ILLINI ELECTRIC MOTORSPORT | FSAE

I ran FEA on the new airfoil geometry with a 3-ply schedule to understand deformation behavior. Key Finding: Extreme spanwise deformation — the first mainplane was acting like a simply supported beam with distributed load. Max deflection scales as L⁴ where L ≈ 50" (span between mounting points). Solutions Explored: 1. Safety cables on endplates to restrict deflection at the wingtips. 2. Carbon spars at the center of pressure (cP) of each wing for flexural rigidity. 3. Rib placement optimization to minimize surface deformation. (In the visualization to the right: light grey = aluminum, dark grey = carbon, yellow = corecell foam. Note: This initial FEA had additional connections making the result non-conservative.)

The wing's internal structure had to absorb inertial loading, aero forces, and cone strikes. I evaluated 13 foam options (Rohacell, Corecell, Gurit PVC) to find a solution that could match our complex geometry. Decision: Selected Corecell M80 (3mm) for the leading edge core. Reasoning: Unlike honeycomb which cannot conform to tight airfoil radii, or brittle foams that shatter, Corecell offers high elongation at break (40%) — allowing the leading edge to deform and absorb energy during a cone strike rather than fracturing. The ribs and spars were waterjet-cut from flat sandwich stock (Corecell + Carbon), enabling rapid manufacturing from single sheets.

Design is 90% complete and manufacturing has now begun. Our approach involves adding a layer of peel ply on the inside of the skins to prep the surface for bonding. The internal structures (ribs and spars) connect together in an almost lap-joint method, allowing adhesive to be added for secure bonding. The assembly sequence proceeds from skin layup to peeling the interior, followed by bonding the ribs/spars and final close-out.