Hi All,
Last Sunday I had an urge to make a new set of blades for my hobby mill. I normally run PVC blades on it as it has no furling. The PVC will spin up nicely, depending on the length, and then stall in higher winds, thus somewhat protecting the mill from burnout.
This time I thought I’d try a set of constant chord, constant pitch wood blades. I looked in my scrap pile of wood. Not much there of any thickness, so I decided to experiment.
I found 3 pieces of very dry cedar 1x4's. Did some lay-out and got to planing. The boards were not choice, but in about an hour I came up with these.
Since I used the face of the 1x4, I had to make some wedges to pitch the blades. I chose 10* as a starting point.
Over the next couple evenings I was able to get everything drilled, balanced, sanded and mounted. The weather was going to cooperate, so I decided to test run them unfinished.
I am real pleased with how the blades did. The mill was up for 2 days, seeing winds from 7-15 mph during the sunlight hours. The rotor is 6 ft. (too much for my mount), and it hit 900 rpm in a 20+ mph gust. The start-up was 6-7 mph and cut in was 8-9 mph. I've got some options to consider now.
Some help now please.
1) If I cut the diameter down a few inches I should get higher speed, but what effect would this have on my cut in?
2) What effect should I see if I keep the length, but change the angle from 10 to 7*