A method of forming a hollow component with an internal structure from first and second panels includes the step of forming at least one protrusion on a surface of at least one of the first and second panels by a material deposition process. The first and second panels are assembled into a preform the panels being oriented such that each panel defines an interior and an exterior facing surface, with the at least one protrusion extending from an exterior facing surface of a panel. The preform is expanded against a die, such that the at least one protrusion is transferred from the exterior surface of a panel to the interior surface of a panel so as to define an internal structure. Forming the at least one protrusion may include encapsulating an elongate member on the surface of a panel by a material deposition process.