Spring 2023: We conducted research on several prospective materials, displayed in Fin Can Materials Research Spreadsheet.xlsx and Materials Spreadsheet.xlsx. Research was also conducted on what materials other rockets with similar or higher apogees used for their fins.
The final decision was to not use aluminum 6061 as we did on Phoenix, as the predicted maximum stagnation temperature calculated from our flight simulations (~600 degrees Celsius) neared the melting point of aluminum.
We also conducted research on different styles of leading edges that would be able to resist high temperatures. The primary candidates were an ablative phenolic leading edge, a thin layer of steel sheet metal bent over the edges, or simply sharpening the fin itself. Sharp leading and trailing edges (hexagonal profile) were determined to be preferable due to the majority of the rocket's flight time being in the supersonic regime.
September 2023: We tentatively decided on 1/4" G10 fins and a carbon fiber fin can, since G10 is much more temperature resistant than aluminum. However, after further calculations were done, we realized G10 would not be stiff enough to resist flutter. Flutter speed was calculated using FinSim.
October 2023: We switched to a fully carbon fiber fin can. The tube itself will be manufactured with a wet layup of carbon fiber fabric around a mandrill. The fins themselves will be made of 1/8" Dragonplate carbon fiber sheets reinforced with additional layers of carbon fiber fabric. Separately manufactured leading edges made of phenolic will be used to resist heating and prevent delamination.
Specific numbers and design overviews can be found in the CDR slides here. Medusa Design Reviews