Talk:Closed wing

Material

 * There are two sorts of annular wing: the plane of the ring faces the direction of travel, or the edge of the ring faces the direction of travel, with the aircraft suspended beneath, in helicopter fashion.
 * Aerodynamic design of the proposed Hummingbird aerodynamic aircraft
 * Stanford University paper discussing nonplanar wing surfaces
 * Conclusion: Although highly nonplanar lifting systems offer the possibility of dramatic reductions in vortex drag for wings with specified lift and span, they are not a panacea. Rather, nonplanar wings likely will provide small improvements in total drag when their effect on wing weight is considered, but may still be worthwhile as increments in performance become progressively more difficult to achieve. These configurations do provide more substantial performance benefits in some cases. This is especially true when the concept is fully exploited by resizing or even redesigning the aircraft. In addition to reductions in vortex drag, some of configurations mentioned here have desirable effects on structures, stability and control characteristics, vortex wake hazards, and other practical aspects of the design'. Some particularly interesting concepts that warrant further study include the split tip design, which demonstrates that by manipulating the wake shape as well as the wing shape, some of the advantages of nonplanar wings may be enhanced. The C-wing configuration remains an intriguing design concept with many beneficial characteristics when applied to large aircraft or tailless designs. The implications of this approach remain to be more fully explored.
 * Conclusion: Although highly nonplanar lifting systems offer the possibility of dramatic reductions in vortex drag for wings with specified lift and span, they are not a panacea. Rather, nonplanar wings likely will provide small improvements in total drag when their effect on wing weight is considered, but may still be worthwhile as increments in performance become progressively more difficult to achieve. These configurations do provide more substantial performance benefits in some cases. This is especially true when the concept is fully exploited by resizing or even redesigning the aircraft. In addition to reductions in vortex drag, some of configurations mentioned here have desirable effects on structures, stability and control characteristics, vortex wake hazards, and other practical aspects of the design'. Some particularly interesting concepts that warrant further study include the split tip design, which demonstrates that by manipulating the wake shape as well as the wing shape, some of the advantages of nonplanar wings may be enhanced. The C-wing configuration remains an intriguing design concept with many beneficial characteristics when applied to large aircraft or tailless designs. The implications of this approach remain to be more fully explored.


 * Applicability of these statements to closed wings must be ascertained.


 * The minimization of induced drag in non-planar wing systems (C-wings and annular wings): Investigation on conditions of minimum induced drag of closed wing systems and C-wings, Demasi, L. Published inJournal of Aircraft, 2007-01-01 , 44 (1) , 81-99
 * Abstract: A theoretical method for predicting minimum induced-drag conditions in a nonplanar lifting systems is presented in this paper. The procedure is based on lifting line theory and the small perturbation acceleration potential. Under the hypotheses of linearity and rigid wake aligned with the freestream, optimality conditions are formulated using the Euler–Lagrange integral equation with constraints on fixed total lifting force and wing span. Particular attention is paid to analysis and numerical treatment of the Hadamard finite-part integrals involved in the solution process. The minimum induced-drag problem is then formulated and solved numerically and analytically. In the case of annular wings, closed-form expressions for the optimal circulation distribution, the normalwash, the induced-drag coefficient, and the efficiency are presented. Optimal annular wings and C-wings are extensively analyzed, and comparisons with available results in the literature are presented. It is confirmed that a C-wing presents almost the same induced drag (under optimal conditions) as the corresponding closed-wing system. However, the optimal distributions of circulation are significantly different. All optimal wing systems are also compared to an optimal cantilevered wing and a biplane.
 * Abstract: A theoretical method for predicting minimum induced-drag conditions in a nonplanar lifting systems is presented in this paper. The procedure is based on lifting line theory and the small perturbation acceleration potential. Under the hypotheses of linearity and rigid wake aligned with the freestream, optimality conditions are formulated using the Euler–Lagrange integral equation with constraints on fixed total lifting force and wing span. Particular attention is paid to analysis and numerical treatment of the Hadamard finite-part integrals involved in the solution process. The minimum induced-drag problem is then formulated and solved numerically and analytically. In the case of annular wings, closed-form expressions for the optimal circulation distribution, the normalwash, the induced-drag coefficient, and the efficiency are presented. Optimal annular wings and C-wings are extensively analyzed, and comparisons with available results in the literature are presented. It is confirmed that a C-wing presents almost the same induced drag (under optimal conditions) as the corresponding closed-wing system. However, the optimal distributions of circulation are significantly different. All optimal wing systems are also compared to an optimal cantilevered wing and a biplane.


 * AIAA research paper on joined wings

Belarus example
Don't know if this plane in Belarus is a production model or a one-off: English Russia: Ellipse Wings (multiple photos). --71.162.81.128 (talk) 14:32, 26 May 2009 (UTC)
 * Great find! I've been searching for more info on this plane since I saw the airliners.net pic years back. AniRaptor2001 19:35, 26 May 2009 (UTC)

The Belarus example is definitely not presented correctly. It's an interesting design, but the description as posted here doesn't make any aerodynamic sense. Power is meaningless in this context and, as is the point of this page, attached vortices exist on every standard wing design and they increase induced drag. This closed design may reduce the vortices, thereby reducing induced drag, but this claim says the opposite. I'm removing the performance claim, if anyone can find a better translation of the aerodynamics claims or find a more reputable source I would be happy to be proven wrong. 24.140.19.68 (talk) 16:05, 1 October 2012 (UTC)

Terry and Miranda
Since at least 2009 the article has stated that "the annular wing dates to Terry in 1964 / the boxplane was first proposed by Miranda in 1972". Who is Terry? Who is Miranda? -Ashley Pomeroy (talk) 00:04, 7 May 2011 (UTC)
 * We will probably never know now. :) &mdash; Cheers, Steelpillow (Talk) 17:41, 7 May 2011 (UTC)

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Not enough detail in "Characteristics" and "C-wing"
Under "Characteristics", the sentence beginning "However any claimed aerodynamic advantages are illusory - -" seems to be intended convey the idea from Kroo's VKI paper that the performance of an open system can closely approach that of the closed system with the lowest possible drag, something that isn't obvious from looking at the lift distributions of the different systems, but is nonetheless true, largely due to the fact that the optimum lift distribution on a closed lifting system isn't unique. But to my mind this idea doesn't come across at all in the current version, especially the non-uniqueness part, and I'm going to suggest a re-write.

The next sentence refers to "the downsides of being a fully closed system". I don't see where Kroo identified any "downsides" to speak of, other than a lack of any significant fundamental advantage over open systems. So I'll suggest rewording this too.

It also seems to me that the current version's discussion under "C-wing" isn't adequate to get the key ideas across, especially the relationship of the results in the accompanying graphic to the non-uniqueness issue I raised above, a relationship ref 20 calls attention to. So I think this section also needs a re-write.

I have drafted my suggested changes in my sandbox. Comments, anyone?J Doug McLean (talk) 23:58, 11 August 2018 (UTC)


 * Hi Doug, welcome back. I would say, go to it. Copy your updated version live here. Few editors seem to pay much attention to this article, so your expertise is appreciated. I may make some edits to it, to make it more like a general encyclopaedia and less like a textbook, which I hope is OK by you, but I will try not to change any of your substance - or if I spot anything I will raise it on this talk page first. &mdash; Cheers, Steelpillow (Talk) 02:58, 12 August 2018 (UTC)
 * Just to clarify one point. I see you have been asked at Talk:Lift (force) to draft any major edits in your sandbox first. However the article here does not have a history of significant contention, therefore there is no need to worry about such precautions here. &mdash; Cheers, Steelpillow (Talk) 16:02, 12 August 2018 (UTC)

Thank you. I've gone ahead and installed my proposed changes. J Doug McLean (talk) 23:32, 15 August 2018 (UTC)

Oops. I left out the C-wing graphic. Now it's fixed. J Doug McLean (talk) 21:56, 30 August 2018 (UTC)

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 * Bleriot III.jpg

What about this "Lockheed" video
Note that the publishing date is 2 days before April 1st, so this could be BS. [[User:JohnGerity|JohnGerity] (talk) 21:42, 27 May 2023 (UTC)


 * Interesting; I don’t think it is a joke. Apart from the weird stuff in the middle, a lot of it looks like some kind of internal flight-of-fancy presentation at Lockheed. I note that, after boosting the concept for the first 8 minutes, the video spends the last 2 mins explaining why it would be impractical.
 * Following some of the leads, I found discussion which states (comment no.13, Hank58) that the ideas man, Rollo Smethers, really was an engineer at Lockheed, and also offers an examination of the concept. It also has (comment no. 6, Toura) the page from the French article (5.57-6.04 in the video), which looks legit.
 * I also found this (from JPL, no less!) on how to make a paper ring-wing glider. Xyl 54 (talk) 23:39, 22 January 2024 (UTC)
 * The youtube video, on the other hand, sets off about 10 BS detectors in my head as I'm listening to it. The author doesn't list any sources at the end or in the description because it does seem they're pulling this stuff (advantages/disadvantages, even the "proposed design") out of their butt. SamuelRiv (talk) 05:40, 23 January 2024 (UTC)