I am currently writing an e-book about how to
build golf clubs from components. It will show golfers
how to make their own clubs, and save a lot of
money compared to the high priced brands, but 
with similiar quality and results.Is there a
demand online for this type of information?

I would question whether many golfers are also avid Internet users but
the success or otherwise of an ebook will depend on the marketing
skills that you use.

However, as most golfers are well-heeled and as there is also a lot of
mumbo-jumbo about selecting the 'right' clubs, my guess is that, if
there is any online demand, it may be only be modest.

But you will never know unless you try and success often comes to
those who prove the doubters wrong.

Good Luck!