Thanks for your valuable contribution.

I've looked at your web site in the past, and like what I've read
there.  I happen to be a sailor and have sailed my homebuilt boat to
Hawaii and back to the West Coast so I know a little bit about tweaking
sail shaped to extract a little more power from the wind.  Of course I
did use some NACA data to layup my foam filled rudder, and even capped
it top and bottom to try to keep the flow over the rudder and not up
and down, bypassing it.

I'm considering building a small vertical wind generator for the boat.
In the 1980s while cruising I built a two bladed prop from NACA data
and used it on a surplus tape drive servo motor.  It was too noisy and
shook the rigging as it oscillated a little through the eye of the wind.
A vertical turbine shouldn't have the oscillation/vibration problem.

You show a bulbous leading edge on your two-blade drawing.  Do you have
any suggestions regarding that shape relative to the rest of the
blade's dimensions?   What do you suggest as an offset for the
blades?  

It seems to me that capping the two blades on top and bottom with the
cap tying the two blades together would help channel the air past the
blades plus add much to the strength of the assembly.  Any thoughts on
this?  

It is extreamely common for "lift" to attributed to both bernoulli and newtonian laws of physics.

Predicting blade performance using vector algebra likely approximates reality because as I see it in the diagrams on your web site the vectors your generating approximate the lift vector described by averaging the pressure differentials on the upper and lower surfaces of the profile except your neglecting drag vector modifications.

If pressure differentials (which is how lift is described as I see it) make no nevermind then how do vortex generators substantially increase performance at extreame AoA's. I'm assuming that given your use of thin airfoils you are not willing to attribute any lift contribution to the upper surface of a wing but operate on a deflection only philosiphy.

Sails and in particular those littler sails ahead of the mainsail (I'm no sailor) act in concert the same way as slats/slots or other leading edge flaps do in an aircraft wing. It's not a new idea it's been around since the messerschmitt ME262 back in 1942-3 ish. Maybe longer but that's the oldest reference I can find.

As for doubling thin cambered profiles I've tried it. Leading edge flaps actually of various sizes and I assure you despite my grandest hopes it induced premature stall at higher rpms. Likely poor design but I don't think two full size blades riding in tandem (and looking just like a bi-plane wings complete with very early Naca profiles) will doing much better.

Speaking of induced premature stall lets talk about induced drag instead. As I understand (because I've read it all over the place)induced drag is attributed to the fact that the air flowing over a wing does not match up perfectly with the air that it parted from at the leading edge. the vortices generated as a result of the air coming together at different speeds at the trailing edge of the wing causes induced drag (drag attributed to lift). This is how I've seen it explained and it makes perfect sense and it has been modeled and visualized and computed and speculated and other ed's all over the place and no-one denies it. The flow visualizations that you see that don't show trailing edge vortecies have made some assumptions to simplify the graphic.

Trust me Anthony we're not a pack of dumbdumbs here and the guys at riso aren't a pack of dumbdumbs nor are the guys at boeing or lockhead or bombardier or saab or cessna or sandia national labs or......

The guys and gals at the airport aren't stupid either that's why when a large passenger jet comes in for a landing a procedure is in place to ensure other aircraft don't fly through the downwash that is created, yes it seems they are aware of deflected air afterall.