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Everything posted by mark
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Hello MEL! My bartack is also a Juki L-1900HS. I'm looking to match the bartacks PD, Precision, and Aerodyne use, figuring they've already done the R&D. Do all three use the same 7-running/32-covering/3-tying tack? Or do they use the 11/28/3 pattern? Do you know of any other center-stop patterns in common use? For example, the small tacks made at a canopy leading edge rib-skin junction look like 28-stitch patterns, and the pattern PD uses to attach lines to stabilizers looks like something else altogether. Do your chips do both 42-stitch patterns you mention, or other patterns? And would you be willing to part with any of your chips? Thanks, Mark
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I own an electronic end-stop bartacker, and I plan to add a chip to do center-stop patterns. The fellow will program the chip does it stitch by stitch, so I need to know what the industry standard is, if any. That is, from the center, how many straight stitches and what direction, followed by how many zigzag stitches and what direction. I know a 42-stitch pattern is most common, but are there others (28, 36, 56, 60) in use as well, and what are the industry standards for those? Can you point me to a reference? Thanks, Mark
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Sorry, not so, and the proof is from mathematics. If the parachute was straight before it was tangled, and if it was not disconnected, then when you have untangled any two adjacent lines from canopy to link(s) on straight risers, the rest of the lines will be straight as well. Mark
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Who should reline a canopy? Rigger? Master Rigger? Factory?
mark replied to kitof1976's topic in Gear and Rigging
Bringing a canopy back to factory spec may or may not be a senior rigger task. Instead of looking at the work as an alteration, look at it as a repair: major (one which if improperly done would affect airworthiness) or a minor one (not major). Replacing the lower brake lines on a Precision main (involving just a larks-head, no sewing) would be minor, replacing a cell would be major, and in between these extremes are shades of grey. Mark -
Did you talk to the supervising rigger? What did he or she say? Mark
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My set includes posters of "Total", "Blown Panel", and "Horseshoe", but nothing for Mae West, streamer, or similar. Does your set have anything like that? Mark
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I recently came across a series of posters intended as visual aids for a static line FJC. I vaguely recall these being used in my FJC, and maybe you do too. These black-and-white posters have stylized figures (not photos), and show things like student position on the step, initial position ("hard arch"), a round canopy with arrows indicating airflow through drive and turn windows, and PLFs. Each poster is marked "United States Parachute Association Publications" and "Paravisualx™ © 1975 John F. Sorensen." I have 10 posters; I'd like to know if that's the complete set. Yes, I've contacted USPA. Thanks, Mark
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Unless the pouch is rigid and airtight, holes are unnecessary. The pressure inside will equal the pressure outside. Katze: Tell me again why this altimeter glove is a better arrangement than wearing an altimeter and (optionally) a glove. And what are the fingertip controls going to do? Will I be able to hold something and still work the controls? Conversely, if I don't want to work the controls, will I still be able to hold something? Mark
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ISP Cat A is silent about flaring or not; Section 5-1 (for experienced jumpers) recommends "minimal control input for landing," but doesn't say beyond that to flare or not. I'd recommend against students flaring either canopy in a 2-out biplane. Flaring takes you from a configuration we think is landable (bird-in-the-hand) to a configuration that might be better or might be worse (two-in-the-bush). If the canopies are not exactly one behind the other, would stalling the front canopy cause an asymetrical wrap and then a spiral in? I don't know; perhaps an intrepid dz.commer can do the test jumps for us so our students don't have to. In any case, a student's approach speed is likely to be low because of all that fabric out (400-500 square feet; I concede it's not the same as having a single huge canopy), so flaring isn't likely to have a great effect on forward speed or lift. Mark
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If you are referring to flaring a CRW biplane for landing, I think it's apples-vs-oranges. To the extent that a student might think it applicable to a personal biplane I think it is bad advice. I agree that in a stable biplane, the main canopy is a keeper. In the one 2-out biplane I've seen, the main risers snagged the reserve after cutaway, but thankfully cleared. Oh, yeah. My only 2-out jump was with rounds, giving JCC/ICC candidates something to critique. A story for another time. Mark
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Several years ago I was working with a couple AFF candidates at a pre-course at Titusville/Space Center. We were climbing through 8000 feet, over the swamp several miles west of the dz on our way to altitude in a moderately full Viking Express (that is, well-maintained) Caravan. There were no tandems and no real students on board, so we would be last out. The group prior to us was also a pre-course jump: a pair of candidates and Glenn Bangs acting as the student. I was zoned out, thinking about my dive plan, when I was startled by a loud bang from the front of the airplane, and I felt the nose pitch down to level flight or a little lower -- best glide, perhaps -- not much, but abrupt and distinct. The pilot was definitely in control, though, and the plane was still flying. I thought to myself, "Wow! I wonder how Glenn got the pilot to simulate an emergency like that! I'll have to ask so I can use it in the actual course." I didn't have a lot of time to think thoughts like that before I heard lots of folks yelling "Get out!" I was a good student. I waited for my instructors to tell me what to do. I was hoping we'd at least get in a practice exit, but no, my guys just left me behind while they bailed out. I didn't have any good ideas, and it seemed like the pilot was doing okay without my help, so I bailed out, too. In freefall, I looked for other jumpers, saw I was clear, thought briefly about practicing some freestyle stuff, then decided that being over the swamp merited pulling high. I still well above airplane landing pattern altitude when I got back to the airport, so I checked the approach paths, crossed above the runway and landed in the experienced area next to the hanger. I should not have set a bad example; other jumpers also landed in the same area, the last few of whom must certainly have flown right in front of the Caravan/glider, who most certainly did not need the additional distraction. The pilot was carrying a little extra airspeed, but he got his airplane stopped before the end of the runway. The tires were ruined, but cheap compared to bringing back the airframe safely. Inspection showed that one of the engine bearings had gone out prematurely; the resulting wobble allowed many of the turbine blades to contact the shroud. The engine was basically shot. It wasn't something Viking Express, Space Center, or Glenn Bangs could have predicted. It was a fun AFF course. Thomas Lewetz brought his kids and a bunch of the Pink Skyvan crew, lots of folks earned ratings, and I found out Dunkin' Donuts really does serve coffee in a box. Mark
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John: Of the 50 biplanes you've landed, how many were personal (2-out) biplanes? Of the 2-person biplanes you've landed, how many were landed still in biplane configuration (top guy's feet still in the bottom guy's lines through touch down)? How many were landed by flaring only the front/top canopy, without the bottom canopy flaring at all? Mark
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Would this Jump Shack article, Rubber Bands Break for a Reason, qualify? Mark
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Initially, the locking stows need only be tight enough to retain the lines until the canopy slumps inside the bag as the bag lifts off. Then the weight of the canopy against the stows is usually enough added pressure to keep the stows secure. Locking stow tightness isn't likely an issue here, though: the D-bag is smaller than before. Either way, I'd be surprised if "line dump" (canopy-first deployment, actually) is to blame. In addition to the new D-bag, there's a new pilot chute, isn't there? Mark
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I have several recent jumps on a 9-cell Para-Foil 282. it is the only canopy I've jumped that opened hard and had end-cell closure at the same time. It seemed like the brakes affected only the forward speed of the canopy. Flaring for landing resulted in very low forward speed, very little swing forward, and very little change in descent rate. I don't have much experience with accuracy canopies, but I think these flight characteristics would be desirable for accuracy with a tuffet or pea gravel target. A smaller canopy would allow you to land going forward in higher winds than a classic accuracy truck optimized for winds within compeition rule limits, and modern non-accuracy designs are more likely to allow softer landings than a canopy intended for thumping gracelessly onto a tuffet. Stable in deep brakes is not the same as soft-landing. Mark
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Strato-Flyer was the main canopy version. The Safety-Flyer reserve had no provision for pilot chute attachment. Mark
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Except http://142.26.194.131/aerodynamics1/Drag/Page6.html Mark
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Might want to rethink that. For example, http://www.grc.nasa.gov/WWW/Wright/airplane/dlrat.html. It's a glider, not an airplane, and similar diagrams are found in most elementary references for aspiring glider pilots. Even if it were an airplane, a diagram of the four forces acting on an airplane in flight is just a convenient simplification of what is actually going on. For example, the actual lift vector is not perpendicular to the line of flight. It slants aft; the difference between the actual vector and the vertical one usually depicted is induced drag. Mark
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While you're there, make a donation. The service may appear free to us, but Jim can keep it running only for so long while he's absorbing all the costs. Mark
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These altitudes are considerably higher than ones I've heard suggested at many of the dropzones I've visited. Can you tell us what factors you considered when choosing these altitudes? Do the instructors at your dropzone agree, or are you free to choose what you think is appropriate? Your profile says "AFF Jumpmaster" (a non-USPA rating); would you recommend these altitudes for a Level 8 or Category G/H AFF student? How about for static line or IAD students? Mark
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Assuming the Javelin is FXC-ready, installation = assembly. If the rig does not already have a pocket, channels, mounting bracket, etc., where would one find drawings and diagrams for this alteration (besides Sunpath)? Not that I would recommend such an alteration. I don't think it's cost-effective. Just curious. Mark
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Classified Ads: "new" should be "new to me"
mark replied to mark's topic in Suggestions and Feedback
Just to be clear, I am suggesting a change to the topmost classified page (http://www.dropzone.com/cgi-bin/classifieds/page.cgi?d=1), the one that lists the different classified ad categories, starting with AADs and Aircraft, ending with Videos and Wingsuits. I think the pages listing the ad summaries in each category are fine. For example, this is okay: http://www.dropzone.com/cgi-bin/classifieds/page.cgi?g=Jumpsuits%2Findex.html&d=1. I don't think a time limit is necessary. If I haven't checked jumpsuits for several months, they're all new to me! And the ads are already sorted by date. By analogy: it's been a while since I visited the CRW forum, so my topmost forum view shows quite a few unread CRW threads. If I check the forum, the threads will be sorted by date of most recent post, I can choose how stale a thread I want to go back to, and when I return to the topmost forum view, the unread thread count is reset to zero. Thanks, Mark -
Classified Ads: "new" should be "new to me"
mark replied to mark's topic in Suggestions and Feedback
Right now, a "new" classified ad is one recently posted. To find out if there are listings I haven't seen before, I have to choose a category. Could the "new" tag be changed so it's more like the unread thread count on the forums: to show only if there are new ads added since the last time I checked a category? Example: -- old way. Click classifieds, see all categories. "Reserve canopies" shows "new." Click "Reserve canopies." Nope, still shows same ads from yesterday. -- proposed way. Click classifieds, see all categories. "Reserve canopies" has no listings added since I checked yesterday. "New" does not show. I save a click and page view; when I save enough clicks and page views, I have time to make an extra jump. Mark -
The field-replaceable cutter coupler can rotate without disconnecting. But you're right: the cable channel and coil(s) usually have enough slack that the cutter can be pulled through the elastic, allowed to relax, and then be pushed back into place. Mark
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http://www.randi.org