Forest City-based Winnebago Industries Inc. reported a nearly 28 percent increase in operating income for its fiscal third quarter. The recreation vehicle manufacturer’s net income was $14.4 million, or 53 cents per share, an increase of 25.5 percent from $11.5 million, or 43 cents per share, in the same period last year. “Continued strong growth in our towables business, combined with a moderate climb in our motorized shipments, drove increased revenues for the quarter,” President and CEO Michael Happe said in a release. Both the towables and motorized businesses had positive retail trends versus a year ago, with motorized registrations in the third quarter pushing toward a high single-digit percentage comparison and towables driving a retail increase of more than 40 percent. Year-to-date, Winnebago’s stock price is up 11.5 percent over the previous year, according to the Business Record’s index of Iowa stocks.