A book I have found useful and still do is
Racing Sailboats by Chris Jackson. It is quite relevant to todays designs and easily obtainable, reasonably priced and quite easy to understand.
Worth a try.
Regards ChrisG

Hi!
There are different types of internals, but I've never needed a book. If you look around here, you will surely find one or the other idea that has already been incorporated. I myself rebuilt and changed the sail guides 6x until it suited me.
I'll have to see if I can find anything in my files.
>> Who seeks will find!!