Hold the mission constant
Reference cruise speed 46.3 m/s and a nominal 12.25 m² wing area; retain the existing fuselage and V-tail concept.
Aircraft redesign / 2015 eFly wing study
More lift per drag.
Better electric flight.
The Robin ATL already existed. The question was whether a redesigned, naturally laminar-flow wing could make its electric-aircraft concept more aerodynamically efficient—without ignoring packaging and pitching-moment constraints.
Conceptual numerical wing comparison; not a whole-aircraft drag measurement or flight-test result.
AIRCRAFT CAD · SUPPLIED SOURCE VIEW+31%Predicted wing L/D vs baseline
40.9Redesigned cruise wing L/D
11.3 mSelected wingspan
63-215Chosen NACA profile
ENGINEERING SUMMARY
Project scope and interpretation
- Engineering question
- Which airfoil and wing geometry best satisfy the conceptual electric-aircraft aerodynamic and design trade-offs?
- System / operating scope
- 2015 University of Zagreb aircraft wing design thesis; baseline 10.25 m span and selected 11.3 m concept as described in the study.
- Work performed
- Assessed airfoil alternatives, redesigned conceptual wing geometry, considered pitching moment, L/D and integration constraints.
- Analysis / input basis
- Thesis-stage aerodynamic calculations plus separately supplied subsequent CFD and numerical-optimization visualizations clearly distinguished in the case.
- Finding or displayed evidence
- Reported approximately 31% higher predicted wing-level lift-to-drag ratio for the concept under the stated analysis basis.
- Limits / validation status
- Wing-level numerical prediction; not a measured flight result, certified aircraft outcome, or demonstrated aircraft-level energy saving.
- Decision supported
- Select a feasible wing/airfoil concept for further aerodynamic development.
The engineering brief
A wing is not optimized by drag alone.
The electric propulsion concept created a multi-objective design problem. The winning configuration needed competitive cruise efficiency, useful internal volume and manageable aerodynamic moments.
Compare, then commit
Assess wing span and taper, three airfoil candidates, and two winglet configurations—rather than optimizing one metric in isolation.
Quantify the difference
Compare the final and original wing at their cruise operating points, then distinguish later CFD visuals from the 2015 result.
01 / Geometry change
Redesigning the wing.
The airframe stays.
The wing evolves.
With electric propulsion driving the design, the study retained the existing aircraft configuration while reassessing the wing. The natural-laminar-flow section, increased span and selected winglet are the principal aerodynamic changes.
Use the overlay to inspect the relative planform; this is an engineering schematic, not a reconstructed production drawing.
The original thesis modeled the wing in isolation; the complete aircraft was not assigned the +31% result.
02 / Candidate selection
Pick the best trade-off, not simply the highest number.
NACA 64A415 delivered a marginally higher predicted cruise L/D, but NACA 63-215 was selected for its more favorable pitching moment at comparable aerodynamic efficiency.
Candidate profile shapes / source overlay
Original source-airfoil contour artwork cleaned for dark presentation · Figure 5.2.1
Cruise comparison at required Cᴸ ≈ 0.4. Profile selection balanced drag, pitching moment and available battery space.
Selected operating-point properties
NACA 63-215
40.9
CRUISE L/DCᴸ/Cᴅ
40.9
|Cᴍ|
0.253
α at cruise
3°
Selected on balanced criteria.
VALUES · THESIS Tables 7.3.1–7.3.3; values are wing-level design-point predictions
03 / Wingtip refinement
Two winglets. One selection.
Selected after comparing predicted aerodynamic performance and spanwise bending moment. The curved winglet was approximated by straight segments within the modeling limitations.
SOURCE · THESIS §7.4, Figures 7.4.1, 7.4.3, 7.4.5 and 7.4.6 · extracted original geometries
04 / Quantified concept performance
Predicted 31% more wing lift per unit drag.
The decision is backed by the study's operating-point results, not just attractive CAD. Read the numbers alongside the model boundary.
Predicted wing cruise L/D · 46.3 m/s
The model compares wing-only aerodynamic coefficients at the evaluated cruise operating points. Same nominal wing area: 12.25 m².
THESIS · Figure 7.5.1 and Table 7.5.1
Calculated relative increase
+31%
Higher predicted wing efficiency.
Result from the 2015 XFLR5 wing-design study. This is not a measured aircraft-level drag reduction or a flight-test result.
Comparison excludes fuselage, tail, landing gear and full-aircraft stability effects.
05 / CFD examination
Inspect the three-dimensional flow evidence.
Original, unmodified CFD renders from separately supplied materials. Explore fields and mesh detail without confusing the ω quantity with a verified transition map.
Drag to pan when zoomed · arrows to pan
06 / Subsequent numerical optimization
Refinement after the concept.
Recorded shape-optimization frames and an approximate coefficient history illustrate further numerical work. The modest drag reduction shown here is distinct from the original 31% wing L/D design comparison.
Original 10-frame AVI sequences converted to MP4 · recording time is not CFD physical time
Drag coefficient by optimization iteration
Iteration 10 · estimated Cᴅ 0.014876
Approximate values digitized from the supplied screenshot, not recovered from a solver CSV. Minimum occurs around iteration 10; small rebound follows.
Review methodology, source figures and engineering limitations ▾
Project context
2015 master's thesis, University of Zagreb: conceptual redesign of the Robin ATL wing for the eFly electric-propulsion conversion. The study retains the existing fuselage and V-tail concept and focuses on the wing. These are historical design-study predictions, not an implemented or certificated design.
Analysis and decisions
Initial XFOIL/XFLR5 verification; existing NACA 43015 wing baseline; cruise requirements; candidate naturally laminar sections; aspect-ratio and taper studies; battery packaging, pitching moment and lift-to-drag comparison; two winglet concepts; final wing choice. Supporting data in Tables 3.1.1, 7.3.1–7.3.3, 7.5.1–7.5.2.
Models and validation boundary
The wing-only comparison omits fuselage, empennage, undercarriage and complete aircraft structural/stability analysis. The CFD/adjoint renders supplied separately do not establish a like-for-like independent validation of the 31% wing L/D prediction. The ω field is a turbulence-model quantity, not an experimentally verified transition map. y⁺ indicates wall treatment but does not replace mesh-convergence testing.
Source
B. Vidović (2015), Dimenzioniranje novog krila postojećeg lakog zrakoplova, University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture. Repository record ↗.
What this work demonstrates
Requirements → design decisions → defensible evidence.
Wing and airfoil trade studies, practical aerodynamic modeling, CFD interrogation and optimization workflows. A comparable industrial engagement begins with defined requirements, verification objectives and clear deliverables.