[nibs]

Now I see that the first post has shown up, I will leave this one because it is a bit different.
MOD feel free to delete if you think it redundant.
Darn, a couple of nights ago I wrote a few paras on this but must not have pushed the post button.
The main thrust of my unsent post was - Why all the interest in exotic blade materials?
Wood with the exception of abrasion resistance is an almost perfect material. Wind turbine and wooden aircraft blades will obviously withstand wind speeds of hurricane force, they can be laminated into desired shapes and carved with hand tools. We used to sell a thin self adhesive stainless steel leading edge cover for our aircraft props, but abrasion was never a problem for our turbine blades.
Buckminster Fuller claimed that wood can be flexed to within 90% of its modulus of elasticity an infinite number of times without failing. There may be another material that equals this, I do not know of it. Wood is tremendously strong in tension, the fastening usually breaks before the wood fails. The greatest amount of stress on high speed turbine blades is radial. The big guys are different, they are not spinning fast so their main load is wind pressure.

Vertical axis blades pass through the wind shadow of the other blades and of the axis column, as they rotate, so I think the downwind argument is a bit thin. I have read that a downwind horizontal machine can set up harmonic vibrations as the blades pass the tower, under some conditions. I have no experience with downwind machines, so cannot comment.

It is late I must go and get rested up in case (not likely) for the pushups Al thinks he will win.