For more than three decades, a display at the Douglas County Fair has told the history of the local timber industry. Now, the display’s sponsor, the Douglas Timber Operators, plans to tell the story the other 51 weeks of the year as well in a permanent display. The Roseburg-based group, which represents more than 140 manufacturing, logging, trucking and affiliated businesses, plans to erect a permanent structure, possibly before next year’s fair. The 50-feet-by-80 feet building will have sliding panels to open and close the structure and will be in front of the Exhibit Building, the same spot where DTO …