Final Design
S-Shaped Stamped Sheet
Design
The stiffeners in traditional aircraft doors are typically comprised of curved aluminum
molds from casting, which can result in unnecessarily heavy doors and higher fuel
consumption. To resolve this weight issue, s-shaped stamped sheets were implemented
into the proposed baggage door design.
The proposed design of the stamped sheets were formed from Al-7050 sheets. The
change from molds to metal sheets drastically reduced the weight of the door. Relative to the
maximum mass constraint given by Collins Aerospace, the total mass of the final baggage
achieved a 44% mass reduction from the cutoff mass.
To maximize stiffness and limit deflection, the combined height of the stiffeners, outer skin
panel, and inner skin panels were maximized to the height constraint of 5 in.
Determination of Base Length and Spacing Between Stamped Sheets
Two parameters must have been considered so the door performance can meet flight conditions: maximum stress and max
deflection. Using the equations shown above and by using hand calculations, the respective "b" values were computed and verified
to see which value satisfies both the max stress and deflection criteria. As a result, the stress condition was more significant. This
value resulted to be 55.6mm. Since this "b" value is the optimal value that meets both deflection and stress conditions, it was
used to separate each stiffener. This illustration can be further be seen in Figure 1.
Figure 1: Spacing between stiffeners
Stamped stiffeners were also ideal in regards to manufacturability. Because the stiffeners were formed out of the same 0.036 in
(0.9144 mm) Al-7050 Sheets as the outer and inner skin panels, the entirety of the door would be made out of the same material,
which could be ordered in bulk. In addition, the stamped stiffeners are relatively easy to manufacture. For the two physical
prototypes, the stiffeners were formed out of 0.040 in (1.016 mm) Al-6061 sheets, and were easily manufactured using
equipment in the UCSD MAE machine shop. These stiffeners were only 1 ft long, and the same spacing used in the final design was
implemented into the prototype stiffener orientation.
Outer Skin Panel
The outer skin panel is 3 ft x 3 ft (914 mm x 914 mm) and serves as the barrier between the plane interior and outside
atmospheric conditions. Sponsor requirements specified that the outer skin thickness be constrained to 0.036 in (0.9144 mm) and
that the outer skin feature a curvature of 20.7 degrees. The final design featured an outer skin formed out of Al-7050, while for
our two physical prototypes, the outer skin panel was made out of 0.040 in (1.016 mm) Al-6061 sheets and were 1 ft x 1 ft (305
mm x 305 mm).
Inner Skin Panels
The inner skin panels were formed out of the same 0.036 in (0.9144 mm) Al-7050 sheets used for the rest of the final
design. These panels provided additional stiffness across the axis not strengthened by the stamped stiffeners, and were divided up
to lower overall weight as compared to one single inner panel.
In addition, the inner skin panels aided in the manufacturability of the overall design. Rivets were added along each intersection
between an inner panel and a stiffener, and these rivets combined with the inner panels ensured that the stiffeners were all flat
and of an even height. Furthermore, beyond the 8 inner skin panels perpendicular to the stamped stiffeners, an additional 8
skin panels were fixed underneath the top of the stamped stiffener pairs to provide additional stiffness and prevent the individual s-
shaped stiffeners from deforming or splitting apart. As per the other components, the inner skin panels were formed out of 0.040
in (1.016 mm) Al-6061 for the physical prototypes.