Estimating Sailplane Mass Properties

Abstract

Estimates of the sailplane inertia parameters (mass, centroid and moment of inertia) are often needed for flight mechanics analysis.  This paper discusses a moment of inertia estimation method for sailplanes using representative geometric figures.  Results are compared with published moment of inertia values.  The accuracy and utility of the method is discussed.  A prismoid wing model was found to be a reasonable geometric representation of the sailplane wing.  Additionally, the requirement for added mass correction to the moment of inertia is considered.  Although it is acknowledged that added mass effects are subtle and simple theoretical estimation methods should be avoided, one estimation method that only requires the principal sailplane dimensions is presented.  Finally, the effect on mass moment-of-inertia when increasing the wingspan is investigated.