I am doing a mini hovercraft project. Regarding my design, I plan to place the fan (LIFT) in the middle of a rectangular styrofoam board (15 inches by 8inches). The position of my fan would be (x=7.5, y=4in); this would also be my center of gravity. My origin (coordinate) is at the corner of the styrofoam board. My thrust fan will be placed closer to the origin. I would like to ask if I do need to include the mass of the styrofoam board (where I will placed all my components)? If yes, what would be its position from the origin. Another thing, concerning the moment of inertial, I know to get it for a rectangular plane (uniform volume and mass), it is I=1/12 (length^2+width^2) . But with the components to be placed with different masses and volumes, how will I get the moment of inertia? I decided my center of gravity is at the middle of the styrofoam.