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By raquo
Another thing to keep in mind: flatland rolling launch / landing with electric power is a reality nowadays with the developments of the E-help system. People do this even with flex wings that are not optimized for such arrangement at all. Gliders that are developed without the need for foot launch from the start will be much better at flatland rolling start, and safer in the air too (using an empennage for pitch stability! crazy!).
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By red
thermaleo wrote:
Mon Feb 12, 2018 1:20 am
Lest you scoff at the engineering required I can only say that once upon a time I piloted a J bar Mooney for many flights, and was always amazed that this 4 seater 150kt + airplane had landing gear that was raised and lowered by the pilot (quite easily if you were under 90kts) by a c.18" long bar, using perhaps 20lbs of force.
It doesn't sound impossible,....
Leo Jones

Some aircraft have the airflow aiding the extension of landing gear, which is seen as an added safety factor for these planes. One plane like that was the Douglas A-4 Skyhawk. That same trick would be good for our use. The fresh pilot after launch can muscle the gear up, while a tired pilot on landing approach only has to release the gear and watch as it deploys.
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By Ground Slammer
Leo your dream glider has been out for 44 years now. Dr Howard Long's Mitchell Wing L/D 16 to 1, not bad for the early 70's. As some of you are not adverse to undercarrage there is no longer the need for static balance-so why short change yourself a cruciform tail. For a rigid HG we have 3 planforms that work well, a swept wing with spoilerons, a swept wing with tip rudders, and the conventional monoplane. The first wing has best static balance, the second is just at the limit for solo launch (tail heavy), and the latter needs a launch assist. Also the latter two do not go thwak!!
As I look at the posts one thing becomes clear, most of you all want a Fledge 4 or higher. The Icarus V had a high aspect ratio knock off called the Arial (spelling?) it brought the L/D from 10 to 1, up to 12 to 1. The same treatment of the Fledge should come in at just under 14 to 1. The sweep angle can be reduced on the longer wing to give an equal pitch stability and about the same static balance- poor but in range for unassisted launch and no thwaking.
The problem with tube and cable brace is the sticker-tube and cable is the lightest frame we know how to produce. With the lust for more performance comes longer wings and the need to brace that wing . So we stand at the point that the foot launch pilot can't handle the span or weight as it is. So those that insist on foot launch you have to ask yourself how much weight do I wish to handle? How much span can I get away with? As for AR with out an undercarrage I keep it at 8 or less.
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By Lucky_Chevy
...so are we talking about a Swift?, less performance like a GOAT air chair, or an Archaeopteryx if you have deep pockets. (Although in comps the Swifts and Archaeopteryx seem within the margin of pilot skill)

If you can do without an undercarriage it will be tough to beat an ATOS.
By thermaleo
"Leo your dream glider has been out for 44 years now. Dr Howard Long's Mitchell Wing L/D 16 to 1"

No, I am not thinking of anything like this. The Mitchell Wing was heavy, only marginally transportable, and certainly not carryable. It didn't fold up, was of complicated design much like a conventional aircraft wing, and the pilot was not in the wing but below it, in a pretty draggy harness/frame.

I envisage a much simpler, lighter design, probably like an Atos, but not excluding a flex wing design, that could be conventionally foot launched and landed. After launching the pilot would (by some yet to be designed mechanism!) simply swing up feet forward and into a thickened center section of the wing, probably with fabric door fairings closing underneath him as part of the "harness". Getting the pilot largely out of the airflow would probably give an Atos type wing an L/D in the high 20s. One could even have a nice bowsprit canard for pitch stability...

It's just an idle dream - I'm not going to try to build one, but I think someone could, and I think the mechanics are do-able.

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By Ground Slammer
I too think the MW is too impractical. I tossed out Dr Long's copy because he would run it off, go supine in the wing, and could look above and below the wing. I think if he added a Bomb Bay cover like a see through vinyl plastic with a draw string zipper- we'd see more than 18:1 more like 20. But unless some one was a home builder with a passion for wooden aircraft; I don't think the wing is a good idea.

PS after a second look at Dr Long's wing that gives me a better angle of just how much of his body was below the wing, it would be a hard job to make a lower cover.
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By lizzard
I have always looked at the bone structure of a bird or flying fox ...
Perhaps it is as always right under our noses.

Imagine having a handle on each extended arm/hand
pull in hard both and the wings fold in (smaller)
twist individually or together for flatter tips and or tail feather movement ...
or body crouch ... but your feet are up for exploitation after launch as well
the pilot would be in the wing ...head just where the bird heads are
a bird that does everything but flap .
imagine flaring with wings folded then extending as required for a zero step landing in a tight spot
The structure would have to be flexible and it would be aerobatic capable and safe due to its flexibility.
Blow a loop and she would just bag out ..bring your wings in ,stabilize ..then ...just like bird

If this were the seventies with what materials we have now ..this is where we would head ..but the test pilot mentality has been complied out of most of us .

Im dreaming ..... or am i?
By Lazypilot
BubbleBoy wrote:
Tue Feb 13, 2018 7:42 pm
Yes you are.
I'm willing to compromise in the interests of safety, and not lie prone with my head sticking out the nose.

The "joined wing" planform is getting more attractive all the time, the sheet foam models demonstrate the structural advantages. I had never given them much thought before, I figured that there must be a lot of drag associated with the wings joining, but I now think that can be dealt with effectively with a proper joining method. I like the concept of sitting between the two keels, and the twistable frame that could be powered in flight by controlling the canard wing's lift distribution.

It's actually starting to look doable, even for a bumble thumbs like me.

I hope that dreamers will get only encouragement from their peers. While the dream may seem to be too far out there, it may be possible as technology advances to realize the dream. And some inventive creative pilot will read the dream, and while stuck in traffic come up with a way to achieve a reasonable facsimile of the dream. I welcome your dreams. Someday we will have a glider that we wear, and control of it will be intuitive, with 100% control of the glider's attitude at all times.

Discouraging a dreamer is a sin. We wouldn't have what we do now if it weren't for dreamers.
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By lizzard
Perhaps Im awake and there is a lot of dreamless sleeping going on.
Not saying a good ss glider on a good coastal site is not just the safest and most relaxing flying .

But here we are with our high tech chutes some with assisted launching .
Carbon fibre,cad ,cnc, 3d printing , good engineering data remote control ,high tech sail materials yet nobody has made a bird wing with folding flexible joints .
many other great ideas here .
if only i was 30 again .... now I'm F*&^%$#g Dreaming !
By Lazypilot
It does seem odd that with all the revolution in the digital arena there seems to be less creativity than there was over 40 years ago. I see people getting all caught up in the process of using computer tech to do things, and not actually creating anything. They're just so fascinated with the means and forgetting the ends.

Experimentation with flying machines is dangerous. But in the years since all the experimenting was done, we've developed the vehicle-based testing, and now there's no reason why a test pilot should be taking excessive risk on a test flight.

Let the imagineering and creativity see a resurgence, get our heads out of the proverbial box and invent new gliders that address the issues that are shrinking our numbers.
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By raquo
How do you actually do vehicle testing, being an amateur HG developer? Europe has a DHV vehicle that I presume you could use (how much would that cost?), but in Americas only Wills Wing and North Wing have such specialized test rigs.

Making your own test vehicle is probably as hard/expensive as making a glider prototype...
By Lazypilot
Vehicle testing can be expensive I'm sure, especially if you're trying for accurate information about lift and drag and pitching moment.

But if you've built a glider and have tested it on the low sand dunes, and just want to make sure it's strong enough and is pitch stable it wouldn't be too difficult to build a fixture that could be bolted down on a lumber rack of a pick-up truck.

I think that mounting the glider inverted might be safer in some ways. Having the glider upright and lifting hard could cause problems, and if it broke you potentially could have an asymmetric lift that would ruin your day. But I don't know for sure.

It really depends to some extent on the type of glider being tested. Weight-shift control requires the glider to always have a positive pitching moment, except in the post stall area where you want a slight nose down moment.

But a glider like I want will have a control system that gives me 100% control of the glider's attitude. So testing for pitching moment would require testing in a variety of AoA and control surface settings, to make sure it will pull out of a dive, and won't try to fly sideways or something. After determining to my satisfaction that the glider is at least airworthy it's time for flights higher than the small dune. Flight testing is potentially very dangerous and needs to be carried out in a methodical manner. I suppose that if you can it might not be too bad of an idea to fly it using radio control. Unless you have a spot way out in the middle of nowhere to test like that, you'll need to get a waiver from the FAA, as "model planes" are limited to a maximum weight of 55 lbs, and I'm sure that they would see the machine as a model plane. But I dunno, I hadn't thought about it til now. All I now is that it would be a sickening feeling to have a full-scale glider up flying and the radio control dies. But Rc systems are relatively inexpensive, so installing two or more systems would provide redundancy and piece of mind. NASA can detonate a bomb to destroy a test airplane if it goes berserk.
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By Ground Slammer
I'm looking at doing some test runs on wing sections. I lucked out and bought a second hand station wagon with roof racks and a sun roof. I think I'll make a hang cage type center that attaches to the racks and test with just a short span to see if my trailing edge idea will hold up, or will the fabric balloon or collapse. If it holds up then I can see just how much ramp I can sew before collapsing or ballooning. I'll also test my idea (assuming it works at some level) against the Kaspar/ Fledge 1 method of running a rear spar and no formed element for the trailing edge. The latter will require a wing attached to a single post with a pivoting head so I can look at diferential lift and drag, half the wing with one type of trailing edge and the other trailing edge on the opposit side. Two man crew in the wagon one to drive the other to run the tests.
The original test cart was created by a friend of mine and some university researchers. They put strain gauges on all the tangs and other stressed zones to get an idea of just what the strain loads are at different angles of attack. Some use a push cart and some use the top of a full size van to make tests today. Push carts are tricky to get to run strait. An old beater van that you use and junk out afterwards might do it, I have an old beater Astro- if I was building a flying wing I might consider it before sending the van out to junk.

PS I think they pulled the 55 pound rule on RC- anyone know for sure?
By Lazypilot
I think that if you had a sophisticated rig with the capability of accurately measuring forces, the way to go would be a pontoon boat. Go out on the lake early before wind and other boats are running, get a perfectly smooth ride. Build a crane like structure that extends out in front of the boat, in clear air, to put the glider on.

I suggested mounting the glider inverted. That way you can watch the tufts.

Have I missed a discussion of your trailing edge? I'd like to hear more about it, if there's a link I'd appreciate it.

A glider with full 3 axis control wouldn't need vehicle testing, unless you didn't have faith in the stress analysis and wanted to see for sure how strong it is.

I'm leaning heavily towards a glider with a straight or fwd swept main wing and a swept aft canard wing, with the tips connected together. I really don't much care for having 4 wing panels, but the structural advantages of the joined wing design argue for it's use. If I do it right I'll be in a semi-reclined seating position, with my head just in front of the main wing's noseplate, and in flight the fore wing would appear to be just above the horizon, and my view would be mostly edge on to it so I don't think it would be too much of a distraction.

My ideas of this were actually inspired by sitting in the hang cage of a Millenium and a Swift. I didn't like the cluttered view and being up close to the wing. That's one of the reasons I'm rejecting the swept back flying wing. I want to sit out in the open, in front of the wing, like a modernized Lilienthal glider. I was researching forward swept wings because I thought a flying wing was what I wanted, and fwd sweep would get me my seating position. But the torsional rigidity issue drove me to consider the joined wing concept.

But ya know, it seems like a fwd swept wing built like a hang glider wing wouldn't have the classic failure mode suggested by the literature on fwd sweep. As loads build it would washout, which would make the glider nose heavy and require the pilot to move aft or add decalage. This is the opposite of what occurs using a more conventional wing structure in a fwd swept wing. And the opposite of what we experience when we load up a Hg, where the glider appears more tail-heavy. I think the fancy term is "Positive aeroelastic structural divergence". Or trying your best to hold the nose down while pulling G load, that's how we experience it. Back in '81 I was looping my Comet, as I was pulling up from the third one the bar got away from me, I just didn't have the strength to hold it back. When the bar went out front the glider got so over loaded the leading edges bent back, the right more than the left, and it was all I could do to make it to Marshal and belly land.

Can't wait to get some aerodynamic control, gonna be so sweet. No more struggling with high wind launches, that alone will be worth the price.

I'm not going into all the discussion over the supposed benefits of fwd sweep. Maybe it's better, as some claim, maybe it isn't. But if the joined wing design solves the torsional issue without having to have a heavily reinforced wing structure, I'm all for it. I'm impressed with the flying models so far. If you're curious grab some foam board, de-paper it on one side or both and cut the sheet diagonally in half. Then tape or hot glue the pieces back together to form a delta wing.

Add nose weight and reflex until you get best glide. Then cut two big lightening holes in the glider the same approximate planform so that you end up with a joined wing glider, Be conservative at first, it's always easier to cut away more foam than it is to add it back on.

Instead of reflexing the aft wing you can add incidence and camber to the fore wing for pitch stability.

I think you'll be impressed by how much better it flies than the delta it was made from. It requires much less nose weight for balance. One thing I'm still getting a handle on is it will behave as though it's balanced correctly, but then it will stall and descend vertically or even tailslide. More nose weight please.

It also has a futuristic feel to the styling of it.

Decisions decisions. Damned if I do, damned if I don't. The prospect of actually designing and building it is intimidating for me. But if I want to fly in a manner that I desire and deserve to have, I gotta do it. There are only a very few that see things the way I do. I don't now why a dumbed-down form of flying is so appealing to most flyers, but it is. I'm greedy. I want more capability in an aircraft than what can be found in the hang glider. I wanna fly like a bird.
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By raquo
It's not the absence of proper 3 axis controls that requires vehicle testing, it's a combination of:

- very low pitch stability to make weight shift possible, resulting in tumble being a realistic failure mode

- significant aeroelasticity that can affect the pitching moment, which might be hard to calculate or test for in static load tests

This is why I think the next garage innovation will come in the form of a fully aerodynamically controlled rigid wing (not just roll, but pitch too). Flex wing gliders are just too hard and too expensive to design and test, and it will be hard to beat modern flexies by essentially amateur-copying what they are.


PS I also finally more or less understood your dream HG design, seems more legit now :)
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By Ground Slammer
My wagon top tests will be done with the airfoil inverted so I am pressing down on the vehicle. No need for hard to engineer drag free mounts or gauges, just relative testing. Does the test wing want to yaw? Does it want to roll? I am not anticipating roll, yaw maybe.

The glider is a redo of the Quicksilver- a Fledge 2 root section airfoil, and an AR of 8 to 1. The Quicksilver trailing edge was a 1 inch tube. I am looking at a spacer behind that of 1.125inch and a 3/8ths inch trailing edge stringer as a possible way to clean up the drag. The trailing edge pocket in the sail wraps around the spar and stringer. The question is will the holes in the trailing edge pocket that accept the compression struts cause the pocket to ram inflate? If I make the pocket extra wide will air pressure cause it to collapse or ram? Will the battens try to lift off the spar? The only reason I am looking at this possible solution is to keep the sail work as simple as possible. The QS sail is about the easiest sail to sew, all I need to do if this is a viable solution is widen the leading edge and trailing edge pocket. I hope this will work as the sail work is the only part I am afraid of.

The Kasper Wing showed us what happens when one cleans up that 1 inch tube trailing edge. Sundance, Cronk Sail and Valkyrie all used the same airfoil as Kasper, but Kasper gets 11 to 1 and the others 8 to 1. Kaspers 7 to 1 AR was only a little bit more than the rest, so most of the drag reduction was the trailing edge. It will be harder to sew- and if my solution will work: the my chance off pulling off an acceptable sail job will improve.

I don't see the QS HG as in need of any help in pitch. Also due to a lack of crosswind taxi in a HG, the high dihedral for roll-yaw coupling is acceptable. The QS as a hang glider was fast and easy to roll, pitch, and coordinate-but it had an entry level airfoil-good for a time when there were no instructors. With higher L/Ds spoilerons are indicated. Or Red would prefer winglets that double as dive brakes so it will pitch up too.

There are some posts on my project on this site and the US Hawks site. I'm not were I can post some sketches right now maybe latter.
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By raquo
Ground Slammer wrote:
Fri Feb 16, 2018 9:19 pm
My wagon top tests will be done with the airfoil inverted so I am pressing down on the vehicle.
Keep in mind that car roofs have a max load limit which is lower than the downward "lift" force exerted by the wing if you want to really stress test the glider. Non-inverted test rigs have to load up ballast in front of the vehicle to keep it solidly on the ground at high speed. Not sure if they do any roof reinforcement for negative load tests. Those are lower speed, so maybe they don't need it.
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By red
Ground Slammer wrote:
Fri Feb 16, 2018 9:19 pm
With higher L/Ds spoilerons are indicated. Or Red would prefer winglets that double as dive brakes so it will pitch up too.
Ground Slammer,

To be more accurate, that would be Red wanting winglets which can be the dive brakes, the sideslip recovery system, the extra dihedral, and the power steering, as needed.

Having the winglets canted outward, they provide "invisible dihedral" which is not there until it is needed in a sideslip, or when making the landing flare. This is good, because excessive dihedral hurts the gliding performance, and winglets do the opposite, helping the glide. I can tell you, in a flare, the glider just settles down to the ground in a very good-natured manner, not at all willing to drop either wingtip. It is as if the actual dihedral runs to the top of the winglets, not to the wingtips. In a sideways dump-out, the sideslip gets self-corrected in a circular dimension. Looking straight at the oncoming glider, imagine a vertical circle above the glider that can touch the keel and the top of each winglet. When the glider slips sideways, the sideways recovery to level flight will be a radius only slightly larger than radius of the vertical circle you may imagine above the glider. The glider does not need to pitch down to recover from a vertical side-slip, or do anything unexpected, it simply slides down to the bottom of that imaginary circle as it recovers to level flight.

From the Fun & Games department: If anything is not clear above, fold up a cardboard model of the wing and winglets, hold it in a vertical bank, drop it and observe the recovery to a wings-level attitude. Ballast the model for a mushing descent, and drop it from a level position. Neither wingtip is likely to drop, in the short vertical distance of a landing flare. If your model performs like my real Fledgling in those instances, you will understand why I flew it for so many years.

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