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Author Topic: Flying Flapjacks  (Read 34632 times)

Offline cluttonfred

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Flying Flapjacks
« on: February 07, 2009, 11:53:49 am »
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
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Offline AeroFranz

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Re: Flying Flapjacks
« Reply #1 on: February 07, 2009, 12:57:24 pm »
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!)
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Offline Jemiba

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Re: Flying Flapjacks
« Reply #2 on: February 07, 2009, 12:59:10 pm »
Does the FMX-4 Facetmobile count ?
(picture from http://www.wainfan.com/facet.htm"
It takes a long time, before all mistakes are made ...

Offline cluttonfred

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Re: Flying Flapjacks
« Reply #3 on: February 07, 2009, 02:55:32 pm »
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.
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Offline Just call me Ray

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Re: Flying Flapjacks
« Reply #4 on: February 07, 2009, 06:57:23 pm »
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.
It's a crappy self-made pic of a Lockheed Unmanned Combat Armed Rotorcraft (UCAR), BTW
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Offline hole in the ground

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Re: Flying Flapjacks
« Reply #5 on: February 08, 2009, 03:05:46 am »
not post war designs but of a similar layout?



images from your one stop R. Payen shop http://home.att.net/~dannysoar2/Payen2.htm
:P

Offline Retrofit

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Re: Flying Flapjacks
« Reply #6 on: February 08, 2009, 05:19:13 am »
The formula has also been tested by Alain Mirouze, in France, in the late 70's and 80's.
Without much success.
The "Pulsar" performed her first flight on November 11th, 1974.
The "Pulsar 2" just some hops in 1984.
« Last Edit: February 08, 2009, 05:35:06 am by Retrofit »

Offline cluttonfred

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Re: Flying Flapjacks
« Reply #7 on: February 08, 2009, 05:40:13 am »
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.
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Offline AeroFranz

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Re: Flying Flapjacks
« Reply #8 on: February 08, 2009, 09:15:04 am »
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).


All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline SaturnCanuck

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Re: Flying Flapjacks
« Reply #9 on: February 08, 2009, 12:50:34 pm »
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.
Saturncanuck

:)

Offline Justo Miranda

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Offline hole in the ground

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Re: Flying Flapjacks
« Reply #11 on: February 08, 2009, 02:27:12 pm »
"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.

Offline Retrofit

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Re: Flying Flapjacks
« Reply #12 on: February 09, 2009, 09:41:12 pm »
I am still looking for more, though, especially something high performance or military.

Several Avro-Canada's VTOL combat aircraft projects may respond to those criterias:


Offline SaturnCanuck

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Re: Flying Flapjacks
« Reply #13 on: February 10, 2009, 07:07:08 am »
Ya, the trouble is that the "AvroCar", aka, Project Y, didn't work.
Saturncanuck

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Offline Retrofit

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Re: Flying Flapjacks
« Reply #14 on: February 10, 2009, 11:58:24 am »
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.

« Last Edit: February 10, 2009, 12:02:31 pm by Retrofit »

Offline AeroFranz

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Re: Flying Flapjacks
« Reply #15 on: February 11, 2009, 10:00:58 am »
Thanks for posting the pictures, now I see what you mean. The rear of the fuselage is concave and provides enough clearance. interesting.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline cluttonfred

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Re: Flying Flapjacks
« Reply #16 on: February 12, 2009, 03:13:12 am »
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
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Offline OM

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Re: Flying Flapjacks
« Reply #17 on: August 06, 2010, 01:11:57 am »
...A few clips of the Flapjack in flight:










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



Offline Antonio

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Re: Flying Flapjacks
« Reply #18 on: August 06, 2010, 06:30:32 am »
What a great renders, I'd love to see it as jpg files!

Offline OM

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Re: Flying Flapjacks
« Reply #19 on: August 06, 2010, 10:57:18 am »
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.

Offline PlanesPictures

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Offline walter

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Re: Flying Flapjacks
« Reply #21 on: August 06, 2010, 11:34:45 am »
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?

Offline walter

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Re: Flying Flapjacks
« Reply #22 on: August 06, 2010, 11:36:11 am »
....forgot to mention it had a largely so called Geodetic construction.

Offline Antonio

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Re: Flying Flapjacks
« Reply #23 on: August 06, 2010, 01:11:35 pm »
Thanks Mr Gatial!

Offline Skyblazer

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Re: Flying Flapjacks
« Reply #24 on: August 06, 2010, 02:40:49 pm »
...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!


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:

Offline OM

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Re: Flying Flapjacks
« Reply #25 on: August 06, 2010, 08:06:38 pm »
Quote
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.

Offline Skyblazer

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Re: Flying Flapjacks
« Reply #26 on: March 26, 2012, 01:50:58 pm »
An item published in the French Science et Vie monthly magazine circa 1946-47:
« Last Edit: March 26, 2012, 01:52:50 pm by Stargazer2006 »

Offline Skyblazer

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Re: Flying Flapjacks
« Reply #27 on: March 26, 2012, 01:54:58 pm »
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!).

Offline Abraham Gubler

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Re: Flying Flapjacks
« Reply #28 on: March 26, 2012, 04:18:45 pm »
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.
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Offline Jemiba

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Re: Flying Flapjacks
« Reply #29 on: March 26, 2012, 09:21:23 pm »
Is it just perspective distortion, or really a twin-seat cockpit ?
It takes a long time, before all mistakes are made ...

Offline Skyblazer

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Re: Flying Flapjacks
« Reply #30 on: March 27, 2012, 12:51:25 am »
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"...  ::)

Offline Dass.Kapital

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Re: Flying Flapjacks
« Reply #31 on: April 01, 2012, 11:22:17 am »
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.  :)

Offline AeroFranz

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Re: Flying Flapjacks
« Reply #32 on: April 02, 2012, 06:54:06 am »
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.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline Dass.Kapital

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Re: Flying Flapjacks
« Reply #33 on: April 02, 2012, 10:19:06 am »
*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.

Offline AeroFranz

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Re: Flying Flapjacks
« Reply #34 on: April 02, 2012, 02:35:07 pm »
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?
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline Tailspin Turtle

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Re: Flying Flapjacks
« Reply #35 on: April 02, 2012, 06:59:30 pm »
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.

Offline taildragger

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Re: Flying Flapjacks
« Reply #36 on: April 03, 2012, 01:52:07 am »
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.
« Last Edit: June 16, 2012, 12:26:15 am by taildragger »

Offline Dass.Kapital

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Re: Flying Flapjacks
« Reply #37 on: April 03, 2012, 12:57:10 pm »
Ah! *Nods*

Cool!

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

Much cheers to you and yours.

Offline Richard N

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Re: Flying Flapjacks
« Reply #38 on: April 07, 2012, 11:14:07 pm »
A shot of the restored V-173 taken in February.

Offline Richard N

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Re: Flying Flapjacks
« Reply #39 on: April 07, 2012, 11:52:45 pm »
Alfa Model ( http://www.alfamodel.cz/index.htm ) of the Czech Republic built a prototype flying model of the V-173 and it appears to have had flapping blade hinges.  I have posted a video of it in flight on the RC Groups site here:  http://www.rcgroups.com/forums/showthread.php?t=1301243#post15939960 
« Last Edit: April 07, 2012, 11:56:16 pm by Richard N »

Offline mboeller

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Re: Flying Flapjacks
« Reply #40 on: April 08, 2012, 07:00:06 am »
I read somewhere, I don't recall where, a modern technical assessment of the XF5U. 

Did you mean this PDF:

http://www.eaach1.org/Design/DGIIcom3.pdf

Offline taildragger

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Re: Flying Flapjacks
« Reply #41 on: April 08, 2012, 10:32:55 am »
No, I haven't seen that before, but the article makes it clear that vibration was a major problem encountered during ground testing.  The account I remember was more of an engineering analysis and speculated that the program would have run into vibration problems that were beyond the current state of knowledge had it progressed to flight testing.  It sounds like Vought actually got a pretty good taste of these and that they may have been a major reason for the project's termination.   

Offline robunos

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Re: Flying Flapjacks
« Reply #42 on: April 25, 2012, 03:00:49 pm »
There's a rather good article about the V-173 and XF5U-1, in the November and December 1975 issues of 'Aeroplane Monthly', written by Art Schoeni.
I wont post the whole article, obviously, but here are some pertinent quotes and images :-


"In a design competition at NACA in 1933
he [Zimmerman] designed a circular-wing aeroplane
that was to fly at high speed and yet
hover like a helicopter.
His design won the competition with its
aerodynamic excellence and sound engineering.
However, NACA rejected the idea for further
development because it was "too advanced".


 As originally planned, the little aircraft was to
carry three passengers lying prone to promote
streamlining, changing to upright position in flight.
The idea was incorporated in a US patent
 procured by Zimmerman in 1938,
but he had abandoned it before
then as being marginal in comfort.

 The design called for the ultimate
lighter to have large props with
helicopter-like flapping blades that
would support it in hovering flight.
Thus there was talk of an
aeroplane that could take off vertically
and fly forward at 500 m.p.h.

Before Guyton made the V-l75’s
first flight, full-scale wind tunnel tests
at Langley Field indicated that the
high induced drag of the low aspect
ratio wing would be partially com-
pensated for by the interaction of the
large props rotating in opposite direc-
tions ahead of the wing. Wing tip
vortices which cause loss of lift on
conventional wings were nullified by
having each propeller rotating counter
to the vortices.

vibration in the cockpit was a per-
sistent problem. This was caused by
resonant frequency between the pro·
pellers and the nacelle structure,
which Zimmerman greatly alleviated
by installing vibration dampers on
the propellers. The problem was not
met in the heavily constructed XF5U-1,
but it led to development of articu-
lated propeller blades in the fighter
to avoid the non-symmetrical airflow
at high angles of attack.

"Being a former naval carrier pilot,
I was keen for the idea of vertically
landing a 500 m.p.h. fighter to a hook
 installation on a cruiser or battleship."
[Boone T. Guyton, V-173 test pilot.]

Full-scale wind tunnel tests of the
Pancake were run in September 1941,
at NACA’s Langley Field, Virginia.
Following successful completion of
these, the Navy asked Vought to
design and build two military versions
of the VS-515, which were designated
the XF5U-1. One would be a flight test
aircraft and the other for static testing
in the laboratories.

completed June 7. 1943. By November
it was decided that the interim propellers
on the XFSU-1 would not do,
and that propellers with articulated
or "flapping" blades would be
required.

Gear box problems in the big right-
angle. drive shafts to each propeller
had negated the chance to fly the
XF5U-1 safely from any airfield other
than Muroc. The quarter-million dollar
price tag on a test programme also
was a factor—the Navy preferred to
spend the money on jet aircraft. The
complicated shafting and gear boxes
developed by Vought engineers
presented problems that might. have
hampered the project anyway. Other
turboprop projects of that era also
were having gearbox trouble.

The original propellers installed on
the XF5U-1 lighter were conventional
Hamilton Standard Hydromatics,
similar to those on the F4U-4 Corsair.
When it was discovered that flapping
blades would be required to avoid
vibrration by unsymrnetrical airflow
and to resist heavy loads when flying
at high angles of attack, Zimmerman
had a problem.
The new props were de-signed by
Zimmerman with Vought engineers’
help and built by Vought. "For a time
it appeared the project would have
to be abandoned," Zimmerman said,
"but after a desperate weekend of
work I came up with a design using
two pairs of teetering blades, similar
to the Bell helicopter rotor, one pair
mounted ahead of the other to form
a four-bladed propeller"

Vought's machine was expected to
achieve a speed range from 40 to 425 m.p.h
with the original engines, 20 to 460
m.p.h. with water injection engines,
and 0-550 m.p.h. with gas turbine
powerplants.

Guyton and William Millar, another
company test pilot later killed in an
F7U-1 Cutlass crash, made numerous
taxi tests in the XF5U-1. On one
occasion it lifted briefly off the runway,
a common occurrence on early
test runs."




In the PDF posted by mboeller, above, it's stated that the XF5U-1 was scrapped at Edwards, whereas Schoeni says that the XF5U-1 never went to Muroc, as it then was, instead being scrapped at the Vought plant.
Likewise the PDF says that the V-173 originally flew with a prone pilot arrangement, however Schoeni makes no mention of this, and I've not seen any images of the V-173 with a prone cockpit, other than the one from the 'Aeroplanes Vought' book, (available online at http://celticowboy.com/AV2/index.htm) posted below.


cheers,
         Robin.
« Last Edit: April 25, 2012, 03:02:22 pm by robunos »
Where ARE the Daleks when you need them......

Offline Johnbr

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Re: Flying Flapjacks
« Reply #43 on: April 25, 2012, 04:06:26 pm »
Here is a cutaway.

Offline AeroFranz

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Re: Flying Flapjacks
« Reply #44 on: April 25, 2012, 06:25:53 pm »
Robunos,


thanks for taking the time to post parts of the article. I have been trying to figure out if there is actually truth to the widely reported statements of reduced induced drag thanks to counter-rotation of the props. In the book "Radical wind tunnels" the assertion is made that wind tunnel tests showed little or no difference with models having either sense of rotation. I need to find the relevant NACA paper on NTRS...

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Offline Sundog

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Re: Flying Flapjacks
« Reply #45 on: April 25, 2012, 07:27:06 pm »
Robunos,


thanks for taking the time to post parts of the article. I have been trying to figure out if there is actually truth to the widely reported statements of reduced induced drag thanks to counter-rotation of the props. In the book "Radical wind tunnels" the assertion is made that wind tunnel tests showed little or no difference with models having either sense of rotation. I need to find the relevant NACA paper on NTRS...

It would seem considering the the size of the propellers to the wing, they would dominate the flowfield, regardless of rotation. I think I would be more concerned with their effect on alpha, more so than induced drag.

However, they may have reduced induced drag at higher alpha simply be energizing the airflow at higher angles of attack. Or to put it another way, at higher angles of attack, propulsive lift relieves the wing of having to lift as much, thereby reducing induced drag.

Which gets into what I would like to know. Did the propellers flow field effectively make the lift curve of the wing itself flatter but at a higher coefficent of lift than an equivalent planform without being in a propellers flow field? let me know if you run across any lift curve slopes for the models in powered flight. I would also like to know how it was effected based on power/prop pitch settings.

Offline robunos

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Re: Flying Flapjacks
« Reply #46 on: April 26, 2012, 02:38:38 pm »
This any help?...


"LANGLEY FULL-SCALE TUNNEL INVESTIGATION OF A 1/3-SCALE MODEL OF THE CHANCE VOUGHT XF5U -1 AIRPLANE"




http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050019375_2005009856.pdf



"The results of investigation of a 1/3-scale model of the
Chance Vought XF5U-l airplane in the Langley full-scale tunnel are
presented in this report. The maximum lift and stalling characteristics
of several model configurations, the longitudinal stability
characteristics of the model, and the effectiveness of the control
surfaces were determined with the propellers removed. The propulsive
characteristics, the effect of propeller operation on the
lift, and the static thrust of the model propellers were determined
at several propeller-blade angles."


"The peak propulsive efficiencies for f3 = 200 and f3 = 300
were increased 7 percent at CL 0.67 and 20 percent at CL 0.74,
respectively, with the propellers rotating upward in the center than
with the propellers rotating downward in the center."


cheers,
         Robin.
Where ARE the Daleks when you need them......

Offline Sundog

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Re: Flying Flapjacks
« Reply #47 on: April 26, 2012, 06:19:25 pm »
Excellent! Thanks Robunos. :)

Offline robunos

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Re: Flying Flapjacks
« Reply #48 on: April 29, 2012, 01:49:45 pm »
I have to say, it's my opinion that any reduction in induced drag/increase in propulsive efficiency was only a bonus of this configuration, and that the main reason for it's use was to allow the use of large diameter proprotor type propellers, to enable hovering and thereby VTOL...


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Offline robunos

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Re: Flying Flapjacks
« Reply #49 on: June 15, 2012, 09:46:57 am »
While looking for something else, as always, I found another 'flying flapjack', the Hatfield 'Little Bird', and the story behind it, is well....
In 1926, at the age of 18, Milton Hatfield built his own aeroplane, from Nicholas Beazly plans. (Does anyone know what this 'plane would have looked like?) He also converted the engine from a ex-police motorcycle engine. He also bought a set of wheels and tyres. The aircraft never flew. Hatfield's father insisted that the young Hatfield get a pilot's licence first. However, since an hour's flying lesson cost two week's wages, Milt still had not soloed by 1932. He had also married in 1931.

Then Milt caught a break. Cloyd Snyder, the inventor of the yet-to-be named Arup, wished to convert his 'Snyder Glider', into a powered aircraft, eventually the Arup no.1. To do this he needed an engine, and some wheels. Young Milt had just what he needed. A deal was struck, Milt would let Snyder have his aeroplane, and Glen Doolittle, Snyder's test pilot, would teach Hatfield to fly. After two hours tuition, Milt soloed and obtained his licence.
By 1935, Hatfield was working in aviation, skywriting. The Arup organisation, in contrast was on it's knees. They sold the engineless Arup No.2 to a stunt flyer named Franks, who installed the same type of engine, a 3-cylinder Szekeley, as in Milt's plane. However, neither Franks, nor several other pilots was able to get the Arup into the air. In the end, the propeller was broken. Of course Franks asked Hatfield for the loan of HIS propeller. Milt agreed, but on condition that he flew the Arup. (He had watched the others' attempts, and worked out where they had gone wrong) With his propeller fitted. Milt climbed in, and flew the Arup without problems. Then he told Franks 'how to do it'. Soon after, Milt was also flying the Arup No.4 as well. He never forgot his time flying these aircraft.
After a long and varied career in aviation, and other industries, Milt Hatfield retired. He started building aeroplanes again. In 1985 he decided to build a microlight version of the Arup concept. Built of steel tube and wood, and powered by a 27 hp Rotax engine, the first version had 'Junkers-style' separate elevons, along with spoilers. The wing was arranged to fold up against the fuselage, to allow the 'plane to be towed behind a car. The structure was fabric covered, the engine cowling glass fibre. and the canopy was heat-shrunk Mylar. Milt named his aircraft 'Little Bird'.
Following fast taxiing tests, it became clear that the original elevons were ineffective. These were removed, and the trailing edge of the wings aft of the rear spar cut away, and hinged to act as elevons. The spoilers were deleted. On May 27th, 1987, the aircraft flew for the first time. Flight characteristics were good, two quirks of the configuration being the abilty to turn using rudder or the stick only-no need to use both- and a stable rapid sink rate at low speeds and high angle of attack.
From 'Aeroplane Monthly', September 1987.


cheers,
         Robin.
Where ARE the Daleks when you need them......

Offline Skyblazer

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Re: Flying Flapjacks
« Reply #50 on: June 15, 2012, 05:33:41 pm »
Very interesting! Thanks for sharing.

Offline robunos

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Re: Flying Flapjacks
« Reply #51 on: July 02, 2012, 09:32:35 am »
Doing a bit more digging, it seems that Milt Hatfield built 3 Little Birds in total, each one differing from the others. #2 and #3 incorporated fibreglass in their construction, to varying degrees. All three still survive, but not in flyable condition.
See here :-
http://www.oshkosh365.org/ok365_DiscussionBoardTopic.aspx?id=1235&boardid=147&forumid=180&topicid=4813
and here :-
http://www.homebuiltairplanes.com/forums/members/littlebird-albums-little-birds.html


cheers,
         Robin.

Where ARE the Daleks when you need them......

Offline pesholito

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Re: Flying Flapjacks
« Reply #52 on: July 15, 2014, 08:16:47 am »
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
I am looking for more information on the Boeing 390, 391, 396 projects. Does anyone have any more, not posted here?

Offline hesham

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Re: Flying Flapjacks
« Reply #53 on: July 15, 2014, 08:42:13 am »
Hi Pesholito,please see;


http://aerofiles.com/_boe.html

Offline pesholito

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Re: Flying Flapjacks
« Reply #54 on: July 15, 2014, 08:49:12 am »
Hi Pesholito,please see;


http://aerofiles.com/_boe.html


Thank you hesham! I saw this. I was trying to search through google but there isn't much. I was hoping for any archive drawings or documents.

Offline Jemiba

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Re: Flying Flapjacks
« Reply #55 on: July 15, 2014, 09:13:16 am »
From Jareds article in Airpower July 2002, some pictures of the model 390, 391 and
396. I'm pretty sure, I've made a drawig of the 390 at least, but cannot find it at the moment.   :-\
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Offline robunos

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Re: Flying Flapjacks
« Reply #56 on: July 15, 2014, 10:26:04 am »
Shiny!
It's hard to tell from these images, did the Model 390/1 in corporate dihedral?

cheers,
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Offline Jemiba

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Re: Flying Flapjacks
« Reply #57 on: July 15, 2014, 10:43:14 am »
Not mentioned in that article explicitely, I think. But if the 3-view found on
the Unicraft site is correct, then :Yes.
It takes a long time, before all mistakes are made ...

Offline robunos

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Re: Flying Flapjacks
« Reply #58 on: July 15, 2014, 11:36:58 am »
Thanks, I ask because to me at least, the Model 390/1 planform is very similar to that of the Arups. Now the Arups 1,2, and 4 all had flat wings (no dihedral) and flew well, whereas the Arup 3 did have dihedral, but was reportedly a poor performer, flying only once. I was just wondering whether the Boeing aircraft would have similar characteristics...

cheers,
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Offline XP67_Moonbat

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Re: Flying Flapjacks
« Reply #59 on: May 15, 2015, 11:09:43 am »
Brief write-up on the XF5U.
http://www.jitterbuzz.com/MAN_1947_01.HTML


And here's a PDF of Modern Mechanix's May '47 piece on Vought's Flying Pancake projects. Love the cutaway graphics! You gotta love these old-school scientific articles! Especially when you can appreciate that no computers were used for the illustrations back then. Those cutaway graphics were done by hand. No CG.
http://www.jitterbuzz.com/manreal/flying_flapjack_mechanix_05_1947.pdf
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Offline cluttonfred

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Re: Flying Flapjacks
« Reply #60 on: May 19, 2015, 02:16:49 am »
Thanks for the PDF, a wonderful find including the drawings by the great Douglas Rolfe!
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Offline hesham

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Re: Flying Flapjacks
« Reply #61 on: October 19, 2016, 05:56:43 am »
Hi,

here is a flying flapjack concept,created by Mr. Charles Zimmerman,maybe it
was a real design.

http://www.avia-it.com/act/biblioteca/periodici/PDF%20Riviste/Ala/L'Ala%201950%2004.pdf

Offline cluttonfred

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Re: Flying Flapjacks
« Reply #62 on: October 19, 2016, 06:06:04 am »
While the Cylons would have loved this one, it is not an actual design according to the caption, but rather the author's conception of a "modern flying saucer derived from the Zimmerman projects."  Oddly, the author's name is Sergei Sikorsky.
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Offline hesham

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Re: Flying Flapjacks
« Reply #63 on: October 19, 2016, 06:12:34 am »
Thank you my dear Cluttonfred.
« Last Edit: October 19, 2016, 06:27:40 am by hesham »

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Re: Flying Flapjacks
« Reply #64 on: October 19, 2016, 06:28:28 am »

Offline XP67_Moonbat

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Re: Flying Flapjacks
« Reply #65 on: October 19, 2016, 02:48:11 pm »
Wouldn't have this lost stability without propellors?
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Offline djfawcett

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Re: Flying Flapjacks
« Reply #66 on: October 19, 2016, 07:41:12 pm »
Actually, the props de-stabilize rather than stabilize the aircraft.  If it were a pusher, then the props would stabilize.

Offline _Del_

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Re: Flying Flapjacks
« Reply #67 on: October 19, 2016, 09:21:05 pm »
But you do lose the theoretical benefits of having the propwash pushing over the lift/control surfaces, I should think.

Offline XP67_Moonbat

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Re: Flying Flapjacks
« Reply #68 on: October 20, 2016, 11:16:42 am »
True. I was a little hazy on that.
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Offline Avimimus

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Re: Flying Flapjacks
« Reply #69 on: October 28, 2016, 01:14:28 pm »
Regarding the Boeing 390: Does anyone have dimensions or specifications (e.g. weights)?

I've found a couple low-quality scans of drawings showing the internal structure but I can't make out any information regarding the scale of the design.

 *edit - largely solved due to the help of an intrepid forum member*
« Last Edit: November 01, 2016, 09:28:31 pm by Avimimus »

Offline Abraham Gubler

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Re: Flying Flapjacks
« Reply #70 on: November 01, 2016, 07:31:57 pm »
But you do lose the theoretical benefits of having the propwash pushing over the lift/control surfaces, I should think.

The key invention of Zimmermann's 'Flying Pancake' design is that the propwash reduces drag. At low velocities it does enable the wing to generate lift and it provides control authority but the location and rotation of the propellers is all about drag. Low aspect ratio wings with high chords towards the tip (ie square or round wings but not deltas) have large wing tip vortices. These vortices generate induced drag and getting rid of them is what winglets do on your typical airliner. On the Flyjng Pancake the propellers are located along an axis very close to the wing tip and counter rotate against the wingtip vortices. So the propwash of the air screws cancels out the vortices and therefore improves the lift drag ratio if the wing. So you get the high lift at low velocity benefit of the very low aspect ratio wing without the high induced drag of the same wing especially at higher velocities.

So everytime you see a Flyjng Pancake design without the wing tip props you can bet it wasn't designed by an engineer and though it would fly it would be very slow like any other typical LR wing STOL aircraft (PC-6 Porter, Scottish Pioneer, DHC Caribou, etc). Perhaps you could make a jet powered Flying Pancake but you would need engine bleed air blowers along the tips. And the power of the blowers would have to increase as your airspeed increased to counter increasing induced drag.
« Last Edit: November 02, 2016, 12:55:07 pm by Abraham Gubler »
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Offline Tailspin Turtle

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Re: Flying Flapjacks
« Reply #71 on: November 02, 2016, 08:43:00 am »
"Low aspect ratio wings with high chords towards the tip (ie square or round wings but not deltas) have large wing tip vortices that spill out and down from the top tip of the wing."

Actually, the air under the wing wants to go up. If you look at the left wingtip from behind, the vortice is rotating clockwise, up and in. The left propeller is rotating counterclockwise when viewed from the rear to counteract this.
« Last Edit: November 02, 2016, 08:47:01 am by Tailspin Turtle »

Offline Abraham Gubler

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Re: Flying Flapjacks
« Reply #72 on: November 02, 2016, 12:53:21 pm »
Lol yes. I tried to write that message three times in the midst of doing something else and for some reason got downwash in the brain making me think the vortices go down... But really I should have been trying to think less and just remember all those great sights of planes landing where you can see the vortices spining up and over behind the wing tips. I think there was a great scene in Top Gun with that...
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

Offline Avimimus

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Re: Flying Flapjacks
« Reply #73 on: December 17, 2016, 08:06:18 pm »
A fairly new very low aspect ratio design for a single seat ESTOLL touring aircraft:
http://pietroterzi.com/site/pro/lucy.htm

Offline hesham

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Re: Flying Flapjacks
« Reply #74 on: December 18, 2016, 04:45:57 am »
A fairly new very low aspect ratio design for a single seat ESTOLL touring aircraft:
http://pietroterzi.com/site/pro/lucy.htm

Is it a real one ?.


Offline Motocar

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Re: Flying Flapjacks
« Reply #75 on: December 24, 2016, 02:28:07 am »
Cutaway Sikorsky concept, drawing by Zimmerman italian magazin L'Ala

Offline hesham

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Re: Flying Flapjacks
« Reply #76 on: December 24, 2016, 04:23:03 am »
Nice work Motocar.

Offline hesham

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Re: Flying Flapjacks
« Reply #77 on: June 04, 2017, 09:09:40 am »
From Le Fana 391.

Offline hesham

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Re: Flying Flapjacks
« Reply #78 on: August 11, 2017, 10:43:24 am »
Doing a bit more digging, it seems that Milt Hatfield built 3 Little Birds in total, each one differing from the others. #2 and #3 incorporated fibreglass in their construction, to varying degrees. All three still survive, but not in flyable condition.
See here :-
http://www.oshkosh365.org/ok365_DiscussionBoardTopic.aspx?id=1235&boardid=147&forumid=180&topicid=4813
and here :-
http://www.homebuiltairplanes.com/forums/members/littlebird-albums-little-birds.html


cheers,
         Robin.

Hi;

http://aviadejavu.ru/Site/Crafts/Craft34682.htm

Offline John Frazer

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Re: Flying Flapjacks
« Reply #79 on: March 21, 2018, 02:28:24 pm »
The Vought/Zimmerman/Sikorsky effort might be called "Zimmerman's folly", or how the navy threw away a superior fighter, by not building the Boeing little 390 test plane, as a sincere follow-on to the performance of the Arup.

The Arup S-2 flew for NACA and the Army and CAA. Zimmerman worked for NACA and was on the team that saw the Arup fly. After that, his idea for a VTOL toy with short aspect-ratio and twin screws gelled. (his patents and his participation in that contest followed the successful careers of the Arup plane He plainly was following the interest overseas and here in low-aspect ratio, and the success of Arup gave him what he thought he needed for his VTOL experiments.)
But the Arup nor the V-173 did not need the giggle-factor-inducing silly huge flappy props over the wing-tips.
They were a distraction from the performances the Arup plane put on, they are an un-necessary over-complication, and in the XF5U they killed what could have been a good plane (simple twin-engine & prop plane would have flown, and probably done extraordinarily well if not for the complex power system for those wing-tip things).

Short aspect ratio planes do not suffer abnormally high drag due to wing-tip wash-around while in cruise. In cruise low-A flight, they are sleek, like a little all-wing. Several planforms of low aspect-ratio all-wing and unitary wing/body test planes have flown well.
In low speed high-A flight, the wing-tip vortices wrap around and join the air over the top of the wing, preventing it from separating and stalling. That gives them low aspect-ratio lanes their phenomenal low-speed, high-A performance, typically staying in flight slower than their landing speed, limited by the height of the nose wheel.
You don't want to counter it. You want the vortex-lift at low speeds, and it disappears in normal flight.

So, we might ask why the Navy chose to explore Zimmerman's toy, and ignored the Boeing plane (which appeared more sinister than silly).  If followed-up with a flapjack fighter, it would have been like a Bearcat, with more speed, range, payload, and >40 kt landing speed. The planform would have taken over the fleet and pretty soon all military aviation. When the Arup patents expired, all aviation would have been using it.

The advent of the Jet Age didn't kill it. The Navy built and operated piston-prop planes for logistics & support and as tactical combat planes until the '70s.
The Vought jet-skimmer or the Sikorsky models would have been built instead of the P-80, and a supersonic version would have followed.
 See the Eschelman "Flying Flounder" for a possibility of what such a thing might have looked like.
The Unicraft model kit is the only thing I can find online for this.

The follow on post about William Horton designs was split and merged with the older thread here:

https://www.secretprojects.co.uk/forum/index.php/topic,5996.msg326793.html#msg326793
« Last Edit: March 24, 2018, 11:59:34 pm by Jemiba »

Offline Motocar

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Re: Flying Flapjacks
« Reply #80 on: March 26, 2018, 06:54:25 am »
The Sawyer Skyjacket II, note in WP:
https://en.wikipedia.org/wiki/Sawyer_Skyjacker_II

Offline AeroFranz

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Re: Flying Flapjacks
« Reply #81 on: September 25, 2018, 01:58:36 pm »
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?

I just came across this interesting video of Jack Reeder, longtime engineer and test pilot at Langley
at 48:30, he says there was little practical improvement with turning the props against the direction of the vortices. He also talks about the need to provide flapping motion for the propellers.
https://www.youtube.com/watch?v=HRZu78WozBo&feature=youtu.be
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Offline Sundog

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Re: Flying Flapjacks
« Reply #82 on: September 25, 2018, 05:48:35 pm »
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?

I just came across this interesting video of Jack Reeder, longtime engineer and test pilot at Langley
at 48:30, he says there was little practical improvement with turning the props against the direction of the vortices. He also talks about the need to provide flapping motion for the propellers.
https://www.youtube.com/watch?v=HRZu78WozBo&feature=youtu.be

My understanding is that the problems with the flapping propellers is why the XF5U-1 was never flown.

Offline AeroFranz

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Re: Flying Flapjacks
« Reply #83 on: September 25, 2018, 08:25:27 pm »
IIRC, the prototype had F4U props, but there was always an understanding that it would get four-bladed teetering props. I think the decision to ax the program had more to do with the obsolescence of props versus jets.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline Sundog

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Re: Flying Flapjacks
« Reply #84 on: September 25, 2018, 09:10:42 pm »
IIRC, the prototype had F4U props, but there was always an understanding that it would get four-bladed teetering props. I think the decision to ax the program had more to do with the obsolescence of props versus jets.

I understand that, but I mean why they didn't just fly it for just the research. Of course, in that regard, I often wondered why they didn't just fly it with the F4U props, from a research standpoint.

Offline AeroFranz

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Re: Flying Flapjacks
« Reply #85 on: September 26, 2018, 07:00:25 am »
Amen, brother. I'm sure there were some interesting lessons to be had from flying a novel configuration...although to be fair, they had tunnel-tested and flown the V-173.
I checked the references i have on the XF5U. The props were supposed to be Hamilton Standard four bladed teetering, especially designed for the vehicle. They weren't ready by the time the prototype was rolled out, so it was equipped with F4U Hydromatic units. Turns out it was a very poor match and they couldn't fly it like that. While waiting for the props, Zimmerman did some redesign based on lessons learned while ground testing. the cockpit was redesigned, and he added a trailing edge surface between the verticals.
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Offline riggerrob

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Re: Flying Flapjacks
« Reply #86 on: September 26, 2018, 04:41:50 pm »
They might have been able to fly it horizontally with F4U props, but could not have demonstrated any high angle of attack flight with conventional propellers. They also had problems with propeller vibration on the (fly able) mock-up.

Offline GWrecks

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Re: Flying Flapjacks
« Reply #87 on: September 26, 2018, 06:55:51 pm »
The Vought/Zimmerman/Sikorsky effort might be called "Zimmerman's folly", or how the navy threw away a superior fighter, by not building the Boeing little 390 test plane, as a sincere follow-on to the performance of the Arup.

The Arup S-2 flew for NACA and the Army and CAA. Zimmerman worked for NACA and was on the team that saw the Arup fly. After that, his idea for a VTOL toy with short aspect-ratio and twin screws gelled. (his patents and his participation in that contest followed the successful careers of the Arup plane He plainly was following the interest overseas and here in low-aspect ratio, and the success of Arup gave him what he thought he needed for his VTOL experiments.)
But the Arup nor the V-173 did not need the giggle-factor-inducing silly huge flappy props over the wing-tips.
They were a distraction from the performances the Arup plane put on, they are an un-necessary over-complication, and in the XF5U they killed what could have been a good plane (simple twin-engine & prop plane would have flown, and probably done extraordinarily well if not for the complex power system for those wing-tip things).

Short aspect ratio planes do not suffer abnormally high drag due to wing-tip wash-around while in cruise. In cruise low-A flight, they are sleek, like a little all-wing. Several planforms of low aspect-ratio all-wing and unitary wing/body test planes have flown well.
In low speed high-A flight, the wing-tip vortices wrap around and join the air over the top of the wing, preventing it from separating and stalling. That gives them low aspect-ratio lanes their phenomenal low-speed, high-A performance, typically staying in flight slower than their landing speed, limited by the height of the nose wheel.
You don't want to counter it. You want the vortex-lift at low speeds, and it disappears in normal flight.

So, we might ask why the Navy chose to explore Zimmerman's toy, and ignored the Boeing plane (which appeared more sinister than silly).  If followed-up with a flapjack fighter, it would have been like a Bearcat, with more speed, range, payload, and >40 kt landing speed. The planform would have taken over the fleet and pretty soon all military aviation. When the Arup patents expired, all aviation would have been using it.

The advent of the Jet Age didn't kill it. The Navy built and operated piston-prop planes for logistics & support and as tactical combat planes until the '70s.
The Vought jet-skimmer or the Sikorsky models would have been built instead of the P-80, and a supersonic version would have followed.
 See the Eschelman "Flying Flounder" for a possibility of what such a thing might have looked like.
The Unicraft model kit is the only thing I can find online for this.

The follow on post about William Horton designs was split and merged with the older thread here:

https://www.secretprojects.co.uk/forum/index.php/topic,5996.msg326793.html#msg326793

This seems more than a little fishy to me. For starters that jet F5U image posted is clearly a shooped version of another one. Secondly, there is plenty of evidence that wingtip vortices exist, so unless the implication is that propellers can't do anything about it that's not really saying much. Lastly, it's worth noting that Convair had worked with a similar layout for their GETOL (Ground Effect Take-Off and Landing) proposals, so there's a convergent evolution process there too.

EDIT: Looks like it's not shopped after all, but the landing gear arrangement is clearly nonsensical (The only real changes were the removal of propellers and addition of jet nozzles, and it still uses the same landing gear!) and as a result I have trouble even imagining this was proposed.

Another thing worth mention, the F5U with piston engines would've been faster than most jet aircraft during WWII. There was a turboprop version suggested but I can't find images of it. All of this points (At least to me) in the direction of the propellers existing for a reason. Oh...

The planform would have taken over the fleet and pretty soon all military aviation. When the Arup patents expired, all aviation would have been using it.

...This is bait, isn't it?
« Last Edit: September 26, 2018, 07:03:59 pm by GWrecks »
↑↑↓↓LRLRBA

Offline TsrJoe

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Re: Flying Flapjacks
« Reply #88 on: September 26, 2018, 11:49:50 pm »
You do realise the drawing for the 'jet Vought' is fake, original source is a piece by Bill Rose, UFO Magazine, Vol. 14, No.5  1999 ! and appearing in his subsequent 'saucer' Secret Projects series volume  :o
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Offline hesham

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Re: Flying Flapjacks
« Reply #89 on: January 28, 2019, 07:18:02 am »
From Ailes 6/1946,

here is a hypothetical drawing to a Vought Flapjack.

Offline Motocar

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Re: Flying Flapjacks
« Reply #90 on: February 02, 2019, 01:16:13 pm »

Offline Motocar

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Re: Flying Flapjacks
« Reply #91 on: February 06, 2019, 03:49:30 pm »
Cutaway Flying Saucer ???, author unknow an retouched by Motocar