I don't believe that manufacturers will support line stretching. There's money in selling linesets that most skydivers can't install themselves vs. selling a service that any jumper can easily perform and would never buy. Lineset replacement is unavoidable and stretching the lines may or may not extend the useful life of a lineset but may give better performance during that time. "Deep Survival"........what a terrific book. "Doing the same thing 1000 times with success is not indication of a good behavior but rather that the right set of conditions haven't occurred yet to highlight the errors in assumption (Paraphrased)." is a pretty well established philosophy though, we are always surprised when bitten by our family dog. Like anything that involves risk, swimming in uncharted waters should be done thoughtfully. That is not to say that we should never attempt to experiment or change at all. In this case I believe the risk to be low enough to justify the benefit. I perceive the risk of causing a line to break to be small while receiving a perceptible benefit in improved line trim. I feel fortunate that this option was shown to me and I choose to use it. It's interesting that skydivers readily accept Spectra shrinkage without wondering if there is a remedy, it's reasonable that they would be wary of an unfamiliar one. Sometimes you eat the bear..............

We can certainly agree to disagree to some extent. Here's the original post: "Has anyone heard of taking a Spectra lineset and stretching it back into trim? this is something ive heard about and have a friend who is jumping a canopy with the lineset stretched and he said it was like a new canopy. Does anyone have experiences with this good or bad?" My response to his question is yes I have experience with this and it has been good. So the breakdown becomes a matter of functionality which I have proven to myself and safety which is not proven except by default. My perception is that this is a low-risk behavior. And I agree that you and I have no need for further argument. Sometimes you eat the bear..............

I can't see the data but thanks for the research. Is the reduction in strength described while the material is still heated or after it has returned to ambient? BTW I would be surprised if heating/shrinking/stretching didn't degrade tensile strength, the question is by how much especially in the skydiving environment. Also note that the lines will never be stretched beyond their original length. What's more is that the shrinkage/stretching is relatively small by percentage. For example if an "A" line on my Sabre-120, which is 278 cm long, shrinks by 10 cm (which is nearly 4 inches) that's less than 4%. I'm not disputing the likelihood of tensile loss, only interested in whether the loss is of significance in lines that are incredibly strong and not typically highly loaded. Sometimes you eat the bear..............

Your position then is that my canopy should be jumped until it needs a new lineset and I should just "Buy the damned lineset and be done with it". That's a really fascinating statement since you have no idea of what canopy we're discussing, it's condition, the number of jumps on the lines or their condition and trim or the performance degradation of this canopy if any. You couldn't possibly know these things because the canopy in question is purely hypothetical. I'm in no way insisting that you use this process, that's your decision. I believe that this is a useful topic and that the OP asked a reasonable question. If your contribution here is that this technique is untested then we allready have agreed that no formal testing has been done. Since I have not had nor heard of any issues I'll continue to use this technique. You do your thing, I'll do mine. Continuing to insist that I or someone else buy a new lineset is dogma. By the way I do have evidence that this idea has merit, that's why I use it. The evidence is simple: I end up with lines that are measurably more in trim than before. One canopy in particular demonstrated markedly improved openings after the lines were brought closer to spec trim. Is this scientific proof? Obviously not. Am I concerned about safety? Of course. If I see evidence that stretching lines weakens them to a degree where they are unsafe then I'll reconsider, so far that's been anecdotal. Doing casual internet research on that subject has brought no result. Since line strength degrades inevitably and as a factor of many environmental conditions it would be interesting to see the effect of line shrinkage and stretching. Sometimes you eat the bear..............

The right thing according to who? Linesets don't simply go from "good" to "bad" as you are obviously aware. They begin to go out of trim gradually and start the process from jump #1. If better trim quality can be safely maintained by a simple procedure then that is the right thing to do. Have you ever tried this procedure? Do you have evidence that it has no merit or that it is dangerous? If not then your opinion isn't particularly useful and contributes nothing to this discussion. I'm not a rigger, I claim no special scientific knowledge. But I have used this technique on three of my own canopies with varying degrees of success and no adverse results. I was shown this process by a man who has many years of canopy design and construction experience, this experience gives him a great deal of credibility. So continue to be a conservative old fart naysayer or instead maybe take a more open-minded approach. Either way, blue skies Pops. Sometimes you eat the bear..............

If your guitar was out of tune would you change the strings? More than likely you would tune the guitar by adjusting the strings many times before deciding to replace them. In any event canopy suspension lines are a unique case, awkward analogies don't mean much. Sometimes you eat the bear..............

Are you implying that my Sabres lined with Spectra aren't fashionable? Sometimes you eat the bear..............

Good to have info on this. What is your source? How much is Spectra weakened by heat shrinkage? How much further weakening is caused by stretching the shrunken line? Sometimes you eat the bear..............

No tutorials that I know of. It would be nice if Brian spoke up here, he has by far the most knowledge on this technique. This subject isn't new, there are posts going back several years. I use as much weight as I can by sitting or kneeling on a carpeted floor and leaning back. I am careful not to stress the attachment point at the canopy fabric. I found that I could hold on better without pulling on canopy fabric by inserting a rod through the finger trapped line loop so the rod rested on the attachment material. I don't know if this is "recommended" practice but it seemed the best solution to hanging on to the line. I use a different method on my paragliders, using a 40 lb weight suspended by a pulley I stretch each line to the same pressure for the same count (like 10 seconds). There seems to be less controversy in the PG world about this, not everyone does it but its pretty common. Sometimes you eat the bear..............

Terrific analogy Sometimes you eat the bear..............

Here's a little fact: My lines are vastly closer to stock trim after I stretch them than before. This particularly applies to symmetry. Safety-wise I am not aware of an increase in line breakage due to this practice. Broken Spectra lines seem uncommon even on badly worn linesets. If line breakage isn't a problem and openings, flight and landings are improved by better line trim then I would say safety is improved by using this technique. The only potential issue I see is brake lines snapping during a swoop, that would merit some study to see if there might be some vulnerability. Value added? For 30 minutes of free labor (you can do this during a weather hold or whatever) your lines are in far better trim. You're right about one thing, people are mostly too lazy to do this. (edited to correct "break" to "brake" ) Sometimes you eat the bear..............

I was also shown how to do this by Brian Germain. The difference it made on that canopy was remarkable. I've done it on several canopies, the results depend on how out of trim the canopy is. (more out of trim shows more benefit from stretching) The effect lasts remarkably long and the lines can be stretched more than once. Paraglider lines lose trim for a different reason but many pilots stretch their lines routinely 1-2 times per season. Personally I believe that stretching Spectra parachute and paraglider lines 1-2 times per season is a good idea, keeping the lines tuned up between changes due to wear makes perfect sense as a maintenance routine. Parachute lines take me 30-45 minutes depending on condition. I don't worry about trim charts, the lines won't stretch past their original length. I'm primarily trying to attain symmetry, also working to stretch outside lines the most since they shrink the most due to slider heat. Note that stretching does not work on HMA and Vectran. As always YMMV. Sometimes you eat the bear..............

I once unpacked an X-braced canopy that had been packed in a very tight container for over a year. This particular canopy was a known sniveler, commonly 1000-1500 feet. When unpacked it not only retained it's brick shape but took 15 minutes of prying to get it flaked out. The canopy would not have opened in time to be useful. OTOH I have jumped another canopy that was packed for a year and opened just fine. Based on these experiences I would find it difficult to make a blanket statement on how long a canopy should stay packed. Sometimes you eat the bear..............

Some US dropzones require an AAD for all jumpers. Sometimes you eat the bear..............

As a fellow paraglider pilot I recommend lightening up some Giselle, the soaring will be better.

News flash, April 1, 2014 Giselle Martins finally agrees that wingsuits can, in fact, gain altitude but no one really cares because they are too busy arguing if the new wingsuits with interlocking carbon-fiber panels instead of traditional woven fabric are still really wingsuits. Sometimes you eat the bear..............

Makes perfect sense as long as the Flysight outputs are OK jumpered together. Sometimes you eat the bear..............

That makes sense. I guess I need a better speaker than the Radio Shack cheapo I'm using, its not nearly loud enough. Earpieces work well but they're too much hassle. Sometimes you eat the bear..............

Presumably a setup like the Autocom, which uses a stereo jack with a single speaker, is only using a single channel from the flysight output. It would be nice if both channels could be directed to a single speaker for greater volume. Sometimes you eat the bear..............

One of my favorite jumps was a night wingsuit 2-way with flyingfishman about 8 or 9 years ago, totally relaxed grips for a full minute and cheshire cat grins. Just us from a 182, unforgettable jump. Night wingsuit jumps are the shit alright. Sometimes you eat the bear..............

Otherwise known as a pop-n-drop. Sometimes you eat the bear..............

As an observation and by no means a criticism your impression of the Stiletto is quite conservative, I don't believe that either the Stiletto or the Katana will make you happy. Definitely talk to PD, they're great. Sometimes you eat the bear..............

Legal isn't my call. As far as I'm concerned modify your gear at your own risk. The issue I see is selling gear that was modified by a non-rigger. Sometimes you eat the bear..............