Twenty Eleven remove Searchbar

I have just updated to this version. The result was that the background colour for the navigation bar changed from turquoise to black, and a search bar was placed into the menu. I think I can work out how to get the old colour back, by setting up a child theme, but I can’t find anything to help remove the searchbar. I do not want it in the menu as it has the effect of changing one line of links into two lines. Any help would be greatly appreciated. Lyn