I built a beautiful set of 11' blades for the machine within a month of going live. I used a variety of sources for designing my final blade profile (mostly OtherPower.com info). They had 4 degrees at the root, and a gradual decrease down to 0 at the tips. Since the hub already has 4 degrees built into it, the profile was pretty agressive. I re-used the 4 blade hub and the thing went into overspeed in the very first wind. The following spring a built a new 3 blade hub, with little if any built in pitch on the hub (can't remember now, it's been well over a year ago, but I think it was 2 degrees). The turbine actually did decent for a couple weeks, and the blade noise was significantly better. Production went up maybe 20%, but 20% of almost nothing is still almost nothing. I feared high winds with those blades without a furling tail, or all the safisticated controls like the Endurance Wind Turbine uses for an A/C induction motor wind turbine (a beautiful machine, but way out of my price range). The 3-blade hub was an "experiment" and as such, was not built up to be used more than a few days. Since it was working OK, I forgot about the temporary nature of the hub. We had a pretty good wind one night and I remember hearing the thing running most of the night. Really early, before daylight, I noticed the turbine was quiet, and figured it went into overspeed. Looked at it as soon as I got up that AM and there were no blades on it. I suspected a shaft failure, but found the hub had "oil canned" since it hadn't been beefed up in the "temporary design" to deal with that problem (like my original hub). With 2 blades pretty much destroyed, one damaged but usable, and one left over from the 4 blade hub, it was evident I could go back to the original system or start laminating and carving again. The original design was reinstalled, I settled for my 50 KWh's a month and started working on my solar prrojects, which actually give me a pretty decent ROI.
I too looked at the Jacobs feathering prop design (I'm a pilot flying with that same concept on my airplane), as well as possible tail furling systems. The real issue is minumum wind for generation. I'm not as educated in wind theory, or have the overall wind generation experience of the guru's on this site, but I can explain in simple layman terms what the issue is for me. Minimum generation for the turbine is 2200 watts, any less and the motor "uses juice" instead of generating it. The generation band for the unit is very narrow. Prairie Turbines gets away with this limitation when the unit is working in wind zones where they can "afford" to waste off some of the wind energy. The narrow generation band and poor efficiency blades work decent in those good wind zones, but do not in marginal ones. I've had days, even weeks I could have produced a 1 KWh, every hour, for that long,with a better matched turbine for my winds, but the unit had not met the "2200 watt minumum" kick in power (well, actually 120 RPM's, but one in the same; not enough wind to support generation with this turbine).
I'm presently about half way through the new book from Dan & Dan, and the first several chapters pretty much explains a lot of the problems I've seen with this design. I need a turbine that will make much less than the 2.2 KW threshold of the Breezy 5.5. I will be much more satisfied with 600-1200 watts all day, for days, than the ocassional 2300 KW's for a few hours.
Finally, my posting about this is not to knock the product, but to make others aware of what to watch for based on their unique wind resources and any close proximity of neighbors. A series of posts like mine, found by me a few years ago, could have saved me a lot of work, heart ache, and money. And I have a bunch of emails and past phone calls from other builders in the Midwest that have experienced the same results.
Tom Sullivan