PFR - Aerospace Engineering Sciences Senior Design Projects ...

Project Final Report – CUDBF April 30 th , 2009
ASEN 4028: Aerospace Senior Projects
The maximum stress from COSMOSWorks produces a stress of 951.1 psi at a stress
concentration close to the wing root. This is expected due to the maximum bending moment at
the root. Using the balsa tensile yield strength of 2,900psi, the minimum safety factor of the
wing is 3.05. The wing also shows a stress drop across the motor mount.
8.4.4 Folding Wing System
The ability of the aircraft to fit into the 2ft x 2ft x 4ft box is feasible only with a well designed
folding wingtip that can withstand the forces along the wing, minimize vibrations, and fold
enough to allow the aircraft ample storage room within the required space. The final wing
folding design can be seen in Figure 60.
Figure 60: Wingtip Hinge Design
First, the hinge selected. A traditional cabinet hinge, a concealed Half-Mortise/Integral hinge,
was used for its ability to provide a degree of pre-stress to the wingtip to minimize excessive
movement during flight. Figure 61 shows the integral hinge [26] .
Figure 61: Integral Hinge
When the hinge is folded, the spring forces the moving parts into the recessed cavity in the door
leaf. This allows the hinge to pull the wingtip into the main section of the wing. Both the tip
and main section are lined along the edge by rubber sheeting. When pressed together, free-play
in the hinge system is mitigated by the pre-stress and frictional force enacted by the rubber
bushing.
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