When it collapses but the trailing edge stays put—the rear area—then I don't have any deformation across the transverse axis, so from left to right, the trailing edge stays still, and it only has to refill half of the volume for the canopy to regain its shape. You simply have much less loss of altitude during a collapse and a front stall. Now, of course, the discussion always comes up: well, what if it goes over the brake? If a collapse or a front stall goes over the brake, that means the turbulence or the piloting error was really extreme. With the brake, I still have the advantage that the rear part retains a bit of air and accordingly opens up a tad faster. But it's not a miracle cure; I'd rather advise against abusing the brake now to catch up with the empty rotor.
Podz-Glidz, the Lu-Glidz podcast.
Stories from the cosmos of paragliding. Today with Michael Nessler. And I am Lucian Haas.
Anyone who has listened to all the previous episodes of Podz-Glidz knows that, first of all, no guest has ever been on my talk show a second time, and second, the intro music is different every time. For this podcast episode 125, I'm making at least one exception with the guest. I already had paraglider designer Michael Nessler in conversation in episode 49 of the Querdenker almost three years ago. Back then, however, we only touched on the topic of paragliding on the sidelines. It was more about topics like flight psychology and the idea of holistic flying. To this day, it is one of the most-listened-to episodes of Podz-Glidz. This time, I'm speaking with Michael in his role as a paraglider designer.
We're focusing on the Rast system, which he invented and Swing patented. On gliders with Rast, a fabric wall is stretched across the inside of the canopy, perpendicular to all the cells. It delays the venting of the rear wing during a collapse and thereby mitigates it. However, Rast also influences many other properties of a glider—from takeoff behavior and the feel on the brake to maneuverability in turbulent air, all the way to suitability for SIV training. Anyone who already flies a Rast glider, anyone who wants to fly one someday, or anyone who simply wants to better understand the technical specifics of Rast will get deep insights into all these topics here. Michael Nesler chats from his personal experience and gives tips and tricks on how to make even better use of Rast's strengths, but also how to compensate for its weaknesses.
And of course, it's also about the question of why Rast hasn't been adopted by any other well-known manufacturer so far, despite its interesting properties. If you enjoy this podcast, please support my work as a patron. You can find out how to do that very easily on my Gleitschirm-Blog Lu-Glidz, specifically on the "Fördern" page.
Michael, who actually came up with this somewhat clunky term "Rast"? In English, it sounds halfway decent. You say "Rast" and then it's Ram Air Section Technology. But in German, it's kind of harsh, like "Rast" and stuff like that—it doesn't sound very nice. Who came up with that?
Oh, I can't really say for sure. It sort of came out of Swing. They discussed for ages what it should be called, and it was kind of a group project in the end. I'd say it was almost accidental. What did you call it at the beginning? Oh, I didn't really have a name for it. I basically got it from way back when I first tried it out, in the early 90s. Back then, the producer who had to sew it, Nike, noticed it. And I'd occasionally call it that as a working name because it was just extremely difficult to sew.
Nightmare Altraum. What was it about back then? I mean, in the 90s, you developed it. What was the idea behind it?
In the 90s, the idea was practically to not just divide the glider by cells, but even into four sections from front to back. So, each line level had a transverse wall in it. That allowed me to reduce ballooning extremely. The glider became almost as hard as a board. So the idea behind it was to get a wing that flies like a kite. So, very stiff. That worked reasonably well too, but the thing was simply way too extreme to sew together and too expensive and everything. And the manufacturer refused to build a second one.
So it was a bit of a financial nightmare, in a way.
Yeah, exactly, because they had no idea how to stitch it in. I mean, they really didn't know how to stitch it in. It took them quite a while.
If you'd basically lived your nightmare with that, why did you go back to it later? I mean, what was the idea that made you say, "I had something like that back in the 90s, I'm going to pick that up again"?
Well, back then it was already noticeable that the thing starts extremely easily because it was high-aspect for a glider of that time. Above all, it was well over six. And yet it had no tendency toward a front rosette. Because the front section fills first and stays that way, it remains fairly stable. That means it doesn't work against itself, which you could also feel during flight. And at Swing back then, one of the ideas, especially for training and beginner gliders, was to do something so that even if someone runs in fast and pulls it up without feeling it, or lays the glider out rectangularly instead of in an arc, it still fills perfectly in the middle. And I thought to myself, yeah, we've had that before, we could build that system back in.
However, it's significantly more economical, with only one wall. And that's how it started. And all the other things are sort of side effects that were extremely welcome.
You just mentioned the word wall. Maybe not everyone listening is already that familiar with the RAST system. So before we talk more about the background of it, could you just explain in very simple terms what the modern RAST—not the Nightmare, but the one built today—actually is? And what is different about a paraglider with RAST, at least in terms of construction for now, compared to a normal paraglider?
Yes, as is well known, the paraglider is divided from front to back by cell ribs. That means we have several cells. And the air can flow from front to back all the way to the trailing edge. With RAST, we basically have nothing else but a transverse wall built from left to right—from the stabilizer on one side to the other side—somewhere in the first third. This means the wall stands in the flow of air from front to back and back to front in every cell. It practically brakes it down. It doesn't seal off a hundred percent, of course, and it doesn't have to. And the trick here is that when I inflate the glider, for example, the front part fills with air very quickly up to the wall.
And the back one needs a little bit longer. You can control that well by making the openings in the wall larger or smaller. And it's the other way around: if the back is full, we have a kind of valve at every cell, at every wall in the cell, which closes briefly if you pull the brake or if the pressure increases at the back due to a disturbance or something, and we get very high stagnation pressure at the back. That means the air is sort of trapped? It stays trapped for a short moment. That moment is about one second.
How does RAST basically change, say, the statics of a glider? Does it, on the one hand—I mean, there's additional fabric and a wall built in now, and stuff like that. Does that change anything about how you otherwise construct the glider? Like, do you say I don't need certain lines anymore because, basically, this wall replaces other lines, because they obviously also pick up some cross-tension?
Yes, of course, the RAST at the point where it's installed—after many experiments, the optimal position is between 40 and 50 percent of the wing depth. You can save the tension band at that point; you don't need it anymore.
Otherwise, the RAST is also subject to very high stress when you do maneuvers—meaning collapse, front part, or anything that simply deforms the canopy. That means, statically speaking, the whole thing in the corners with the Insignia—so a kind of adhesive sail—is very strong and reinforced. And the seams are also designed accordingly to hold the tension. In the early stages, we repeatedly had cases where, for example, during an accelerated collapse or something similar, the RAST walls were broken, especially at the fold line.
They just tear, or they were torn back then, right?
Yes, they were torn, some even ripped completely through. Because the stress is just there. Because the load was too great. But by now, we have that pretty well under control, because we know that if you don't go too far back, there's less load on it, and with the reinforcements, it holds up great. And how
does RAST change the flight behavior of a glider? Maybe we can just go through the different stages of a flight and you can explain what RAST does at each point? Maybe it doesn't do anything in some areas, but just explain it. Let's start. I'm inflating my glider now. So I'm launching. How does RAST influence the glider's launch behavior?
Okay, that's pretty complex because there are different scenarios. Let's say you have no wind or a light tailwind. Then you pull up the glider. You need one or two more steps until it's completely full. In exchange, as long as it's not completely filled at the back, it creates a kind of reflex profile and doesn't overshoot. That means even with a tailwind, if you run into it brutally, it stays above you, and as soon as it's full, you have to run significantly less because it lifts off horizontally instead of taking on the slope's incline. With normal headwind, you probably won't feel much of a difference with RAST, except that if you pull up very abruptly, you won't have a front rosette or at least very little tendency toward front rosettes. That's of course also a matter of design, depending on which glider you have.
And if you have very strong wind and you haven't pre-filled the glider, but it's still empty at the back, the RAST gives you about one second, one and a half seconds. That means it has a second of time once the glider is pulled up before it develops lift. That means it delays the collapse. That is one of the advantages that most people really love, because people in Europe don't have experience with really high winds. When they go on vacation, for example, I was just in South Africa and I saw it clearly; the RAST really helps them because they can turn quickly enough and don't get collapsed.
But there's also the thing where, if you're pulling up—so if you're at least not used to the RAST—you can, at least from my experience, when you first pull it up, because the front part fills faster, the back part lags behind for about a second or so, and sometimes you think, I have no pressure on the brakes at all, and it feels weird, and you might even abort the start because of that. Do you experience that?
that too? Yes, if people don't have experience with it yet, it naturally happens from time to time that they think the glider has no pressure. But it's also a good sign in that moment. It's a clear sign that they simply pulled it up way too fast, because the RAST is designed exactly so that in zero wind, if you pull up normally—meaning you initiate it the way you're actually supposed to with modern gliders—it should be fully inflated by the time it's over your head. But if you pull up brutally fast, it gets over your head and isn't full yet. That's when you abort because you think it has no pressure in it. A glider without a RAST, however, would overshoot massively in that case. So, in that sense, it's also a bit of a teacher. I
I've also seen it where a pilot in light wind launched, and it took a while for the back to fill; she kept running and it wouldn't fill, and of course, she wanted to go for pressure, so she held the brakes deep, then it filled even worse again, especially in the back. In the end, this little launch attempt ended in a small bush below the slope, and she didn't understand at all why that happened. Would you say that could perhaps also be a disadvantage in terms of launch behavior?
I don't actually see it as a disadvantage, because you know we do a lot of training in Leverkusen at the launch site, and the launch site is relatively difficult for normal pilots because it's short. It's not particularly steep, but you just have very little runway and everything has to be perfect. And of course, we have a lot of people with RAST, and at the beginning, they run in and the glider isn't full, and that's exactly what you just described happening. They're still braking because they don't have a pressure-sensitive brake, so the rear section can't fill properly at all and you have to run extremely far. With a glider without RAST, it would be the same scenario, only it would have a pressure-sensitive canopy, but it would also take the slope's incline and you'd have to run really brutally despite the headwind, you see that time and again.
Some people also get a front collapse or something else during takeoff; it just doesn't need to happen. It's always two sides. On one hand, I can of course dampen the whole thing constructively if someone has a bad takeoff. On the other hand, if you have a glider with RAST, you can really take your time, and that's also the current teaching that you don't just yank the glider up, but rather divide the takeoff phase into stages—meaning, set it up, make sure it's full, and then accelerate, even if you have almost no wind. And that really works with the new gliders. But you have to learn it. And RAST naturally helps you a bit there, because if I pull up too fast, I have a tick more time. I just have to take two steps to compensate.
But if I just start running with a half-filled glider, that obviously doesn't help much. But you shouldn't do that even without RAST.
But it would also mean, okay, if someone is coming from a normal glider and switching to RAST, it's best to do some ground handling for about half an hour to really get to know this new or slightly different launch behavior, so that you can get a bit familiar with it.
Yes, that also depends a bit on what kind of glider model or class it is. If someone switches to a RAST beginner glider, they can just do whatever they want. Nothing happens. The openings there are also relatively large. That means it's not a full second, but only a half-second delay. They won't notice it at all. And if they have a higher aspect glider, a High B or something like that, we often issue those for test flights too, and people have no experience with RAST at all. And as I said, the Lewikow from difficult launch sites just pulls the thing up so slowly that in an emergency, it's more likely to fall down than to overshoot. And then they don't have any problem with it at all.
Let's move on to the flight analysis. I'm in a normal flight now, flying straight and stuff. Does anyone notice a difference with a RAST glider compared to a glider without RAST?
No, you don't notice any difference at all. I mean, it flies completely normally, with or without it. We've often done the comparisons. With some gliders, I've repeatedly cut the RAST out just to see what happens. So in normal flight, you notice nothing. You notice that the more turbulent the conditions become, the more you feel it when the RAST starts working.
The RAST is working. What kind of work is it doing?
Yes, that's one of the things that has very rarely been communicated. And that's exactly the point—thermals at RAST are the most exciting. Because as an experienced pilot, you don't get many bodies and wingtips where you really need the RAST. Due to safety. But the RAST, if it's properly installed, has an advantage when flying in turbulence that I personally like extremely well. And I'll try to explain that. If I'm flying the glider with little brake and I enter turbulent air and I absolutely want to fly a turn, meaning circle, even though it's bumpy and moving. If I don't have the RAST in there and I pull the inside brake quite radically down to, so to speak, fly into the turbulence with a slight wing-over, then something very peculiar happens.
The right side, when I pulled to the right, makes the turn. The left side needs a moment. That means it bends the canopy. You can see that clearly if you do it and look up. And then the turn practically begins to initiate. The right side makes the turn first and then, at some point, the left side follows. And that's practically a movement that you could describe as a slight whipping motion.
So the glider basically bends a bit in the middle. The banana gets bigger, roughly so, and then snaps back again. Exactly, that's very
well described. I need to take note of that. And with RAST, it's like this: if I pull relatively quickly, the pressure at the back increases, the valves close. That means the entire trailing edge briefly becomes a rigid block and it takes that block completely as a unit around the corner without it buckling. The result is that I have constant speed at the exit, on the first wing, right from the start, and can turn into turbulent, shredded thermals much better. That's actually the difference I like best.
But that's really because the entire wing stiffens. When I flew the first RAST gliders, I always had the impression, okay, if I pull the brake on one side, sure, they close. Then I also felt like I had a large flap on the back, because then it's not just the brake edge at the back being pulled down, but a larger part of the wing somehow moves down with it due to my brake force. And because of that, it basically has the good effectiveness in the turn. But what you're saying is also exactly this very stiff part, that the entire wing basically becomes rigid and that then affects all the way to the outer wing accordingly.
Yeah, exactly. I have to say though, to get to where we are today, it was an extremely long road and many attempts, because if you close the valves too much, for example, the effect is—I'd say—almost overbearing. Then exactly what you described happens. It was like that in the early days too, where if you pulled, the trailing edge didn't come down like it normally does, but instead made almost like a block, like a flap on an airplane. While that's relatively okay in terms of lift value now,
but let's just say, for thermals flying in turbulence and such, it's rather strenuous because the control pressure is just too high.
Through experiments, trial and error, and also by repeatedly rebuilding and taping the Rast onto an existing glider, we finally reached a point where it's a balanced ratio, and then it works very smoothly.
That means, behavior in the thermals, if I'm circling there or something, would you say a glider with a rest is basically more reactive?
That depends on the pilot. If I initiate it quickly, it's significantly more reactive and precise. If I'm flying normal turns, you probably won't notice any difference. And that's exactly what it's about—I always say, it's about a second. If I increase the stall pressure in less than a second by pulling on the brake—meaning a quick pull with weight shift, of course—then I have a higher stall pressure for a brief moment, where the glider goes around the corner as a block. But if I pull slowly and leisurely, as people often do normally, then you won't notice any difference.
Do I basically need a different control technique for a rest glider then? Does that make sense?
Good question. So if you're flying in normal conditions, no. You sit on it, fly, and you'll probably feel just as comfortable as on any other glider, or maybe even more so. If you're flying in strong turbulence and difficult thermals, and especially in strong thermals, then you can learn to use the effect of getting the glider around the corner as a block. And that means you don't initiate the turns normally anymore; instead, you do the weight shift first, then pretty quickly the brake on the inside, then the glider comes around as a block, and because it comes as a block, it also has to brake just a tiny bit on the outside, otherwise it would go around the corner too fast.
Could such behavior in gliders also be realized without such a Rast system? I mean, could you build it to be more blocky somehow? Or is that really something where he says you can only achieve that with Rast?
So I keep getting inquiries from customers who want a glider from me without a lock, because there's a patent on it that really bothers the manufacturers. And they've really tried to think about what could be done to achieve the same effects. You can replace the lock in some cases by simply installing a brutal amount of rods. But as for the effect of getting around the curve, I haven't found a way yet for it to come around the curve as a solid block.
What about the feedback from the glider to the customer? If I pull the brakes now, I basically always have a relatively hard—or what I mean by hard, a very compact—rear part of the wing. Do I, as a pilot, ultimately get less information back from the glider?
Actually, you get more feedback because the whole canopy moves. The feedback that a floppy trailing edge conveys via the brake is just indifferent. I don't know what's going on there. But if I go over it, I don't know what's going on either. If I have a flight on the brake in the rear area, the whole glider is hanging on it. And the feedback is relatively precise and also easy to understand.
But now many pilots say that with paragliders, they lie particularly solidly and calmly in the air, and many of the turbulences aren't actually passed through to the pilots as much, and you somehow feel safer. Where does this effect come from then?
Okay, that's probably due to the fact that most gliders come from me.
And personally, I prefer profiles that have good performance but also dampen turbulence well. And above all, you need profiles and a concept that allow a glider to fly properly at the lower or upper limits. Because manufacturers want large weight ranges, too. That means with 25 kilos between the upper and lower limit, the thing simply has to fly well. And there is a certain profile class that many manufacturers now use, which also dampens turbulence accordingly well. But that actually has little to do with the brake itself. It's more a matter of profile design, of ballooning, exactly.
What I've noticed sometimes when flying with Rast gliders is that with smaller turbulence—not large ones, but where you sometimes get the impression that, oh, maybe a small front collapse could happen or something—I can actually feel that quite well with gliders without Rast, depending on how they're built. I then move briefly onto the brake and I get this feeling—let me describe it like this—the pressure wave I create with it, where it's pushed forward a bit, and also the brief change in angle of attack that I make with it, actually prevents the front collapse from happening immediately; instead, it just flops open. And with some Rast gliders, I had it more often that I wouldn't get a large one, but always just this little front fluttering.
I didn't feel it on the brake beforehand. I was still able to react to it, though. Nothing else happened at all. But I always had the feeling that I'm getting a bit less of some of the air with it. Is that a mistake on my part, or is that basically integrated into the design, more or less?
Well, I don't think that depends on the Rast. I assume I can figure out what kind of gliders were flown based on the description.
You could start a whole big topic now, but let's leave that. It's more about the type of profiles and especially the pre-tension, so the billow, as they call it nowadays, or ballooning, and the quality of the assembly. Because it's the things you just described, okay, the brake would probably mitigate the whole thing, but the tendency to get these little front collapses usually comes from the leading edge being sewn with too much tension. Okay, the problems are known. People know how to deal with them now, and yet you still can't get it completely out of production. That's one point. The second is, if I get a front collapse now,
then it's not like it's being pushed down from above, but it happens purely because of that, just like any collapse, because the negative load briefly creates a low-pressure zone at the bottom surface, and that pulls the parts of the glider down. That's where the low pressure is created on the bottom surface. And that's also profile-dependent. The straighter a profile is on the bottom surface, the less it causes the effect. The rounder it is, the more power I have, but correspondingly, it could also come down at the front faster. That's why I'm actually pretty sure it's more about the profiles and how it's manufactured than the brake. Yes, with
I only noticed it with the Rast; I said that with other gliders, I feel something like that beforehand. And on the Rast brake, I sometimes felt like I sensed those subtleties of what's happening at the front just a little bit less.
I'd have to give you one of my new gliders, then, you probably wouldn't have that problem. Okay, you have
also learned that too?
Yeah, sure. I don't want to do any self-promotion here, but the Lilo, for example, is built completely differently in terms of wallooning compared to the previous gliders. And the riser is also quite different and in a different position, and accordingly, it just feels different. Because the goal was to be able to fly thermals really intuitively with it, so that you really feel exactly everything you just mentioned, what you don't feel right now. And I think we've managed that really well.
Before we get to the Lilo, let's go back to the flight itself. Now we have the thermals flight behavior, a bit of feedback for the pilots. What is the behavior in extreme situations? What happens if the glider actually collapses? And explain side collapses and front collapses. What does a raster do?
Okay, if I get a side collapse, every collapse has a relief preceding it. That means if I make a flight error and don't move my weight into the relief—meaning I don't move my weight to the relieved side but just stay straight, or I even move to the open side before it collapses—then the collapse normally becomes huge, the glider completely breaks away, and things can get pretty sporty. With a brake, it's like this: if I move to the brake on the relieved side at that moment, I increase the internal pressure in the rear area; then the leading edge collapses completely, but the trailing edge stays mostly in place. What happens? As long as the trailing edge stays in place, I can still keep the glider relatively well on axis and controlled using the brakes, and it also takes less time to refill.
And that is one of the major advantages in terms of safety with Rast. Because if I collapse or stall the front—it actually doesn't make a difference—the part that generates lift when it collapses, but the trailing edge stays put, the rear section... I don't have any deformation across the transverse axis, so from left to right. The trailing edge stays put, and it only has to refill half the volume for the canopy to get its shape back. And the difference is, you can always test that, and test it yourself: you simply have much less altitude loss during a collapse and a front stall. And you have more control. Of course, we always have the discussion: what happens if it goes over the Rast? If a collapse or a front stall goes over the Rast, that means the turbulence or the flight error was really extreme.
And I know this from my SIV training too: whether I have a Rast or not, the wing still collapses. With the Rast, I still have the advantage that the rear part retains a bit of air and consequently opens up a tad faster. But it's not a miracle cure; I'd advise against abusing the Rast and then trying to fly it with a collapsed rotor.
But basically, would you say that if a pilot with the same skills flies a normal glider and a glider with a rest, meaning it has that rest wall in there and he gets, let's say, flies into the same level of turbulence and gets the same collapse because of it, then that collapse with the rest system would basically always break at the rest itself, not go deeper. And ultimately, it might be open again after a third of the time compared to the normal glider. Or how would you assess that?
Yeah, the good thing is, I don't have to claim or say anything. I get videos or photos from our customers every now and then, because most people fly with a camera these days, so it's pretty well documented. And I haven't actually received a video yet from someone who went completely over the reserve, except for those who try to do it with all their might during SIV training. But that's a completely different topic.
If a collapse really goes over the rest bar—and a really big, deep collapse, as the DHV so beautifully calls it—I've made the observation, though this is only during SIV training, that when it opens up, you actually get a counter-collapse more often, especially with rest gliders. When I saw that back then and experienced it myself, I explained it like this: probably because that rest wall is in there, the ventilation is such that when one side snaps back, it most likely pulls the air out of the rear wing as a cross-flow, and basically causes the other side to collapse again as a counter-collapse. Is that understandable, or is it a stupid explanation?
Yeah, that might have been the case back in the day, like with gliders from two or three years ago. Nowadays, I have two cells in the spanwise area of the glider—meaning the rear section, left, right, and center—that no longer have any vents. None at all? No, it means the air can't really flow completely from right to left, but it gets massively slowed down. Then there are...
both wing halves decoupled, so to speak? Specifically from four parts. But I have to ask one thing now, because you just said during a turn flight—well, okay, if I pull the inner brake, the rest wall closes and the entire rear wing stiffens. But if I have the closed cell on one half now, then I don't have that effect on the entire rear wing anymore.
No, that's why you have four. It's not on the half; rather, the two closed cells are in the outer area. The middle section goes straight through.
How much of the outer area does that account for, in other words, the part that is no longer coupled to it? So with the Lilo, it's, well, if at all, 20 percent. Okay, that means the majority of the outer wing, if I brake on the inside now, will then also take that increased internal pressure accordingly. Exactly.
That's pretty complex, because if you move the cell—the first cell is at the transition, the closed-open cells—that's not always sufficient. That means you have to move two or three cells further toward the center, from the perspective of the Stabilo, so from the first open cell, you have to seal off a second area at the back a bit. That way, let's say, if he then puts the ears down or something, the glider doesn't resist against it. You have to be able to put the ears down at some point, and just as well the counter-collapse.
That prevents that quite well.
But that sounds like a lot of development effort just to try all that out. Where do I put the closed cell there? Where do I do that? Rast there and something else? It's not Rast—now let's jump topics for a second—is Rast actually a nightmare for construction too? I always imagine it like this: with a classic, a more classic paraglider, it's been the case for a long time that you still tinker around in the glider a lot, you snip through some tapes and then glue them back in a bit further, trying to create tension changes that way. But that probably doesn't work with a Rast wall that has so many functions, like holding back air and other things. You probably won't be able to tinker around as much there; instead, you get a proto and say, if the wall fits well, then it's great, but if it's wrong, I can basically chuck the proto into the corner, something like that.
Well, I have, or rather I have, extremely much experience and have experimented a lot, and this has been going on for six or seven years now, the whole project with Rast, or even longer if you include the 90s. And I think I've tried most of it by now and documented it experimentally as well. In the meantime, however, and this has to be said openly, if I want to build a good glider today, it's probably 30 percent design work on the computer, another 30 percent testing and adjusting—sometimes even less if the work on the computer was good—and the remaining 40 percent is quality control in production, to ensure that the thing is sewn for the series and not just as a proto, as one might imagine.
Because in the past, when we had fewer cells and much more tolerance and the fabrics were more elastic, and, and, and, it wasn't that critical, but with the high-end materials and the models built to the limit that we have today, the most important part is now production, so the assembly. Just to give you an idea, if I have to develop a new glider now, I need a maximum of one or two protos, because I know what I'm doing, but I then need many more hours in production so that it actually fits in the end.
That means no more prototypes are delivered, but instead, devices are delivered before serial production where you then say, "Something's not right here, you need to do the seam a bit differently," or something like that?
Yes, that's one part. So nowadays, they also specify the critical lengths in production. That means at the trailing edge, you have every distance—basically everywhere a profile rib ends, the trailing edge tape is marked before it's mounted. And the marking points have to match the ribs, of course. That already eliminates a lot of problems. And yes, then you also look at the interior to see if it was sewn cleanly and so on and so forth. And yes, I could tell you a lot right now about what the problems are in production, but that would probably make you a bit uneasy too.
Maybe we'll save that for another podcast sometime—let's call it the production-anxiety podcast. But let's stick to the brake today and leave the production stuff out of it. The last flight phase that still needs to be cleared up is the landing. Are there any differences during landing with a brake glider?
Well, the same thing applies to the landing. If I pull quickly, the brake kicks in. If I pull normally or slowly, you don't notice the brake at all. To put it another way, if you flare out now and do it cleanly with a forward move and so on, and you wait for the automatic bundling in the ground effect without going on the brake, and you let it flare for a long time and then pull through slowly, then it's a completely normal, flared-out landing. But if you go onto the brake radically after a flare, the valves close, you get a relatively fast, hard control pressure, and the thing stops instantly. You can like that and use it, but you don't have to. That means it really depends on how you shape your landing whether you notice a difference or not.
Has anything changed over time regarding the landing behavior with the Rast system? I remember that at least with the first gliders I tested with Rast—that was the Arcus RS and then the Nuyos RS—I always noted in my tests that they don't flare as nicely as some other gliders. You can land them cleanly, no problem, but I felt like I couldn't flare them out as gently as other gliders. That was the case with the Arcus 2 RS, for example; I didn't feel that way anymore. I thought, "Okay, it's doing that properly now." Did you change something on the Rast, or would you say no, it's profile-dependent, and the Arcus 2 actually has a different profile than the Arcus 1 had, and that's why it behaves completely differently?
Okay, I can reveal a secret now. The flare behavior depends mostly on where I position the C and D points—the attachment points—at the back, and where the brakes are positioned. For example, a glider that doesn't have the brake attachment points on the sad ribs, but rather in between, flares significantly worse than a glider that always has the brake attachment points on the same rib, no matter where. That's just where the lines have to hang. And the further back I move the D-surface, the better it flares.
out. Why is that? I mean, what does the D-surface have to do with the flair? I'm pulling the brake, not the D-surface. That's very simple.
explain, if you look at the glider from the side while braking, and you're braking about 30 percent, you'll see that between the last suspension point and the trailing edge, with moderate braking, an upward hump forms. And that upward hump creates extra lift, which pulls the canopy forward a bit. As a pilot, you don't do anything different; you just keep pulling until the hump is pulled flat downwards. And as soon as the hump is gone, it has proper lift again. But the hump phase is the phase where it would stop the flare. That means it would pull forward, it has to brake a bit more, because otherwise it would already be heading towards the ground, which you don't want. And the trick here is simply to prevent the hump as much as possible through the correct positioning of the rear line attachment points.
Of the three gliders I just mentioned, did you change anything regarding these line points that would make you say an Arcus II RS might flare better than an NUOS RS, the one?
Well, on the Arcus II RS, the rear line levels are set quite far back. At the D-level above, where it climbs up, we're at 82 percent of the wing depth. The first NUOS had it at 76 percent. That makes a brutal difference.
As a designer, do you have the percentage values for all of your gliders in your head?
From the important ones, yes. That's one of the parameters that is simply decisive in the design.
Let's go back to the Rast. Does the Rast actually provide a performance gain if I had the same glider with or without it?
In calm air, no. You don't notice any difference at all. It doesn't provide any performance gain. Not in calm thermals either. But the more turbulent it gets—and we've repeatedly compared the same glider with and without the Rast—the larger the difference becomes as the turbulence increases. Once, because it can circle differently. And the second is also an effect; I've thought about this for a long time and formed my own theory. I can't prove or document it a hundred percent yet, but if I have very turbulent air and it's flying slightly accelerated, I already have high internal pressure in the rear area due to the faster flight speed. And a paraglider flying horizontally in turbulent conditions gets a wave motion caused by the turbulence.
This means, for example, a small area of lift first hits the leading edge, then passes through to the trailing edge, and on its way there, the canopy diffuses slightly within itself and gets a wave motion. And that wave motion partially slows my speed down. Now there are two possibilities. I can build in rods in the rear area, on the upper and lower surface, so that the wave motions are blocked or reduced by the rods. Or I can build in the Rast. And both of those work reasonably well.
But the brake, if I'm not pulling on the brakes and therefore not closing the valves or anything like that, why does it dampen the wave motion for me? Because in accelerated flight, I'm actually not supposed to use the brake.
Exactly, you don't need to go on the brake; the wave movement closes the valves itself. As soon as the wave practically passes behind the brake, you usually push the downsail up a bit, and that closes the valves automatically. That's actually the trick. That's why it's so noticeable—when I have little turbulence and movement, I hardly notice anything at all. But when it's really choppy and going up and down like that, you notice the difference clearly. I have a GoPro on there every now and then.
to see what the grid actually does, and in that way I also noticed that the valves need a slightly different cut than we had at the beginning. And since then, it's been working satisfactorily. I have to say, what you might not have noticed yet, but almost all grid gliders have practically no rods, except in the nose.
I've noticed that, but I didn't order it because of that; there are other manufacturers who can build gliders with almost no rods in the rear section that still stand very well, or at least you get the feeling that they're well-braced in the back without necessarily having to have rods for the full wing depth. Yeah, sure. Now we've talked about the advantages of the ridge, but almost everything in life usually has a downside somewhere. What's the downside of the ridge? What disadvantages do I have to accept as a pilot?
Well, first of all, you have extra weight and extra volume. Depending on the glider, that's about 250 to 300 grams of extra weight because of the raft wall, since it's a relatively large surface area. You notice the whole thing when packing too. Especially with raft gliders, if you pack them nicely into the cell pack bag, the bottom part of the cell pack bag is half empty, the top is too, and in the middle, you just have the lump where the raft wall is. It doesn't personally bother me that much, but I also can't make the raft out of an extremely thin material. There is a Nehmer material available at 13 grams per square meter, which would reduce the whole thing, but it's simply not strong enough. That means I have to put a bit of material in there, and then there are also the reinforcements on the four corners of each wall.
So, bottom line, it's about 200 to 300 grams, depending on the glider and construction. And in terms of flight technique, the biggest disadvantage is that I have to slow down my launch technique or should, which I personally don't see as a disadvantage, because if I do a slow inflation and then a targeted launch phase—the run-up—then I also have less risk of something going wrong. And otherwise, in my opinion, the biggest disadvantage is the SIV training, because if I have a line and I simulate the collapse myself, the more brutally I pull, the smaller the collapse becomes. That means I have to start working with really nasty tricks, either pulling the AB or going full acceleration and then removing the weight when I pull the collapse,
if I get a collapse urgently and then a problem arises with the instructor—I've observed this repeatedly—he has no idea how a rescue glider works, but he absolutely wants to bring the glider down. He has to prove that a rescue glider can also be bypassed, and the poor pilot just does whatever he's told over the radio, and then it can happen that I actually go over the rescue glider with a nasty trick, and then you have a total destroyer that is just so far from reality,
as a normal flight operation would occur. But the disadvantage is, I can't really train for collapses and front stalls—meaning large collapses and large front stalls—with a Rast glider in SIV training.
Should I go to an SIV training as a rest pilot and get a different glider, to say, at least I can practice proper collapses?
Well, you can always do that, I'd recommend a two-liner, then it's even more fun. No, but jokes aside. I can learn a lot of things in SIV training, and the most important thing in SIV training would actually be getting a basis for it, finding a descent aid that suits me and that can achieve decent sink rates. In my opinion, that would actually be the primary goal in SIV training, because most people can fly thermals well, they can handle collapses and front stalls to some extent, but if it only goes up from then on,
that's an issue with two-liners, how to get down, but that's a different topic. That would be, so to speak, the first part of the SIV training that I would definitely want to learn and practice with rest gliders, even independently after the SIV training. You can also simulate collapses; they aren't particularly large, but the behavior I exhibit during a collapse can be simulated perfectly. And if I then really have the need to practice with really large collapses with wing collapses and so on, then I have to take a glider that doesn't have a rest.
Well, there is...
We're drifting off a bit now, but there's this discussion regarding the new INC two-liners, saying that one of the problems is that while they all fly great, people getting into them might not be able to train certain things in SIV training quite like they used to. Or they might experience certain flight situations as being somewhat untrained because they don't get to practice them enough outside of SIV training. You don't just pull a collapse with a two-liner to say, "Let me see, I'll get used to that again and again." Is that something where you'd say a Rast glider could basically have, how should I put it, a habituation effect, where you get used to the comfortable flying with the Rast, and then when things really get going, you might be slightly under-trained with it?
That actually depends on the pilot. For our gliders, the recommended descent aid isn't "ear-leaning," but rather a held collapse. I can get my 6, 7, or 8 meters of sink rate, it can hold its direction and so on, and I pull it slowly so that it empties out nicely. That means it becomes a sort of 60% collapse. You hold it on axis, and after 10 seconds you can release the outside brake because it won't turn away anymore anyway. And that's actually a good exercise that you do again and again, whether you want to get down quickly or just for fun. And it also prepares you for the right reaction if you actually get a real collapse. Let's be completely honest, with all the feedback I get from our Rast pilots,
either only collapses that were stopped with a Rast, or front stalls, or a few where the glider completely turned over. In those cases, the Rast doesn't play a role anymore because then things just go south. If I have a flip, it's over anyway.
If you have a total destroyer, as you call it—or as I call it now—you have a roll like that; it's not that the pilot necessarily jumps over the canopy, but from what I understand, you look at the upper surface of the canopy from below once, and then it snaps back up properly, quite powerfully. Does a glider with a canopy behave differently than a normal glider in that situation?
The only difference there is that it doesn't empty out at the back immediately. That means it's less prone to doing a rosette forward or backward in the initial stage. That might give you a faster opening, but otherwise, there's not much difference compared to gliders without a reserve. The main problem, though, when you have something like that, is always characterized by the fact that more or less most of the lines are sagging. That means the canopy does whatever it wants anyway. What
is with full stalls? We were just talking about SIV training. So, with full stalls, does a rosette glider behave differently or do you need a different technique to initiate a full stall with a rosette glider?
No, not at all. I mean, a full stall is a slow-flown maneuver. You're pulling slowly, which means the brake doesn't really come into play because everything is being pulled down relatively slowly. Then you go into flyback, which is completely normal. And when you're in the pre-inflation phase, it fills up anyway because it's all relatively slow, and there's no difference during the inflation either. So, all maneuvers that are controlled slowly via the brake actually make hardly any difference.
But that also means during this inflation phase, because you say that during the start, only the front part of the glider inflates, so during a normal start. Is it also during the inflation phase after the full stall that you notice the front area inflates first, and because of that, it might shoot forward less because that S-shape profile forms briefly again?
Yes, but you're laughing, yeah, during a full stall, the filling takes time, meaning it happens relatively slowly from the start. If you do it very quickly and abruptly—meaning you pull the full stall, wait for it to go over your head, and just release the brakes to shoot up—then it will fill from the front, will probably make an extreme reflex because it's empty in the back, and will significantly dampen that forward surge. But I wouldn't rely on that voluntarily right now.
Okay, that would be more for the phase where it maybe slips out or something, then you might still have that as a possible help. Exactly. What else occurs to me as a disadvantage? You have this transverse wall in there now. I'm flying at the dune, have a lot of sand in the glider or something, and then I can't just shake it out like that. With classic gliders, for example, there's a technique where you say you just pull it up in the flyback and let the sand just trickle out, but I basically have a barrier in there now that prevents that. How do I get a Rast glider clean again?
Oh, I have a lot of practice with that because I've been to Ecuador and South Africa with it several times, and I don't know how the sand manages to keep getting into my glider, but it just happens. And the simplest technique is, you pull it up normally, bring all the sand to the trailing edge, practically shake it all into the trailing edge at the end of the exit, then you either lay the glider on its back—so on the upper surface or the lower surface—and slowly tap it up and shake the sand forward, because at that moment, when you've practically turned it over and the sand is at the very back and you shake it forward, it slides through the valves and comes to the leading edge, where you can then shake it out again. We have that pretty well under control by now, it's quite quick and works great.
The trick is just to move it to the back first, and then to the front.
We've talked a lot about RAST now, the pros and cons. If you listen to me, you'd say, yeah, RAST is a great system, actually many more gliders should be built like that, but when you look at the market, there are very few manufacturers who actually do that. So, among the well-known manufacturers, it's only Swing as a larger one, and you with your brand Profly and your own gliders Lilou and Lilou Tandem, who have a RAST system in them. Why? I mean, why only you? Why aren't other manufacturers copying that too?
There are some other manufacturers, not from the paraglider sector, that incorporate RAST as a license. For example, SkySails on their power kites, which practically generate electricity. Then there's a high-end model builder who incorporates RAST into his gliders. Then there are some projects that practically—well, how should I put this, I have to be a bit careful because it's not entirely public—retrieving satellites from outer space using a paraglider that is controlled; that one also has RAST in it or will also have RAST in it. The reason is, there are three reasons that really speak against incorporating RAST. The first is, as
no paraglider manufacturer wants to buy a patent from someone else. They aren't exactly on good terms with each other anyway. They always act like it's a community, but in principle, it's a cutthroat competition. And you don't want to admit to someone that they invented something and I have to or can have it and pay for it. That's out of the question. The second point is, if a manufacturer—and I've had this discussion with manufacturers several times—builds a glider with RAST, he has to equip all the other models with it too. Because he's going to advertise it with all its advantages, which are undeniable. And why should I then buy the other models from the manufacturer without RAST? That means he would have to completely renovate his range in the shortest possible time. Which is an extreme amount of effort and also very expensive.
And I don't know if you caught this, but this year, it was also extremely weak in terms of sales. They're seeing losses of up to 50 percent in sales. No one can really afford that right now.
The transition, you mean?
Yes, the transition. Yes, not just the transition, you have to adapt your gliders to it, you have to do the development and so on and so forth. I mean, it took us five to six years to get that right. If you want to transition an existing model range now, you'll definitely need two to three years.
Was was da mal passiert ist – now you can share a bit of behind-the-scenes info if you want – were there ever manufacturers who maybe built their own glider as a test? Just to try it out? Yeah, that's a cool story. Michael, let's check and
what came out of that? I'm not going to name names, but there's a major manufacturer that equipped the C-glider and the D-glider for its team pilots with a ratchet two or three years ago, and they were on the verge of getting both ratcheted gliders certified because they couldn't get a handle on the certification issues. And then, at the last moment, we found a way to get the whole thing through the quality seal without the ratchet. And the feedback was extremely positive. They even started discussing how to handle the license and the patent. But the whole thing fell through because we found another way that was significantly cheaper. Significantly
cheaper. If you look at it this way, for example, if you build a glider that is completely stacked with Nitinol from back to front so that it stands well there. And I have a glider where I achieve a similarly good standing effect with a ridge. What is actually more expensive? Stacking Nitinol all the way through or installing a ridge wall with the additional fabric, but especially that significantly higher material sewing effort that you have to put in there?
Wow, that's hard to define. You can get Nitinol from China extremely cheaply nowadays. It used to be expensive when you still had to buy it from Euroflex in Germany, but now it's also being manufactured in China. That means it's a relatively inexpensive material. Most manufacturers only have Nitinol in the tip anyway, if they have it at all. Otherwise, it's plastic rods, which cost next to nothing.
But the effort involved in the sewing, I think, is significantly higher with the Rast. And with the Rast, it's also hard to say, but you really have to sew cleanly. You can't just sew the walls in really quickly; they have to be glued first so that the lengths are correct, and that takes a lot of time and effort. So it's not exactly cheap. How much more expensive
how much more expensive is a glider with or without a Rast? Is it 2, 3, 400 euros?
Yeah, if you pass that on to the customer, definitely. I mean, for something like a Nios or a Lilo, the extra labor for the brake was probably around 10 to 12 hours plus the material. At that point, you're already at 150 to 200 euros in production.
You said there was this one manufacturer that was almost there. Do you expect, or are you counting on, more people jumping in eventually? I mean, if you say you still want to make progress in paragliding, and this is at least a way to perhaps still develop certain things further where you might say that in other areas, technically or otherwise, things aren't moving forward anymore, but I can get stability into the glider with basically no rocket science required. You can do that with the usual procedures as they've been done until now. That it might still work out eventually,
So I think as long as the patent is there, it's going to be difficult. There are some companies coming onto the market now, new companies, new brands, because they can afford it; they'd rather start with it than without. At least one company will come to market with it in the near future, but otherwise, I don't think that as long as the patent is there, a larger manufacturer will decide to do it. I know that some manufacturers are trying desperately to find something similar to bypass the patent and get the same effect, but I have to be honest, the patent lawyer Swing hired to protect it really well was actually very good. He closed pretty much all the loopholes.
And I've tried to find a way to bypass it myself, but it's really difficult because the whole system is just so simple. That means the patent belongs to Swing, it doesn't belong to you at all. Yes, I'm the inventor, registered as the inventor, but the patent belongs to Swing because I wouldn't have been able to afford all the patent fees worldwide and so on.
So that means if you develop your Lilu now, you have to pay patent fees to Swing?
No, I have a contract with Swing—practically not with Swing, but with Günter Wörl, who is the patent holder—that I can use the Rast freely for my own gliders.
So you're not building for Swing anymore, but instead you're taking your already existing brand, ProFly, and saying, okay, I'm going to scale that up—or not, what does scale up mean—I'm going to build my own gliders under it and market them under my brand name. Why did you actually leave Swing and then say, well, now I'm going to make a Lilu?
Well, then came Corona. That means during Corona, since Swing wasn't employed by them or involved or anything, they were just a completely normal customer of ProFly, and then the orders stopped coming and so on, and I actually didn't know what I was really supposed to do during Corona. And I thought to myself, this is exactly the moment where I'll build my own glider, just as I imagine it, without anyone butt-in and saying it has to be cheap or it has to do this or that, so I'm building the glider that I personally would love to go flying with the most. I got massive support from my wife, who is also a partner and the boss of the company, and then we built the first one and it convinced us so much that we said, with this thing, we can actually go into series production.
and bring it to the market through direct sales to friends and acquaintances. It was actually a project where we said it's fun and you get to know every pilot beforehand because otherwise, they wouldn't get the Lilo anyway. Bottom line, after two years of flying and selling the Lilo, I have to say I've met an extremely large number of great people, we have a lot of fun together, and I don't actually need a second manufacturer for whom I have to calculate anything. That
So you're not building for anyone else at the moment, or do you still get inquiries? Yes,
I do some smaller projects every now and then, like for example a new brand that's testing out a tandem and a battery-powered glider with a line, as a side thing, but I don't put myself out front and promote it or really get involved; that stays with my own company.
So no major manufacturer saying, Michael, we need your extensive knowledge in paragliding.
So far, no one has asked, and I don't know how I'd react to it, but probably not, no.
Lilo, so far you've had the Lilo as the one glider, then you also built the Lilo as a tandem. Do you want to expand ProFly as a brand somehow, meaning will you eventually become a sort of full-range provider from A to D, or do you say, no, I'll keep it small and refined and have my little community, and the system works the way I want it to and I have less stress and just have fun. That
You've expressed and described it perfectly, that's exactly how it's going to be. We built an ENA glider just for fun, the way we imagined it. It's finished, and there are two prototypes of it; it was mainly made because we wanted to try out a collaboration with Michael Küng. The idea was to build a glider that he could also sell well. Then we flew it, it fits so far, everything, and when we sat down with our business editor—we have one in the company who checks the whole financial side and so on—he said, "Look, stay away from that, he'd have to sell it through schools, that won't bring anything." Because we're not in the market where you can produce in large quantities, and also in large quantities...
...can distribute, we have neither the logistics nor the inspiration for that. And that's why it will stay as it is with the Lilo, and the tandem is also a very special project; it's only produced in limited quantities, and once that's reached, you have to wait, or wait until the next cycle comes for me to get any at all. What I am doing is, of course, continuing to experiment; I just built a Lilo two-liner for myself, a pure two-liner that I could get through B without any problems as it is now. Without a folding line. So I don't need an extra line or—no, I don't need it. You don't need a folding line in that case. And I'm going to fly with it for about half a year now, and then I'll think about whether I'll bring something like that to the market or not. Lilo two-liner,
does it work as a two-liner in the B sector because you have this brake, or could the system as you built it also be B-capable, even without the brake?
Oh, I couldn't really say that off the bat right now; I'd have to cut the line out of my prototype for that, which I really don't feel like doing. But at some point, we'll probably cut it in to see what actually happens. I was just in Turkey at Babadag recently with it and, of course, I thought, I need a two-liner over water now. I brought a life jacket and was already very excited to do the first maneuvers, and at some point I realized, I can pull as much as I want. The thing is just completely normal B, just like all the other lilos too.
What's special about it? I mean, how do you build a two-liner that suddenly behaves like a B-glider? Is it also completely stacked with Nitinol all the way to the back as a two-liner? Or do you not need that either?
I think one of the reasons why it works so well is because it doesn't have any rods at all, except in the front nose, and those are extremely short.
How
do you get the wing's rigidity right? What I always see, all those ENC two-liners, they're all stacked from front to back, or almost all of them, because they say otherwise we won't get the corresponding rigging and the forces coming from the lines won't be distributed properly onto the sail if we don't do it that way.
Well, first of all, it's, how should I put it, a pretty delicate game. You have to get the loops—so A, B, C, D, because every two-liner has four loops on the canopy—into the right position; they have to be well-engineered, you have to adapt the profile to the line loops. That means if I move A and B backwards now, I also have to change the curvature of the upper sail a bit, either forward or backward, depending on what I want to achieve. And the load distribution—meaning the center of gravity moves further forward on a two-liner. And if I don't work out or calculate the whole thing precisely, and I just do it by guesswork, then I'll need a hell of a lot of rods to keep the thing standing up reasonably well. Especially when I'm accelerating.
And there, I think, that's a certain risk regarding aging, because if I have a glider that somehow only holds its shape through rods, it becomes porous, then the internal pressure drops, and then the rods have to do all the work. And then it's quite possible that I might, when accelerating, push A and B together or something, and the thing just doesn't fly properly anymore. And my goal was to take the Lilo canopy, one-to-one as it is, and adapt it so that it can fly as a pure two-liner. And that worked right away. So I don't have any additional rods in it; I have the rigging just as normal as in a Lilo. And yes, I'm going to fly with it now.
I read that in a few months the Lilo 2 is coming to the market, but it won't be called a 2 because it's a two-liner, but rather you're still bringing it to market as a completely normal three-liner. Why not as a two-liner?
First, I want this thing to fly for a long time, and I need to be 100% sure that it doesn't have any flaws. Then I have to calculate whether I can even afford it, because I can only produce a limited number of units and I don't want to make more, otherwise I won't be able to keep up with my customer base.
And that would also be a bit more expensive in production, sure. You'd really have to calculate whether we can finance that and if it's worth it for us. And I did a survey with our community. We have a WhatsApp group for all the Lilo pilots where they all exchange information. It's not managed by us, they do all that themselves. And the survey showed that they just want small changes to the existing model for a Lilo 2, and we've implemented that, so that will be the Lilo 2. Is it
Does the Lilo as a two-liner have significantly more power than the three-liner, or does it not make that much of a difference?
So, I obviously went comparison flying with it in Bassano in the same size, and the differences weren't there in normal glide. So if you're flying side-by-side in calm air, there's no difference. In the thermals, I had a massive advantage, surprisingly. But that's also partly because I adapted my flying style to the two-liner when circling, and in accelerated flight, there is indeed a clear difference,
so a clear advantage. With accelerated flight, it should be obvious because the line drag is probably slightly lower, and that then scales with the square of the speed...
...swinging like that, but why did you have an advantage when cranking?
If I had an answer for that, I'd tell you, but it was just obvious, but I don't know. Or was the Lilo two-liner just newer and maybe rose even better because of that or
So? No, the other one was just as new, they both arrived at the same time. And you said you adapted your flight style to the two-liner, in what way? Well, I...
I find that two-liners generally pull into the thermals a bit less; that is, for my taste, they are a bit too damped in turbulence and in the thermals. I prefer a glider that pulls in cleanly and where I have to brake more, rather than having to release the brakes so it turns further. And with the Lilo two-liner, I basically braked much less, let it run more, and practically flew faster circles so that the damping effect comes into play a bit less. And that's just how it is, you know—the faster I fly, the more lift I generate, and if I can manage that in the turn, then I also get the better climb. To me,
I just thought of another question in the context of Rast. If I use the Rast—it actually jumps back quite a bit into the technical stuff—but I find this question interesting now: if I build a wall there and basically stiffen the rear wing a bit, couldn't I actually use thinner profiles with that?
Yeah, sure, we've tried that too. I built a NIOS that normally has an 18% airfoil thickness, and I built one with 14%—same basic shape, all the same classes. Those things fly more or less identically, but in maneuvers, you just have more stiffness with the thick airfoils; it recovers faster, strangely enough. It's heavier to pull, and from a flight technique and safety standpoint, I found the one with the thick airfoils—the normal ones—more pleasant in maneuvers than the one with the 14% airfoils, but you can do it without any problems.
But it's not a really noticeable performance advantage, if you say, "Alright, then maybe I can work with slightly thinner profiles."
So not in the B-class, maybe if you're building a super high-performance wing and you put in thinner profiles—it's also about the Reynolds number, so the smaller the Reynolds number, the thinner the profiles should be. That means if I only have 2 meters of wing depth instead of 3 meters, a thinner profile would already bring significantly more performance. That
does that also mean that with really more elongated gliders, C and D gliders, if I were to build them with stays and could perhaps thin out the profile with them, could I still squeeze out a real performance advantage from that?
Yes, probably so.
That means it could also be a way, a method, how everyone is still longing for more performance despite everything, especially in the C and D ranges or with competition gliders, where you could say that maybe Rast would even have a chance at some point, because you say you can't get any further, but with that, you might be able to get a little bit further.
Yeah, you're hitting a sore spot there, because all this obsession with performance isn't really my philosophy. After all, it's a sport where you're supposed to have fun and discover yourself and so on, and squeezing out that last bit of performance at the expense of—I'd almost say—safety, that's not the right way from my perspective. It only happens because the people talking about performance mostly don't know what else to talk about, so it just becomes all about performance. And it's funny, they haven't even precisely described what performance actually is yet. Is it gliding performance? Is it climbing performance? Is it handling? Is it the whole package? And usually, when people talk about performance, they just want to glide more and go faster, and if that's the case, Rast probably won't bring much.
at least in the competitive field, but there it really makes sense to switch to other production techniques.
Everyone is talking about performance, but we've spent an hour talking about Rast, partly about performance, but also about many other things. I'd say let's leave it at that. We've covered a lot now, and it was very interesting to see everything that's connected to the Rast, or rather how you can use it and how you can perhaps offset some of the small disadvantages that are there. Just this trick with emptying the canopy—getting the sand out of there—by shaking it first towards the back so it can then glide gently forward, that might be a tip that many Rast users will like to hear, because I know some people in my club who fly the Rast and they say, everything is great, it's just getting the stuff out of there that's always a pain. But maybe that will help you.
That's true. I'm glad. Thanks, Michael. Thank you.
That was episode number 125 of Podz-Glidz with Michael Nesler. In the show notes for this episode on the paragliding blog Lu-Glidz, you can find some additional links. If you enjoyed the episode, then please subscribe to Podz-Glidz. You can do that anywhere podcasts are available. If you also leave a positive rating there, you're helping to make Podz-Glidz even better known. Or just tell your flying friends about it. Podz-Glidz and Lu-Glidz are free of paid advertising. I do this out of conviction and for the sake of independence. Nevertheless, a lot of professional work and, of course, costs are involved in these offerings. To fund them, I rely on the concept of voluntary support.
If you've listened this far, the podcast should have provided some value for you. As a supporter, you can simply give something back. You can decide the amount yourself. A commonly chosen support contribution is 60 euros a year, or about 5 euros a month. But no matter what you pay, every amount helps me continue to operate and develop Podz-Glidz and Lu-Glidz in the service of the paragliding scene in the future. For that, I say thank you. All the necessary information, such as how your support contribution reaches me, can be found at www.Lu-Glidz.blogspot.com. There, you'll find the menu item "Support." Lu-Glidz writes Lu-Glidz.
Until next time. Don't fall from the sky. Ciao.