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August 28, 2009 4:00 AM   Subscribe

The ring wing or annular airfoil is an aircraft design which has been experimented with throughout the history of aviation with some interesting variations. It has served as the inspiration for several paper airplane designs, model airplanes of course, and a variety of children's toys. The capabilities imagined by the French coléoptère engineers of the 1950's and 1960's and the U.S. "flying tank" designers are available today at least in the form of unmanned vehicles (large PDF brochure, 6 minute video download, 1½ minute YT news clip). The technology has also been adapted to become the surfboard tunnel fin and there are underwater UAVs as well.
posted by XMLicious (13 comments total) 9 users marked this as a favorite
The autonomous UAV in the "6 minute video download" is what made me think of Doctor Who.

There was one more link I didn't put in: this image, from the bottom of this page, which is listed as the "August Klein Ringwing" from 1910 Germany. But I couldn't find an independent reference to it or a German aviation guy named August Klein.
posted by XMLicious at 4:10 AM on August 28, 2009

I don't have an avante garde surfboard, but I do have a surrealist one.
Although a lot of people think it's a bowler hat.
posted by le morte de bea arthur at 4:14 AM on August 28, 2009

Since you didn't link to it, I guess you must not have heard about this the same place I did recently.
posted by DU at 4:20 AM on August 28, 2009


I "invented" this myself, as a kid, with the bottom of a caulk tube..the metal ring gives it a little weight and the cardboard can be sanded down to make a airfoil.

They fly like nothing pitch it like a baseball and it hauls ass a loong way, raising and dipping a bit but otherwise straight as an arrow.

For me the years 1985-1989 were chock full of boomerangs, White Wings, and Aerobies, so having a homespun flying toy that worked this well seemed like the ultimate score!
posted by chronkite at 4:27 AM on August 28, 2009

Paraphrased from the variation link: The prop encountered incredible stress when moving from channeled air to unchanneled air.

So my question is, why a channel and not a full ring?
posted by Pollomacho at 4:42 AM on August 28, 2009

Annular ring airfoils suffered the same aerodynamic problems that relegated bi-planes and other multi-wing designs to history's dust bin, except in niche applications: comparatively high drag and high weight, for the lift they produce. The hope of early aeronautical engineers who experimented with them, was that they would offer more forgiving stall characteristics than conventional wings, particularly in maneuvering flight, but that was never satisfactorily demonstrated.

Perhaps one of the "stealth" applications for the idea survives in the improved engine nacelle designs of Boeing 737-300 and later variants of the 737 "Classic" series, which in conjunction with wing shape refinements, allowed Boeing to fit higher power turbofan engines to the later 737 models, without a complete undercarriage redesign, to allow for the much greater engine diameter. Juggling the nacelle shape and forward position of the engines, relative to the regular wing was an important bit of aerodynamic engineering, which borrowed from previous annular ring wing research.
posted by paulsc at 5:19 AM on August 28, 2009

So my question is, why a channel and not a full ring?

Because you're trying to produce lift. Airfoils are drawn towards areas of low pressure, so by putting a wing surface below the area of low pressure created by the engine, you're producing a net upward force.

A full ring wouldn't produce force in any particular direction.
posted by cillit bang at 5:31 AM on August 28, 2009

The airplane in the first link needs to be circumcised.
posted by mr_crash_davis mark II: Jazz Odyssey at 5:53 AM on August 28, 2009

A full ring wouldn't produce force in any particular direction.

That's only true if the wing is radially-symmetric and, more importantly, is flying at zero-angle of attack. All the examples I have seen so far have full rings.

I can't see the video, but the channelled/unchannelled problem sounds like it happens because the engine mount (and fuselage) is not at the centre of the wing, so the prop spends roughly half its time "outside" the annulus and half its time "inside" it, and sees rapid changes in pressure when it travels between the two.
posted by cardboard at 7:51 AM on August 28, 2009

Airfoils are drawn towards areas of low pressure, so by putting a wing surface below the area of low pressure created by the engine, you're producing a net upward force.

Not exactly. Airfoils will generate areas of low pressure inside an airstream, but that's not really the full explanation of aerodynamics. See Kutta-Joukowski theorem. The Kutta Condition states that there must be a stagnation point at sharp corners in a moving fluid, which applies to the trailing edge of an airfoil. This is where the sort of hand-wavy explanation about pressure and wings comes from - that air going over the top and bottom of the wing must reach the trailing edge at the same time, and the curve of the wing equates to a longer distance on top, so the top flow must go faster to reach the trailing edge which produces low pressure over the wing. This is useful as a qualitative way to grasp the concepts, but is basically wrong.

Airfoils do generate low pressure on the top surface. Propellers are airfoils that travel in a circle. So, you can think of propeller propulsion as a big fan in front generating low pressure in front of the propeller to suck the airplane forward. So you're actually getting a high pressure system behind the prop, which then flows over the top surface of the wing - but there should be low pressure on top of the wing! Confusing, huh?

You're right that a ring would not generate any net upward lift (if the entire thing wasn't also spinning, but that's for another class), but there are advantages to it. Wings (and propellers and jet engine fans) are prone to inefficiencies at the wing tips (see wingtip vortices). What's happening is that the low pressure air on top of the wing wants to equalize itself with the relatively higher pressure air underneath, and takes the path of least resistance to get there. Since the airplane is moving forward, you end up with a big spiral. You can mitigate this by designing the wings differently (elliptical wings are good for this, but difficult to manufacture), add wing tips, or encase the whole fan in a ring with very tight tolerances. The inlet of the jet engine is shaped much like a ring airfoil, and then the fan blades maintain extremely tight spacing against the fan case to minimize losses.
posted by backseatpilot at 7:56 AM on August 28, 2009 [2 favorites]

This post. Looks like everything old in aviation gets hauled out again at a certain point, perhaps (and we've had this conversation here before), it's because the materials and powerplants (and processing power) to make certain flight structures and platforms can no be properly built for a more feasible cost.

I hope this weird and wonderous wing makes a comeback. It's fun to look at. Speaking of which, I'm flabbergasted at how much pleasure I'm deriving from reading this old Popular Mechanics magazine, on so many levels, the sheer joy of a country on the precipice of making the future a real thing, the optimism and imagination and can do know-how quality, the fact that at the time, there were tons of interesting manufacturers in this country who made interesting products displayed and spoken of with pride in the ads...

I do hope, this country gets back to making things, instead of simply consuming them. Maybe all the money being promised towards a high speed train system by the Obama White House will bring some of that back.

Anyhow, apologies for the derail, just musing out loud.
posted by Skygazer at 10:35 AM on August 28, 2009

That first link is a really frackin' cool (looking) design.

Does anyone have any information about this particular aircraft? The cabin/body seems, to an untrained eye, to be poorly affixed to the annular airfoil.

Do the annular side parts do anything beneficient over, say, a biplane, in this configuration? GIS for other annular airfoils tend towards either completely circular foils.

What ever happened to the "floating body" (?) shape - whatever the kind of body the X-33 was supposed to have.
posted by porpoise at 9:12 PM on August 28, 2009

Yeah, the plane in that first link is how I came across the whole topic because at first I didn't think it could possibly be real. (What actually happened is that I set out to prove that it was a photoshopped image with the ring wing made in a 3D modeler.)

That's the best picture I could find of it, which is from this site and was taken in 2004. Its registration number is EW-067LL and it was built by a guy named Arkady Narushevich (Аркадий Нарушевич in Cyrillic) in Minsk, Byelorus. You can find a few other threads about it around the internet like this one in Spanish with another picture, and this article in Russian seems to be some of the original coverage on it, but unfortunately there doesn't seem to be much info available about it and there don't seem to be any photos of it in flight.
posted by XMLicious at 1:36 AM on August 29, 2009

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