Added masses computation is a crucial aspect to be considered when the density of a body moving in a fluid is comparable to the density of the fluid displaced: added mass can be defined as the inertia added to a system because an accelerating or decelerating body displaces some volume of neighboring fluid as it moves through it. The motion of vehicles like airships and ships can be addressed only by keeping into account the effect of added masses, while in case of aircrafts and helicopters this contribution is usually neglected. Lighter Than Air flight simulation, unmanned airships flight control system, airships flight dynamics are typical applications in which added masses are fundamental to achieve an effective and realistic modeling. A panel based method using the mesh of an airship external shape is developed to account for the added massed. While the mathematical background of the methodology is described in literature, what is missing is a proper description suitable for unconventional manned/unmanned airship. Two applications of the methods have been carried out to check the precision of the methods, and results have been also compared to a case study whose added masses are described in literature. A sensitivity study on the effect on the added masses of the number of elements in which the envelope is discretized is performed. Finally, for an unconventional unmanned airship model, the computations of the terms of the added masses matrix are shown.