NACA Wing

Motivation:

The goal of this project was to design and build a lightweight aircraft wing that could support a 97 lb load at its tip while keeping weight and deflection as low as possible. We wanted to see how much weight we could remove from the wing without sacrificing its structural strength, while also working within the limitations of the materials and manufacturing equipment available to us.

Design Approach:

We started by comparing several spar designs, including I-beams, C-beams, and box beams, using FEA in PTC Creo to evaluate stress and deflection. We eventually settled on a tapered H-beam made from 7075 aluminum, with wider flanges and holes along the web to reduce weight. The spar was machined on a 3-axis CNC mill using two separate setups. The rest of the wing consisted of nine bulkheads, with the root and tip bulkheads waterjet-cut from 6061 aluminum and the interior ribs and leading edge 3D printed from PLA. We then wrapped the structure in 0.016-inch aluminum skin and secured everything using rivets and adhesive.

Key Challenge:

One of the biggest challenges was finding a spar design that was both lightweight and strong enough to support the required load. Our initial design used 6061 aluminum, but after running simulations, we realized it would yield under the target load and switched to 7075 aluminum. Manufacturing the spar was also difficult because its tapered geometry required machining both sides separately. Alignment issues between setups caused some uneven material removal, leaving us with a slightly asymmetric spar. Despite these issues, we were still able to finish the wing and move forward with testing.

Result:

Our finished wing weighed just 1 lb 3.8 oz and successfully supported the required 97 lb load, roughly 78 times its own weight. At this load, the wing deflected 4.125 inches, slightly less than the 4.5 inches predicted by our simulations. We continued increasing the load and found that the wing could support 150 lbs before eventually breaking at 195 lbs. Overall, the project gave us hands-on experience with structural design, FEA, CNC machining, and testing, while showing how closely the actual performance of a design can compare to simulations.