Here is a link to a free book by
John Letcher's, the bible on , "Self-steering for sailing craft" It is an incredible read by an incredible man not only is the book worth reading , it is worth doing some research on John and his self designed and built yacht, Aleutka 25ft bilge keel sailed engineless in the early sixties.


jesterchallenge.wordpress.com/articles/self-steering/

That is a great link.
Thanks for posting it.