A device for assembling a composite structure is disclosed. An illustrative embodiment of the device includes at least one carriage track, a linear rail carriage carried by the at least one carriage track, a yoke assembly carried by the linear rail carriage, a linear actuator assembly engaging the linear rail carriage and adapted to move the linear rail carriage along the at least one carriage track and a pair of mandrel cradles pivotally carried by the yoke assembly. Activation of the linear actuator assembly facilitates movement of the linear rail carriage along the at least one carriage track and pivoting of the pair of mandrel cradles with respect to the yoke assembly.