GeeMac,
I did a Vawt for my first project and used the metal duct like you mention. Here's a link to a short video.
http://s241.photobucket.com/albums/ff74/compoast/?action=view¤t=savonius4.flv
I never completed it with alternator because my design lacked integrity. It was basically two half rounds made from duct pipe and capped at each end by plywood rounds. Overall 60" tall by 24" wide. It spun real nice in very light wind but in higher winds it vibrated badly.
I may try a VAWT again one day and if I do I will forgo the more efficient designs like Ed's Lenz II because I'm just not that good at building. Instead I will go with a basic Savonius design (two half rounds) and what it lacks in technology I will make up for in simple, light weight, sturdy construction and with emphasis on balance and bearings. Instead of metal half rounds I may try those cardboard tubes used as forms for pouring concrete as a mold to form fiberglass half rounds. Probably go with 60 or 72 inches tall by 30 inches wide. Just an idea I may never get to and if I do it wont be much power anyway. I did this because I live in town and thought I couldn't get away with a HAWT. But my HAWT has been flying for almost a year now with up to 6 foot blades and no one has complained. In fact, people love it.
Andy
