# Design of a Human Muscle-Powered Flying Machine
## 6 Structural Development of the Human-Powered Aircraft
### Selection of the Profile and Determination of the Wing Geometry  
During the selection of the wing profile, the XFoil Direct Analysis module of the XFLR5 program was utilized. The first step involved calculating the Reynolds number with the help of Equation (5), which is a crucial parameter for determining the profile properties. For a chord length ranging from 0.3 to 1 m, with a kinematic viscosity coefficient of 1.51\(\cdot\)10\({}^{-5}\) m\({}^{2}\)/s and a velocity of 10 m/s, the Reynolds numbers varied from 198,675 to 662,252. Analyses for this range of Reynolds numbers were conducted using the XFLR5 program (Figure A1a). Based on the obtained aerodynamic characteristic curves for angles of attack ranging from \(-\)10\({}^{\circ}\) to +10\({}^{\circ}\) (Figure 5a), a profile was selected that meets the construction requirements. Next, the comparative analysis of various profiles from the existing UIUC Airfoil Coordinates Database [50] helped to select the Eppler 395 profile, which best met the adopted assumptions (Figure 5b). To conduct a 3D analysis, it was necessary to perform a series of aerodynamic analyses for the E395 profile. For this purpose, the Batch Analysis function was utilized. When determining the wing geometry, the Wing and Plane Design module of the XFLR5 program was used. Upon initiating the Define a New Plane function, the Plane Editor window appeared (Figure A1b), enabling the definition of the geometry of individual wings. At the initial stage, the geometry of the vertical rudder (Fin) and horizontal rudder (Elevator) was marked. The next step was to define the initial wing geometry in order to determine the optimal angle of attack. Then, the analysis was carried out using the ring vortex mesh lattice method VLM2. The graph (Figure 5c) shows that the optimal angle of attack is around 3.5\({}^{\circ}\). The wing support structure was designed based on the construction used in the Daedalus human-powered aircraft [9]. Therefore, it was assumed that, similar to that design, due to the large wingspan, the wing would experience flexing during flight. Using the Natural Sketch module in the 3 DExperience program, the anticipated flexing was determined based on the Daedalus project sketch [11] (Figure 6a). Taking into account the deflection, the final geometry of the wing was determined (Figure 6b), where the span was 28 m, the wing elongation parameter was 42.2 and the area was 19.08 m\({}^{2}\). Next, an analysis was conducted aiming to achieve the parameters specified in the assumptions--an initial velocity of approximately 10 m/s, a lift force oscillating around 1000 N, and the lowest possible drag force. For this purpose, the VLM2 method was once again utilized, considering a constant angle of attack and variable velocity (Figure 7). From the graph, it can be inferred that the velocity required to maintain the aircraft in flight is 9.43 m/s, with a drag force of 16.8 N. For the project's purposes, a velocity of 9.5 m/s was adopted. Figure 5: (**a**) Plot of lift coefficient \(\text{C}_{\text{I}}\) to drag coefficient \(\text{C}_{\text{d}}\) for an example profile, (**b**) Eppler 395 airfoil profile (XFLR5 program), (**c**) plot of the lift force versus drag force \(\text{C}_{\text{I}}/\text{C}_{\text{d}}\) depending on the angle of attack \(\alpha\) (alpha). After determining the geometry in the XFLR5 program, a structural model of the wing was created (Figure 6c) in the 3 DExperience program, based on the structure of the Daedalus human-powered aircraft [9]. For this purpose, the Part Design, Generative Wireframe and Surface, and Assembly Design modules were utilized. Similar to the design of the Daedalus, the main spar consists of a composite tube based on carbon fiber, with a diameter of 90 mm and a wall thickness of 0.56 mm (4 layers of laminate). The tube tapers towards the wingtips to a diameter of 32 mm and a wall thickness of 0.28 mm (2 layers of laminate).