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A FREE 3 MONTH PRO MEMBERSHIP GOES TO the first one to post their bamboo bladed turbine in the comments below. Yeah.
These are really easy and require pretty much no money, no skill, no precise measurements, nor attention to detail.
And they work nicely!
Seriously, try it out and see. This project is doable with almost entirely salvaged materials so it's a perfect first foray into mid sized wind projects.
Step 1: What You Need
-Saw (circular saw recommended)
-Angle grinder with sanding disk (maybe you could use a sanding block)
-About 1 hour per blade.
Step 2: Cut to Length
Step 3: Cut Into Thirds Lengthwise
Step 4: Cut the Leading Edge
Mark 6 inches (15cm) from the base on one edge (the top edge in this picture).
And mark about 2 inches (6cm) perpendicular to the other edge at the tip (up from the bottom edge in this picture).
Step 5: Sand Into Shape and You're Done!
First sand the nodes flat. I still had some unevenness on the concave side at each node but whateva'
The leading edge is simple; just round it off
The trailing edge is also simple; sand from the concave side only to give the blade a standard airfoil shape.
The tips can be a bit thinner. I think they will spin faster if the ends are lighter plus they will have less resistance when they are thinner. Also you will notice that your angle of attack is different at the tip than at the base.
Step 6: Nothing Fancy But It Works!
Actually, reinforce the base of the blades with some metal first (see image note).
I was inspired by some other instructables like this one https://www.instructables.com/id/EDXXV4R4SLEP286NHD/ but PVC is really unhealthy to work with and I didn't like the thinness of the design so I thunk up this here design with a deeper curve at the root.
The point of these blades was to see how little care and how much inaccuracy I could get away with. Word on the street is that a perfect airfoil and a crappy airfoil only differ by about 20%. So you can probably get 80% of the result with only 20% of the effort!
Also bamboo is cheap/free in my neck of the woods so...
And remember to ask me to clarify any points that you don't get.