There is not a lot to go on with PVC blades. "Try it and see" is what I do.
The PVC blades I make come down to a guess on the first set.
The 2nd set is a guess at fixing the problems the 1st set had.
The 3rd and 4th sets are trys at getting a little better.
Longer/shorter and/or wider/thinner.
The smaller ones look OK. Root may be a little wide.
I don't like the big ones.
The huge root looks like it will just cause drag.
Plus I think 4' is about the limit on PVC. Loaded, in a strong wind, they bend back more than most people would expect. It would not surprise me if the 5.5'-er hit the tower.
Most reports show PVC blades will break. Maybe not today, but it will happen.
That's a big chunk to go off at high speed.
Might find a 4' that is a little wider than the 1st 4' set will drive the treadmill motor OK. I believe PVC can somewhat 'drag past stall'.
Might make a decent low wind machine, with less danger.
On the bright side, the trailing edge is in the right place. :-)
G-
