What 's your opinion of this theory.

[Deskpilot]

I'm referring here to the last part of this page. It's interesting, intriguing and definitely 'outside of the square'.

 

I just love the mag cover design as well, pity we can't have twins in other than the 95 cat.

 

http://www.rexresearch.com/delouise/delouise.htm

 

 

[turboplanner]

The US Air Force didn't go ahead with it

 

8 lots of control linkage

 

And I'd like to see the model flying to see what pitch control is like.

 

As you know you can hook a model aircraft engine on to a dinner plate and make it fly at full rpm.

 

 

[Thalass]

It'd be interesting to see flying. This is one of the things where an RC-style fly by wire system would be advantageous - whether you trust it in an ultralight is another thing of course. An Ardupilot board could handle the coordination of the control surfaces, you just have to give it some stick/rudder input and it'll tell the (probably large and heavy) servos what to do.

 

Just carry an extra battery to act as backup in case of engine (and therefore generator) failure. :P

 

 

[Deskpilot]

It's been a long time since I started this thread. 2 replies referring to the mechanics of the thing but no comments on the theory. Anyone really read it and be prepared to put some thought forward. Note the way the control surfaces operate, not their connections.

 

 

[Head in the clouds]

Good post Doug.

 

I don't know whether you came across it over on that 'other' forum but this kind of thing was touched on there, with Aircar making some good contribution. It may have been in the Stratos thread but more probably on Flying Car or Flying Car Design.

 

An embodiment of this concept was designed and built many years ago with the intention of getting it narrow enough to be roadable, in fact Mad Moller has used this general concept in one or more of his Skycar scams. The problem with each of them, and a couple of very early ones (I think there is a real (historical) one featured in the opening scenes of Incredible Men...Flying Machines) is that folks have invariably tried to stack the wings the wrong way i.e. the lowest wing at the front and so on. The more recent proposed flying car did at least get it right and the highest of about ten stacked wings was at the front and although it doesn't look all that sexy it does at least provide a good situation for pilot/pax and their outward visibility.

 

With that arrangement it's necessary to consider it as a multi-plane (as in bi-plane) and modify the set incidence of each wing in order according to the downwash effects of the preceding ones, so allowing for a relatively short ten-stacker with not very much distance between the trailing edge of one and the leading edge of the next, (like a partially closed venetian blind) then the incidence modification of each succeeding wing becomes exponential resulting in the last wing having a very high incidence, maybe in the 30* region.

 

But back to a two surface proposal as in the thread subject - the rear wing would require a slightly higher rigged incidence theoretically but perhaps that might not be applied in fact, to additionally ensure that the front wing stalled first, canard fashion.

 

I think the overall concept has a lot of merit and I wonder why we haven't seen more experimentation along these lines, might be worth toying up a model for a bit of fun research.

 

But - as it is described in the Patent document it has a few flaws. The first is one that caught Charles out on the Stratos, and I'm not meaning what caused the fateful crash, but an early experiment that wasn't right. Charles had various ways of manipulating the control surfaces by changing the settings of the mixers, at one stage he could make those changes in-flight, I don't know if the later version had that feature. Anyway he could set it up so that all the surfaces (or at least one on each side of each wing) deflected downwards with back stick and v.v. which is just as suggested by this tandem wing and so he could climb without pitch change and also descend without lowering the nose. He got a big scare when he found himself diving steeply nose-down and with the controls configured that way because although he could 'translate' upwards, he couldn't raise the nose...

 

Charles also set up the ability to, for example, deflect front right and rear left surfaces down and at the same time have front left and rear right surfaces deflected up and IIRC they were connected via a mixer to the pedals which ordinarily operated independently of each other i.e. push right deploy right tip-rudder, push left for left tip-rudder, push both for both tip-rudders as airbrakes. But by using the diagonally oppositely deflected control surfaces it created a force vector which allowed him to 'shift' sideways without banking or yawing, his thought was that it could be useful for aligning with the runway in a crosswind.

 

Back to the design under consideration - This is proposed as a two-axis control system but I can't see how his rudder deflection would induce the roll as he states, especially since there is no dihedral shown on the drawings or suggested in the Specification. And I can't see why he wouldn't simply add a mixer and use his eleflaps as eleflaperons. He makes a lot of the aircraft not being able to skid but I can't see why it wouldn't with application of rudders alone, and I also can't see why it wouldn't slip if it was banked, although he doesn't mention slip, but the slip would be the undoing of it because the nose would inevitably drop and without positive pitch and roll controls he wouldn't be able to recover from the spiral dive which would develop.

 

He mentions that if upset it would return to straight and level but I can't see where the lateral stability would come from. And he also goes on about not needing to be able to slip/skid because of the lack of speed build up by descending without nose down, so he's only considering the slip for drag, whereas we all know that we need it for cross-wind management as well. Well some of us do, others use the crab technique of course.

 

I think he has considered the CG position well and I do like the overall configuration. The ingress/egress is great, structurally it's terrific, the prop is well back from the upper wing t/e and so the wing-wake shouldn't be a big issue. The engine/prop position is well back from the point where the fuselage needs to be widest so the fuselage taper ratio is mild which would assist with the usual pusher problem of laminar flow breakdown/boundary layer separation. The fuselage could be very boxy (cheap and easy to build and with good volume) without adversely affecting the aerodynamics or the aesthetics. He'd probably want to go with different airfoils front and rear considering the much higher wing-loading on the front wing and add some dihedral.

 

 

[Kyle Communications]

well dont stop here...this is a very interesting design ...is there any videos around of the models flying. I do remember watching something on the stratos about a year or more ago I might have to find it again and have a look'

 

 

[Head in the clouds]

The Sunny Boxwing is in the same general configuration -

 

 

 

[Kyle Communications]

There must be 5 or 8 degs of upthrust on the engine in sunny box thing

 

 

[Head in the clouds]

There must be 5 or 8 degs of upthrust on the engine in sunny box thing

I see what you mean but is it up thrust? Shaft is pointing down so I'd probably call it down thrust but then I guess it might also depend on whether the prop is in front of or behind the CG ? Hmmm

 

 

[Kyle Communications]

That second one sure is nice seawings I think it is called ..sort of like a thruster on steroids

 

 

[Kyle Communications]

ell the engine is pointing up but the effectice reaction is down.....but still quite a lot I would have thought....It would dramatically change the aircrafts pitch if the engine stopped all of a sudden

 

 

[Head in the clouds]

ell the engine is pointing up but the effectice reaction is down.....but still quite a lot I would have thought....It would dramatically change the aircrafts pitch if the engine stopped all of a sudden

I think the vertical centre of Drag is probably quite high on that machine so the engine is probably angled like that to provide a thrustline that is below the dragline so that power on produces a nose-up reaction and then it's probably trimmed for nose down with power off.

 

 

[damkia]

I can remember quite a few years ago there was a similar "linked wing" experimental ultralight concept that was constructed. Ligeti Stratos was the name of the aircraft.

 

http://www.homebuiltairplanes.com/forums/attachments/aircraft-design-aerodynamics-new-technology/17017-ligeti-stratos-ligeti-stratoss.png

 

It was "arrow" shaped with raked back front low wings linked to a straight rear wing and a rear engine with ducting around the propeller all done in composite.

 

From reading articles on it there were a few aerodynamic issues that popped up, resulting in the accident that caused the death of the inventor.

 

Very similar stated abilities (crabbing, compound lifting body, etc).

 

 

[dazza 38]

I can remember quite a few years ago there was a similar "linked wing" experimental ultralight concept that was constructed. Ligeti Stratos was the name of the aircraft.http://www.homebuiltairplanes.com/forums/attachments/aircraft-design-aerodynamics-new-technology/17017-ligeti-stratos-ligeti-stratoss.png

 

It was "arrow" shaped with raked back front low wings linked to a straight rear wing and a rear engine with ducting around the propeller all done in composite.

 

From reading articles on it there were a few aerodynamic issues that popped up, resulting in the accident that caused the death of the inventor.

 

Very similar stated abilities (crabbing, compound lifting body, etc).

The Ligeti Stratos has had a following here at recflying . Actually Charles Ligeti's son has posted here before.

 

 

[Head in the clouds]

Yes, I really only mentioned the Stratos earlier because of the slight similarities of some aspects of the proposed control system functions but there the similarity ends unless you were to fly the Stratos backwards perhaps.

 

The Stratos had quite a rearward CG, and that was its undoing because it couldn't recover from being inverted.

 

The boxwing that this discussion centres around has a forward CG and is a reasonably conventional canard in many respects, except aspect ratio certainly, and in particular the rear wing could never be blanketed by the canard wash and also recovery from inverted flight would be as simple as 'hands off'.

 

Barnaby Wainfan has clearly demonstrated, with the Facetmobile, that low aspect ratio can sometimes work very well, and efficiently, quite contrary to most opinion prior to 10 or so years ago.

 

The main difference between this concept and the boxwing is the lack of sweep of the canard and that lack does introduce some interestingly different dynamics.

 

C'mon folks, there must be some other wannabe design commentators and theorists here...? This is a very interesting and compact configuration with good internal space, access and lots of potential in these days of ever more limited hangar space. Any ind. designers out there want to draw up a prettier version?

 

 

[Thalass]

When i first read the article i pictured an aircraft with two mainplanes, both mounted high, with conventional controls mixed for the flapailervators - that is pull back on the stick and the forward flapailervons would drop while the aft ones rose. With a standard flap position input causing both to droop. Much like flaperons. And like that i thought it was ok, though there is quite a bit of hippy artist dribble in the description.

 

Reading again i come to the same conclusion as Head In The Clouds did. Assuming nothing goes wrong0 and you only want to fly in a straight line, it should work. Bit if you need a major change in pitch like recovering from a stall, you're out of luck. And while you may be able to change heading with rudder, the flapevons seem to be a single peice across the whole span - so no roll control. (i could be reading the diagram wrong again, i'm on my phone.)

 

An aircraft that swaps a horizontal stab for second mainplane should work fine - i've seen a picture of a larger version of the Osprey that was like this. But in the real world you need control of all three axis.

 

 

[Old Koreelah]

Some awesome innovations! This thread is a breath of fresh air.

 

Charles Lugeti is an icon for experimenters. Much as I would love to build something with linked-wings, like many others I postponed flying until later life...the worst time to become a test pilot.

 

My Holy Grail of design is an aircraft that will do it all: fly fast, land short then fold up for the road or a standard garage. Not so hard to please...

 

Despite my prejudices, I have to admit that some of the new gyro designs are closer than anything I can dream up.

 

 

[Deskpilot]

Some years ago when I first came across the Sunny Boxwing, I was quite taken by the design and contacted the designer (can't remember his name). He informed me that it was a very stable and safe aircraft BUT, he had sold the rights to some one else who had modified it some what. (I think the wing spacing was reduced) The aircraft is now, in his opinion, dangerous. Again, I can't remember the details and have deleted his emails......bugger!!).

 

I'm so pleased that this thread has gotten you all thinking.......perhaps..."outside the square" (See my original post and signature)

 

 

[Deskpilot]

Just Googled a bit on the Sunny Boxwing. From the original designer.

 

http://www.sunny-boxwing.de/english-overview.htm

 

 

[Himat]

C'mon folks, there must be some other wannabe design commentators and theorists here...? This is a very interesting and compact configuration with good internal space, access and lots of potential in these days of ever more limited hangar space. Any ind. designers out there want to draw up a prettier version?

One joined the forum due to this remark:wave:.

 

I do think the idea do have it merits. Reading this thread and the patent it point to I do consider if it is applicable to a seaplane that is designed to not rotate on takeoff. The hull design could then maybe be optimized. At http://www.rcgroups.com/forums/showthread.php?t=1438226 there is a thread with some interesting information. I have not been able to trace down the patent macboffin mentions. Searching “Outrider UAV” and there is some more information and pictures to be found. Actually the patent shown in this thread was interesting and showed the way to both some interesting patents on previous art and references to newer patents.

 

 

[Guest Maj Millard]

One design that I really liked was Caig Catto's Acro X....it was an outgrowth of the Cunard Goldwing. Similar fuselage as the Goldwing with the same Cunard and an enclosed streamline canopy. Instead of the single low swept back wing, the Acro X had two shorter wings in a biplane arrangement but they were joined at the tips with vertical surfaces incorporating rudders. The top wing had a large degree of dihedral, and the lower wings a high degree of anhedral, hence the X in form. Closest comparison was Luke Skywalkers fighter plane in Starwars.

 

As far as I know only one was made using the same glass over foam construction as the Goldwing, and I believe Craig flew it to Oshkosh about the same time the Legiti Stratos was shown there.

 

It was lost shortly after his return to California when the bubble canopy flew off and caught in the cross bracing in the wings, causing considerable drag on one side. Craig fortunately that day was wearing a parachute, and was forced to use it. I remember him saying it just ended up as broken bits of blue foam !......It offered good speed, an almost unbreakable structural design, and increadably striking and modernistic good looks.............Maj...

 

 

[winsor68]

http://eaaforums.org/attachment.php?s=259e46240d556c6b751d31a7bfa5b22a&attachmentid=3130&d=1374681562

[Guest Maj Millard]

Yes that's it Don. The nose wheel retracted like the Variezys, and it looked very slick in the air ..thanks...........Maj...

 

 

[Guest Maj Millard]

Thanks also corvairkr....hell, let's just build one !.....................

 

 

[Head in the clouds]

One joined the forum due to this remark:wave:.I do think the idea do have it merits. Reading this thread and the patent it point to I do consider if it is applicable to a seaplane that is designed to not rotate on takeoff. The hull design could then maybe be optimized. At http://www.rcgroups.com/forums/showthread.php?t=1438226 there is a thread with some interesting information. I have not been able to trace down the patent macboffin mentions. Searching “Outrider UAV” and there is some more information and pictures to be found. Actually the patent shown in this thread was interesting and showed the way to both some interesting patents on previous art and references to newer patents.

Excellent and interesting link Himat. In a quick search I couldn't find the patents Macboffin refers to either so I'll spend more time on the USPO site after work. I'd guess they'd be expired by now anyway but would be interested to see what claims they made and what prior art they referenced.

 

Were you referring to a Google search of Outrider UAV or in the USPO?

 

Good thoughts about the non-rotating seaplane thing, getting rid of many of the problems associated with equipping a seaplane with flaps for the same purpose, and then battling the resultant pitching moment issues - particularly when they're often combined with a high thrust-line.

 

I had a PM conversation with John McGinnis a couple of weeks ago about the progress on Synergy, it's going ahead well apparently but he's keeping details close to his chest for now - too many attacks from detractors have taken their toll on his openness I suspect.