You can't go DDWFTTW with sails. No one has gone DDWFTTW on water. It will take a propeller to do when it happens. If you want to contradict this you need to

You can't go DDWFTTW with sails. No one has gone DDWFTTW on water. It will take a propeller to do when it happens. If you want to contradict this you need to post a link of someone agreeing with you, else you misunderstand DDWFTTW. (The link on Wingsail leaves out 0 and 180 degrees for the Points of Sail which are the only two we care about, directly downwind and directly upwind, the wiki article makes no comment on DDWFTTW. This thread is just people saying random words like AC72 or broad reach. If your ideas correct someone else will sum it up for you and you can link it. )