Keeping an Engineering/Project Notebook has different rewards than a blog. For me, the method of approach is also quite different. I think that is why I haven't managed to keep one going on previous attempts. I've always thought that such a notebook should be kept on the computer. But, I've never managed to find anything which works as well as a physical notebook for the wide-ranging "stuff" which accumulates in a project notebook. Even Emacs doesn't have all the approaches I would want for quickly and accurately capturing ideas on the fly.
So, for the time being, until I have kept a notebook long enough to design a program to encompass it, I'm keeping a notebook on paper. Already I have a hard time figuring out how I did without it. Read the article linked above, it is good.