Yes and no. there are vertical ribs much like a covered wagon of bygone days. These are spaced along the unit at regular intervals. The skin, both the inside and the outside, is riveted to them. You will see the vertical rows of rivets on the inside and the outside at the same location which defines the rib location.
"Not all who are laundering are washed" say Bill & Heidi
'78 Excella 500,"The Silver Pullit". vacuum over hydraulic disc brakes, center bath, rear twin. '67 Travelall 1200 B 4X4 WBCCI 3737