alan

Funny you should talk about comparing apples to apples and then go on to compare the research in the paragliding industry to that of sport parachuting. That data is based on radically different wing loading, planforms, aspect ratios, cell numbers, trim angles, airfoils, etc.. I'm not slamming you, I just want people to know why other canopy manufacturers are not relying as heavily on paragliding data to question the validity of competing designs. alan

My best guess is that when John wrote the seminar, he was giving skydivers credit for some intuitive knowledge of how the meaning of responsiveness applies to canopy flight characteristics, especially given the context of his seminar. Additionally, when he presents the seminar, participants have the opportunity to ask the question you just did. I don't think a precise scientific definition is needed or useful. Essentially, responsiveness is how a canopy responds to the variety of control inputs it may be subjected to, which include range and rate, both as inputs and responses. Here is the source part of your misunderstanding. The canopies do not scale exactly in the real world. The canopy fabric does not scale, meaning and 89 ft2 canopy uses the same fabric that a 220 ft2 canopy uses. The lines do not scale exactly because an 89 ft2 canopy may use the same Vectran lines found on a 169 ft2 canopy. The seams in the fabric do not scale, etc.. It seems to me like you have theoretical questions that have no real world application.....as least for all practical purposes. That is healthy. I'd be willing to bet that if you contacted the author of the seminar, he'd be very willing to answer your questions and defend his conclusions. Maybe you could then share that with us. On what do you base this assumption? Your conclusions don't have to be wrong because they were different from John's. It is possible that yours are correct and his are in error. It would be nice if you were to share your conclusions with John and give him the opportunity to defend his. You might both learn something from such an exchange and if it was shared with the rest of us, we could all have the opportunity to learn and benefit. I know firsthand that John takes a student mindset to skydiving and is always open to learning. alan

......hmmmmmm, seems as if Paul and Simon should get together and talk, so they give consistent information, or better yet, join Dan Preston, Bill Booth, Chris Martin, George Galloway, Bill Hallett and the others who have been posting here directly (sorry if I missed anyone). The contributions they have made have been valuable to the many skydivers that read Dropzone.com and follow their favorite forums. The real value comes in differring opinions, points of view and information that are supported with experience, sound reasoning and research or testing data. It gives each of us the opportunity to evaluate it for ourselves and form our own opinions. It does not need to mean that one has to be pitted against the other, but many rumors and myths about skydiving and the gear we use could be dispelled and a healthy debate in a moderated forum can result in the exchange of important information. With the amount of money manufacturers spend on advertising to get out information about their products, it amazes me that they don't all post here, especially given that it is free and the number of readers that Dropzone.com has. That is not an open invitation to come here and openly/blatantly advertise or promote their products, but to simply respond to requests for information, whether it is about performance, maintainence, safety concerns, etc.. I think that Dropzone.com has a more personable flavor to it than the skydiving related printed media. As an interesting side note to this, John L. has stated that the Stiletto uses the same airfoil as the Sabre, and more recently, they used that same airfoil on the Spectre. It just demonstrates that a good airfoil design can be the basic building block of performance, but planform, line trim and other factors all interact to determine the performance and flight characteristics of a canopy. alan

Please read this article, you should find it very helpful and informative. http://www.performancedesigns.com/docs/wingload.pdf alan

A little bit of fun is OK, but the Talk Back Forum is really where you should take this or to private messages. All work and no play sucks, but the majority of readers/posters in this forum come for serious questions and answers about gear and rigging related topics, as that is the purpose of this forum and why it is moderated. Sooooo.........use good judgement and know when to say when. Posting in this forum is a privelege that can be revoked if it is abused. alan

I asked Simon Mundell at Icarus if the FX and Stiletto had the same airfoil. He said they did not. I asked Chris Martin at Precision if the Xaos and FX had the same airfoil. He said they did not. Quade has in earlier threads referenced some published materials that may give you some insights. They had to do with principals of lift and aerodynamics( from a thread about stalling?). A search of his posts or a request to him should provide the links. You are looking for the relationship between the airfoil design, center of lift, center of mass, center of gravity, angle of incidence, wing loading, planform and how they all interact to effect canopy pressurization. I don't understand it well enough to attempt a summary here in just a few paragraphs. Quade, care to try? alan

The Javelin bridle cover flap is sewn onto the bottom main pack flap. It can make it _more difficult_ to stuff over the stiffener found on the top of the bottom flap, but it will not prevent it. As an experiment, I purposely did a rush job on tucking the bridle in and stuffed it aggressively. It was fairly easy to tuck it up over the stiffener and cause the pc in tow, just as in a rig w/o the cover flap. alan

No need to go as heavy as Ty-17 webbing. Most bridles/extensions I have seen are manufactured from 1" square weave type IV support tape. Various combinations of 1" nylon binding tape, type IV support tape, and Kevlar tape are often used for the bridle on kill-line pcs. I've seen the tubular webbing used for bridles on round canopies. Contact Precision Aerodynamics if you want the specs for the bridle extension they recommend. alan

The GK's used them to jump into the Seoul Olympics. The one used by Willy Lee is still in use at my DZ, as a matter of fact, the complete rig is being jumped as it was then. It has a BUNCH of jumps on it. Opens very slow, so it is the rig of choice for Mr. Bill jumps. Still flies and lands good, but the guy has a wing loading of about .8 or .9. alan

Another hint, go easy on the risers during the inflation stage, it is easy to "over steer" without realizing it. Risers, with brakes still set will give a lot of input and cause over steer on a fully inflated canopy as well. Try using more weight shift in the harness during inflation and just be ready on the risers for emergencies. alan

When you are pricing an articulated harness, make sure you know whether you are getting hip and chest rings, or just hip rings. alan

My understanding of line dump is that situation occurs when the canopy has exited the bag before line stretch. I've also heard it referred to as canopy dump. So, as long as the locking stows perform their job, the lines stowed in the pouch can dump with no real ill effects. In practice, as billvon, has pointed out, they generally deploy in a fairly orderly manner. My concern would be that the locking stows are secure enough to prevent bag strip and yet not be susceptable to bag lock. alan

My opinion is that the Voodoo is the most rigger friendly rig manufactured in the US. Talon2 is right behind it. I do not like the Wings as the shape of the reserve pack tray, in my opinion, makes it difficult to get the pc to seat neatly and stay that way. I also have an issue with the reserve pc bridle routing. The way it is tucked under the side flaps on the bottom of the pack tray, inhibits the pc launch after the first meter or so. I don't find the split freebag as any easier to get the canopy into, maybe even just a little more screwing around when, with good technique, I've never had any trouble with the standard molar freebags. I've never used a molar strap either. I prefer the Javelin and Vector over Wings. Mirage is OK, but a little extra work compared to Javelin and Vector. Racer is definitely the most work. alan

Contact the manufacturer of your container, they are usually the most reliable source for correct sizing information. alan

I wonder just how much we really know about the helmets we use for the various disciplines in skydiving. They are apparently manufactured and sold w/o much in the line of testing or meeting any specifications. Do they really do what we assume or think they do? Is it possible that they do more harm than good and it goes unnoticed because they do not have to meet any safety criteria? alan

Thanks bill. The issue of broken/failed risers hasn't gotten much attention in the latest RSL threads. They seem to be more of an issue on tandem rigs, but it does happen on sport rigs, even after the industry went to _reinforced_ TY-17 mini-risers. The Collins Lanyard is simple, effective and inexpensive, but as you pointed out, it is one more thing and many of us already seem overloaded with with what we have now. Thanks again for sharing. alan

bill, Because of your familiarity with the Vector, I'm sure you are also familiar with the "Collin's Lanyard". I think it is a great innovation and would be practical improvement on all sport rigs. Would you care to explain to people what it is, why it is different, and maybe share some personal thought s on it? alan

Nice going guys, you have managed to take a subject that deserves healthy discussion and one worth repeating every now and then, and turned it into a flame war. It doesn't matter "who started it". FYI, in addition to what bill von has posted, I'll add that an RSL is to help deploy the reserve in the event of a low cutaway. I don't necessarily buy into the arguement that if you have a highly loaded elliptical, you shouldn't use it. Taking the time to get stable is fine IF you have the time. You may not. What if you find yourself low due to a hard cutaway from a violently spinning mal under an 89 VX @2.4? Do you still want to "get stable" before deploying the reserve? Hint: There is a good chance I wouldn't be writing this if I had bought into the highly loaded elliptical arguement. Another hint: Had the other riser failed rather than the one that did, that RSL that may have saved me, may have killed me. Yes, I pulled silver, but the RSL beat me to it. I was on my back and spinning and my Raven-M 135 deployed on heading. I was lucky, I landed in a very muddy bean field. I stuck in the mud up to my knees like a lawn dart. In my mind, the time the RSL saved over my pulling saved me from injury, and if I had been over hard ground or a runway I think I may very well have died from the impact.....with a fully deployed reserve over my head. Just a few more things to think about when we each make our own personal choices.......hopefully without being judgemental of others. One more flame and the lock goes on. alan

http://www.afn.org/skydive/sta/highperf.pdf Here is the link to Jerry Sobiesky's article. It is a rough draft and I have read a better revision of it, but this should be some of what you need. It is very technical in some areas and is becoming a little dated as well, but when used with the other resources mentioned, you will learn a lot more than you may have expected. alan

Some of you may have noticed that I've been less actively posting lately. Well, I've been checking in often and have been very happy to see that the threads have been informative and have stayed on topic. We can all be very happy to have some new visitors/posters here. John LeBlanc freely answers questions and lets us cut and paste his answers. Derek (hooknswoop) has been a great addition here and in the swooping forum. bill von is always a reliable and friendly source. We now have Bill Booth here. George Galloway and Chris Martin are watching and posting. Dan Preston has offered valuable insights. Chuck Blue (skymonkey one) has become a moderator after making many valuable contributions. Lisa (skybytch) has been there for many posts with expert advice. Geez...I don't know where to stop. Quade, thanks for your contributions and you too Rob (riggerob). I've learned much from all of you and if I have, just think how many lurkers out there have benefitted. All of the regulars here......thanks, you have made the job of moderator an easy and enjoyable one. Mostly, thanks to Sangiro. He has made this all possible. I think Dropzone.com has become the premier electronic skydiving magazine and one of the best, if not the best source of information. I think it ranks right up there with Parachutist and Skydiving magazines. alan

VX 89 currently at about 2.5 or 2.6 ( depends on clothing and accessories) Jedei 136 at about 1.6 to 1.7 Around 2000 jumps I guess, I quit logging when I realized I just jump for the fun of it and the numbers became meaningless. alan

This came up a year or two ago on the rec.skydiving ng. Here is a cut and paste of the post made by John LeBlanc in reply to the thread. I hope it answers your questions. FYI, when I do them, I start with double front risers or a carving front riser turn to build up speed. Nothing radical, a 90 degree turn will do the trick. Then let the canopy plane out on its' own with neutral controls. With an efficient canopy and the extra speed, it will start to climb a little. At this point, I gently go to about 1/4 brakes to increase the climb and angle of attack. Be careful to be smooth and do not let too much speed bleed off. While the climbing canopy still has some of the extra speed induced by the front riser(s), I smoothly ease up a little on one toggle, while at the same time smoothly adding a little more of the opposite toggle. As you go over the top, begin to smoothly return to neutral and depending on your skill and the canopy, you may have to counter steer at the bottom to stop it on heading. I find it helpful, at the beginning, to pick a spot on the horizon for a reference to start and end the manuever. Your canopy should rotate about this point as you fly towards it. Imagine spiralling down around a point on the ground, then tilt that axis up 90 degrees to the horizon. You are going to have to be capable of flying a canopy at a higher wing loading of about 1.5 or higher. "This barrelroll talk is getting pretty wild, and I think someone could get hurt. First, this stuff started years ago when people saw the barrel roll I made (in front of cameraman Gus Wing) that was used in the Tom Sanders movie "Over the Edge." It is in the PD commercial at the end, if you're still watching by then. Its not in the Blockbuster movie rental version. Second, it is not a tandem photographers trick, and it is not bull****. As to how far above the canopy you can get, Tom freezes a frame at the top with the horizon in view, so it is pretty clear how far over the top it is. (I did buy beer, but I doubt I was the first.) At the same time, in the upside down part of the maneuver, you are starting to go "downhill," so the canopy is slightly behind you. It needs to be there to keep the canopy loaded up, for self-preservation. This doesn't mean it is not a barrelroll. People doing barrelrolls in aircraft not certified for aerobatics do the same thing: They keep the wing positively loaded all the way around, and they're going downhill at the top. A roll made in a straight line is called an aileron roll, and parachutes won't do one. If the nose gets too far out in front of you, the canopy will get a negative angle of attack, and you will fall into it, whether the canopy is airlocked or not. Third, and most important, it is not a radical maneuver! Don't start yanking down on the toggles and risers aggressively, or you'll be in real serious trouble. It is an energy conservation maneuver, where speed is transferred into lift for a steep climb, then a smooth, gentle "turn" is made in brakes, which creates the barrell roll. One toggle is only three or four inches lower than the other. It is very similar to a big wide spiral dive at the ground, but it is made horizontal to the ground instead. If this is not clear, don't mess with it. I've been getting questions on this for years, and I've always kept quiet on the newsgroup about it until now, but the guesses and poor advice I'm seeing is really troublesome. I've talked to many people about this, and many of them have been in deep... trouble. Certainly, any manuever involving stalling one side of the canopy, either on toggle or rear risers, is a real mess. Also avoid any radical turn reversals from right to left or visa versa, unless you like spinning line twisted mals. You need a really efficient canopy, but not one that is too small, as this kills lots of efficiency. The elliptical planform helps keep the turn rate up at the comparatively slow speed over the top. The PD Stiletto, and Vengeance do nice barrelrolls. I haven't flown a Diablo yet, so I couldn't comment on it. So if you want to risk it, start gradually. Always stay smooth and slow, not radical. Start with a clear and pull alone at 13500, and stop experimenting at 5 or 6 thousand feet. Work gradually up to it over many, many jumps. It is an energy conservation maneuver, not an aggressive testosterone thing. You might want to insure your rig is good for cutting away from line twists with no problem. Large three rings and hard channels in the risers for the end of the cutaway cables are prudent, as are hard cutaway cable housings. Fly smart, don't kill yourself. As Jacques said, "Please don't try this based on my thoughts." John LeBlanc" alan

I charge $30 for a repack and inspection, which includes the main canopy, for the people at my DZ. Other people, I charge $40 until I get to know them. It is a small, privately owned student DZ and the people there are my friends. I don't do it for the money, I want them to jump safe, well maintained gear. The extra money is just to keep my workload down, but it doesn't seem to be working. They also get a note of anything I notice during the repack/inspection, trivial or not, which includes a gentle reminder or two about safety items...like inspecting and cleaning the cutaway system at least once a month, or inspecting and changing the closing loop. When I give them the rig, I usually do a quick little safety/information session about something that came to mind during the job. alan

Here is a link to an article that you may find very informative. It is pretty technical, but is has a discussion and the formulas on determining canopy performance. Pay attention to the text around page 50. http://www.afn.org/skydive/sta/highperf.pdf You may also want to read a seminar by John LeBlanc titled "Wing Loading and Its' Effects". It can be found elsewhere here at dropzone.com or by visiting PD's website. The short answer is that on a 200 sq ft canopy a chang of 20 sq ft is only a 10% change, but on a 100 sq ft canopy it is a 20% change. And yes, there really is that much of a change in performance with a change of 6 sq ft on an extreme canopy in the sub 100 sq ft sizes. alan

Precision Aerodynamics proudly advertises that their Nitron canopy is a German-made Nitro, manufactured under license. The Nitro has in fact used the HMA lines for several years now, with some of them getting regular use at a few of the larger CA and AZ DZs. HMA lines have performed quite well in the real world (Europe and the US) for several years now. Spectra, in various stages of development/refinement has been in use for over 15 years, with many, many recorded cases of it breaking or failing. I don't believe any of the materials currently in use is perfect. Some are better than others, while still others perform better only in certain applications. Overall, we have seen a general improvement in the products our components are manufactured from, even Spectra. alan