Help yourself to a huge free knowledge base from the radio hams at http://www.arrl.org
Most YAGI recipes have been refined for years, with extensive use of computers to search out the best gain and front-toback ratios. If you want to build one, there is LOTs of info.
I know this may just be a cultural thing for me, but I am ignorant about the term "uda" . Does this mean I have maybe completely missed the point?