About 6 months ago I was doing some blade calculations and came to the same conclusion as some others have lately. The root acording to theory should be much wider, but I had this nagging in the back of my head that said it wasn't right(not to say my nagging feeling is). My intuition tells me the root if covered by large cord blades will be a sespool of turbulence. Could be wrong so I went on a hunt to find a turbulent wake analysis for a wind turbine and found one at the risoe site. I'm no pro at interpreting these images but they confirm what one would expect. Most turbulence is concentrated at the tips and the root with the center of the rotor area being much less turbulent. Does this mean we can get away with greater cord widths at say 30 - 40% blade length?
Doesn't a turbulent root area serve to compound the betz effect and further deminish efficiency. The faster the turbulent air behind a turbine blade reforms into smooth flow the better, right? the longer the "tail" of turbulent air the larger the cone in front and I think this is shedding too much potential power "around" the rotor rather than through it.
Here's a thought and an image after. Ditch the root and make it of a strong material with additional depth but much reduced cross section to produce as little interference with air flow as possible. Basically the exact opposite of the status quo. Place the maximum cord at 30 - 40% blade length, this is now where the effective or lifting portion of the blade starts and don't be afraid to make it much wider than normal.
Theory in my head is that the relatively unobstructed air flow through the center of the rotor area should "invigorate" for lack of a better word the center of the turbulant tail and reduce the cone ahead and the tail behind, possibly allowing the air through the effective portion of the rotor area to slow beyond the 2/3 theoretical limit, sort of like the center is becoming a venturie and pulling air through the blades rather than the air shedding around them.
Just a thought that been rattling around in my head.
BTW. this is why I was so attracted to the maple seed, It's cord distribution follows my theory.