Caladorcp, we get people that post in these threads asking all kinds of questions expecting various types of replies. Don't expect us to read your mind in order to know what type of reply you want. Most folks want a real answer with an explanation as to why it won't work. And then some of them go on to say why they disagree and then say it will work. Funny thing that is, it makes me wonder why they asked in the first place.
BUT, not many people come on here like you. You posed a scenario first. Then you said you just wanted a yes or no answer and a simple explanation which you got from me along with reassurance that you are definately among many others that have had the same idea. You are NOT alone. Then you complain about other posters making you feel stupid. In my opinion everyone has given you just what you asked in the first place. If you feel stupid, it is not our fault and quite honestly I cannot understand why you feel that way since as I previously stated, many other people make the same assumption.
Last thought: As many of these discussions as I have watched, no one EVER comes up with the idea of putting a sail on a vehicle. Not really practical in city driving, but the point still stands.