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Everything posted by RiggerLee

  1. I might also point out that there is no force spreading, pealing them apart till the slider descends bellow the cascade. By then you are past the worst of the opening shock. All the real force is in straight shear. Lee
  2. All the canopies that I can think of that were made that way were lined with the wide flat dacron. You could really sew the hell out of it. It was also harder to fingertrap with that tighter weave. I doubt it was as strong as a proper fingertrap. I think you would have needed about twice the stitching that they had in it to get to the same percent of strength that you can get with a finger trap, at least with a modern loser weave line. Lee
  3. I think there are factors affecting the perception of this. On the whole I think skydiving has gotten safer over the years that I was involved in it. It seems like accidents and even more so injuries have come in waves. It seems that we go through cycles where some thing new is introduced to the sport and the malfunction, injury, fatality rates spike for a time till we adapt. Having lived through those lessens I would have to say that the equipment and sky diving has gotten safer. But there are other factors that affect the perception of it's safety. It would be interesting to corrolate the attitudes expressed here with the age of the jumpers in the sport. The longer you stay in the sport the more likely you are to bairy a friend. It's a reality check when you watch some one die. I think average time in the sport has gotten shorter. We used to say that the average time was 5 years. A few years ago some one told me that it was down to three before they wondered off and... took up golf. If you stay in the sport long enough statistics catch up with you and you have to attend a funeral. So I think there is a disconnect between lifers and average jumpers in terms of the perception of the dangers in the sport. And I think that difference is growing larger with the lower average time in the sport. So I would say that there is a difference in perspective between older jumpers and the average. It's both from Lifers having lived through times that were actually more dangerous and the average jumper not having been bitch slapped with reality yet primarily do to the lower average time in the sport. I remember when a well liked local jumper died. For a number of that generation it was the first close friend that they had lost and it really affected them. Some of them stopped jumping after that. It was a big reality check. Lee
  4. RiggerLee

    Buying canopy jumped in the desert?

    It will be easy to pack. Canopies that live there do have shorter life spans. The lines need to be replaced more often. But it's only 50 jumps. That's like one good long boogie. If he hasn't gotten it real dusty it wont be bad at all. I wouldn't worry that much about it. Even if you baught a brand new canopy you should make trip to Eloy for the Christmas New Years Eve boogie any way. And then it will have 50 desert jumps on it any way. And then you should take it to South Padre and then it will have beach jumps on it. And then you should do water jumps with it... Lee
  5. RiggerLee

    Freefall Speed

    Not sure exactly what you are looking for. Depending on what you are looking for you might want to correct it for density altitude to get a corrected air speed. If you just drop it in to exel for instance you'll wind up with true air speed which is relevant in some circumstances but in for some things corrected might give you a better reference across the jump. Lee
  6. RiggerLee


    Over the years I saw a number of canopies and harnesses damaged on hard openings with larger people. The amount of energy that has to be absorbed goes up with weight but it also goes up with the square of the speed. Falling even just a bit faster makes a big difference. But it's not as simple as that. Fill time of the canopy goes down with faster speeds. That's part of the reason that high altitude openings are so brutal. True air speed and volume fill rate go way up and make a disproportionate change in the opening shock. That's why a preme at a higher altitude is so dangerous especially if you are free flying or sit flying. Snatch force also goes up with airspeed causing more load on bags and canopies. the higher forces combined with heavier canopies are a good set up for line dump and staging problems. It's easier to break rubber bands with the higher load and a heavier canopy to pull against that will resist acceleration longer. Also bags are wider on larger rigs which with older bag designs means more line in between the stows trying to pull them lose. Right now I'm working almost exclusively with recovery systems dealing with 1000-2000 lb loads and the next air frame will be some where north of 7000 lb. All these things become more exaggerated, it's been interesting. You are going to want large canopies. Don't be afraid to go big. Large canopies fly so nice and you have the weight to drive them. You'll make it back from spots that no one can fly from. The opening issues are why I recommend an Optimum. It actually opens a bit slower then other reserves. That sounds like a strange thing to say about a reserve at least in a positive context. With the higher speeds that we are seeing these days I actually see advantages in it. It also seems to be more tolerant of higher speed openings. I know a couple of people that demoed them and made a point of opening them at high speeds from head down dives with no deceleration. I think they have a wider speed envelope then other reserve canopies. You're going to want a slow opening main to begin with but you might also think about having it lined with dacron line. I know it sounds strange, old school, but it does improve the openings. I don't really buy the "line stretch" theory but it's got other things going for it. There is a lot more friction on the slider. It sounds like a small thing but I think it makes a big difference in when the canopy becomes dominant over the slider and starts to push it down and how fast it pushes it down. They also have a lot more bulk and friction on rubber bands so you get better staging on the canopy deployment. That alone can be a life saver, literally. I've seen people killed by hard openings. A slightly larger or domed or flagged slider can be a good idea. Even if you don't seem to need it on normal openings it might save you on the anomalous hard one. But one change I would strongly suggest you make is to consider getting a "Speed Bag" from Jump Shack. Basically every line stow on the bag is a locking stow, they are a bit closer together, less line between them, and there are more of them then on a normal bag. It's about the most line dump resistant design out there. It's a bit harder to pack but you get used to it. Double wrap your bands. You'll break a lot of them but it's worth it. Just buy a big bag of them and keep them in a zip lock. And welcome back. Lee
  7. RiggerLee


    Technically this is not the wanted section so I'll assume that you're looking for advice. Not sure how long you've been away. I see a frap hat and what look like kroop goggles. You're a big boy but not ridicules. And you're licensed so you get to be a big boy. A student they would be more worried about TSO max weights and liability. Booth and some others actually build sport versions of their tandem rigs for big boys rated for 500 lb loads. In reality I would recomend that you just go with sport gear. Used... tough to find unless you go with a student rig with an adjustable harness. Unless you get really lucky on here you're probable going to have to pony up and pay for a custom rig. PD makes some large reserves. I think the PDr is larger at 281 but I'd recomend that you go with an Optimum. Even though it's a little smaller and rated a bit lower I think they are more tolerant of higher speed deployments. You have your choice of mains up to 260, any of which would be good for you, but over that you're looking at a student canopy like a navigator. No mini risers or mini rings. Only full size risers and rings for you. Lee
  8. RiggerLee

    How much does slider size actually affect openings?

    Interesting. Taking a wag at the cell width of a 97 I would guess that it was about 21 inches. Allowing about an inch on each side for the inset of the grommets. That still makes the slider about 8 inches wider then the cell. The depth of the stabilizers also factors in. Some canopies have a stabilizer attachment on the B line a good bit lower then the A attachment points. I doubt that it's 4 inches on a 97. So for a 97 the front of the slider is probable setting on the bottom skin but not by that much. The back half of the slider will not be supported on the bottom skin and is probable doing most of the work of holding the canopy closed during the initial part of the opening. Doing more math, by the time you get to a 135 I'm pretty sure that the whole slider is fully engaged. None of it would be sitting on the bottom skin. So I can kind of see where they getaway with a universal slider size and I guess they add just a bit for the larger sizes to help hold the slider up an decelerate the jumper. That also explanes why there is a market for after market slider for their canopies. It leaves a good bit of room increase the width on larger canopies or play with the aspect ratios. Lee
  9. I used to print a t-shirt, "CAN I BE ON YOUR ASH DIVE?" DZ is not a place for thin skinned snow flakes. If words bother you what are you going to do when your friend bounces and you get his gooey stuff all over you? Say what is all that stuff? When I was a student I figured there would be a lot of blood but when peoples bodies break open it's all this clear gooey stuff that dries and looks kind of like thin snot. Any body know what it is? Lee
  10. RiggerLee

    Extreme engineering

    Don't get too hung up on a major or specialization. My experience is that if you are an engineer you are an engineer. What you study in school is just a starting point. You will grow into what ever industry you wind up in. Example, I'm working for a rocket company. We're rocket scientist. The head guy is an electrical engineer. My boss who does the engine development and got put in charge of recovery systems came out of the petroleum industry. I'm not sure about his degree if he has an engineering degree it's probable in mechanical? Another is just a blue collar guy out of the air gas industry. He does all of our cryogenics and most of the construction on the rocket. There is a contractor that is a dynamacist that I'm sure has aerospace degrees. But I think I might be the only person here at the shop that was an AE, aerospace engineering major and I'm the seamstress. Maybe that should tell you some thing about the viability of that degree path... If I was to actually give you advice, I'd tell you to study your math. Maybe even get a minor in it. Regardless of what your paper says, some thing general like mechanical engineering or EE or some thing more specialized like AE, there will be a place for you in what ever industry you presue. But just as an example. I'm working for this company as their parachute rigger. Thinking back on what I've used from school. Alot of my work with pattern sets and design uses a lot of protective geometry and differential geometry. Unrolling sections of surfaces out of 3d space in to 2d to form pattern sets. Reentry models goes back to my AE courses. I cracked an old Thermo text a couple of weeks ago looking at a problem we were having with our pressurization system. Analyzing INU data from drop test. People say that you will never use what you learned in school, I've found the exact opposite. Particularly the math. But more than that I find the things I studied in school just generally inform me of how things will behave. And I never actually finished my degree. Some time I wonder what else I would have learned. It was invaluable but it was also just a starting point and nothing more then a foundation upon which to start building your experience. What you learn afterwards is what your career is built from. Lee
  11. RiggerLee

    How much does slider size actually affect openings?

    I was going to suggest he cut a hole in the center of his slider with a coffee can but I figured people would give me too much shit in this day in age. Lee
  12. RiggerLee

    How much does slider size actually affect openings?

    I don't really understand your post. If you want to alter the openings of the canopy your packing technique is by far the easiest thing to change. Is this a new canopy or used? The first thing I would check is the line specs, particularly the break lines. Could it have been built with the wrong break lines? Did some one replace them between relines? Altering the break set depth is the next easiest way to alter the openings. The slider is the third option. How big is it supposed to be? Was it assembled with the wrong slider? Did some one, perhaps of a different weight or tracking habits change it out to slow it down? Changing it's size or it's ratio can alter when the canopy becomes dominant over the slider on opening. Between the three you should be able to get nice openings out of a canopy. Lee
  13. This is a good example of some one off the center of the bell curve where a larger or domed or flag slider could be handy. A better question is are the openings with dome sliders more consistent? That's a different question to whether they can fix a problem under those conditions. Let's say you plotted opening shock for a hundred openings. You get a bell curve. What we want is to avoid the out liers at the top end of the graph, they hurt. Their are a lot of decisions you can make in design, including slider size, that can shift that curve right or left. Keeping in mind that you don't want it to open too slow as well. Are domed sliders better? The question would be if they can tighten that bell curve. Make it narrower. Avoid the out liers at ether end. No more hard openings, no snivils, smaller standard deviation. There is no question that we can shift that curve right and left. That's what we have been doing with these after market sliders for years. We just needed a higher drag slider on some canopies for some jumpers. They will tell every one about how great it is because it fixed they're problem. That is not to say that it's a fundamentally better slider design. A problem we had with the canopies for our system here is that the manufacturer tryed to build the slider too big. It's actually more complicated then that, the damn thing has 22 grommets but the point stands. I built things like this for people for years but what I was doing was shifting the curve. I have no reason to beleve that it actually reduced the spread. So I can't say that a domed slider is fundamentally better then a flat slider. I can just get a bit more drag out of it. Lee
  14. RiggerLee

    Video and telemetry

    You might check out... https://dekunu.tech/dekunu-one#data They are Australian and no one can pronounce the name of the thing but it's an interesting unit. I was talking to them at PIA and it's a small INU with GPS, accelerometers, gyros, pressure transduicer etc. It's basically a little data logger but what is really interesting is the back end cloud software for analyzing and sharing the jump. Got a student? Let's see what your holding pattern really looked like. Where was every one relitive to that big way CRW formation as it built? How hard was that opening. I literally got mine yesterday so I have not had time to play with it but I cant wait to pull data out of it. You're supposed to be able to get the raw data from it as well. If you go to their web sight and scroll down to a video you can get some since of it. It's edited in with a lot of bull shit video like a toy commercial but there are shots of the interface as well. Looking forward to playing with mine. Lee
  15. Flat sliders are easier to build. You try to design some thing that you can build. You try to design the canopy so that you don't have to resort to things like domed sliders. There are some tandem canopies with slightly domed sliders. But you try not to have to go their. You'll see most of these things after market where people are trying to deal with a bad canopy that is prone to aberrant hard openings. Lee
  16. RiggerLee

    Thunderbow manual needed

    I never had a manual. What I remember is mainly about the crown lines. As I recall it splits into three sub bridles. You had to make sure that each of them was clear. From that point onwards I don't recall it being that diffrent from a PC in terms of flaking. I think their might have been some excess control line to be stowed at the cascade to take up the slack. I might be confusing that with another canopy. It was the coolest thing I ever jumped. Wish I could have hung on to it. As I recall the crow lines were the key thing in packing the canopy. Lee
  17. I doubt there is even a copy right much less a patent. Have any of them actually filed any thing? Lee
  18. That's a cool project. I may have to revise my opinions of the training in the modern rigging schools. Lee
  19. It depends on the complexity of the project. Having some thing to copy certainly helps. Coping peaces... you almost have to make pattern sets from them. Get the markings right. Order of construction. And then on the next one you're almost starting over from scratch. It's doubtful that they actually have any peaces in common. But yah, you could do it. You'd have to source all the materials and get good thread, etc. You could do it. But at that point I think some one could argue that the rigger is actually in business illegally coping other peoples suits. I really prefer the open source idea and the kit plane materials concept. You can buy plans for an ultra light. You can buy the materials kit for an experimental air plane. You can buy the parts kit. You can even buy the "quick build" kit. Lone Star could live again. Being here in the US is one thing. But lets say you lived in some back woods country or one with tariffs. Look at Quag and his canopy project. No canopy manufacturers in the UK and it's kind of pricey to buy one from out side of the country over seas. I'm surprised their are not more home grown builders popping up in some of these countries. Theirs another guy in south america. He's working on a pilot rig. It's hard to get them down their. Lee
  20. If you were to build something noncommercialy for your self, I think you would be fine. Copy rites and things protect the commercial exploration of a design. Or at least that is my understanding. I don't think any thing can prevent you from building things for your self. I think it could be argued that the rigger is stealing the design and selling it commercially if he accepts money to build it for you. Having said that. I could do some thing like this. I can do it because I have twelve different types of sewing machines lined up behind me and pallet racks of fabric to the left of me. So when I get board, yah, I do fucked up shit like that. But if even I set down and counted up the hours I had in one of these projects it wouldn't make since to do it. It's only practical if I'm idol and really board. Prices are getting out of hand. I think you will start to see more of this. Like the guys building their own canopies. Mostly for fun at first but once the idea gets around, who knows. I could see some open source drawings getting out and it turning into a little kit plane kind of thing. Then they will start selling quick build kits, here are the pre cut ribs and panels... Lee
  21. RiggerLee

    1 or 2 Pin AAD on 2001 Infinity?

    Their is absolutely nothing wrong with an honest question. Every one here will be happy to help you. Your questions tell us a lot about your experience level. Don't be embarrassed by that. We all start some where and the most important thing is that you are asking these questions. When we give you advice, like that you should spend some time with your local rigger learning about this or any gear that you are considering it's in that spirit of trying to help you. You need to sit down with him as he inspects it, takes it apart, see how it works, and how it's built. And their are limits to what you can learn on the internet. We will help you, There are good resources here but it's no replacement to working with it with your own hands. Your best resources are always the ones right in front of you. Lee
  22. RiggerLee

    1 or 2 Pin AAD on 2001 Infinity?

    Frankly if you know that little about it you should really get it sent to a local rigger to make sure it's the right rig for you. Their's more to this then just picking some thing out of an add column. Lee
  23. RiggerLee

    1 or 2 Pin AAD on 2001 Infinity?

    One pin if it's an infinity. 2001 implies that. There was an older Northern light that was a two pin. Lee
  24. RiggerLee

    Tandom baglock

    What kind of system? For example the strong drogue stays fully inflated and with only 25 0r 30 lb under it would come down very slow. Sorry don't have any kind of number. Vector on the other hand partially collapses on drogue release and wouldn't drift as far. Call the company, they might have a number on decent rate. Lee
  25. RiggerLee

    Shortening laterals

    Their are some local riggers that sew as well if not better then the manufacturer, and you don't have to ship it back and forth. But I'll tell you this, I wouldn't do it for $150 and I'm about as cheep as they come. $150 is a smoking deal and I don't know why you wouldn't take advantage of it. Lee