US Hawks Hang Gliding Association

Always liked "Brave New World", so I thought I'd borrow from Mr. Huxley a little bit.

As some of you are aware, I'm a critic of HG, which in my book is Ok 'cause our harshest critics are in reality our bestest friends.

I'm working on a scale mock-up of my Brave New Glider (BNG). The idea is to select what components of our current tech are in fact good things, and retain them, while picking out the bad ones for the trash can.

I'm sure that some of you have ideas of your own. I want to get a conversation started on this subject, so I'm starting this new topic.

I'll be posting details of my design in the time to come, right now it's such a crummy rough draft that I'd be embarrassed to show it. But it's time will come.

May I suggest a starting point of simply listing the good and/or the bad for discussion.

Or don't.

The bad I see with today's design for hang gliders is the PIO at high speeds within the gliders VNE.

The simple fix so far has been to plug on a vertical stabilizer.
It's not so much a PIO problem as it is a design problem (DIO).

Well, I kinda like the airframe. It keeps the glider from falling out of the sky in turbulence.
The sail seems like a good idea, too.
Most complaints about hang gliders is that they fly too fast during landing.
This is a function of the airfoil shape as determined by the camber of the battens and sail cut.
More camber gives a slower wing. Less camber gives a faster wing.
Guess which one most pilots like best?
Variable camber would be a good start.
But as I've argued before, it's not a redesign.
It's an evolution.
Unfortunately, the introduction of greater complexity also introduces a greater number of new opportunities for failure.
Complexity also introduces greater cost and, generally, greater set-up times.
I've always thought you could design and build a really fantastic higher variable geometry hang glider.
I've never thought enough people would buy it to make it economically feasible.
If they could pick it up.

I like the term "brave-new-glider!

Dayhead wrote:May I suggest a starting point of simply listing the good and/or the bad for discussion.

Here are my favourite good/bad properties.

good:
* pitch control by weight shift in normal flight. The control is both, intuitive and effective.
* weight . OK, less mass is always better. But 30 kg is still very light weight compared to every other flyer except for para gliders.
* the ability to foot launch and foot land. This is of course related to weight. But it also requires low minimum speed.
* penetration. Good for soaring. Wind speeds that exceed the maximum speed of a traditional hang glider would be considered a storm in many places.
* relatively low cost. The keyword is "relative", That is, relative to general aviation. The price still asks for a decent income.
* made from fairly low tech components. Compare a Do-It-Yourself glider project with a Do-It-Yourself graphics card...

bad:
* roll control. Maximum roll rate is at a level that would be considered a dangerous design flaw in sail planes or general aviation.
* yaw control. There is no way to directly control yaw.
* pitch stability is marginal. This is one of the reasons tumbles can and do happen in real world conditions.
* a proper (foot) landing is more difficult than desirable.
* size of the package. A 4 m roll is a no go in typical public transport. Airlines ask for hefty charges.
* negative loads are a sure way to break the glider in mid-air. This makes tumbles life threatening and limits the fun in aerobatics.

---<)kaimartin(>---

Thanks for the inputs.

My BNG design is intended to bridge the gap between Pg and Hg. A very light, fast set up glider with a very low stall speed, but enough top end to avoid the "blown over the back" scenario so often seen with Pg's. My 40 years of flying have taught me that high performance is less valuable to me than User Friendliness. A weight less than 50 lbs, and set up less than 5 minutes.

I want more control than I'll ever need. When I say Frog I want that glider to jump.

You'll understand where I'm coming from a lot better if you can think out of the box, for example I want a straight wing with no sweep back. I want an adequately sized vertical fin, or a V-tail. Tail incidence under direct control of the pilot, allowing ground handling with ease, even when it's blowin' 25.

The glider should be relatively easy and cheap to repair. It would also be neat if it could be built by a handyman with everyday tools and materials. I'm thinking here of the day when there won't be "manufacturers" to purchase from, and home built gliders will be more common.

$10K+ for a slow responding glider? That's crazy.

Dayhead wrote:Thanks for the inputs.

My BNG design is intended to bridge the gap between Pg and Hg. A very light, fast set up glider with a very low stall speed, but enough top end to avoid the "blown over the back" scenario so often seen with Pg's. My 40 years of flying have taught me that high performance is less valuable to me than User Friendliness. A weight less than 50 lbs, and set up less than 5 minutes.

I want more control than I'll ever need. When I say Frog I want that glider to jump.

You'll understand where I'm coming from a lot better if you can think out of the box, for example I want a straight wing with no sweep back. I want an adequately sized vertical fin, or a V-tail. Tail incidence under direct control of the pilot, allowing ground handling with ease, even when it's blowin' 25.

The glider should be relatively easy and cheap to repair. It would also be neat if it could be built by a handyman with everyday tools and materials. I'm thinking here of the day when there won't be "manufacturers" to purchase from, and home built gliders will be more common.

$10K+ for a slow responding glider? That's crazy.

$10K+ for a slow responding glider? That's crazy.

Yes! That is real steep.

Dayhead wrote: I want more control than I'll ever need. When I say Frog I want that glider to jump.

Yes!!
We are in violent agreement about this issue.

I want a straight wing with no sweep back. I want an adequately sized vertical fin, or a V-tail. Tail incidence under direct control of the pilot, allowing ground handling with ease, even when it's blowin' 25.

This sounds like the general layout of a sailplane to me. Do you plan to go for a regular airfoil? If so, pitch stability requirements call for a tail plane on a rather long boom. This would collide with the desire to foot launch from a slope.

In other posts you mentioned a "short coupled tail". Is this tail going be to short enough to not collide with a -20° slope when the glider is held at +0° relative to the horizon during launch? How much longer than the keel of a current flex win g can such a tail be made?

How about the landing? I hear that pilots managed to damage their keel with an aggressive flair. This would affect the tail of your brave new glider, too. Do you plan to include some precaution in your construction? A Maybe the ability to hinge upward just before touch down. This may even be beneficial to the flair

It would also be neat if it could be built by a handyman with everyday tools and materials.

The good news: The tools available to DIY have become quite a bit more versatile since the early days of hang gliding. Think 3D printing, decently prized milling machines, powerful glues or fibre enforced epoxy.

I'm thinking here of the day when there won't be "manufacturers" to purchase from, and home built gliders will be more common.

If significant numbers of pilots desire a brave new glider, manufacturers will probably be glade to jump on the train. )

---<)kaimartin(>---

One more thought on pitch stability. I feel like there is a potential conflict of goals:

• Pitch stability prevents the glider to go over the falls, or perform a full blown tumble in rough air. Seen from this aspect, plenty of pitch stability is desirable.
• The full flair of a two-step landing works by destabilizing the glider with the centre of gravity moved moved aft. Once the glider is unstable with the nose pointed up, it automatically lifts the nose even more and eventually enters the desired deep stall. The more pitch stable the wing is, the harder this destabilization becomes. So for ease of flair landing the less pitch pitch stability the better.

Some compromise is needed. Current hang gliders are both known to tumble (albeit seldom) and require proper technique to pull off a flair landing. This suggests that there is not much margin for the compromise.

---<)kaimartin(>---

Thanks for chiming in Kai. At this point in time, I'm "imagineering" the BNG, just thinking things thru, and making rough sketches on a dry-erase board.

So far as pitch stability and the tuck/tumbling phenomenon go, My plan is to have the decalage, or the difference between wing incidence and tail incidence, variable by the pilot. While a positive pitching moment is desirable, it is possible to have too much of a good thing; witness trying to launch a Falcon-type of glider when it's blowin' in really good. I want to be able to easily control pitch even in strong winds.

One approach to the tuck and tumble thing is to provide a bunch of nose-up moment at low alpha. Way back in the '70's this was the method we chose. I do find myself wondering if just maybe we should try reducing the glider's tendency to nose down when the AoA get's really high. If that can be done it's possible we could reduce tucking episodes, which in turn would reduce tumbling accidents.

But for sake of argument let's say that tucking and tumbling are just a fact of life, and there's little we can do about it, other than the "long tail boom" solution.

If that's the case, then we should look at what happens in a tuck and tumble, and figure out a way to make a glider that can tumble and fly out of it, without suffering any significant damage. How was Witold Kasper able to perform intentional tumbles with his swept-aft flying wing at air shows? Our present tech isn't working very well here. It seems like almost every time a topless blade wing tucks and tumbles, the pilot is flung violently around, loses his grip on the bar, then hits the glider, which in turn either explodes or simply folds in half.

The answer, IMO, is to severely restrict the pilot's ability to get thrown out of position. If he can stay in place and not get tossed all the way around the trailing edge and on top of the glider, then the CG wouldn't go extremely aft and work to sustain the tumble.

So the BNG will have a pilot positioning system that will ensure that the CG can only go just so far aft as is necessary for normal operations, such as landing. And the pilot will never be able to move too far away from the control bar or whatever is used for control.

Although it will be possible to full-flare the BNG for foot landings, I know that I personally will be landing on large diameter wheels. My goal is for a glider that will stall appreciably slower than most current Hg's, and when combined with a really excellent glide angle control system, will enable me to safely land in very small areas. The biggest hurdle will likely be my requirement that the glider be fully controllable even when stalled. That goal may prove elusive, but any improvement over what we have now will be appreciated. The idea is simply to reduce to an absolute minimum those scenarios where a pilot is low and slow and gets involuntarily turned off course, whacks and damages his glider and quite possibly his body as well.

We're always saying things like "Don't launch in conditions you wouldn't want to land in", even though we do it anyway. So we constantly find ourselves coming in to land at 2:00 on a Hot Summer Day, with flags and streamers arguing with each other about which the wind is blowing, and dust devils and whatever else plotting against us.

I want "Right Now" control of my flying apparatus. Of course there will always be a limit to what we can handle, but that limit shouldn't be as low as it is now.

There will be those that will defend the status quo, saying we should just suck it up and practice more, or attend some kind of clinic, and adapt ourselves to the equipment now available.

I say hogwash. The equipment should adapt to MY needs, not the other way around. I want to be the Master, not the Slave.

I've often referred to Hg as "athletic aviation". For people that are athletic, there doesn't seem to be much interest in trying a different path. And perhaps those folks don't need something else. But I'm ME and I'm not so athletically inclined, so I want to build a glider that even an all-thumbs guy with two left feet can safely enjoy Personal Flight.

As for the tail, I'm sketching out some variations on the theme presented to us in the form of the Aolus Hg from back in the early-mid eighties. That glider had minimal sweep and a bird-like tail built into the root area of the sail. My thinking is along those lines. I want very little, if any, sweep-back in the wing, primarily because I want a glider where wash-out has nothing to do with pitch stability. A swept-aft wing doesn't need a vertical fin or V-tail, but it does have to have a lot of torsional rigidity so that the washout will remain even under negative loads. I'm thinking a straight wing, with a pitch-neutral or slightly positive moment airfoil, will require minimal torsional strength. That should allow for a much lighter structure. Perhaps out at the extreme wing tip area a negative-moment rib could be used, that would allow the wing to washout under high loads and reduce the bending moment on the spar. I'll need every little trick there is to reach my weight goal, which right now I've set at 50#'s.

Some of my sketches have been of planforms having a few degrees of forward sweep. But for simplicity's sake I want the wing spar to be in a straight line, although the planform may end up with a little forward sweep. Straight-wing HG's have been built, but they were very sensitive to the CG location and easy to over-control in pitch. My thinking here is for a wing planform that will have a very long root chord length, enough so that the "overall length" of the glider would be similar to what you have if you measure from the trailing edge of the wingtips to the nose on a current design. This long root chord contains the tail, which can be hinged so that it can move upward and not have a problem with the terrain on the launch ramp. This would also allow the pilot to fully flare for landing, and as I mentioned earlier, could even reduce or eliminate the glider's desire to nose down sharply at high AoA, which may prove beneficial in reducing tucking incidents. If we reduce or eliminate the tuck we also reduce the tumbling. Not all tucking incidents are caused by a large negative pitching moment at high AoA, but it's my belief that most, if not all, of my tucks were inspired by a turbulence induced high AoA. "Fixed Washout", which is the way we've tackled the tucking/tumbling thing to date, is an "after the fact" solution. Reducing the nose-down moment that comes with high AoA is more of a preventative measure, as opposed to using a high positive moment to try and stop the tuck from tumbling. In truth there will be a combination of these techniques to improve safety in turbulence or in blown aerobatic maneuvers.

So far as my BNG goes, I'm trying to arrange a list of priorities for the design. My list will probably be similar to anyone else's, with the possible exception of the order in which performance is balanced against other desires. Number One is "user friendliness", where low weight and fast setup concerns will trump flat-glide-at-high-speed. I'm basically striving for a glider that will do everything a Pg can, without the baggage of poor penetration and susceptibility to becoming un-airworthy in mid-flight. I know my glider won't fold as small or be as light as a Pg, but if I can come up with a design that reduces the gap between Hg and Pg I will have succeeded.

I want my flying to be as stress free as I can make it. Should I desire an adrenaline rush, I'll merely roll to inverted and thermal upside down with you in a thermal. Now THAT would truly be COOL.

I remember listening to ATOS pilots grousing over breakfast at the Apple Cup Cafe at Chelan, Washington.
One pilot said, "It's not a matter of if but when the ATOS was going to tumble." Shortly after that I was seeing T-tails and V-tails and finally a T-tail with a hinge at the front so as not to fight the pilot during a landing flare.
I'm never going to lift one of those heavy rigid wings but I always thought that for someone that will and fly one that a hinging T-tail or even a hinging V-tail was a cool idea. The hinging tail wouldn't during a tuck but would during a flare.