d123

wonderful http://www.youtube.com/watch?v=5uzheDRK24c dip trip ... flip fantasia http://www.youtube.com/watch?v=DcuHWJSTvZs Books from boxes http://www.youtube.com/watch?v=X20UmfmTVnE spin you around http://www.youtube.com/watch?v=Z35ba-jSiEA higher http://www.youtube.com/watch?v=Ea_iZ3NfwSU damn it feels good to be a gangsta http://www.youtube.com/watch?v=rL9ihXiFAko she sells sanctuary http://www.youtube.com/watch?v=cfK1tqL9JMY fear http://www.youtube.com/watch?v=V75ybmmoGMs kryptonite http://www.youtube.com/watch?v=q233CxlIZtk The strangest party http://www.youtube.com/watch?v=IoiCchYXOIo get back to serenity http://www.youtube.com/watch?v=G7iEHlO76Aw heavy http://www.youtube.com/watch?v=eFX2pk-FtEU snow http://www.youtube.com/watch?v=ahSfsCjlcBM just to name a few ... Lock, Dock and Two Smoking Barrelrolls!

There's Something About Mary. Lock, Dock and Two Smoking Barrelrolls!

Well I've meant this for student gear.

Interesting subject. I was not aware that the reserve card is an important thing. As a student, I was never told to check the reserve card. In fact I wasn't even aware of the reserve card existence until I've bought my own shit. Wouldn't checking the reserve card, 4 times a day every day, destroy the card in less than a year? My reserve card is already pretty fragile. Can I photocopy it and show only the copy when I visit a new DZ? What happens if I lose the card? Lock, Dock and Two Smoking Barrelrolls!

I've tryed that but you just can't put 2 hands on 1 front risers. When you try to put your left hand on the right front riser the erected left risers and MLW are in the way. At least on Navigators. Going with the left hand behind MLW might be possible but IMHO that's asking for trouble. Lock, Dock and Two Smoking Barrelrolls!

Okay, try this. Put that same partially inflated air mattress in the swiming pool with suspension lines attached like a canopy. Put yourself on the bottom of the deep end with a harness on (and a ton of weight to hold you down). (The air inside the mattress will move opposite of what it should do in the sky, but the idea is similar.) Pull down on one front riser and watch the pressure try to equalize on the surface of the water (which would be where the air meets the bottom of the canopy and the open nose while in the sky). Now fill the mattress fully with air and try the same thing. Having all of the lines under tension doesn't allow it to pop up like a beach-raft, but it makes it incredibly hard to pull under. Sure, this is an extreme example (a pool full of water pressure versus air in a mattress), but it works. By the way, how many injuries / fatalities were there during the days of pioneering the square canopy before cells were cross-vented? Would a radical turn collapse the canopy? - David Hi David, An air mattress is as hard to deform when you pull from the 1st half (front risers) as it is when you pull from the 2nd half(back risers). If the front riser tension/pressure/resistance to "pull" (when you do a double front risers) comes from the internal pressure of the wing (the "air mattress" effect) this means that it will be as hard to deform the wing (think mattress) with the back risers as it is with the front risers and this is not true. Is a LOT more easier to deform the wing with the back risers. We are having different tension/pressure/resistance to "pull" between back and front risers because of different distribution of the lift as billvon suggested it. The center of lift is a lot more closer to AB lines than it is to CD lines and that's the truth. As Kallend suggested and hackerguy

Hi UDSSkyJunkie, You might have a point with the internal pressure adding something to the "equation" but in full flight we have the same internal pressure inside the entire wing (from nose to tail) and we can still deform the wing a lot more easier with the CD or break lines than with the AB lines. I'm sure that internal presure might play a role on the riser presure when the air speed is higher than full flight. Lock, Dock and Two Smoking Barrelrolls!

No they don't. These discussions are only for the curiosity. I'll doubt that they have any real application. The airfoil got invented a long time ago and same thing for parafoil and I doubt that there are going to be changes in the way we fly in 21 century. I'll still like to know more about it not as a monkey that tries out anything that reads on the internet but rather out of my (and some other people) curiosity. These are only pass time talks and maybe they should be placed in a different thread as you suggest it. Edit to add: Anyway, me personally I'll love to be able to read somewhere here on dz.com what other people like Kallend, Billvon or wing designers are thinking about the physics of flight. Not for the practical reason just to know about it. I don't know if this is bad or good or is offending you or other people from here but I would really love to understand more and I think that this should be the place. Lock, Dock and Two Smoking Barrelrolls!

Anyway, I think you were right about it. When you "pull" (shift your weight to) AB lines you decrease the wing AoA. For a "gliding" wing at equilibrium the lift is equal with the load. If the air speed increase (and it does) this means that the AoA decrease. In other words if you increase the air speed in order to have the same lift (your weight) the AoA needs to decrease. So I really think you were right. As you pull on AB the center of lift moves a bit backwards(away from the nose) as Kallen pictures suggest. Lock, Dock and Two Smoking Barrelrolls!

I can only guess and it might be a bad guess but anyway here is my guess. I'm guessing that the front risers pressure on Sabre is lower since you can "pull" them. This might suggest that the "center of lift" is located a bit farther away from the nose of wing and it's offering a more uniform load distribution between AB and CD lines. With that distribution in mind I'm guessing that maybe by putting all your weight on AB lines you are deforming the wing so much that the flow gets detached sooner than it suppose to be. This means that you have a borderline airfoil. Was the tail bouncing or did you feel any bouncing of the wing? That might be the air flow attaching and detaching. I can really feel that happening on few of my parafoil kites when I play with trimming (Beamer I 2.5 meters for instance). Spin turns might be trickier to analyze because of the Centrifugal force. With the centrifugal force you can load the left AB lines (if you are doing a left spin) a lot higher than your own weight. This might mean even a bigger deformation than in double risers case. Why is changing from day to day? Maybe air temperature/density is changing enough to make a difference. I've wrote a few months ago to PD and ask them if I can get the glide ratio graph for different toggle input on Navigator and they told me that glide ratio change from hour to hour due to harness position, air pressure/temperature/density so it's quite hard to do a lot of flights for each wing to get an average for my graphs. I should share that e-mail. In the end I can only speculate about the physics involved and just like you I'll like to know more about what are we dealing with. Maybe someone will like to bring some new ideas, new food for the mind about the front risers physics. One thing that I like about kiteboarding and paragliding magazines is the fact that different companies talks about their wings designs with under the hood details about the wing profile, planform, bridle system and describes what everything is doing. Not a lot of info but just a bit. I would love to see the same thing in skydiving. Lock, Dock and Two Smoking Barrelrolls!

I I've understood correctly those pictures the main question is: are we increasing the AoA when we symmetrically load the AB lines(put our weight on both front risers)? If yes Center of Lift moves closer to the nose. If no Center of Lift moves away from the nose. Just to clarify. AoA is the angle between the wing (chord line) and the relative wind and not the angle between the wing and horizontal axis nor the angle between the flight path and a horizontal axis. Lock, Dock and Two Smoking Barrelrolls!

Ok, I see your point. The center of lift can be also changed by the AoA. If I read those pictures correctly on lower AoA the center of presure is "well" distributed (at lest for that specific profile but we can "extrapolate"). This translates to lower front riser presure. The current parachute profiles are still close to Domina Jalbert original profile design with the bump near the nose? http://www.kite.com/kite/jalbertp/jfig2.gif Great pictures btw! Made everything clear really fast! Lock, Dock and Two Smoking Barrelrolls!

Hi Kallend, I have a small theory about why the front riser pressure is high on some wings and maybe you can take a look over it and let me know what you think about it. I'll try to explain it as clear as I can but I doubt it that I'll do a good job since English is not my first language. I'm guessing that the weight distribution between AB and CD lines is controlled by the parafoil profile and not by trimming (RiggerAngleOfIncidence). Off course that I might be wrong also but anyway here goes: If front riser pressure is high this means that the AB lines sustains most of your weight and CD lines just a small fraction of your weight. In that case, I believe that most of the lift is generated near the nose of the canopy where the AB lines are connected to the wing (but on the upper skin). Probably somewhere in the CD area the flow gets detached and that's why there's only litle lift created in the CD area. Also somewhere between the AB lines the wing camber has the biggest thickness and from that "bump" on we have the "down wash" of the attached flow that "creates" the lift. By changing the trimming (Rigger Angle Of Incidence) I don't know if you can change the place where the main lift is generated on the wing and I'm still expecting to have strong front riser pressure. If we move the area where the wing camber has the biggest thickness (that "bump") somewhere closer to the center of the wing this might change the place where the main lift is generated and change the weight distribution between AB and CD lines = lower the front riser pressure and increase the back riser pressure. I know 2 other things that might suggest that the main lift is generated in the front of the wing if I'm interpreting them right. 1. Some wings have ZP only on the 1st half of the upper skin. I've seen one like that somewhere but I forget where exactly. 2.In paragliding only on "some" wings you have something called B Lines stall. ABCD lines are not cascaded. By pulling on the B lines you can lower your glide ratio BIG time. I'm thinking that you actually mess around with the area where the main lift is generated and that's close to the B lines for those wings. If I'm right and most of the lift is generated in the AB area for the wings that have high AB presure then maybe by pulling on left AB is similar with pulling on left ABCD. So when you pull on left AB you basically change the weight distribution between the left and right just like in a harness turn. The difference might come from drag because the wing is changing shape when you put most of your weight on left AB. Let me know if this could make sense. Just to politically correct: Apparently "B lines stall" is a DANGEROUS thing to do and it doesn't work on all the wings. I never try it and I heard from my instructors that recovery from B lines stall gift wrapped few people. Lock, Dock and Two Smoking Barrelrolls!

Hehehe , This is going on like a bad movie that I once saw as a kid. For real!! It was a movie about plane pilots vs. geeky radar guys and the drama in between. Can't remember the name. It was bad. Ever wonder how do people keep finding funds for making bad movies. I swear it's happening every year. Life is really strange. There's a lot to weight. Does good piloting stands for good understanding of the phenomenon? Can understanding the phenomenon help you land safely? Should an instructor teach methods and make jump decisions based on obsolete and unrealistic models? Designing a wing that could fly means understanding all there is about flying? Should an instructor be responsible for the exceptions (cracks) of his teaching methods? Should we change a "working" system because few people might die? Is it worth few people dying because of lack of knowledge? Accepting cracks in the system implies that life has no value. Fixing the cracks might kill the sport. Hard to find instructors that are curios and second guess themselves. Mykel: We just don't click. Thank you for the offers it was a nice gesture. CrazyL: This post was not directed to you. Keep up the good work! To anyone else: every post in any forum, every document or letter you write, every sentence you say represents a slice in time of your opinions. Time deforms everything. Mods: this thread and the one in safety and training are worthless nothing will be changed and nothing will be learnt. Is like rotating the shit to see on which side smells worse. Before I go to smoke a joint here is a good bye present: The wind. http://www.upl.cs.wisc.edu/~aselle/fluid/ Download fluid.exe and play with it, If it open a few minds I'm happy. Lock, Dock and Two Smoking Barrelrolls!

THis will only steer the shit up but I'm to drunk to care, to old to ask permission and to stupid to stop... I'll rock the tree a bit just to see what falls... Skydiving: Almost 1 year Off the student status. Officially no instructors but I'm looking for shit to learn. Former instructors: mix ideas about the wind changing case. Paragliding: Not having my license. Instructors: wind changing is BAD! They couldn't quite explain to me why but that's their teaching. Anyway, One guy from here wrote something that begin to make sense to me about that wind change thing. It was right here on this forum and that's Billvon in the post called "Flying in Turbulence". Search for it. Read the original post. This is a PM that I've sent to Billvon about that post in Jun.2007 For all the bullshit happy fingers out there I think that Billvon can confirm if he got an email like this one or not. I have it in my sent messages. Billvon forgive an old retard like me for dragging your name in here but I'm just to stupid. Anyway, one debatable person could say: You know, that's freaking debatable because it's a thermal! And that's wind rising. Also that's paragliding and that's high aspect ratio wings and they are bad & shit, I mean I hear about collapse on those things all the time and besides things don't really scale! OK, let's move on. Gliding: http://en.wikipedia.org/wiki/Wind_shear#Gliding debatable person: That's wikipedia and anyone can write shit there and it doesn't make it true. Hell, even I can write an entire poem right there on that page right now if I want and beside just a bit higher in that link they say about downdrafts in a wind shear and I'm sure that's what is causing the increase the sink rate. OK, forget about all those things, kid. Use your common sense. Walk with me on this one. Let's take a perfect horizontal wind but gusty. It goes from 40 km/h to 0 in less than one second. When the wind drops there's a transition volume, a gradient in wind. The wind gradient. I like that name. If the length of the wind gradient is smaller than you parachute chord I personally believe as an amator bullshiter (as other strong characters imply I am) that you parachute will collapse not only stall but collapse. Why? Take a look over the attachment. Now what's the relative wind speed for that wing in that condition? Not that easy now to say out loud a number! That's a collapse. That collapse is not created from rotors or turbulence is just from the wind gradient itself. In my simple and humble existence and at this point in time I believe that if the wind gradient is larger the effect will be less dramatic. Maybe not a collapse maybe just a stall or maybe just a change in relative wind of the wing that could make you sink. Something like Billvon suggested. Moving on! Let's take a DZ. An ideal DZ. No obstacles. LZ larger than time. A sweet 80 km radius of objects free landing zone. A yeah with "experienced" instructors that just don't believe that wind change can affect anything more than your horizontal speed relative to earth. Take some students that are teach by the same believes as you. Wind doesn't count. Wind is not even gusty at that point. Nothing bad. One student like me jumping with his shy wing goes and jumps trying to learn and get better. He flares low and fast. The wind drops fast as he flares. The relative wind of the wing is now 20 km/h and not 40km/h. As I flare nothing happens. I don't feel any resistance in the toggles as I usually do. I hit the ground hard as I'm just about half flare. I go in because the instructors from that DZ failed to teach me something and more than that because I usually flare fast and lower there's not going to be any lessons learnt. Any human there will assumed that I've just flared badly. This is a classic example why people like should go to schools to get educated. Now, to all the happy hunters out there:TRASH ME, KILL ME but mark my words: there's something going on the wind changes case and this thing is here to stay. Ignorance will not make it go away! Lock, Dock and Two Smoking Barrelrolls!

Deep breaks for almost 2 sec. I didn't see it stall I've just fell on my back. Local instructors told me about my mistake. One my friends has that on tape. I've done stall before with back risers as part of my training but I never succeeded with toggles on our navigators. On PD9 260 it was easy. Next jump I've stalled twice in the air. Contrary to some opinions PD 9 Cells still has a flare. Lock, Dock and Two Smoking Barrelrolls!

The 260 was a rent from that DZ. Actually it is used as student gear. I've bought the 230 2-3 weeks ago. Haven't jump it yet. Lock, Dock and Two Smoking Barrelrolls!

That is not my intention. My intention is to learn and by safer. I like big canopies and I like to choose my winds. I see a lot of segregation based on jump numbers to a certain extent this is good. I see tandem guys doing weird patterns and when I do something like that I hear it's not safe. How come is safe for them? How about for the student? You and dragon2 told me that i've said was BAD. I've open an invitation to explain what was bad. I've received again it's BAD. This feeling of segregation kinda fill my glass. In the end IT WAS ME. I've ment vertical speed and not horizontal speed. I'm not saying you are bad or I'm good all I'm saying is that I'm willing to learn and I need some assistance some explanations. When one posts in the Canopy control he get messages why do you post something trivial like that in the SWOOPING FORUM? There is a silent segregation and today it was my worse day. I apologias if I gave you bad vibes or I've simplified you life to a post that is not my intention and I know how it feels. I want to learn !!!! Lock, Dock and Two Smoking Barrelrolls!

In a PM DSE told me where was my mistake. I've writed horizontal speed instead of vertical speed. Here is reply to DSE. Lock, Dock and Two Smoking Barrelrolls!

Well, the 1000 - 600 - 300 method DOESN'T WORK. If I copy the black and white attitude that you shown here and I listen 100% to that method I over shoot land in the trees. I don't want to fly over tents or packing area and I’m not comfortable with to turning low. What I know for sure is that 1000-600-300 doesn't work. Now I'm going to hear the: well, you can take things in your own hands because after all you signed the waiver and it's your life and not our responsibility and we can only give you advices and guide lines. OK, so suddenly the situation it's gray!! 1000-600-300 it's a guide line and not a black and white rule. Well in this case I better gather as much information as I can. This means different methods & different approaches to all the aspects of skydive. Methods like flare fast & lower vs. slow and higher. What's the down part for each method? What's the good part? Which one behaves better or leaves more room for errors if the winds drops with 10km/h 1 sec before you start flaring? These are some cases that I've think off after only 40 jump. After 3200 jumps one could have a lot more to say about it. But not you sir!!!!!!! Your instructors WILL tell you do flare test up there and feel the flare. You can't see shit regarding your gliding ratio up there. You don’t really know if your down speed is slow enough for landing. The only thing you feel is that you got more G load (deceleration) when you flare fast. You see the pitch angle changing a lot more when you flare fast too. edited to remove PA's Lock, Dock and Two Smoking Barrelrolls!

No, it certainly doesn’t make any sense at all... Oho, Good call Sir. Fuck them hard!!!!!!! It's really fun to do that!!!! Lock, Dock and Two Smoking Barrelrolls!

You know, no real informations or lessons comes with your reply. - it can be my bad exprimation - or my bad understandings of the phenomenon In my limited experience the only ways that could land on your back (not ass, back) are stalling your wing close to the ground or the wind is pushing you back. Don't read this with an aggressive tone.I just want to see why it doesn't make any sense. Lock, Dock and Two Smoking Barrelrolls!

Good stuff!! Save the drinking for the bonfire

I've seen the picture while I was reading emergency procedures. http://www.dropzone.com/safety/emergencies/emergency_aircraft.shtml#opem The jumper whose reserve escaped out the door of this aircraft was lucky; he survived. The 2nd picture says something about a static line student but nothing detailed. It might be lekstrom10k story. Edit: to add the link. Lock, Dock and Two Smoking Barrelrolls!