Luc Armant talks about The Moment Coefficient, Enzo 3 Certification Debate & Physics of Stability

I mean, I'll only put out parts which are matching to the video. I want to put out the whole thing. Yeah, yeah, yeah. But it's also also for you, yeah. Exactly so that I can understand. Yeah, but you will read the document also. Yeah. So profile theory, we have a moment coefficient on profile, which is the shape of the profile doesn't rely to rigidity or whatsoever. It could be, it could be made of steel would be the same because we are airplanes without tails, OK, You see the pitch stability, we don't have tails, right? You see airplanes, you have tails, right? Right, right, right. Right. OK. So our stability relies on the

profile profile shape. OK. So this profile shape we could, we could it profile it has a moment coefficient and the moment coefficient can vary from something very stable where the lift resultant the force lifting you is very in the front of the profile and when the moment coefficient is more negative or smaller, it's more on the back. The more you're, when you have a very stable profile, the more you diminish the angle of attack, the more the lift force move forward, Yeah. And the more you have stability that you can understand if you think deeply about it. And the other fact is to change the speed on the paraglider, We

we do like that we change the twin by applying speed system and then the angle of attack of equilibrium changes and the force can move forward or backward depending on the CM. OK, when you have ACM that is low. CM full form. Coefficient of moment OK. When your CM is low, your force is more on the back and help to create even more speed up aggressive more speed out of a given speed range. So on the CCC, the holes make a limitation on the speed system, which is everyone, every wing should be within 14 centimetre of speed travel. And so when you make a profile that is very stable in pitch,

you don't get a lot of speed out of this 14 centimetre. I see. OK. So when you go competing with this wing which will never collapse on the bar because it's very stable, you won't be able to compete properly because on final light you will be slower than the guys. OK. So this system of rules makes an optimum powerglider to win competition to be very limit on stability, on pitch stability. Otherwise you you're not competitive.

So this is a problematic situation because manufacturers and pilots, they are pushed into compromising stability in order to get more competitiveness spirit. Yeah, out of the. 14 range basically. Yeah, exactly. This is quite clear and a lot of people have understood this. When we set up the rules, it was it was not of use. I was on the team that set up these rules many years ago and it was having some advantages because it's super easy to check. It's quite clear there is no cheating around. It's, it's a good rule anyway. But the, the side effect is that it doesn't let the, the safety because people are pushed to

compromise the stability, you understand, for, for more speed.

So there are different solutions to that. But maybe we can talk about here the competition. So we are in a very, very competitive environment where the the the pilots are very homogeneous level. Everyone lands in 30 seconds. You see, yeah, yeah, you see, it's very impressive tactics. Tactics is very important. And and so you earn your points at the end on the final line when you're very top pilots. And so it is very important to have a faster blighter. This situation has been not answered correctly on this CRV primary in December yet, but it will, I mean things take time and it will be better. I think we will find a better solution.

The IT was voted to limit the trimming to 10 millimetre instead of 20 millimetre where this doesn't change anything on the on the real problematic as you can understand.

And so it's adding more troubles to the organization and to the pilots because a lot of checking and more work, basically more, more work. But still the compromise to make is still there. You understand, it's even, it's even more compromise to make because it's like having a smaller speed range almost. And if if the speed range was not 14 but 1010 centimetre, it would be even worse. We would the the winner would be the one making a very, very unstable wing that would be even more reward for instability I. Don't understand? I'm sorry. Yeah. So you will read my document because it's, yeah, it's, it's well explained.

OK, Anyways, Yeah, it's it's well explained. And if you don't understand you, you come to me. Yeah. But yeah, that's the situation here. What else can be said?

So the ASO 3 which is made for this holes as pitch stability that is very marginal. So it's like anything instability when you're on the boot side of things, it's kind of staying if you go, But if you are very on the edge, you go on the bad side and then it's it's not good enough. It's and it's only a small difference makes a difference between enough stability, not enough stability and then when you don't have enough stability, you can get collapse on the bar without so much warning. So you can try to pilot it, but eventually you get to collapse. Because the profile is inherently unstable, basically. Yeah, the shape of the profile

and these, these wings, they are structured with some outside plastic rods like mini. And because this profile is just borderline stability, the plastic plastic rods can have an effect on the shape of the profile. Plastic rods are for line stability the attachment points. Then. I know these lines, but what are they stable for? Well, what are they making stable like? What do they help with? These lines when they are big tension or loose tension, they affect the shape of the of the profile. Right. So so their what is their purpose? To be inside the kind of? Like why do we? Yeah, we have it for good

performance and good rigidity of the profile. OK so basically to for profile shape that is why we put lines. Too Yeah, yeah, yeah This is this is to keep to keep the shape of the profile because it's a 2 liner there's not so many lines if we don't have plastic. This is this shit is not flying. OK, OK, OK. Like it won't hold well. No, it won't fly. Basically this is we can't make a paraglider like this without this plastics. OK, OK. So basically the length of the plastic in in the in the in the profile is deciding the behaviour of the wing. The shape of the profile yeah, exactly.

And, and, and so because this profile is just at the limit of stability if you push the plastic, you put some staple to make it very tight, tight, tight then you will get more speed like I just explained on the start, but less solidity, right, right, right. So it can. Just go. And then when it then it's it's not nice because you can get collapse without warning. Makes sense. OK. And so at the moment on the Enzo 3, we are having sometime issue with some gliders because they, they tend to shrink then you know, the close is 9 plus and they, they shrink quite fast. Can can shrink fast and depending on condition humidity,

we not controlling still very well this process and some in those three ends up being quite unstable. And the the the pilots have issues with collapses. So specially tip collapses. The more you fly your wing, the more the fabric shrinks. That's why the lines, the plastic rods get tighter. Yeah, because they get tighter. Profile becomes more unstable. Yeah. And that is why collapses can come without warning. Yeah. And this is, it's important to understand that it is specific to Enzo 3 and other CCC gliders because they are built really for racing on the edge of stability. So we're talking about 5 millimetre difference on a plastic rod that is more than 2m

or not 2m long. Wow. Yeah, it's. Insane, man. Yeah, it's so sensitive. Yeah, yeah, right. It is. It is insane and on the more general public products they don't, we don't have this problem of working with a given speed travel, you know EN paragliders we can put 20 centimetre whatever is necessary for a given profile and and so the profile are much more stable. They have big margin and then the plastics movement doesn't really make an effect because we are, we are not on the edge of the stability. So we are far stable and the change of plastic doesn't make any difference. It's not, it's not significant.

Yeah, it's too, too. Yeah, minimal too, too. Small. Yeah, Yeah. What is the fuss about? Why are people angry? What what are they saying? That they have to trim the rods or this engine is not as it was like? What is? What is that whole discussion all about? Yeah, some people, they're not happy because they are not fast enough. They're not they're. Not winning, no, but I mean the the glider is not fast enough compared to others. So they're not collapsing, but they're not fast enough. Some others, they're they're complaining because they are collapsing. They're fast, but they're collapsing. And for sure, it's difficult to, like I said, it's, it's, we are pushing a compromise between

collapse and, and velocity And the other things is that they are the, the production have some variation of course, in some cases because we're talking few millimetres, 2 wings build at the same time and goes to different people. Eventually they end up different instability. And so it makes people not happy because their previous industry was not the same as the as one here. But we're dealing with our customers like like usual. I mean, it's been, this wing is on the market since 2017. And so it's always been this problem. Can I ask you about the certification? Thing that no. Why do some people say that they

are not the same as certified Like what is their argument in that? I don't know. I'm not sure someone say that because nobody can know how it was certified for, for us it, it is like certified since 2017. We changed the plastic in 2021 because before 2021 we were having plastic which shrink faster than the clothes was shrinking, right. So after one season the people were complaining because they were not fast enough. So the people with my new wing, they were just killing them on the final guide. And so they were the solution was to re tight the plastic with temples to make them tighter again. And then they eventually it was

making it too tight and they were collapsing.

But it was nice gliders, very stable when it was shrinked like that, very stable gliders. Fun to fly. Fun to fly for cross country it's perfect, but then for high level competition it was not competitive enough because of this consistent but so this CCC certification is is a compromise that has been found between manufacturers and CRVL in 2013 fourteen something like that to try to have something that is not open class, but that is not EN to not put pressure on the EN

certification. That was a problem in the past where we had the competition wing ENDS and it was creating problems on the the END certification mean confidence that the pilot have and it was a better situation to create a specific sports class which is CCC. Sorry, competition class now yeah, not open but it's a compromise where it's there's still some tests to do. We cannot do any manufacturer cannot do stupid wings. There are some tests, so it's not open class like it was before 2011, but it is much more open than Ian. So you can certify the small wing and all the other size. You can sell certified by the manufacturer, but you need to

store the sample, make videos and it's simple, more simple test to perform for the certification. But for me, the biggest issue we have is not about so certification, because the certification doesn't really help us in a way because it's, it's not intuitive, but to create a collapse because we you got collapse when you go for speed in the turbulence. But when we do certification, we create a collapse, create a collapse. It's a better behaviour when the the the profile is more fragile, yeah. So when it's more stable, it's. Easier to. It's easier, the results are better, but in the reality it's not the case anyway. So I mean, this certification is not where we can help the system

to to help the safety at the moment is the the the the solution. In my opinion there are several solutions proposed and we need to all agree to something that will work. I have a very pragmatic approach is we need to kill this incentive on final glide. So there is no advantage anymore to go faster than his fellow pilot. So for that there is either conical and expectation. So instead of being a cylinder, it's a cone shape and of protection or it's altitude bonus on the cylinder. But it could be made equivalent anyway. And the effect of that would be that there is an optimum speed because you know the glider has

a polar. When you go faster you will arrive nowhere always. OK, so, so there is a compromise then and we can set the parameter. So the compromise is high speed or speed or speed or even full speed. But because it's very flat, the result, you don't make any difference. You can go faster, but you will not earn more points, you understand. So when you do that, you will help a lot on the safety of the whole thing. You will help for the safety of the models which are designed differently for this ecosystem because now there is no more incentive to go crazy unstable in in year 4 in the profile we

close year 4. And why is it not being adapted? Like what's what's stopping this bureaucracy?

Yeah, it's it's also people need to make their mind and agreed on on things. I mean I. It's hard to convince a bunch. Yeah, because another solution which is brought by some Moses, is to limit the speed. Like have instruments which would measure airspeed and we would limit the speed live, you understand? Yeah. So you'll have on your cockpit, you'll have your speed. And like on the road, you don't pass a certain speed. OK. Wow, that's kind of. Cool. Yeah. That's fun. So you're going to have speed limits in the air, so. Speed limit on the air. So that's the other solution. But this one for me is not very pragmatic because we don't have

the tool to do it right now. Yeah. Probably you'll have to put it in the hardness. Somewhere you you also need a lot of backup because you know how it is. We have instruments. Sometimes they war, sometimes they don't war. They need to be reliable. They need to be comparable. All of this is is quite complicated for a small sport, like we are very small sport with little means. And so I think we need to be pragmatic and change a little bit our scoring system and our rules of CCC to make something that will encourage or not even encourage. We'll make the best wing, a stable wing.

I think I can close the wig.