Brent Swain has a home mede wind generator on his boat. Works very well. e-bay generator and a home made blade out of a 2 x 4 gives him a steady 2 amps. He has to strap the prop on occasion so he doesn't over charge...
His book has several - DIY projects for budget wise boaters. do a web search for Brent swain - his book is called origami boatbuilding.