In the late 1970's I wrote a book, High Speed Sailing Design Factors, that one might have thought to be too mathematical to appeal to sailors and too much about boats and sailing to appeal to mathematicians. Unaccountably, the book sold well on both sides of the Atlantic. In the 15 or so years that have elapsed since the book was written, my ideas have evolved and the focus of my interest has shifted from conventional sail rigs to alternative means of harnessing wind power. As these ideas unfolded, I would work them out and write a paper. In this way, a body of unpublished work has accumulated and we now have this book. This present book, like High Speed Sailing will make use of equations, but on no more than a high school level. This is necessary in order to make quantitative statements as opposed to qualitative speculations. The Conclusions drawn from mathematical analysis will always be spelled out in plain English, so that those who find equations intimidating will not be left out in the cold. This book covers: Performance Criteria Hulls and Outriggers Wingsails Wind and Water Tubines Rotors Boards and Rudders Hydrofoil Applications Symmetric Multihulls Asymmetric Multihulls as well as a postscript and some afterthoughts.