Method for manufacturing a central underbody portion including a multi-part tunnel

A method for manufacturing a central underbody portion of a structural body of a motor vehicle, to delimit a bottom of a passenger compartment of the vehicle, including a longitudinal structural tunnel, comprising:

• providing a floor of the central underbody portion, the floor including a raised central portion and lower portions extending from the central portion to peripheral edges of the floor in a transverse direction of the vehicle;
• attaching a front end piece directly to a front end of an integral central profile as an extension of the integral central profile in a longitudinal direction of the vehicle and attaching a rear end piece directly to a rear end of the integral central profile as an extension of the integral central profile in the longitudinal direction, the integral central profile including a base and wings;
• and
• after the attaching the front end piece directly to the front end of the integral central profile and the attaching the rear end piece directly to the rear end of the integral central profile, attaching the integral central profile to an upper face of the floor at a center of the floor in a lateral direction of the vehicle, arranged in the longitudinal direction of the vehicle and having a length that is dependent on a length of the central underbody portion in the longitudinal direction,
• wherein the front end piece and the rear end piece form an extension of the central profile so as to have an interface providing a connection and a function of absorbing and transmitting forces with at least one of a structural portion of the body that is separate from the central underbody portion and the floor,
• wherein the attaching includes adapting the length of the central profile as a function of the length of the central underbody portion in the longitudinal direction of the vehicle,
• wherein the the attaching the integral central profile to the upper face of the floor is performed such that the raised central portion is positioned above the lower portions in a vertical direction of the vehicle,
• wherein the attaching the integral central profile to the upper face of the floor is performed such that the wings are connected to the upper face of the floor at the lower portions of the floor, and the base extends between the wings above the raised central portion of the floor, and
• wherein, after the attaching the integral central profile to the upper face of the floor, the floor, the central profile, the front end piece, and the rear end piece form the longitudinal structural tunnel that delimits a hollow body.