Yes and so? Don't leave us all hanging. Should this idea be scrapped or can something be done to maintain torque under load? Otherwise it is just a tease.

It is my opinion on the matter that these "pipe", "PVC", "gutter", "tube", or what have you, blades are actually worth while and need some thought applied to them. The leading edges as cut out are invariably sharp with no rounding at all, like a knife edge, even just a sort of dull knife. This works for a narrow range of TSRs, requiring that the blade spin at a rotational speed that is close to a fixed ratio of the wind speed. So if an extra heavy load is applied the rotational speed is reduced below this speed and the torque stalls out. Or so it would seem.

Those who follow this line of endeavor usually go on to the "logical" conclusion that more blades are needed and then add them. Six and eight bladed rotors are the result.

Another, possibly better, answer is suggested herein. The leading edges would hold the flow attachment for a wider range of TSRs if they were made more rounded like the leading point of a comet with its radius of curvature. This can be done by maybe bending some sheet metal aluminum (or even steel) to the proper shape and fastening it on to the leading edges with some pop rivets - easy and simple to do. (I think pop riveting is a great way to fasten things together.) The result? Blades that are now thicker at the leading edge but will have better start up torque and will maintain torque under load better.

I have placed this post thread on my hot list for purposes of keeping an eye on it. I bend aluminum sheet metal to within close tolerances of curvature by means of wood dowels as a template and get the folded edge to close back quite well with with some padding applied to the surfaces that is struck with a rubber mallet. See the images on my website.