ph8068 0 #1 January 8, 2005 Measured my Spectra lines on my Spectre 135 over Christmas - its got about 500 jumps. Couldn't believe that some of them had shrunk by 5 inches. Anyway, it got me thinking about the lines currently available for skydiving canopies and how unsatisfactory they were: Spectra - Lasts about 800 jumps, quite durable but ruins your trim as it shrinks over time. Dacron - Lasts a very long time, super-durable but so much drag that useless for any high performing canopy. Vectran - No performance disadvantages but only lasts 400 jumps and prone to damage HMA - Low drag but lasts only 200 jumps In this world of high technology, I can't believe no one has developed a material which is strong (and so thin), doesn't shrink and doesn't break. Or is there something out there I don't know about! Quote Share this post Link to post Share on other sites
riggerrob 558 #2 January 8, 2005 Durable lines are available, they are just too bulky to be fashionable. For example, 825 Spectra lines last at least twice as long (say 800) as 500 pound Spectra (maybe 400 jumps), but their larger pack volume loses fashion points. 800 pound Dacron is even more durable, but even less fashionable. Precision has compromised by installing Dacron on the lines that wear out soonest: lower control lines. Big Air has compromised by making line kits mostly out of Spectra, but with Vectran on the corners: which shrink first. Quote Share this post Link to post Share on other sites
mark 102 #3 January 8, 2005 QuoteHMA - Low drag but lasts only 200 jumps I have 600 jumps on my HMA-line X-VX, about 300 on my HMA-line X-FX; I don't expect either set to need replacing any time soon. The Vectran lines I had previously went about 700 jumps before I started getting concerned. Mark Quote Share this post Link to post Share on other sites
nate_1979 9 #4 January 8, 2005 QuoteHMA - Low drag but lasts only 200 jumps I had always heard about 400 jumps to replace the HMA's.... I'd be curious to hear what others have to say about this considering my canopy has mostly HMA lines and I do know that they will not show wear.... FGF #??? I miss the sky... There are 10 types of people in the world... those who understand binary and those who don't. Quote Share this post Link to post Share on other sites
diablopilot 2 #5 January 8, 2005 QuoteHMA - Low drag but lasts only 200 jumps Not true. I have over 800 on one of my linesets and have seen some with more than 1000 in great shape. The manufacturers that use the stuff approve at least 500 jumps if not more.---------------------------------------------- You're not as good as you think you are. Seriously. Quote Share this post Link to post Share on other sites
diablopilot 2 #6 January 8, 2005 QuoteI do know that they will not show wear.... Incorrect. HMA most definately shows wear.---------------------------------------------- You're not as good as you think you are. Seriously. Quote Share this post Link to post Share on other sites
nate_1979 9 #7 January 8, 2005 QuoteQuoteI do know that they will not show wear.... Incorrect. HMA most definately shows wear. Good to know Guess there is just alot of opinions about HMA running around.. FGF #??? I miss the sky... There are 10 types of people in the world... those who understand binary and those who don't. Quote Share this post Link to post Share on other sites
FrogNog 1 #8 January 8, 2005 QuoteQuoteQuoteI do know that they will not show wear.... Incorrect. HMA most definately shows wear. Good to know Guess there is just alot of opinions about HMA running around.. Is this opinion just another view of the "HMA snapping" myth? -=-=-=-=- Pull. Quote Share this post Link to post Share on other sites
nate_1979 9 #9 January 8, 2005 Quote Is this opinion just another view of the "HMA snapping" myth? That's what I had always heard.... They will look just fine and then *snap*... Edited to add: Of course, a couple lines snapping just really doesnt worry me too much.. Prefer that it doesnt happen, but i'm flying a boat so I'm sure I'd be alright My steering lines arnt HMA so I dont have to worry about the HMA steering line snap on landing that I had heard about (rumor?) FGF #??? I miss the sky... There are 10 types of people in the world... those who understand binary and those who don't. Quote Share this post Link to post Share on other sites
billvon 2,400 #10 January 9, 2005 >I do know that they will not show wear.... You can see the wear, they just wear differently than other sorts of lines. There was a problem with people not recognizing worn-out brake lines and having brake lines break on early HMA linesets. I replaced the brake lines on my first HMA canopy with spectra just in case. My latest canopy has thicker HMA brakelines to compensate for this tendency. Quote Share this post Link to post Share on other sites
ph8068 0 #11 January 9, 2005 Just to dispel the HMA myths completely (or not as the case may be), has anyone actually had a HMA line snap on them? If so, was it during deployment? So is there anything to stop me relining my Spectre with HMA? Now fair enough, the performance advantages are not going to be that huge, but my Spectra lineset is almost past it after 500 jumps anyway, which is the regarded life for HMA. Is an HMA reline likely to be much more expensive than Spectra? Would any rigger be able to sort this out for me, or is an HMA reline a specialised skill? Thanks for all your help. Quote Share this post Link to post Share on other sites
diablopilot 2 #12 January 9, 2005 QuoteSo is there anything to stop me relining my Spectre with HMA? No. QuoteNow fair enough, the performance advantages are not going to be that huge, but my Spectra lineset is almost past it after 500 jumps anyway, which is the regarded life for HMA. You'll have a conopy in trim throught the life of the lineset. QuoteIs an HMA reline likely to be much more expensive than Spectra? The difference in material cost is not large. QuoteWould any rigger be able to sort this out for me, or is an HMA reline a specialised skill? Any rigger that is skilled in cutting their own linesets should be able to do the work. A small dificulty will be re calculating the length of the seperate lines since it is not generaly recomended to cascade HMA, but it's a simple problem in geometry. Quotehas anyone actually had a HMA line snap on them? Yes. QuoteIf so, was it during deployment? Yes, and the linest had more than 1200 jumps on it with a couple water landings. One line broke, I believe it was a center "C" line.---------------------------------------------- You're not as good as you think you are. Seriously. Quote Share this post Link to post Share on other sites
sundevil777 93 #13 January 9, 2005 QuoteA small dificulty will be re calculating the length of the seperate lines since it is not generaly recomended to cascade HMA, but it's a simple problem in geometry. Do mfgs give the distance from riser to each attachment point on the canopy directly? In order to determine equivalent line lengths to make a non-cascaded lineset, I would think you need to know the angles invloved for the cascaded layout, and not just the lengths.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
tonyhathaway 0 #14 January 9, 2005 QuoteDacron - Lasts a very long time, super-durable but so much drag that useless for any high performing canopy. What do you mean? High performance canopy( velocity, katana, etc.), or high-performance landings, (relative to itself with any canopy? -TonyMy O.C.D. has me chasing a dream my A.D.D. won't let me catch. Quote Share this post Link to post Share on other sites
ryoder 1,384 #15 January 10, 2005 One thing you don't mention; Dacron has a characteristic that NONE of the other materials has: The ability to absorb shock on opening. According to Booth, the other materials can TRIPLE opening shock as compared to Dacron."There are only three things of value: younger women, faster airplanes, and bigger crocodiles" - Arthur Jones. Quote Share this post Link to post Share on other sites
AggieDave 6 #16 January 10, 2005 QuoteAccording to Booth, the other materials can TRIPLE opening shock as compared to Dacron. The difference in the linse is very noticable on tandem openings, that's for sure. With the Dacron lined tandem canopies, the rare time the canopy snaps open, its not as bad as with a micro-lined tandem canopy. Atleast that's been my very unscientific experience with different tandem canopies.--"When I die, may I be surrounded by scattered chrome and burning gasoline." Quote Share this post Link to post Share on other sites
ryoder 1,384 #17 January 10, 2005 QuoteQuoteAccording to Booth, the other materials can TRIPLE opening shock as compared to Dacron. The difference in the linse is very noticable on tandem openings, that's for sure. With the Dacron lined tandem canopies, the rare time the canopy snaps open, its not as bad as with a micro-lined tandem canopy. Atleast that's been my very unscientific experience with different tandem canopies. Some years back I had a canopy on which I replaced dacron lines with Kevlar, (yes a lot of years back). With no other changes, this made a previously pleasant opening canopy quite uncomfortable. It is my observation both from personal experience, and observing others, that ANY canopy is likely so to slam you about once out of every 100 jumps. The last time my very snivelly-opening Dacron-lined canopy slammed me, it left me sore enough that I didn't jump for the rest of the weekend. The last time my Spectra-lined canopy, (which normally gives very smooth openings), slammed me, I saw stars, and was barely conscious enough to initiate emergency procedure to get rid of the spinning elliptical. I have come to the conclusion that non-stretch line is shit, and the downsides don't justify putting up with it UNLESS you are in swoop competition. I have just had my last Spectra-lined canopy relined with Dacron."There are only three things of value: younger women, faster airplanes, and bigger crocodiles" - Arthur Jones. Quote Share this post Link to post Share on other sites
diablopilot 2 #18 January 10, 2005 QuoteIt is my observation both from personal experience, and observing others, that ANY canopy is likely so to slam you about once out of every 100 jumps. I have never been slamed by any of the HMA lined canopies I've owned..... well over 2000 jumps on them.... all Precision built. I swear.---------------------------------------------- You're not as good as you think you are. Seriously. Quote Share this post Link to post Share on other sites
mjosparky 3 #19 January 10, 2005 QuoteQuoteA small dificulty will be re calculating the length of the seperate lines since it is not generaly recomended to cascade HMA, but it's a simple problem in geometry. Do mfgs give the distance from riser to each attachment point on the canopy directly? In order to determine equivalent line lengths to make a non-cascaded lineset, I would think you need to know the angles invloved for the cascaded layout, and not just the lengths. Most manufactures use differential measurement to determine line length using the length of the "A" line as a base reference. For example: "A" line = 131 inches "B" line = + 9" or 140" "C" line = + 22" or 153" "D" line = + 36" or 167" I just pulled these number out the blue, but that is the way they work. You measure from the inside of the loop at the connector link to the inside of the loop at the connection point at the canopy. If you don't tell the line there is a cascade on the way up, they will never know. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
billvon 2,400 #20 January 10, 2005 >Most manufactures use differential measurement to determine line >length using the length of the "A" line as a base reference. Agreed, but unfortunately you can't use the same measurements for cascaded vs non-cascaded lines. If the A line on a cascaded lineset is 131 inches on the packing table, it will _not_ result in a distance of 131 inches from link to line attach point in the air, since the cascade point makes the line 'turn a corner' at the cascade point. On the other hand, if you have a non-cascaded line set, it will be 131 inches from link to canopy. Quote Share this post Link to post Share on other sites
ph8068 0 #21 January 10, 2005 QuoteIn order to determine equivalent line lengths to make a non-cascaded lineset, I would think you need to know the angles invloved for the cascaded layout, and not just the lengths. Quote"A" line = 131 inches "B" line = + 9" or 140" "C" line = + 22" or 153" "D" line = + 36" or 167" I just pulled these number out the blue, but that is the way they work. You measure from the inside of the loop at the connector link to the inside of the loop at the connection point at the canopy. If you don't tell the line there is a cascade on the way up, they will never know. The example set of line lengths you give is certainly the system used by PD. I have one question though. How do you know the point at which the lines should cascade? For example, see my attached drawing. Both configurations would give the correct line lengths, with cascades at different points. Seems to me that the lengths given are sufficient to check whether your current lineset is still in trim, but not to manufacture a new lineset. Or am I missing something? QuoteI have come to the conclusion that non-stretch line is shit, and the downsides don't justify putting up with it UNLESS you are in swoop competition. QuoteWhat do you mean? High performance canopy( velocity, katana, etc.), or high-performance landings, (relative to itself with any canopy? Doesn't matter what canopy you have, it you reduce the drag from the lines, your lift/drag ratio will be higher, giving you a shallower glide angle and a more efficient flare. The smaller the canopy, the bigger the performance benefits you will see. Quote Share this post Link to post Share on other sites
mjosparky 3 #22 January 10, 2005 Quote>Most manufactures use differential measurement to determine line >length using the length of the "A" line as a base reference. Agreed, but unfortunately you can't use the same measurements for cascaded vs non-cascaded lines. If the A line on a cascaded lineset is 131 inches on the packing table, it will _not_ result in a distance of 131 inches from link to line attach point in the air, since the cascade point makes the line 'turn a corner' at the cascade point. On the other hand, if you have a non-cascaded line set, it will be 131 inches from link to canopy. You measure with all the lines anchored to the same point. You finger trap in all your cascades first, anchor all the lines and measure for the canopy attachment point starting with the "A" lines. All measurements should be "finished" length and allow for any finger trapping. See drawing and don't laugh. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
sundevil777 93 #23 January 10, 2005 Since you don't know the angle the lines make at the cascade (it is related to the canopy 'angle of attack' as it is laid down), how do you know how long to make the non-cascaded B line? As said before, it is enough info to make a replacement line set, but not enough to make a non-cascaded set.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
mnealtx 0 #24 January 10, 2005 I'm obviously not a rigger, but if you had the line set information, it seems to me you could: 1. Lay the canopy out in a flat pack. 2. Measure the line so that you know how much shrinkage you had. 3.Use that adjustment to measure from the riser attachment point to the canopy attachment point. Wouldn't that give you an accurate, non-cascaded lineset?Mike I love you, Shannon and Jim. POPS 9708 , SCR 14706 Quote Share this post Link to post Share on other sites
mjosparky 3 #25 January 10, 2005 QuoteSince you don't know the angle the lines make at the cascade (it is related to the canopy 'angle of attack' as it is laid down), how do you know how long to make the non-cascaded B line? As said before, it is enough info to make a replacement line set, but not enough to make a non-cascaded set. Angle has nothing to do with it. It is the length of the line groups that determine trim or angle of attack. If you measure all the lines from the same anchor point, length is length, cascade or not. If you measure a given line at the canopy end it does not know if it is a cascade line or not. How you figure where to put the cascade is another matter. As far as I know there is no set rule. You would have to go by what the old line set is. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
