Login to your blogger account and from the dashboard go to Layout--> Edit HTML. Go through the code to find section of code starting like 'Navbar1' or 'Navbar-iframe' or something similar (depending on your template) and modify the content between the braces replacing the previous codes with the following. (Make sure you backup your full template first before modifying anything in case anything goes wrong)
Now save the HTML and view your blog. The navbar should be gone.