Try clicking on advanced search button first. Then enter ribs in the keywords box followed by a comma then a space then rudder.
You should get posts with only “ribs” in some posts, some posts with only “ rudder” and if you look through all the pages that come up from the search, there may be posts with both keywords IF there are any posts with both keywords inside any posts. Also when you go to advanced search, highlight the little boxes “forums” and “posts”. Beyond that, I can not guide you further.