I congratulate you on no heroics, coulda lost the both of youse…
The older I get, the more I realize that heriocs are usually a bad idea.
I don't think the blades hit the tower. All the evidence suggests flutter causing failure at the blade root, and then tower contact after root failure. Evidence to support this:
1. The blade roots were indented from the hub on both the back side and the front side, suggesting flutter.
2. One blade was found mostly intact, and there is no scraping at the tip where tower contact from flexing would have happened. I know what this looks like because my first set of blades flexed and hit the tower. They had a very defined scrape at the tips.
After those first set contacted the tower, i made wedges and gave the generator a nose up angle for better clearance.
I guess now I just need to decide if moving the generator farther out to increase the offset is worth the trouble, or if I should rely on my manual furling like i have been doing.
I also think there is an assymetric thrust component to all of this. I changed the rotation on this set of blades from the last ones. I think the next set will go back to the clockwise rotation of the set that were the most successful.
Right now, my plan is to build another set of blades very similar to that successful set, but better balanced and finished. The balance and noise were my main complaints with that set, and that is easily fixed.
I'm also going to extend the hub about 4" (100mm) farther out along the blades. I'll just weld on some steel plate ears. I always thought that hub was a little small, and I'll feel better with a bit better support.
A new yaw bearing is in the mail. I'll machine an adaptor for the tower top to hold it in place better. Right now its just kind of sitting there. I've never really been happy with that setup, so now is my chance to make it right.