I built my mill (
http://www.fieldlines.com/story/2007/2/19/173948/328 ) and people mentioned that my blades were mounted too close to the center of the pipe. They also mentioned that the angle looked too steep. So I changed it, and remounted them right on the edge.
Now, of course, they're even steeper. I want to make a set of the "Zubwoofer" blades, but I have the following questions. Thanks!
Using Zubwoofer method, you measure 7 degrees and 25 degrees from a point on the outside of the pipe. Since we're measuring angles from the outside rather than an invisible point in the center of the pipe, you only really have 180 degrees of available angles. So I figured out the circumference of the pipe (pi x diameter) and divided it by 180, then multiplied it by 7 or 25 as appropriate. I mention this so you can follow my math (and tell me where I'm wrong?)
That would result in the following measurements of the root and tip of the blades (multiply the root by 2 if you make a double blade out of a single piece like zubbly and wooferhound describe):
- inch pipe = 0.733 inches wide at tip. 2.618 inches wide at root
- inch pipe = 0.977 inches wide at tip. 3.48 inches wide at root
- inch pipe = 1.22 inches wide at tip. 4.36 inches wide at root
My current blades are made from 3 inch diameter pipe. And using that same math as in the zubwoofers, my 2 inch tip is 38 degrees, and my 4 inch base is 76 degrees. So I see why you guys said they look too steep!
Question 1: I am surmising that to get blades that aren't teeny, I need to use a 10 inch or larger pipe. Is that correct?
Question 2: My current blades use what I'm calling "thick" PVC. Maybe 1/4 inch thick. Do I need to get the "thin" stuff to make these blades? I like the thick stuff because the blades do not bend much (and therefore catch more wind?) if at all. They are very tough.
Question 3:I've read in other posts that 4 foot diameter is preferred on these Ameteks. What about width. If my math is correct above, should I go with 6, 8, or 10 (or even bigger?) pipe? As you can see, the base gets pretty big.
Thanks for your help! And if you are one of the non-PVC believers, and say that wood is the best, please post a simple guide to wood blades, or email them to me at mobile(at)jeharper.com
Once again, thank you guys! Wind power is awesome! Even when I don't THINK the wind is blowing, my voltmeter tells me otherwise!