Glider Design : A Fundamental Approach- ICARUS 1.0
This project marked my first deep dive into aeronautical engineering, where we explored the principles of wing selection and stability for a glider. The goal was to design an efficient, stable aircraft capable of sustained flight. Here’s how we approached it — from theory to practical implementation.
1.Design Criteria
The glider should perform under the following conditions.
Wingspan — 40 cm
Wind speeds — 5 to 10 m/s
As given, the glider wingspan should be 40 cm and the airfoil we select, must lift at least the weight of the glider under 5 to 10 m/s of windspeed.
2.Understanding the Basics
Before diving into calculations, we familiarized ourselves with key aerodynamics concepts:
- Lift and Drag — How airfoil shape influences performance.
- Aspect Ratio (AR) — The importance of wing span vs. chord length.
- Stability — The role of the tail in maintaining equilibrium.
Since gliders rely solely on aerodynamics (no propulsion), we understood that optimizing lift-to-drag ratio was critical.
Another key aspect of this design was weight. Materials and dimensions for this glider had to be chosen carefully, to not exceed the lift possible with a 40cm span. This was a challenge. We under estimated the significance and the design process had to be iterated, to solve this oversight.
3.Concept Design
Initially we started with a simple sketch. The dimensions for the fuselage, wing chord, size of the horizontal stabilizer (vertical stabilizer was ruled out of scope for this design ) were determined by observing the dimensions of real world gliders and light aircrafts.
This sketch was changed several times in the future, along with some dimensions. Next phase of the concept design was to estimate a rough weight for the glider. For this, we modelled the above sketch only with the essential components using SolidWorks 2022.
The mass turned out to be around 40g with relatively higher density materials. This approach turned out a success as we managed to identify the issues that will arise in the future.
4.Airfoil Selection
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Software Used: XFOIL , Python , MATLAB
4.1 Infinite Wing Analysis
We used a Python Script to inject code into XFOIL command line and stored .txt files of a large number of NACA 4 digit series airfoils.
Utilizing the data we evaluated the airfoils by plotting Cl vs. α and Cl/Cd. The higher Cl/Cd ratio airfoils were chosen for further analysis.
While this approach seemed functional, there were many errors which surfaced later. For a more thorough analysis, we switched to MATLAB.
Using further code , we filtered out airfoils with irregular lift curves or poor stall characteristics. Around 10 airfoils out of a 100, were chosen for further analysis.
4.2 Finite Wing Adjustments
Next step was to consider the effect of a finite span of an airfoil. The finite span effect refers to the aerodynamic differences between an infinitely long wing (2D airfoil, which we calculated for, in 4.1 ) and a real, finite-length wing (3D wing). These differences arise due to wingtip vortices, which modify airflow around the wing and impact performance.
Source : https://www.grc.nasa.gov/www/k-12/airplane/Images/induced.gif
For the finite span effect, the following correction was applied.
Lift and Drag values were recalculated.
After comparing performance, NACA 6409 emerged as the best choice due to:
High CL/CD at moderate angles of attack.
Smooth stall behavior.
Good lift generation for gliding
There were airfoils with more lift generation but the Angle of Attack at the at the lift value was too close to stall.
Result: NACA 6409
Manufacturing this design proved to be more challenging.
