RV Repair: Flagstaff Pop-up Camper wood rotting, pop up camper, cedar plank

Question
I have a 1996 Flagstaff Pop-up camper 10' box.  The wood on the sides of the "top" are rotten.  I have removed one of the sides and found it to be 1/2" thick OSB type board but it is 10'-7" long.  Where can I buy wood long enough to replace this?

Answer
I would maybe replace it with a board.  Like Cedar plank 12 foot long.  That won't rot and bugs don't like it.  Or you can just use a decking plank.  That would be treated.  These types of wood would accept screws and things better than OSB, during the repair.  Good luck