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Everything posted by pchapman

  1. Yeah, I don't know all the in's and out's of Kevlar abrasion resistance, in particular how old Kevlar lines got a poor reputation for degrading so quickly. Was it because of Kevlar on Kevlar between lines? Or a lot of flexing with say coarser weave lines? Or the formulation of Kevlar at the time? Certainly Kevlar doesn't tend to get for example the same 'line burns' that spectra or nylon might, being more resistant to heat and that kind of abrasion. (E.g., in Kevlar reinforcement on some kill line bridles.) Kevlar is better in that way.
  2. To humbly expand a bit on Mark's statement: The wear & abrasion (to itself) issue was the big problem that people talked about. It was all a bit before my time, but Kevlar didn't work out on main canopies, while it was used on a few early ram air reserves, where the frequency of packing was less. (As the OP may know, but I'm just giving a bit of history.) It also was used for a while for high strength reinforcements -- Like reinforcement circumferential bands on lightweight National Phantom round reserves, or being used as reinforcement tapes in ram-air reserves, or being used as the reserve closing loop for the then-popular Racer rigs. I guess it was the first 'extra strength' material out there in use! Kevlar is "an HMA", a high modulus aramid, but must be formulated & woven in a different manner than our current HMA lines which last better. (Although clearly they have their wear issues too, if made really skinny...) So Kevlar had a real wear problem. While for the other things Mark mentions, it was more a case of "being ahead of its time" rather than being inherently deficient -- We didn't all have stainless grommets to resist abrasion, and canopy designs & packing techniques weren't ready either. Just like the early days of Microline / Spectra, where there were more problems with instant openings, broken risers, too small sliders, etc. Thus part of the whole problem was the changes in rigging technique & design needed, for the new material. Here's an example from a 1980 [Edit: corrected. Not '85] CSPA rigger's bulletin, where they quote GQ Security (which produced the Unit ram-air canopy, some of which had Kevlar lines) on some of the pitfalls for riggers to watch for:
  3. Of all the copied media out there, I don't think this is very high on the list for tracking down those sharing it. But it does beg the question: (which might be answered in some other Lone Star thread somewhere) Who is behind Parakit Inc., of Georgetown Texas, who copyrighted the Lone Star manual in 1985? Are they still around? Or are relatives still selling the manual or hanging on to it to sell for millions down the road? I'm guessing not. Reference - link from a friend - it's on the Internet Archive! -- https://archive.org/details/lone-star-parachute-assembly-kit-scanned-manual Sure has some good practical detail on building a canopy, even if an old fashioned one.
  4. Here's what I have, data from about 30 years back when I was new to the sport and a bit obsessed with collecting data and understanding the sport. 1. Two pages from I guess the Italian skydiving magazine in 1992 listing the early tandem fatalities in order. (Apparently there was also one on a European Galaxy rig sometime in that era, that isn't in those stats.) First tandem fatality is shown as the one with one snap not done up, TI spent entire jump trying to hook it up, without deploying anything (even the drogue). 2. An html file from UPT listing tandem fatalities and causes in order (but with no dates). From 2008, back when they listed that on their web site. 3. Scribbled pencil notes of mine from the early 1990s, where I listed a bit of the evolution of tandems (eg the date when Strong & Booth got their FAA exemptions to allow tandems), plus all the early fatalities and dates. I think most of the data on dates comes from an article in Parachutist,July 1989. (Which I can't find at the moment.) That list puts that first tandem fatality -- with the snap not done up -- as Oct 19, 1986. Back in those days people were wondering what the heck was going on with Vector tandems, as in the first dozen fatal accidents, there were 10 on Vectors, and 1 on a Galaxy, before there was 1 was a Strong Dual Hawk. There sure were a lot of different causes of accidents -- Stupid stuff we're not allowed to do with tandems now, main bags that much more easily came out of the container early, plus a lot more casual training and attitudes towards tandems. Which brought in the idea that 'it isn't just another skydive'. It also took a while to come up with the first tandem CYPRES, and eventually the idea of making one mandatory for tandems. (Wish I had the dates for those.) RWS tandem fatality list as of Feb08.htm
  5. I had a look at the manuals to familiarize myself with them. Basically in line with what Jerry is saying, - the earlier Peregrine Glide has a semi-exposed RPC - the newer Peregrine Falkyn had a covered RPC
  6. Here's all mine. (Did you get yourself a 'dactyl?) Paradactyl Manual (slightly expanded version).pdf Paradactyl - shorter Guardian manual [P Chapman scan from M Stevens copy].pdf Paradactyl manual (DactylManual)[M Stevens scan].pdf
  7. A tip -- If you can turn off Javascript and refresh, most WaPo articles can be viewed. (Depending on the browser & operating system, that can be very longwinded to do, or easy to do with some browser extension.)
  8. From BasicOne's posts, I get the idea that the M2 cutters are like this: a) The old ones had the "flat plate plunger" design that shears the loop at both cutter holes. Something not at all known to the public before, I think. Quite a different design. b) Then I guess after Airtec/CYPRES' patent expired on single blade cutters, newer cutters use a single blade like a Cypres. That the kind BasicOne did tests on, using 2019+ M2 cutters, and was concerned with the amount of damage to the cutting edge after firing.
  9. Boy this brings back memories of the AAD wars from a decade or more ago! As far as I recall, this is how I'd put this into context compared to the other AAD companies: Cypres always had the hardest, best cutting cutters. Vigil has the circular cutters (effectively 2 blades), that they tout as being a good concept, but have come under some criticism, even though they generally do the job. (eg, one serious critique in "What's going on with AAD's" by Kirk Smith, 2011) Argus had serious cutter issues. They also used circular cutters. (I got the impression that was due more to a Cypres patent in the early days?) Most issues were actually with their older style cutters, before upgrades in hardness & manufacture, but in any case the tide turned against the company and their AAD's are pretty much irrelevant now. Mars M2.... don't recall hearing of cutter issues before (for actual cutting), but never saw any engineering data on their cutter hardness. (There was one accident relating to their very old MPAAD design, not the M2.) Someone should ask Mars about their M2 cutter hardness. That's just one measure of goodness, but a decent one. I would still have to dig up info on other designs, to see what metal hardness values were found for other companies. .......Hmm, here's something I had on the Argus vs. others: (My interpretations of the Polish report on the fatality there in 2009 that involved the Argus.) So, I wonder what an M2 cutter is like. Great testing by the original poster, BasicOne, thanks, but I'd like to see independent confirmation too! [Edit:] After all, the M2 has been reasonably popular in recent years too, and surely cutting loops successfully, even if not out there in number like Vigils and Cypres'.
  10. Sorry, can't be true. I don't know anything about what may have gone on in the background, but the canopies are very different. Excalibur wasn't tapered -- Adding taper was a huge change in canopy design complexity! Excalibur had different nose inlet shapes. Different standard sizes. The Precision built FX's were of course licenced from Icarus in NZ. Maybe that's what you were thinking of? (I still fly an FX but don't know all the history from back then!)
  11. Space X uses Pioneer drogue parachutes for the return of their Dragon spacecraft. (But Airborne Systems provides their main parachutes.) High speed parachute design is a specialized thing, so even Space X didn't do it in house. Still got my Pioneer Titan canopy, though it has been a decade since I used it at Bridge Day... Will be interesting to see what happens to Strong.
  12. Interesting. How much of an issue is this in practice? I don't know, but I see the EG18X smoke grenade is on the list as no longer exempted. Its baby brother -- with less smoke volume -- is the EG18, isn't mentioned, so that one is still OK without the extra regulations. I have used the EG18X on demos. A pretty decent grenade for that use, at a reasonable price. Some years back they seemed to be the best I would see available. But in recent years there are pricier grenades out there with higher performance. So I don't know what high end, well sponsored teams use. But for smaller demos, the EG18X's were nice to have. So it kind of looks like the higher end, better stuff, is getting more regulation.
  13. Since this 2018 thread was revived: It is interesting to consider the "two ways to double stow" issue that sundevil777 brought up after Westerly's observations. To recap, there's the "wrap around twice like wrapping it with tape" , and there's "make a single stow, stretch the elastic, make a half twist to create a new 2nd loop, and put that over the line bight". One sees the first method, for example, in one PD tips youtube video. I confirmed that both methods are equivalent topologically in the sense that the final result can be changed from one to the other while the elastic is in place on the lines. If you try it, you can look down at the line bight in its double stow, and move one loop of the elastic over a little and be back to the first instead of the 2nd configuration. Like sundevil said, there's technically no actual knot created. But the 'twist 180' method does seem a more secure or little more grabby, as there's more rubber band overlapping other parts of the rubber band. Whether there's any significant effect on line deployment in practice, who knows. So far I'm not worried about which method I use. I also tend to do the twist 180 method. Which one does will depend on what one is used to , but perhaps also likely on how tight the elastics are when trying to wrap the bights. The simple wrapping method works better for me if there's a lot of stretch in the elastic relative to the position of the lines needing to be stowed. As for Westerly's elastic breakage issue: I may not be imagining correctly what Westerly did. I'm not sure if he meant putting in the 180 twist, or even adding another 180 on top of that, which does change things and make it impossible to simply slide the elastics around once in place on the line bight, to change to the other configurations. That might in effect be 'tighter' and put more stress on the elastic when the bight gets yanked out of it.
  14. Lines out of trim. (If they are the kind that go out of trim. Any Spectra in there,as main lines or brake lines?)
  15. Still F-111 if I recall correctly. An invention a little ahead of its time, just waiting for ZP to arrive...
  16. Paragear 1991-1992 catalogue, the first with the Cypres in it: Cybernetic Parachute Release System (Cypres) $1225 (In current dollars, that's $2770) (Compare to Cypres 2 price at Paragear now, over 30 years later: $1199, less than the original dollar price, with a longer life and no mandatory servicing either.) Also in Paragear that year: FXC AAD $695 (A lot less than the Cypres, but its 2 year factory checks added up too, for the diligent DZ's that did them.) RWS Vector II $978 (Cheaper than the Cypres) (In current dollars that's $2210.) (Vector III at Paragear now is $3350, over 50% more despite accounting for inflation, although it certainly does have a few more features than a Vector II. Still just certified as a Wonderhog.) [Edit: Inflation calculated online with 1991 average, to Sept 2023, the most current data, for the US CPI]
  17. Lots of things are not 'recommended', or 'unsupported' but are perfectly safe and/or are accepted in the industry. But leaving that aside... One pack volume chart, from Parachute Labs, shows a Tempo 150 at 312 cu in, and a Smart 160 at 416. While pack volume measurements are notoriously uncertain, this does suggest the Tempo is quite a bit smaller in volume. Sounds a bit iffy to me. You could of course just pack it up and have a look, to see whether it is loose in the freebag (and not putting tension on the safety stow?) or makes the rig close up oddly. Would be interesting to know how it turned out. Usually the problem is totally overstuffed rigs (ugly, bulging, poorly fitting flaps & PCs, and hard to close) rather than ones with too small a reserve in them...
  18. I have seen so many stows where the internal elastics are breaking but nothing has seemingly been done about it for ages. So on the one hand I have replaced many that I think should have been replaced earlier, but on the other hand I'm also willing to let things slide to some degree, as it is as if the local consensus is to leave these things a long time. I think riggers don't always try pulling them out a little way just to see what condition they are in. (Or if they are a horribly ugly home job with terrible stitching... every rigging horrors album has a photo of those.) After all, it seems like there's still a ton of strength in the fabric of the stow even if all the internal elastics are broken -- through some combination of stretching over time, and overaggressive sewing when building the stow, that damages a lot of the elastics from the start. I've seen ones look pretty damaged when almost brand new. What I tend to object more to is the state of stretch, whether the stow is getting really stretched out and holding the lines only loosely. Yeah the mass distribution of lines, and accelerated mass of the canopy in the freebag "should" keep the stow functioning, but one does also want the safety of it being able to grip the lines securely when just sitting there. FWIW, I'm also in the old school camp of just sewing them up myself, using 'standard' good quality shock cord material from ParaGear. Rather than snapping to attention and intoning, "That is a TSO'd component! A replacement must come from the manufacturer (unless I have specific authorization from the company to make replacements according to their plans.)" Like a lot of rigging stuff, don't sew them up yourself unless you can do a decent job of it. It can be, I dunno, 10 years before a safety stow is starting to get sketchy, overstretched and losing grip. Some might be less, and start to go after only half that time. It varies a lot.
  19. This is the earliest all digital Javelin manual I have, with the file dated 2004. (not sure when it actually came out.) The next version I have is Rev02 in 2007, because then Skyhooks were added as an option. Javelin Rev01-Issue01.pdf
  20. I'll believe that! Did a stall on mine and it took a full 10 seconds (on video and not just in my imagination) before I had it flying again properly. It wanted to dive off in just about any direction before finally I got it to -- or it chose to -- fly forward again.
  21. Haha! (As you might say) There's more to the situation: The old Jav's actually did have reserve tray loops for non-diapered round reserves. Going from one of those old manuals that Gowler refers to:
  22. Good question; this is a messy topic where we just don't have well validated procedures to use or teach. More so in skydiving than paragliding. These are just my impressions, not necessarily better than others' thoughts. My method - brakes down enough to remove the slack only: As a sort of compromise, for skydiving I try the idea of pulling brakes down only to remove the slack in the brake lines, not to actually significantly brake the canopy. Just to have a tiny bit of pressure that one feels on the brakes, so one will notice if the pressure goes up or down all of a sudden. (Even though it sounds like the latest in paragliding, according to jeanneretjerome, is that they don't even want that little bit of brake pressure -- at least with the latest designs. I'm not familiar with the latest in that field.) Active flying: That allows for easier "active flying" in that one has a better feel for what is happening to the wing (PG terminology) or canopy (skydive terminology). In keeping with the active flying concept, don't worry about the canopy bouncing around a little, long as the canopy stays within some box closely above your head (or where ever it should be based on whatever turning and banking one is doing). One doesn't need to control the canopy in that case, and yanking brakes here and there will likely just make things worse. Have seen that with people being too quick to use toggles on final approach to keep the canopy as stable as possible -- and lose airspeed which can result in a crappy flare especially when one might need extra when trying to land in turbulence, eg a last moment downdraft or loss of headwind. Now if the canopy surges too far forward or tries to turn & dive suddenly, then one can brake as appropriate, as part of the active flying, to keep the canopy roughly in the right area. (But if the canopy surges back, one just has to wait it out as one doesn't actually have 'a little brake on', which one could let go to help accelerate the canopy forward.) But still all that is just a subjective feel for what seems to be decent; it sure is hard to get well validated ideas on flying skydiving canopies. Slight acceleration to pressurize the canopy, by using a gradual turn: I also like that idea of being slightly accelerated in a gentle turn, if one is under a modern canopy, to keep the speed up to 'cut through' turbulence as one might get close to landing time. I seem to recall Brian Germain first pushing the concept. A given size gust will make a smaller change in the angle of attack of a canopy, the faster the canopy is going. Although the 'continuous gradual turn' can conflict with all the strict "90 degree turn only" rules at many DZs, but a little fudging may be allowed as long as one isn't just whipping into a steep swoop turn. (Without going into detail, a 5 mph gust won't change the vectors for speed and angle of attack as much for a 50 mph canopy than a 25 mph canopy. Although it gets messy looking at different situations. Gust downwards? Or horizontally from the front? With the canopy descending at an angle in a glide, how each affects the canopy depends on canopy dive angle, angle of attack, and speed. Lots of vector math to figure out different scenarios!) General aerodynamics & risks of high vs. low angles of attack: Our skydiving canopies are often trimmed fairly nose low for extra speed that translates into more flare power. So they might be at a bit lower angle of attack than paragliding canopies naturally are, I surmise. (Although even the PG canopies aren't expected just to be super floaty at a minimum sink speed -- they want some speed too, to get places and not go backwards in high winds. They can still use speed bar (think front risers) for extra speed, or brakes for slower floaty flying.) So skydiving canopies with a lower angle of attack would take a lot of extra angle of attack before stalling at whatever their upper limit for angle of attack is. With a lower angle of attack, one would then think that skydiving canopies are more susceptible to collapse from a too low angle of attack. Typically it might happen easier just on one side of the canopy than the over the whole front (a full frontal collapse in PG parlance). I think that a low angle of attack collapse (rather than high angle of attack collapse = stall) is the one most likely happen to a jumper, and thus be the greater risk near the ground. Still, our canopies seem more resilient than otherwise expected to frontal collapses, because the airfoils are pretty heavily forward weighted, with a lot of lift near the front of the airfoil. (To some degree that's the case with all airfoils, but with skydiving airfoils more front loaded than some other airfoils). After all, on most skydiving canopies one can front riser on one side pretty suddenly without collapsing the front of the airfoil. (I remember a couple scary old ZP skydiving canopies that were extra light on the front risers and one had to be careful with front risering; plus that made me uncomfortable with them in turbulence.) (PG pilots will I guess note that when PG pilots fly, they can induce leading edge collapses more easily as they don't have combined A & B lines, but can pull down just what are effectively A lines alone.) Slowing down in turbulence for airplanes: They may do it, but that's because of structural limitations. In skydiving, we don't have canopies break from flying too fast. Although certainly the canopy fails by collapsing if it goes to 0g or below in effect, by going to a negative aerodynamic angle of attack and having the nose of the canopy collapse downward. Slow vs. fast in general: In general I'd rather be under a faster canopy that will be less affected by turbulence, 'cutting through it'. But if there is an actual collapse, one would rather be under something big and slow! I'd rather be under half of a Manta than half of a typical Valkyrie. In extreme conditions, even if the big slow canopy is more likely to collapse, it may still be safer under that canopy, with the slower speed and slower accelerations when not flying straight. Dealing with turbulence vs. avoiding it: Sometimes we get hit by turbulence and it would be good to know how best to deal with it. Still, the best strategy is to avoid getting into the situation in the first place. It reminds me a bit about the debates about airlocked canopies, which were all the rage at one time, but for various reasons have faded away. One argument against them being the greatest thing ever, was that sure they might be a little safer in turbulence, but if you were likely to be in turbulence so strong that the canopy might collapse ...it would be better to stay on the ground in the first place, than trying to rely on your airlocked canopy to keep you safe.
  23. Did you also find out how many neighbours now hated you? :-) Looks like a fun series of photos will follow, as you reveal more of your project.