Bob uses a combination of woods, with quilted maple on top, swamp ash on the bottom, and strips of walnut and rock maple that run through the entire center and make up the neck and head stock. It's all glued together first, looking like a big square block with a four by four post sticking out of it. It's all one solid body, no bolt on neck or anything like that. For additional strength, Bob runs carbon fiber rods down the neck, one on each side of the adjusting rod.
Here's a pic of one I clear coated showing the different woods involved.