[Rick Masters]

Consider that at takeoff the wing becomes self-supporting and weight becomes irrelevant.
Weight is not a factor in performance. It is a convenience.
Consider that aluminum tubing and Dacron fabric remain vastly inferior to torsion-proof wood construction, such as the 1970s Mitchell Wing.
The transition to Rogallo-type was never a performance improvement. It was for convenience.
Abandoning wood construction, even in favor of carbon fiber, resulted in no improvement in performance. It was for convenience.
Any performance gains came from improvements in aerodynamic design, not by the use of materials replacing wood.

My Sensors have repeatedly demonstrated just how light weight and simple to assemble a vertical fin can be.
So perhaps we don't need the sweep as much as we've always thought we did.

Consider that sweep is unnecessary for flying wings, as demonstrated by the Flying Plank.



Consider that vertical surfaces are unnecessary -- even on a rigid wing.
In the mildly-swept Mitchell Wing, free-flying elevons with slightly inverted airfoils aft of the centroid of lift served the purpose of the tail.
    
Howard Long won the legendary Escape Country meet on the Mitchell Wing which had no vertical surfaces.


This is one of Don Mitchell's powered B-10s. No twist. Note the free-flying elevons.
I don't think the pilot has attached the rudders, yet, or possibly this B-10 didn't use any.
Don Mitchell only added wingtip rudders because his second client, George Worthington, demanded them.
Don was certain they would only add unnecessary drag to the ship.
(That was before Don discovered the pitch-reversal problem induced at flare by the mid-chord pop-up spoilers.)

Somehow this sport got hooked on doing things a certain way, and I for one think that it's high time we stopped and took a second look at the direction we've been going in for three and a half decades, and maybe see if we shouldn't do a U-turn and look for a Different Way.

I can see only incremental progress culminating in almost insignificant progress in hang gliding performance since the introduction of the Comet in 1980.
Dick Boone's Dawn was a topless hang glider in the early 1980s.
There isn't really anything new. Fred Fronius is rediscovering primary gliders with his Goat Air Chair.
I love those. They were around in the 1920s. That's one direction we should go.
The coolest things, to me, are the electric Swift species.
But I have to disagree on most of the redesign thing.
You want a better flare? Flare harder.
You want higher performance? Fly smarter.
We haven't tapped out that stuff, yet. An old glider may still be able to outperform a new racer with the right pilot.

One of the "vintage" gliders there was the Aolus, a very wide nose angle flex wing that sported a bird-like tail. I think this concept deserves a second look, but this time by eliminating the sweep altogether, and moving the spar further aft within the wing. If the spar is located in a thicker part of the airfoil section, it can be made taller, and I heard somewhere that if you double the spar's thickness, you quadruple it's stiffness. So a built-up spar, made from a vertical-grain balsa shear web and carbon capstrips, could be built much lighter, for the same strength as what we now get from a 2" diameter tube.

An advanced version of the Aolus was built in 1982 or 83, called the Sonic. I never saw one. Mike Brewer flew one, possibly the prototype, and liked it, I think. The Comet Clones drove the Aolus and Sonic to extinction. They couldn't compete. We found that while those kind of tails seemed to enhance thermaling performance -- I used to flatspin in tight thermal cores -- they inescapably added drag to flying wings and, worse, didn't really help flaring because they enhanced the ground effect cushion at landing. Tails are simply not needed on flying wings unless they show signs of divergence - in which case the tail becomes a kludge to make up for problematic design issues.


My first 35 mile flight to the Nevada Line from Paiute Launch, September 1981.

[magentabluesky]

Ecclesiastes 1:9
What has been will be again,
what has been done will be done again;
there is nothing new under the sun.

Surprised there is no mention of Jim Marske’s Monarch.

Though not foot launchable (weight) the plan form is interesting in resolving aero issues encountered with swept wings.

Clean up the fuselage and get rid the struts would add to the performance.

[Dayhead]

Ecclesiastes 1:9
What has been will be again,
what has been done will be done again;
there is nothing new under the sun.

Surprised there is no mention of Jim Marske’s Monarch.

Though not foot launchable (weight) the plan form is interesting in resolving aero issues encountered with swept wings.

Clean up the fuselage and get rid the struts would add to the performance.

Words of Wisdom. A smaller and lighter and foldable version of the Monarch would be an asset for the "Airchair" community, and perhaps for HG as well. Thanks.

[Dayhead]

More ranting and incoherent ramblings from yours truly. You should probably skip it.



I'm not a Pulitzer Prize winning writer for many reasons, I'm sure. And one reason that stands out, for me, is that what I write is often not what I meant to say.

When I started this topic, I had no desire to design a high performance hang glider, or at least not a high performance glider as we usually consider them.

The Atos and Mitchell Wing gliders, as well as the Goats and Super Floater types, are a long ways away from what I'm thinking of.

In looking at the State of the Sport today, we have to look at the differences between what we call hang gliders and what we call paragliders. And the term "performance" comes under scrutiny.

I think I asked if the ability to land practically anywhere trumps flat glide angle. Not for setting distance records or flat-out racing, but for everyday use by the majority of pilots, who likely never fly more than 100 times a year, if that much.

I'm thinking that a hang glider should be geared more for lightness, slower stall speed, tighter circling capability, MUCH better roll control, MUCH better "landability", and of course easier and faster set-up and breakdown.

And so the title of the topic. It is my contention that, for whatever reason(s), we chose a design that, while very successful in the early years, may have run it's course. And the "design" I'm referring to is the one we call "Rogallo", consisting primarily of two leading edges, two X-bar halves, a keel and control bar. And secondarily, a kingpost and washout struts.

Also I have to mention the idea of controlling twist by using high sail tension. I think of that as being a "brute force" method than one of gentle finesse. A "Different Way" is the subject here.

I'm using restraint in that I'm trying not to outline an actual design here. I'm trying to keep my part of the discussion in the philosophical vein, but to do that I have to bring up certain concrete ideas, such as "What is the price of sticking to the swept-aft planform?" This planform, combined with using what is essentially sailboat technology, deserves a second look when we want to reduce costs, not only monetarily, but in terms of weight and structural complexity.

In the beginning, the Rogallo concept (Or should it be the Rogallo/Dickenson concept?), fit the bill beautifully. We all voted for this design with our feet, preferring it to the much better performing rigid wing designs. But it is my contention that maybe we've come full circle, and that this design philosophy needs a critical re-assessment.

This thread has a lot in common with the "Five-foot" thread. Perhaps they should be combined, but probably not, IMHO.

One area where I feel we're paying excessively is the idea that our flex-wing Hg's have to be controlled by weight-shift only means. My paragliding friends have aerodynamic controls, for cryin' out loud!

We're told that competition drives the market. Well, OK, if you wanna compete in the flex-wing class, you just go right on ahead. But honestly, out of all the flyers in my home site LZ at the end of a flying day, how many are competitors? On average, I'd say no more than 5 or 10 per cent. So 90 to 95 per cent of us are stuck with a choice between an easily controllable glider or a glider with a flat glide angle over a wide speed range. All because every glider made has to be eligible for contest flying, even though only a single digit percentage of those manufactured gliders will ever see a contest.

Anyway, getting back to technical stuff: Where is our 2015 version of the late '70's tall keel pocket, or the early '80's floating cross-bar? Can anyone here offer up a credible excuse for why we've only seen hardware/sailmaking refinement and incremental performance improvement for THREE AND A HALF DECADES? Please excuse my yelling, but this subject and the Starbucks French Roast are conspiring to get my dander up.

I'm crying as I look at what has happened historically, compared to the lofty ideals I had for this form of aeronautics that I once had. Our head-in-the-sand attitude has allowed the paraglider, which most if not all frequenting this website don't like or want, to practically take over.

We can't just blame the PG and those that fly them for our woes. If we don't take responsibility for over three decades of complacency, and act on it, well then we'll deserve what we get.

Unfortunately, I haven't the skills or resources to create The Brave New Hang Glider. I'm more of a stand-up aeronautical philosopher than an engineer, or even a mechanic. I'm just trying to find some consensus here from some of you. By speaking up, and by being willing to endure some on-line ridicule if need be, I hope to inspire others, those who are better equipped than I am to offer actual mechanical solutions.

I can't go to my grave knowing that I didn't at least try. How many here recognize the significance of the scene from One Flew Over The Cuckoo's Nest, where Nicholson, as McMurphy, tries to pick up that stone fountain and throw it through the window so the men could go downtown and watch the ballgame? He couldn't lift it, but he inspired Chief Broom, and that's what really counted.

[brianscharp]

Probably not what you're looking for but an innovation none the less. The link takes you to the end of the article. Once there you can turn back a couple pages to the beginning.
http://issuu.com/us_hang_gliding_paragl ... _final2/39

[KaiMartin]

The more I meditate on it, I think a wing planform having little or no sweep, and possibly a little forward sweep, may have some advantages.

Ok, so I'll be that stability guy again ...

The problem with our current understanding of the situation is that we need a negative moment to provide feedback to the pilot when the AoA is at a higher positive value than it should be, so that we won't inadvertently stall the glider.

I'd put the reasoning a little differently:
Negative pitch moment makes the AoA of the wing return to "trim" after a deviation. (Note, I use the term "trim" the way general aviation does. Not the hang glider "trim" which involves hanging with no hands on the bar.) The actual AoA in turn determines speed and glide angle. This works both for a temporarily increased, or a decreased angle of attack. Trim is determined by the position of the centre of gravity.

The pilot represents the brunt of the mass. So his axial position determines trim and by extension speed. In essence, a negative pitch moment allows the pilot to put his weight at an arbitrary point ant just watch the glider adjust its AoA and speed accordingly. There is no feedback to the pilot in the sense of regulation theory involved, simply because the pilot does not regulate. It is nice to have such feedback in terms of bar pressure. But this is not necessary for pitch stability.

And so I propose a different approach to this problem.
We get rid of most or all of the Aft-sweep in the planform. We use a hinged tail, which can be an integral part of the wing root chord area, like a bird does. In normal flight, the tail simply streamlines, and has only parasitic drag. But the hinge only allows the tail to lower a certain amount, so when the AoA is lowered to a certain value, the tail provides a nose-up moment, just like our currently used washout struts and/or luff lines do today.

No, or almost no sweep leaves us with a main wing with positive pitch moment. This means, a small deviation of AoA from trim will amplify, amplify more, and amplify even more. If nothing is done about it, the wing will flip within seconds.
A hinged tail with a stop for low angles only comes into play when the wing is already far off trim. At this point, nose-down rotation has already picked quite some speed. Due to significant moment of inertia It is at least questionable if the blocked tail can stop the rotation. The floating tail does nothing against a nose-up deviation. And it is explicitly made to not interfere during normal flight.

But what the straight wing really needs, is a way to stabilize pitch during normal flight. With conventional planes this stability is provided by the fixed tail plane on a long boom. The flying plank approach uses an airfoil with massive reflex. If we dismiss both, I see only one option left: Go full bird mode and aim for pitch dynamic control by the pilot or some electronic magic.

The electronic solution gets us into the realm of quadcopters and model helicopters. Due to the size of a human carrying glider everything is slower by an order of magnitude compared to models. So this should be no problem to the digital control hardware. The hard part is to find a viable solution how the electronics actually moves control surfaces efficiently. Where to put these control surfaces so they have enough impact?

As you all may know by now, I find the solution to put control into the hands and feet of the pilot the most attractive...

---<)kaimartin(>---

[Rick Masters]

At flare, because of decreased speed, the tail becomes baggage, hinged or not, long boom or not. I'm thinking drogue chute, again. For even more glide path control, how about a line to the apex that spills air, controlled by the pilot?

Drogue Chutes can be such an asset for flying. I like to use mine to help land in a tighter area when there's little landing options around. I also find it really helps to keep landings shorter, so even if I'm landing in a large field, it keeps you out of any lee-side turbulance on the far end of the paddock. Not to mention saving a long walk back to the retrieve vehicle with a heavy glider. Using a drogue chute is very simple and easy. There's just a few things to know before you start using one; be sure you read through the Manual and Safety Considerations before you use your drogue. And practice using your drogue in a large LZ until you become comfortable. I've seen a number of pilots, mostly europeans (!), that give drogue chutes a bad name as you see them pop out the drogue chute, then proceed to whack? in!! The fact is, that these guys would be whacking in, with or without the drouge chute, as they need to get some re-training or stop flying gliders beyond their ability. While, I think drogue chutes help flare timing slightly, they should really only be used for getting a steep final glide into a tight spot.
http://www.warrenwindsports.com.au/cata ... ogue-chute

[KaiMartin]

Probably not what you're looking for but an innovation none the less.

I like the thinking:
Get more control on twist.
Do not exclusively rely on sail tension to keep the sail in shape.
Use the full vertical distance from wing to base bar to achieve favourable levers.
Shave off weight by being able to choose less massive components because of the favourable levers.

---<)kaimartin(>---

[KaiMartin]

At flare, because of decreased speed, the tail becomes baggage, hinged or not, long boom or not.

I disagree. A tail plane still flies and produces maximum lift when the main wing stalls. This initiates a strong nose-down moment. In mid-air this is a desired property. It results in a strong tendency to recover from stall without intervention by the pilot. At a flare landing, the very same property is a recipe for whack.
Gliders with tail planes on a long boom would be difficult to flare land. But you wouldn't want to flare hard anyway, as the tail would have an issue with ground.

I'm thinking drogue chute, again.

Like you say, drogues provide glide path control. However, this is only part of the equation. And most of the time not the most important one, too.

Drogue chutes do not increase the flare window. They do not affect the need to push in a fluid swift motion. Yet these are the number one reasons for whacks and bent down tubes.

For even more glide path control, how about a line to the apex that spills air, controlled by the pilot?

This would have to be massive with regard to the chute to have a significant effect.

---<)kaimartin(>---

[Dayhead]

It's time for a "fun break".

After watching a pilot just barely make the LZ while using a drag chute, I was reminded of an "invention" I created while drinking beer around the campfire, some years ago.

Here's the picture to visualize: A glider is flying away from you, and it is performing a nose-straight-up flare. You see a cord attached to the top of the kingpost that leads to a drag chute, fully open.

In big letters around the drag chute: "ACME FLARE-O-MATIC". And of course a drawing of our friend Wiley.