That's the classic thorny question that I'm always getting asked.
In actual hours I'd guess about 50. In elapsed time once I pick up the stave probably an average of 3 weeks.
Mind, maybe you'd be better off asking Mrs Cat
I only work on a bow when I want to, I generally work in short bursts and spend ages just thinking about it (which I don't account for) and writing it up on my 'Bowyers Diary' blog.
As an illustration of how hard it is to actually know how long we spend, I went out to the garage 'for a few minutes' to do some final clean up on the back of my latest Yew bow which was just about finished and had already had several coats of Danish Oil (I'd noticed a few fine tool marks).
I went over one limb with scraper and fine wet & dry paper...
just so happens I'd noticed the time I when I went out, turns out I was at it for 45 minutes on one limb of a bow that may would have considered 'finished' already
.
Maybe I should revise that 50 hours to 75?
Just as well I enjoy it
Del
Did one in an hour a couple of years ago with only an axe, just to prove I could!... I had 10 minutes to spare too