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All techie stuff here
By blindrodie
#383991
Pretty good basic info to understand. Flat winglets and the Horton wing included.
Enjoy...

8)



User avatar
By AIRTHUG
#383993
Yea.... but in my opinion these guys are trying to milk a rock...

They talk about using a flying wing... with increasing outboard twist to adjust the lift distribution so the tips aren't creating lift...

Does this sound familiar? What's the name of this site again? :rofl:

And I'm pretty sure hang gliders have adverse yaw (like crazy)... and we CERTAINLY don't have PROverse yaw!

It'd be nice though... but unless they just left a lot of information out of their video... they aint got spit...
User avatar
By Bouyo
#383995
AIRTHUG wrote: we CERTAINLY don't have PROverse yaw!
Yeah, but that's what we could possibly get, if we use their amazing research. Exciting times.
By miguel
#384020
Thanks for posting the Bowers youtube.

Really informative!
User avatar
By AIRTHUG
#384021
Bouyo wrote:
AIRTHUG wrote: we CERTAINLY don't have PROverse yaw!
Yeah, but that's what we could possibly get, if we use their amazing research. Exciting times.
I think one of us is missing something... did you see something in the Prandtl video that makes proverse yaw (or even "just" eliminating adverse yaw) sound like a possibility? Other than that they SAY it's a possibility I mean.
User avatar
By Dave Jacob
#384023
Cool video. They are claiming a 60% (at least it sounded like 60 not 16) increase in efficiency. I would be curious what they were comparing. Either number is pretty big.
User avatar
By Bouyo
#384037
I think it's 11.5%. That's just efficiency though, with proverse yaw other benefits come into play in terms of stability. Pretty neat if they nail it.
By miguel
#384043
AIRTHUG wrote:
Bouyo wrote:
AIRTHUG wrote: we CERTAINLY don't have PROverse yaw!
Yeah, but that's what we could possibly get, if we use their amazing research. Exciting times.
I think one of us is missing something... did you see something in the Prandtl video that makes proverse yaw (or even "just" eliminating adverse yaw) sound like a possibility? Other than that they SAY it's a possibility I mean.
Watch the Bowers video :thumbsup:
User avatar
By red
#384048
Bouyo wrote:
AIRTHUG wrote: we CERTAINLY don't have PROverse yaw!
Yeah, but that's what we could possibly get, if we use their amazing research. Exciting times.
Campers,

Speak for yourselves, ladies and gentlemen, but I had proverse yaw (and power steering, and power brakes) in 1985.

Image

http://user.xmission.com/~red/history/fledge2.jpg

If you rigged a control cable to lift one washout strut higher (for the inside wing of a turn), you could have much the same benefits on a flexwing as this NASA "discovery" would give you.

Unfortunately, the competition rules which have stifled HG development for all these DECADES would not allow such progress, and ease of flight.

Hey, just PISS on the RULES, pilots! Comps are irrelevant!

:mrgreen:
User avatar
By Paul H
#384050
Yeah, sure, those rules have stifled glider designers. That's why todays comp wings handle so well, are so fast, and land so easily. Progress sucks.
User avatar
By icaroaccordi
#384051
Ok, that is not new and it HAS proverse yaw. It uses the bell shape lift distribution created before the Second World War by the Horten Brothers. Hang glider has adverse yaw because it tries to use elliptical lift distribution. Elliptical is the optimum induced drag lift distribution for a given wing span while bell shape can be the optimum for a given bend moment of the root section (structural requirements). To know more there is a good book called Tailless Aircraft in Theory and Practice. This book has a chapter for hang gliders as well.
User avatar
By Bouyo
#384056
As I understand it, the proverse yaw inherent in the design of the wing is special because it's a product of the geometry of the wing without using any control, i.e. the tips are naturally disposed to proverse yaw without the need for control surfaces to obtain the proverse yaw (unlike Red's gilder).

Why are people (experts) excited about this new wing geometry if it's old hat?
#384059
red wrote: If you rigged a control cable to lift one washout strut higher (for the inside wing of a turn), you could have much the same benefits on a flexwing as this NASA "discovery" would give you.
Sorry Red, but disagree... and disagree... and disagree again.

Hang gliders have anhedral, your Fledge had dihedral. With dihedral, when a rudder yaws the wing, the "upwind" wing is lifted, and roll in the same direction as the yaw occurs.

In flex wing hang gliders (which require anhedral to be weight-shift steerable), when the glider yaws, the "upwind" wing is lowered, and the glider rolls in the opposite direction as the yaw.

Look at RC gliders that have rudder-only for roll... dihedral wings.

Also, using a rudder to yaw a wing is not adverse OR proverse yaw... as it's not a byproduct of rolling the wing. Using rudder, you experience adverse or proverse ROLL :wink:

Also- hang glider manufacturers don't give a spit about comp regulations or classes. They care about what the pilot community wants, first and foremost, and they care about what they're passionate about building. There's a reason they make flex wing hang gliders and not foot launched sailplanes. There's a reason- many reasons- I fly flex wing hang gliders and not foot launch sail planes... or regular sailplanes... or general aviation planes... or hot air balloons...

There's a reason hang glider designers don't make paragliders :stirpot:

Anyone "in the business" of hang gliding... is in it for love, 'cause it sure don't pay well... even the designers, manufacturers, etc etc...

I also disagree putting an adjustable line on washout struts would = a Fledge. One has vertical rudders... which control yaw... the other would essentially have ailerons... And aircraft with ailerons have adverse yaw :rofl:

Well maybe this Prandtl thing doesn't... but I still don't see them using something different from what we have, yet claiming VERY different results. I agree it *sounds* great! It'd be real nice... but I just don't see it...

Sorry to be so disagreeable Red... still love ya! Cheers from NY :thumbsup:
User avatar
By Bouyo
#384062
AIRTHUG wrote:I still don't see them using something different from what we have, yet claiming VERY different results. I agree it *sounds* great! It'd be real nice... but I just don't see it...
I see it. There's a graph of it in the lecture posted above. Am I missing something?

I found this sentence on the tinter webs which neatly explains the difference between the current approach and NASA's experiment: 'For a given wingspan the highest lift you can get with the lowest drag happens to be an elliptical lift distribution. For a given amount of lift you want to achieve the lowest drag happens to be the Prandtl lift distribution.'

In practice this means that NASA's wings have to be wider to get the same lift as an elliptical wing, but even though they're wider they achieve more in the way of aerodynamic efficiency and have the huge benefit of inducing proverse yaw.

Maybe it's not proven by a third party as of yet, but if you take NASA's researchers at their word then I think their results are interesting.
User avatar
By TjW
#384073
Bouyo wrote:
AIRTHUG wrote:I still don't see them using something different from what we have, yet claiming VERY different results. I agree it *sounds* great! It'd be real nice... but I just don't see it...
I see it. There's a graph of it in the lecture posted above. Am I missing something?

I found this sentence on the tinter webs which neatly explains the difference between the current approach and NASA's experiment: 'For a given wingspan the highest lift you can get with the lowest drag happens to be an elliptical lift distribution. For a given amount of lift you want to achieve the lowest drag happens to be the Prandtl lift distribution.'

In practice this means that NASA's wings have to be wider to get the same lift as an elliptical wing, but even though they're wider they achieve more in the way of aerodynamic efficiency and have the huge benefit of inducing proverse yaw.

Maybe it's not proven by a third party as of yet, but if you take NASA's researchers at their word then I think their results are interesting.
There's other "efficiencies" as well. Because there's less lift at the tips, the structure can be lighter. I don't really think this will help much with hang gliders, which tend to be on the stout side, because of the limitations of working with cylindrical parts to hold loads that are tapering.

But Al Bowers has been around homebuilding pretty much his whole life, so I suspect he's got an appreciation for the differences between theory and practice.
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By Bouyo
#384082
Yep, I don't think these innovations can apply to Hang Gliders as we know them, but it could perhaps creep into sailplanes. Also maybe Rigids? Wouldn't that be cool - an Atos with 60ft wing span. All it will take is some imagination.

As Airthug said - he doesn't want to fly sailplanes.
User avatar
By red
#384083
Bouyo wrote:Yep, I don't think these innovations can apply to Hang Gliders as we know them. All it will take is some imagination.
Campers,

Yep, HGs use anhedral already, as Ryan said. We just need to make better use of that option. I'm all in favor of HG progress, and my big Moyes is just fine, but I would jump on power steering and air brakes in a heartbeat. They are absolutely great for flaring a landing with no chance of ballooning up, and making a high approach into a nice short-field landing. Turning becomes almost effortless. PGs have plenty of anhedral, and power steering and power brakes, so it can certainly be done. I have no intention of flying a PG, though.

These simple tricks are simply not available on today's HGs, and they should be. Anybody who does not choose to use these options can certainly avoid using them, like the new pilot who has never pulled the VG cord. The glider flies just fine anyway, then. I would call that scenario Progress, but I really don't see much.

:mrgreen:
User avatar
By Bouyo
#384084
red wrote:These simple tricks are simply not available on today's HGs, and they should be .... I would call that scenario Progress, but I really don't see much.
Well if you can classify an Atos as an Hang Glider ... :)
#384086
red wrote:PGs have plenty of anhedral, and power steering and power brakes, so it can certainly be done.
Dangit Red, missed it again. So not like you friend!

Paraglider's "brakes" pull the trailing edge down. I could see how you might see this as aileron-like... but the difference is, to turn right, pull right brake, lower right trailing edge, wing turns right. Think about that for a second. LOWERED right trailing edge... as in, INCREASED angle of attack... and the wing turned toward the higher AofA?

To call on similarities between what makes a Fledge turn, what makes a flex wing hang glider turn, and what makes a paraglider turn... you're in a heap of trouble. All three are just about opposite eachother (figure that one out LOL)
red wrote:These simple tricks are simply not available on today's HGs, and they should be. Anybody who does not choose to use these options can certainly avoid using them, like the new pilot who has never pulled the VG cord. The glider flies just fine anyway, then. I would call that scenario Progress, but I really don't see much.
Like I said- a guy like Steve Pearson as an example is passionate about weight-shift flex wing hang gliders... so he devotes his life to designing and building them. If you're passionate about a different style design... cool! Build it, or find someone with similar passion... but what you're saying is people with a similar-but-slightly-different passion than yours are wrong, and yours is better. Better is a sticky word, because everything is a balance of trade offs... so what you see as better, someone else sees something different as better... and you can both be right. And that's cool! I'm not talking about tolerance... I'm talking about perspective. You shouldn't tolerate people building gliders different than what you seem to want... you should open your mind to accept why that is... and take responsibility for YOUR choices (if you want it so bad, build it yourself. The only reason you don't have what you want is you. Unless you're CHOOSING not to have the glider you want... in which case, that's no one else's fault... especially not the competition classification system?!)

Also- "anyone who does not choose to use these options.... the glider flies fine anyway..." Again, I find it hard to believe a Fledge pilot said that. How well did your Fledge fly via weight shift only? :wink:

Here's the deal- I fly hangs and paras. I enjoy both. I've also flown a myriad of other things in my life, if only a time or two... Hang gliding is the only thing where I do not feel as though I am manipulating a wing in order to fly. The weight shift connection is organic and intuitive. It feels like *I* am flying, like MY BODY is the aerodynamic control. In my paraglider, I like to weight shift a lot, but in active air there's no getting around the need to work the toggles actively. It does not feel like I am flying with my body, it feels like I am working a wing, and that wing is flying and carrying me.

I have not flown an ATOS or Stalker or similar... and I would still love to have a Swift (stick controlled with rudder peddles)... but for me, and many others, we're hooked on weight shift flex wing hang gliders... join the club dude :thumbsup:

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