They key to good 3D is good 2D. Once the curves have been created and well thought out the sculpting process can start. Just like construction a real aircraft includes putting the frame together then the outer skin.
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Image 1 shows us the body frame, and Image 2 shows us the coons 4 side surface. The previous examples show a good finished model build upon these principles. All the features consist of a good curve, curves that can be projected to surface for trimming. Having worked on the board (Old days) built a strong foundation, understanding 3d blueprints and seeing them built in 3D and constructing linear perspective and isometric mathematical drawings. If you can’t see in your mind the end 3D project you will never have a good design.
Cad Surface Modeling 