This design guide was written to capture the author's practical experience of designing, building and testing multi-rotor drone systems over the past decade. The lack of one single source of useful information meant that the past 10 years has been a steep learning curve, a lot of self-tuition and many trial and error tests. Lessons learnt the hard way are not always the best way to learn. This book will be useful for the amateur drone pilot who wants to build their own system from first principles, as well as the academic researcher investigating novel design concepts and future drone applications.