Thinking Inside the Box: An Investigation into the Aerodynamic Efficiency of Box-Wings

Transcript:

Hi, my name is Jack Lang and my project is called Thinking Inside the Box, an investigation into the aerodynamic efficiency of box-wings.

The International Air Transport Association has made the ambitious goal to reach net zero emissions by the year 2050. This will require multiple strategies, and one such strategy is to improve the aerodynamic efficiency of commercial aircraft in order to reduce fuel consumption.

My project focused on optimizing the box-wing, which is an alternative wing that is designed to minimize induced drag.

I built an automatic force balance gauge which measures lift and drag at multiple angles of attack and used a wind-tunnel to test several 3D-printed original box-wing designs of differing stagger and gap configurations against a conventional model. This gauge was coded in Arduino and used a stepper motor to adjust the angle and allowed for thousands of data readings per trial.

My results indicated that box-wings are indeed more efficient, with the positive stagger model performing best due to its reduction in wing interference.

Thank you, and see you at the fair!

Every year, more than 5.8 megatonnes of CO2 is created by Canadian domestic aviation alone [15]. By 2050, projections estimate that the global demand for individual air passenger journeys could exceed ten billion [6]. The International Air Transport Association has set an ambitious goal to achieve net zero emissions by 2050 [6]. To meet this goal, it is important to investigate alternatives, as advances in conventional aircraft design have only produced marginal gains in aerodynamic efficiency over the last several decades.

One such alternative design is the box-wing, which consists of two wings in a biplane configuration that are staggered and joined. Prandtl described this configuration as the “best lifting platform” in 1924, as its joined wingtips create a reduction in wingtip vortices and therefore less induced drag. There are several variables that can be investigated in box-wings, including wing stagger (horizontal distance between the wings) and gap (vertical distance).

The purpose of this investigation was to compare the aerodynamic efficiency (as measured through lift-to-drag (CL/CD) ratio) of a conventional aircraft wing configuration to several box-wing configurations of original design, to determine if the box-wing is more efficient.

It was hypothesized that all box-wing models would be more efficient than a conventional model due to their reduced induced drag. When comparing positive to negative stagger, positive stagger would be more efficient as it has less interference between the wings. However, after the negative stagger model had been optimized to reduce interference, it would ultimately perform best.

A wind tunnel is an apparatus that creates a stream of air in a chamber and is used to study the aerodynamic properties of objects. The wind tunnel used for this experiment was built for the 2025 CWSF and was designed based off well-known parameters. Several improvements have since been made, including a more powerful fan as well as modifications to the data collection system.

To make testing more efficient, a force balance gauge was fabricated to automatically perform trials and measure both lift and drag. This instrument was adapted from the gauge described by Weakly (2024), with modifications made to adapt to the specifications of the wind tunnel.

The force balance gauge consists of two load cells; one to measure lift and one to measure drag. The angle of the model was adjusted using a stepper motor and controlled using an Arduino Uno. A preloading mechanism was used to minimize backlash in the stepper motor gearbox. The force gauge allows for 10 lift and 10 drag readings per second. Each model was tested from -5 to 15 degrees angle-of-attack, and each angle was measured for 10 seconds, allowing 2100 lift and 2100 drag readings per trial. Over eighty trials were conducted on several prototypes and airfoils.

The software used for designing prototypes was Blender, and files were brought into a slicer for 3D printing.

Before testing, the wind tunnel was commissioned using a NACA2410 airfoil with known lift and drag properties to prove the wind tunnel was providing accurate and repeatable results.

The controlled variables were wind speed, air density (atmospheric pressure, humidity, and temperature), wing size, fuselage size, tail size, Reynolds number, and the lift & drag forces created by the sting/motor. The independent variable was the wing configuration, and the dependent variable was the lift-to-drag ratio.

To date, there have been three iterations of trials for this project. The first used five full-fuselage box-wing models of varying gap and stagger configurations with a conventional model based off a Boeing 747. The second iteration used an Airbus A320 in addition to the original box-wing models & Boeing 747 model, however, the fuselages were replaced by a plate. The third iteration optimized the box-wing plate models for the best direct comparison to the conventional wings.

The results of the first iteration showed that all box-wing models had greater efficiency than the conventional Boeing 747 model at cruising angles of attack, as expected. When comparing positive to negative stagger with the same gap, it was shown that the positive stagger had greater efficiency, as expected. When comparing the positive stagger model to the negative stagger model with increased gap, the positive stagger still performed better, which was unexpected. It was determined that this was due to the increase in parasitic drag caused by the larger tip-fin being required for the increase in gap, as well as the aerodynamic benefits of the positive stagger being significant in terms of lowering wing interference.

At cruising angles of attack where most fuel is burned in commercial aircraft, all box-wing models had higher efficiency than the conventional model, with the positive stagger model performing best with a 206.8% efficiency increase. However, this increase was deemed to be much higher than what the literature suggests.

It was determined that there was a flaw in the methodology of the first iteration. The wing-area-to-fuselage ratio penalized the conventional model, as the fuselage for the conventional model is larger compared to its wing area and is therefore creating a larger percentage of the drag coefficient.

To account for this concern, the plate fuselage models were designed. This method effectively removed the lift and drag produced by the fuselage so that the resulting CL/CD represented only the wing configuration efficiency. Results for this iteration were unexpected, with the box-wings still performing better than the original Boeing 747 conventional model, however they did not perform as well as the Airbus A320. This was deemed to be due to the highly optimized design of the Airbus A320 in comparison to the rudimentary designs of the box-wings.

The third iteration took the best performing box-wings and optimized them using a wing based off the Airbus A320 and improved the aspect ratio. After this optimization, the results showed that the positive stagger box-wing outperformed all models, with an efficiency increase of 62.7% as compared to the Airbus A320. This increase in the positive box-wing performance is significantly less than the first iteration of the experiment (which was 206.8%). However, it is more reasonable given the conventional models are no longer being penalized by the fuselage, and therefore the data is providing better representation of actual aerodynamic performance.

It was proven through this investigation that box-wings are more aerodynamically efficient than current conventional models, with the optimized positive-stagger high-aspect ratio model being the most efficient. This is due to the reduced induced drag of the box-wing design, as well as the design allowing for higher-aspect ratio wings.

A reduction in drag by even 25% of a typical aircraft at cruising angles could save the industry billions of dollars (US) annually and significantly reduce fuel consumption and emissions [3].

This experiment was a purely aerodynamic investigation, and as such did not account for real-world limitations that will need to be overcome to realize the effectiveness of box-wings. These include structural issues, such as managing compressive forces in the rear wing. The increased weight of the box-wing structure offsets a portion of the aerodynamic gains. There are also fuel storage considerations, as box-wings have higher-aspect ratio wings, which creates difficulty with fuel storage. Additionally, there are logistical and regulatory constraints. Box-wings introduce unique challenges with propulsion, control systems and flight stability. If these issues can be solved, the benefits from the increase in efficiency could be enormous.

Commercial aircraft designs have remained relatively unchanged for several dozen years. The Boeing 747 rolled out in 1968, and even the most common airliner today, the Airbus A320, first flew in 1987. If there is any chance of reaching the goal of net zero emissions by the year 2050, it is time to start thinking outside the box and looking into alternatives.

Increase Reynolds number through half-model or semi-span testing

Improve angling mechanism to reduce inaccuracies with backlash

Improve wind tunnel instrumentation to a six-axis force gauge to limit cross-talk as well as measure moment & pressure, as the current orthogonal strain gauge configuration causes some lift to be transferred to drag

Improve 3D print quality with acetone vapour smoothing

Test different aspect ratio box-wing configurations

Investigate how to solve noted problems with box-wings (structural issues, fuel storage issues, stability issues, control issues, regulatory and safety issues)

Investigate other alternative designs, including blended-wing body and truss braced wings

Thank you to Tim Balcarras for generously donating a 3D-printer and providing advice on how simulations can improve wind-tunnel testing, and to Daniel Guindon for taking the time to chat with me about aerospace engineering and my project. Thank you to my teachers at Sullivan Community School: Mark Kuhl, Kyle Smith and Deanna Bertrend for always being supportive of my research, and to Tim Gard from STEMVOX Academy for challenging me and teaching me how to think like an engineer. A huge thanks to the Bluewater Regional Science Fair volunteers who work tirelessly to make this whole experience possible, including Diane Wall, Heather Christie, Anji Cottrill, and Brad & Patti-Jo Lacey. A special thank you to my Dad and mentor, Patrick, who I admire tremendously, and to my Mom, Heather, for always cheering me on and letting me keep my 9-foot wind-tunnel on the kitchen table for over a year!

[1] Boeing 747 Longitudinal Stability and Control Data. (2026). Cornell University, Department of Mechanical and Aerospace Engineering. https://courses.cit.cornell.edu/mae5070/B747_Data.pdf

[2] Doerffer, P., & Szulc, O. (2026). High-lift behavior of half-models at flight Reynolds numbers. Task Quarterly, 10( 2), 1–16.

https://www.researchgate.net/publication/228940403_HIGH-LIFT_BEHAVIOUR_OF_HALF-MODELS_AT_FLIGHT_REYNOLDS_NUMBERS

[3] Gagnon, H. & Zingg, D. (2016). Aerodynamic optimization trade study of a box-wing aircraft configuration. Journal of Aircraft, 53(4). Aerodynamic Optimization Trade Study of a Box-Wing Aircraft Configuration | Journal of Aircraft

[4] Gharbia, Y., Derakhshandeh, J.F., Alam, M. M., & Amer, A.M. (2023). Developments in wingtip vorticity mitigation techniques: A comprehensive review. Aerospace, 11(1), 36. https://doi.org/10.3390/aerospace11010036

[5] Hileman, James I., et al. (2013). The carbon dioxide challenge facing aviation. Progress in Aerospace Sciences, 63( 63), 84–95. https://doi.org/10.1016/j.paerosci.2013.07.003. Accessed 17 Dec. 2025.

[6] International Air Transport Association (IATA, 2026). Our commitment to flying net zero by 2050. Retrieved from https://www.iata.org/en/programs/sustainability/flynetzero/

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[8] Khalid, A., and Kumar, P. (2014). Aerodynamic optimization of box wings – a case study. International Journal of Aviation, Aeronautics, and Aerospace, 1(4), 1-4. https://doi.org/10.58940/2374-6793.1034. Accessed 12 Oct. 2025.

[9] Magnacca, Fabio. (2025). Do box-wing aircraft configurations add financial value? Results from an academic-based experience. Research in Transportation Business & Management, 60. 10.1016/j.rtbm.2025.101323.

[10] National Aeronautics and Space Administration. (2023, January 21). Drag. Glenn Research Center. https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/drag/ Accessed 22 Feb. 2026.

[11] Olugbeji, Paul, et al. (2023). An analysis of aerodynamic design issues of box wing aircraft. Journal of Aviation Technology and Engineering, 12(2), 15-24. https://www.researchgate.net/publication/373763299_An_Analysis_of_Aerodynamic_Design_Issues_of_Box-Wing_Aircraft

[12] Prandtl, L. (1924). Induced Drag of Multiplanes. NACA Technical Note 182. https://ntrs.nasa.gov/api/citations/19930080964/downloads/19930080964.pdf

[13] Salem, A.S., Palaia, G., Frediani, A., & Carrera, E. (2025). The box-wing configuration: a critical review of design approaches and applications. Progress in Aerospace Sciences, 157(1). https://www.researchgate.net/publication/373763299_An_Analysis_of_Aerodynamic_Design_Issues_of_Box-Wing_Aircraft

[14] Stolzer, Alan. (2002). Fuel consumption modeling of a transport category aircraft using flight operations quality assurance data: a literature review. Journal of Air Transportation. 7(1). https://commons.erau.edu/publication/115

[15] Transport Canada. (2025). Greenhouse gas emissions. Retrieved from https://tc.canada.ca/en/corporate-services/transparency/corporate-management-reporting/transportation-canada-annual-reports/transportation-canada-2023/greenhouse-gas-emissions

[16] Weakly, J., Ho, S., Feehery, E. Kothmann, B., & Sung, C. (2024). A Low-cost, Adaptable System for Lift and Drag Measurement in an Educational Wind Tunnel. ASEE Annual Conference and Exposition. Portland, Oregon. https://sung.seas.upenn.edu/publications/wind-tunnel-force-balance/

IMAGE & FIGURE SOURCES

[1] Bravo-Mosquera, Pedro David, et al. (2022, Nov 30). [Picture of a box-wing configuration] [Photograph] Exploration of Box-Wing Aircraft Concept Using High-Fidelity Aerodynamic Shape Optimization. 33rd International Council of the Aeronautical Sciences, Stockholm, Sweden. www.researchgate.net/publication/365870494_EXPLORATION_OF_BOX-WING_AIRCRAFT_CONCEPT_USING_HIGH-FIDELITY_AERODYNAMIC_SHAPE_OPTIMIZATION.

[2] Marino, Matthew & Sabatini, Roberto. (2014).[Picture of box-wing configuration] [Photograph]. Advanced Lightweight Aircraft Design Configurations for Green Operations. Practical Responses to Climate Change Conference. Melbourne, Australia. Retrieved from https://www.researchgate.net/publication/268814067_Advanced_Lightweight_Aircraft_Design_Configurations_for_Green_Operation

[3] Cruz Riberio, Fabio, et al. (2017). [Picture of gap and stagger on a box-wing configuration] [Photograph] Wing Geometric Parameter Studies of a Box Wing Aircraft Configuration for Subsonic Flight. 7th European Conference for Aeronautics and Space Sciences. (EUCASS), Hamburg University of Applied Sciences.

[4] National Aeronautics and Space Administration. (2026). [Picture of induced drag and wingtip vortices] [Photograph]. Induced drag coefficient. Retrieved from https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/induced-drag-coefficient/#aerodynamic-drag

[5] Weakly, J., Ho, S., Feehery, E. Kothmann, B., & Sung, C. (2024).[Picture of wiring diagram for load cells][Photograph] A Low-cost, Adaptable System for Lift and Drag Measurement in an Educational Wind Tunnel. ASEE Annual Conference and Exposition. Portland, Oregon. Retrieved from https://sung.seas.upenn.edu/publications/wind-tunnel-force-balance/

[6] Nautilus Horizon Blended Wing Body. (2026). [Picture of blended wing body aircraft] [Photograph]. Nautilus horizon blended wing body can transport 200 passengers with cargo. Retrieved from https://www.techeblog.com/nautilus-horizon-blended-wing-body-aircraft/

[7] National Aeronautics and Space Administration. (2026). [Picture of truss braced wing] [Photograph]. Truss braced wing test. Retrieved from https://www.nasa.gov/image-article/truss-braced-wing-test-2/

[8] Lin, C.-Y., Ahmad, A. R., & Kebede, G. A. (2020). [Picture of six-axis force gauge] [Photograph]. Novel Mechanically Fully Decoupled Six-Axis Force-Moment Sensor. Sensors, 20(2), 395. https://doi.org/10.3390/s20020395

[9] Climate Action Tracker. (2025). [Graph of Aviation Emissions Projections] [Photograph]. International Aviation Summary. Retrieved from https://climateactiontracker.org/sectors/aviation/

[10] Prandtlplane ARchitecture for the Sustainable Improvement of Future AirpLanes. (2025) [Pictures of PARSIFAL concept box-wing] [Photograph] European Comission. Retrieved from Prandtlplane ARchitecture for the Sustainable Improvement of Future AirpLanes | H2020 | CORDIS | European Commission

*All images without sources were made by author.

*Title Page imagery from [2] assisted with Google Gemini