EFFECT OF FIN GEOMETRY ON THE STABILITY AND AERODYNAMIC PERFORMANCE OF A MODEL ROCKET

Fin geometry is the single most design-accessible parameter governing the static stability, drag, and altitude performance of a model rocket, yet it is frequently selected by convention rather than analysis. This paper presents a systematic parametric study of trapezoidal, clipped-delta, and elliptical fin planforms using the Barrowman method for center-of-pressure prediction combined with a wetted-area skin-friction drag model and a simplified one-dimensional powered/coast trajectory estimate. A representative single-stage, three-fin sport model rocket is used as the baseline configuration. Fin aspect ratio, taper ratio, leading-edge sweep angle, and fin count are varied independently, and their effects on static margin, fin drag coefficient, and predicted apogee are quantified. The results show that static margin is comparatively insensitive to aspect ratio once fin count and planform area are fixed, is reduced by increasing taper ratio and sweep angle, and increases nearly linearly with fin count while incurring a corresponding drag penalty. Elliptical fins offer the lowest drag of the three planforms studied at equal area, at a modest cost in static margin. These trends are consolidated into practical fin-design guidance for hobby and student rocketry.