installation angle for simple PVC blades

[asheets]

OK, I cut my PVC blades very simply, by ripping them down the middle with the table saw (so every length of pipe yields 2 blades with minimum waste).  Then, as I was putting them on the rotor of the Ametek, I started thinking about what the alignment out to be.  I came up with 3 trains of thought, but couldn't decide which one was best.

1. Neutral -- flat side of the half-circle parallel to the ground (looking from the edge of the blade toward the rotor, with the blade parallel to the ground).  Average lift, no drag.  Closest to an airplane's wings while sitting on the ground.
   
2. positive lift -- flat side of the half-circle rotated counterclockwise.  More lift (unless you rotate too much, at which point the wing will stall), no drag.  Closest to an airplane's wings while yawing during a climb or takeoff
   
3. negative lift -- flat side of the half-circle rotated clockwise.  Less lift, more drag. Closest to an airplane's wings while yawing during a decent, but closer to the design of a cup anemometer.
   
   

I'm also considering filling in the half-circle with some kind of foam so that the half-pipe is closer to an actual airfoil without doing any real carving.

Any thoughts on the matter?

[asheets]

Now that I think about it a bit more, replace the word "yaw" in all instances with the word "pitch".  I went through pilot training -- I should have known better

[Countryboy]

I google searched the board for 'zub woofer', and quickly found this gem.

http://www.fieldlines.com/story/2005/4/17/6437/83378

[ghurd]

I'll go with Woofer's sketch, in Countryboy's link.

Lots of trys, but nothing got better than that.

I thought about it, but never got around to 'touch-n-foam' in them.

I have a feeling it would not be as good.

G-

[georgeodjungle]

so far for me:

6 to 8" sdr cut in 6ths.Not in half.

there's been a lil stall "forward" on top end.

tried foam with a fiber glass wrap.

not good for low end.

& sdr not pvc has worked vary vary well.

[wooferhound]

Do not use the program in the link above, it is inaccurate.

This program is not accurate because it measures from the center of the space inside the pipe, and not from the centerline of the outside diameter, as the diagrams show.





Here are the complete plans . . .

http://www.fieldlines.com/story/2003/11/11/172721/53

[wooferhound]

[Seaspray0]

I was thinking about the high end stalling.  The leading and trailing edge is what bothers me.  The trailing edge especially.  I was thinking you might get better performance at the high end if the trailing edge was cut slightly different.  For a 7 degree tip, hold the protractor at 7 degrees and align it with the inside edge of the tube at the centerline.  Then I'd mark the outside edge where the protractor hit it.  I'd cut the trailing edge from center at the hub straight line to the new mark rather than the centerline (will give you a bit more chord at the tip where the high end needs it).  File the excess off the inside of the trailing edge until you get a sharp edge (align the file to your leading edge as you go down the blade to get the proper angle).    Give a bit of rounding to the leading edge and you should see more of an airfoil shape, especially at the tip.

[Seaspray0]

What if you put the outside diamater of your pipe into that program, wouldn't it then give you the proper measurements?