1. Joining of Different Type “Wing-Body” Surfaces of Aircraft Structure
K. Leonavičius, Vilnius Gediminas Technical University, Antanas Gustaitis Aviation Institute
Riga 2002

2. Contents Introduction 3D models in aviation Modern modeling methods
Joining of Different “Wing-Body” surfaces of Aircraft Structures 2
Contents
Introduction
3D models in aviation
Modern modeling methods
Basic types of surfaces
Types of surfaces joining
FUSELAGE – fin joining
fuselage - FIN joining
FUSELAGE – FIN joining
Examples of models
Conclusion

3. Joining of Different “Wing-Body” surfaces of Aircraft Structures 3
Introduction
Development of the 3D model – one of the most important stage of a design process in aviation.
Complex shapes in aviation - new possibilities of high technology:
Modern computer aided design (CAD) and analysis (CAE) software
Computerised manufacturing (CAM), new composite materials and technology
There is the strong demand of new 3D design methods of complex shape objects in aviation

4. Some features of aircraft modeling
Joining of Different “Wing-Body” surfaces of Aircraft Structures 4
Some features of aircraft modeling
Differences between aircrafts and other objects (cars, ships) shapes
One “Skin” instead of separate “Faces”
Development of aircrafts shapes
Lines, arcs - Conic curves – splines, Bezier curves
Assimilation of separate airplane shapes (nose-cabin-tail) into one smooth surface.
Joining of fuselage and wing surfaces

5. 3D design of light airplane
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3D design of light airplane
Shape is closely related to form of internal content – crew, load, powerplant, etc.
Influence of aerodynamic – max laminar flow, min drag area
Influence of strength – optimization of shape and weight
Influence of high tecnology -
CAM
New composite materials
Curve of Zmax

6. Basic methods of airplane shape design
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Basic methods of airplane shape design
Buttock-planes method
Radiusography
Method of Conic curves
Splain, NURBS curves methods

7. Method of 3D design using spline curves
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Method of 3D design using spline curves
Step – by – step explanation
Draft project
Shape editing
Contour editing
Results
Numerical mock-up
Flow analysis
Strength analysis
Surface lofting
Temporary sections
Izocurves
Basic sections
Contours
Coordinate system
Internal components
Initial layaut
Main views

8. Types of surfaces Lifting surface (wing, fin, stabilizer)
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Types of surfaces
Lifting surface (wing, fin, stabilizer)
Curves or surfaces composed by “clouds of points” (airfoils). Geometry is parameterized by coordinates of points.
“Free Form” surface (fuselage, fairing, cowling).
The geometry of such surfaces is parameterized by mathematical functions (Conic curves, polynomic spline curves - NURBS).

9. “FUSELAGE – fin” type joining
Joining of Different “Wing-Body” Surfaces of Aircraft Structures 9
“FUSELAGE – fin” type joining
Fin airfoil
Fin surface model
Fuselage surface model
Fillet
Blend
Transition zone (fairing)

10. “fuselage – FIN” type joining
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“fuselage – FIN” type joining
Fin airfoil
Fin surface model
Fuselage surf. model
Fillet
Blend
Transition zone
(front edge fairing)

11. “FUSELAGE – FIN” type joining
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“FUSELAGE – FIN” type joining
Fin rooth airfoil
Fin airfoil
Fuselage geometry
Contour
Fin geometry
Transition zone geometry
Blend
Loft UV

12. Joining of Different “Wing-Body” Surfaces of Aircraft Structures 13
Conclusions
Modern high technology in aviation allows very complex shapes to be developed and manufactured. The “Free Form” surfaces of double curvature are typical for a light and sport airplanes.
There are two basic methods of aircraft surface parameterization – numerical (fuselages, fairings, etc.) and geometric (wings). Development of the transition zones between them creates an additional problems.
There are some typical ways to connect a surfaces of different type - “Fuselage-fin”, “fuselage – Fin”, “Fuselage-Fin”. Proper CAD technique is recommended for every type of joining.
It is objective to change geometrically parameterized (by coordinates) curves into mathematically determined curves (Conic, NURBS). Special methods and software would be created and integrated with modern CAD-CAE packages.
Development of transition zones is possible by joining the design CAD software with the CAE strength (FEM) and flow (CFD) analysis software.