[wingspan33]

In another thread authored by Joe F he included a video interview with early hang gliding pioneer Eddie Paul. Considering Eddie's perspective on the dangers of (early) hang gliding, I put together the below response. It touches upon the things that make hang gliders unique flying craft.

Along those lines I think this subject deserves its own thread. So, here it is. I'd love to have some views expressed beyond my own on this topic. Positive criticism of my thoughts is even welcome!

Original post -

I notice how Eddie Paul holds a perspective on hang gliders similar to how many of us now see collapsible canopies. Some of his comments, as they relate to (even modern) Rogallo wings are still true . . . But with the advent of defined tips, airfoil shaped battens and more highly defined (aerodynamically speaking) double surface wings, many of the issues which he speaks of in the video are, or are close, to non-issues at this point in time.

I would have to mostly admit that when a hang glider is "weightless" (falling not flying) weight shift can not control the wing.

However, I've had my glider intentionally inverted, on one occasion, (looping it baby!) when things got very quiet at the top. Yet, I could use my body mass as an "anchor spot" and thrust the base tube forward. This caused the lighter mass of the glider to change position (with its attitude now nose down compared to the horizon). Both the glider and myself had forward momentum, yet not flying speed. Considering this, I think that Eddie Paul's comments are overly simplified and based on "old" technology. I wonder if he's seen a late model high performance topless comp wing?

What will always be true about hang gliders is that they fly at similar air speeds to those very commonly present in the lower atmosphere. While flying at 20 - 30 mph, it's not impossible at all for the dynamic air around us to, due to various types of turbulence, equal our speed from behind - causing our wing to have an unpredictable air speed of zero. At that point, your wing is not flying. If that condition is only momentary, great. If it lasts very long you will go from momentarily "floating" to falling - until aerodynamic flying speed is regained. Hopefully that happens before you hit the ground!

This can also occur with faster small aircraft, and even commercial jets - byway of those nasty Gust Front events. So everything that flies can stop flying - due to pilot error OR nasty old Mother Nature.

Finally, consider a small to medium sized boat unexpectedly surrounded by large waves. The captain of such a boat can find him/herself and the boat in BIG trouble. But a surfer, on a MUCH smaller surf board, with just as big - or BIGGER - of a wave, can have lots of fun!

A similar context pertains to hang gliding. A small to medium size aircraft can find air turbulence uncomfortable (at least). However, a hang glider pilot can find mild to medium or even strong turbulence (i.e., thermals) VERY enjoyable!

[wingspan33]

Here are some other unique features of hang gliders.

It should be understood that hang gliders DO have control surfaces. In fact, our control surfaces are very similar to those of the first Wright Brothers Fliers.

As I recall, the Wrights had a seat (or shoulder paddles?) that, being slid side to side, caused a cable system to deferentially warp/twist the wings in opposite directions on either side of their aircraft. While more complex than modern ailerons, the effect was the same, or close to the same.

Since the development of hang glider sails with "roach", the shifting of weight (which loads the sail on either side in a differential manner) causes the roached section of the sail to rise on the more loaded wing side and flatten out on the less loaded wing side. The mechanism accomplishing this is not the same as the Wright Fliers, but the result is similar.

In hang gliders, the more exaggerated ability to load one wing more than the other, PLUS the mechanical effect which raises the roached area of the sail, creates a unique turning control system. That system includes differential weight distribution (i.e., wing loading) between right and left wing AND a mechanically induced asymmetrical change in angle of attack within the two roached (wing tip) areas of the sail.

While a hang glider's control system becomes ineffective when the aircraft is weightless, there are very few times when this is the case. And consider aircraft with Rudders, Elevators and Ailerons. A condition where they become weightless is likely to include zero air speed. Zero airspeed causes every one of those control surfaces to also become utterly ineffective as well.

A unique benefit of the control system in a hang glider is that there are times when the pilot's mass and momentum can hold and exert positive influence over the attitude of the much lower mass aircraft - even in a zero air speed situation! No other aircraft (that I know of) has a similar attitude control ability.



How many other examples of what makes hang gliders unique could there be? Hmmmmmm . . .

[reluctantsparrow]

hey wingspan,
when I saw the title of your post, I felt to post almost exactly what I read in your first comments. The boat analogy was a good one. Yes, a surfer can have a great time on Waves that can cause boats that rely only on rudders or props a difficulty because the surfer is relying on gravity for propulsion the same as a hang glider, working with nature rather than against. I have been in a large boat picked up by a wave and for a short time we lost all directional control as water surged under the boat from behind and our rudder was useless for a short time.
Same goes for the secondary source of control you experienced inverted. The gravitational pull on your body was greater than the gravitational pull on the mass of the glider and did not require airspeed to create an influence.
this is one of the things i love most about our gliders, since gravity is actually our main source of propulsion we are working with nature and not against it to do what we do.
i have ideas i am working on with this as the foundational premise. What can be done by working with nature instead of against?
a rocket ship works against nature to break the grip of gravity. A rocketship fights natural law.
I think someday soon we will look back on rocketships as extremely primitive aviation devices.
Our Rogallo wings work with gravity as do sailplanes and para-gliders. it is a concept we all share so I guess using gravity as our main source of propulsion is not really unique to hang gliders but using gravity for both propulsion and CONTROL (weight shift) might be. i will have to think about this some more.
I am working on an invention right now along this very train of thought. a new way to fly that perfectly obeys natural law and does not fight against gravity.

[wingspan33]

Thanks for the response Reluctantsparrow,

Having flown HGs since almost 41 years ago, I intuitively know a lot about how they can be controlled and not be controlled. But as you say, hang gliders (as well as surf boards, kite boards, sail boats, etc.) work with natural energy systems (including gravity in some cases!) to be propelled along. Talk about being one with nature!

But I had a secondary thought while thinking about that silent point (in that loop I once performed) where my mass and momentum allowed attitudinal control of my wing. I partially expressed that thought - That no other aircraft can be controlled in this manner.

But, specifically, collapsible canopies had come into my mind. And however similar they are to hang gliders (as far as where we both fly) they don't have the mass and momentum control feature. Now certainly the occupant in a collapsible canopy has more mass than does his or her canopy, but can they have any positive effect on their wing using this method? I think not. How do you "push" on control lines? If your canopy is moving at zero airspeed can you use your own weight to "push" it into a more positive, aerodynamic position? I think not.

So, the pilot's ability to positively control his/her hang glider using their own mass and momentum (MaM) seems to be truly unique to hang gliders.

New Idea Popping into my head, . . . Can wing suit "pilots" use this control mechanism? Not sure on that one. How could a person "push" on the minimally aerodynamic clothing they are wearing?

PS - I have used MaM control on my wing on lots of occasions while at typical flying air speed. Typically, that would involve accentuating yaw control by quickly snapping my body out of line with the keel and towards being closer to parallel with the base tube. It's hard to know how much effect this had on the wing, since it's most often used connected with entering or staying in a thermal. Could be the effect is minimal considering the fact that your trying to leverage a wing tip 15' away.

[Rick Masters]

A rigid or otherwise secure suspension system is long overdue for hang gliders.
As soon as the suspension strap goes slack, the pilot's influence on the center of gravity goes bye-bye.
This is nuts and has always been nuts.
With a proper negative suspension system, a failed maneuver would only be a sloppy maneuver.
At some time in the future, when this issue is resolved, we will look back on all previous hang gliders as insufficiently-designed prototypes.

How could it be fixed?
I like the idea of a pressurized hang strap/harness support bladder that could be charged by a foot pump or cartridge after takeoff, then later depressurized for landing.


But 35 years ago, Eric Raymond, flying prone, used straps connected to his lower control frame to prevent his body from falling into the keel during aerobatic attempts on the Sunseed.
He told me that it worked fine.

Yes, this also explains, partly, why paragliders can become death traps in turbulence.
Unlike hang gliders, there is no potential fix.
Many hang glider pilots, going inverted, have fallen onto their keel without causing structural failure, then managed to right the hang glider successfully, without damage.



We have all seen videos of failed aerobatic attempts on paragliders.
Sometimes the helpless falling human even falls into the canopy and is enveloped, then continues to fatal impact.

[wingspan33]

Rick,

I agree with you 100%. A design of a prototype hang glider (mostly still in my head) utilizes a "rigid" main support.

My thinking involves the main support containing linking sections that, once the pilot has rotated to prone position "locks" together (think of those aluminum tent poles that pug into each other). On dropping into vertical position for landing, the the links disengage.

Part of the idea behind the design involves the distance the pilot hangs below the wing being decreased for most of their flight time. Before take off, when the "links" are disengaged the pilot can ground handle the glider comfortably with a semi slack attachment to the wing. Also, with the suspension strap longer (when the sections are disengaged) the pilot's head is not pushed up into the lower wing surface. However, once engaged, the now prone pilot is suspended only, say, 18" below the wing.

Any rigid suspension system would be good to still allow the pilot to maintain MaM control.

An Interesting Point -

I think it was a picture of Eric Raymond doing a loop in his Fledge that once caught my eye. He had one leg bent at the knee with his leg/foot extended out of his cocoon harness. I was puzzled at first as to why he would be doing this. But at some point I realized that, should he lose air speed at the top, he could more quickly rest the extended leg on the sail/keel - before he FELL the full distance into it. A firm grip on the control bar would also allow the MAM control I've described above. Many pilots who never though of this precaution have fallen 3-4 feet onto their sail/keel and had their glider structurally fail as a result.

I would also agree that collapsible canopies clearly have a problem with their loose and much longer attachment method. MaM control is non-existent for them. In deed, MaM sometimes sends them into their sail causing an extreme "non-aerodynamic" event to ensue.

[Rick Masters]

Yeah, I've thought about metal structures but you wouldn't want them for anything but perfect landings.
Also, metal joints tend to degrade and jam over time.
Insofar as pulling the pilot closer to the sail, in weight shift, you sacrifice control authority for every inch.
That said, for rigid wings with aerodynamic controls, I like the idea but it is no longer necessary in ships like the Swift where the pilot is belted in.

[wingspan33]

. . . Insofar as pulling the pilot closer to the sail, in weight shift, you sacrifice control authority for every inch. . .

Ahhhh, well I've thought about that as well. The attachment point on the keel can involve a side to side "slider". Kind of like (but not like) those old fore to aft "french connections" pilots flew with in the early 80s.

It would be nice if I could transmit the complete plan of the prototype I've got sitin' up in my cranium. It involves all sorts of nifty control mechanisms which would aid simple weight shift. If I could (or when I do) get it all on "paper" I think the average (thinking) HG pilot would be very interested. Lookin' for investors!

[wingspan33]

Oh, and about this -

Yeah, I've thought about metal structures but you wouldn't want them for anything but perfect landings.
Also, metal joints tend to degrade and jam over time . . .

There are lots of ways to make the arrangement non jamming and even non metal. The example given was meant to generate a simple image of one possibility. An alternative method would be 3-4 inch long 1 1/4" outer diameter Poly carbonate tubing sections with a climbing rope (or two) fed through the center. With the rope shortened or lengthened, the whole column would go from loose to more or less rigid.

As an inventor, I found out long ago that there are an infinite number of ways to solve a problem. But it's better to avoid the "Rube Goldberg" type of solutions. K.I.S.S. is the best way to go.

BTW- I welcome your comments! They lead me to think in finer detail.


How many other ways are hang gliders unique?

[Rick Masters]

The attachment point on the keel can involve a side to side "slider". Kind of like (but not like) those old fore to aft "french connections" pilots flew with in the early 80s.

I flew with a French Connection for years. That's it in my avatar photo (left).
It provided, of course, enhancement of pitch.
I never heard of anybody mounting a French Connection side-to-side because in a tight turn, I would think, it could throw your weight to the outside, degrading your ability to thermal - perhaps worse!
And God knows what would happen in control emergencies.
These are my thoughts, based upon speculation.
Prove me wrong.