Flying Flapjacks

cluttonfred

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I am sure everyone is familiar with the 1940s V-173 and XF5U-1 projects. If not, the Vought Heritage Museum has some nice pages and pics here: http://www.voughtaircraft.com/heritage/products/html/v-173.html

I know of the similar Boeing design from the same era, the Model 390/391. Aerofiles.com has a little info and a pic on that one here (scroll down to the 390): http://aerofiles.com/_boe.html

I know of some pre-war and WWII-era design like those, but does anyone know of any similar low aspect ratio designs in the post-WWII era?

And no, I don't mean something like the Lockheed F-104, which certainly has low aspect ratio wings. I mean low-aspect ratio flying wings or something otherwise similar to the Vought and Boeing designs above.

Thanks and regards,

Matthew
 

AeroFranz

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I was reading in "Radical wings and wind tunnels" that Zimmermann first got interested with low AR circular wings when he saw the Arup S-2 (supposedly designed by a podiatrist!)
 

cluttonfred

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Thanks for the Arup, which is one of the pre-war inspirations, and the Facetmobile, which certainly does count. I had in mind something high performance, however, whether jet or prop, military or civilian.

I am not so sure how useful the XF5U-1 would have been as a fighter for the U.S. Navy, but it would have made rugged ground attack aircraft to support the Marines.
 

Just call me Ray

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I have a Sport Pilot magazine article about that plane (incidentally it's one of the few artifacts recovered from old Aurora Airpark in Colorado before they closed for good, I just happened to have been there a few days before its demolition). I'll dig it out and summarize in a bit.
 

cluttonfred

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Thanks, I am a big French aviation fan so I know about the Payen and Fauvel designs, some of which are very low aspect ratio flying wings or near-flying wings, but the Mirouze designs are completely new to me. Anyone have any more on the Mirouze designs? In French is fine....

I am still looking for more, though, especially something high performance or military.
 

AeroFranz

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Nice post, i had never seen the Mirouze designs. The pusher prop looks awfully close to the fuselage...was there a slot for it to go in? I can't tell from that picture.
Regarding the Flapjack, one curious bit of information that I read somewhere was that the planform of the V-173 was arrived at by drawing an ellipse and half a circle. The ellipse was the front part, and the half circle was the rear and had the same diameter as the major axis of the ellipse (see attachment).
 

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saturncanuck

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Mole said:
Thanks for the Arup, which is one of the pre-war inspirations, and the Facetmobile, which certainly does count. I had in mind something high performance, however, whether jet or prop, military or civilian.

I am not so sure how useful the XF5U-1 would have been as a fighter for the U.S. Navy, but it would have made rugged ground attack aircraft to support the Marines.
Here is some info on how it worked...

"The positioning of the propellers was paramount to the design, and, in effect, offered the V-173 its unique low-speed characteristics. Traditionally, a wing with such a low aspect ratio will suffer from very poor performance due to the induced drag created at the wingtips, as the higher pressure air below spills around the wingtip to the lower-pressure region above, causing wingtip vortices. With a conventional aircraft, these vortices carry a lot of energy with them, and, thus create drag. The design of the V-173 – and the location of the propellers – overcame the wingtip vortex dilemma, by using the propellers themselves to actively cancel the drag-causing tip vortices. The propellers were designed to rotate in the opposite direction to the wingtip vortices, thus retaining the higher-pressure air below the wing. Since this source of drag was eliminated, the aircraft could fly with a much smaller wing area, and this small wing would offer a high degree of manoeuverability. As well, the contra-rotation of the propellers virtually eliminated the aircraft’s natural torque, making the V-173 much more agile and easier to fly"

"Although criticised as being underpowered, the V-173’s low aspect ratio wing allowed it to take-off at only 29 mph, and in calm winds required a take-off run of only 200 ft. Landings were possible in considerably less distance. As well, the aircraft could successfully maintain controlled flight at a 45 degree angle-of-attack – three times that of aircraft with conventional wings – and the aircraft was found to lose speed rapidly when entering a tight turn. This was theorized to be an advantage during a dogfight situation"

Oh, the V-173 and XF5U-1 used the same concepts.

These excerpts taken from "Clipped Wings – The History of Aborted Aircraft Projects", AeroFile Publications, Markham, 2007.
 

Justo Miranda

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Please see http://www.secretprojects.co.uk/forum/index.php/topic,6213.msg51204/topicseen.html#msg51204
 

hole in the ground

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saturncanuck said:
"the aircraft was found to lose speed rapidly when entering a tight turn. This was theorized to be an advantage during a dogfight situation"
I guess this depends on how quickly the aircraft can accelerate out of the turn.
Might be a good defensive manoeuvre, tightly turning inside your opponent and have him overshoot you but you've then got to be able to keep up to turn on the offensive.
 

Retrofit

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AeroFranz said:
Nice post, i had never seen the Mirouze designs. The pusher prop looks awfully close to the fuselage...was there a slot for it to go in? I can't tell from that picture.
No slot. In fact, Mirouze's system was trying to force the airflow over the central section of the wing extrados, a little bit as on Custer's Channelwing experimental aircraft.
 

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AeroFranz

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Thanks for posting the pictures, now I see what you mean. The rear of the fuselage is concave and provides enough clearance. interesting.
 

cluttonfred

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Philippe,

Thanks again for the Mirouze posts and info. Are you (or anyone else) aware of any reviews or flight tests done on either of these designs? How well did it work? I can imagine a high-bypass turbofan in the same position to really amplify the effect, if it works.

Thanks!

Cheers,

Matthew
 

OM

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...A few clips of the Flapjack in flight:

http://www.youtube.com/watch?v=JBGhMN2KEvw


http://www.youtube.com/watch?v=5Gj_eFnFzpw&feature=related


http://www.youtube.com/watch?v=N2yzoMt6etc&feature=related


...And a clip with some renderings, thrown in for...oh, frack, just consider it syrup for the pancake :p

http://www.youtube.com/watch?v=n1tFy9Rgx68
 

Antonio

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What a great renders, I'd love to see it as jpg files!
 

OM

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pometablava said:
What a great renders, I'd love to see it as jpg files!
...What I'd like is a decent-poly 3DS or LWO mesh of the Flapjack.
 

PlanesPictures

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http://www.secretprojects.co.uk/forum/index.php/topic,1671.0.html
http://pmc.sk/gatial/angelfire/lastnews.html
 

walter

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The only info I ever found on the (first) Mirouze Pulsar.
Two-seater with 90hp Continental C90 engine.
Wingspan 5,20 meter, length 4,70 meter.
If I remember well, the aircraft may have joined the RSA collection years ago, so possibly it still exists?
 

walter

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....forgot to mention it had a largely so called Geodetic construction.
 

Antonio

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Thanks Mr Gatial!
 

Stargazer2006

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OM said:
...A few clips of the Flapjack in flight
Well, not quite, actually... :D

- First video is of the NACA Tank Model 133 test model (not a related design at all).
- Second video is of the XF5U-1 Skimmer, but in wind tunnel model form.
- Third video is of the only real Skimmer, but not in flight, since it never took off, only doing taxiing tests!
- Fourth video is of the Skimmer in flight, but only in artwork form!


pometablava said:
What a great renders, I'd love to see it as jpg files!
Not top quality, but that's the best I could get from the video:
 

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OM

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First video is of the NACA Tank Model 133 test model (not a related design at all).
...Fine. I'll leave it to you to let the guy who posted the clip know his description was wrong.
 

Stargazer2006

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And the XF5U-1 even got cover art treatment in this 1946 issue depicting it in olive drab camo, suggesting an Army rather than Navy use (or, most likely, how little documented the artist must have been!).
 

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Abraham Gubler

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Stargazer2006 said:
And the XF5U-1 even got cover art treatment in this 1946 issue depicting it in olive drab camo, suggesting an Army rather than Navy use (or, most likely, how little documented the artist must have been!).
Great picture. Shame it isn't landscape as it would have made a great wallpaper.
 

Jemiba

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Is it just perspective distortion, or really a twin-seat cockpit ?
 

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Stargazer2006

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Looks like it... but asking the cover artists of the time for technical accuracy is like expecting gourmet food from a McDonald's!

Let's call it "artistic license"... ::)
 

Dass.Kapital

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Hello.

so, my firts post and I have a question about the 'Flapjack'.

Why was it better/necessary for the propellers to be made/operate in the way that they did?

Much cheers to you and yours. :)
 

AeroFranz

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short answer: supposedly the swirl imparted to the airflow by the props cancels out the tip vortex shed by the wingtips. This should lower the induced drag/give you a higher apparent aspect ratio.

In practice I have no hard evidence it worked. By hard evidence i mean an NACA paper or similar.
 

Dass.Kapital

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*Nods*

Thank you for taking the time to answer my query.

No, not the 'counter-rotating to counter tip vortex' thing.

But some sort of articulation 'flappy-ness' in the actual blades themselves.

I seem to recall it was one of the things that caused the machines production to fall behind. With the company not seeming to thknk it was needed, then much testing and errors coming about and the system thence bwing 'put back the way the designer intended'.

I also apologize if my sever lack of any technical knowledge is a hindrance. *Bows*

Much cheers to you and yours.
 

AeroFranz

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Oh, sorry for misunderstanding ;)
The flapping of the blades might have been necessary because at high angles of attack the props are operating in a strong edgewise flow (not unlike a helicopter rotor). The advancing and retreating blades see differing inflow velocity and need to flap to balance thrust across the disc.
Maybe someone else has a better explanation?
 

Tailspin Turtle

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AeroFranz said:
Oh, sorry for misunderstanding ;)
The flapping of the blades might have been necessary because at high angles of attack the props are operating in a strong edgewise flow (not unlike a helicopter rotor). The advancing and retreating blades see differing inflow velocity and need to flap to balance thrust across the disc.
Maybe someone else has a better explanation?
That's basically it. If the propeller on the flapjacks didn't flap, there would be excessively high loads at the attachment of the blade to the hub as the lift on it increased and decreased as the blade advanced and retreated relative to the inflow. While these loads are present on all propellers when operated at high angles of attack, they are much higher on the V-173 and F5U because of the higher angles of attack they were capable of and the length of the blades.
 

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I read somewhere, I don't recall where, a modern technical assessment of the XF5U. The verdict was that, because of the flapping airscrews, Vought had unwittingly ventured into the helicopter vibratory realm and that, had it flown, this would have ground the program to a halt. I can't defend this theory, but it seems plausible in the absence of any evidence. The pancake was unlike anything else flying at the time and might well have been shook in ways that were beyond the structural engineering knowledge of the day.
 

Dass.Kapital

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Ah! *Nods*

Cool!

Thank you all very much for your time and responses. :)

Much cheers to you and yours.
 

Richard N

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