Howard Wilkinson wrote:
Paul:
You wrote:
Chuck, quite some time ago, as I recall it was at the first Golden State
Flyin over a year ago, Don Bates analyzed the IVO and found that the
roots of the blades were going into a negative angle of attack around 180
MPH.
Tracy tried one and confirmed this. Now Jim has tried it and also
confirmed this. I think it has nothing to do with the pitch.
Paul Lamar
I suspect that this refers to the way the IVO changes pitch. As the
material in the blade twists under the influence of a steel rod with an L
shaped end well out from the center, it stands to reason that the outer
portion of the blade changes pitch the most, and the root probably not at
all. When you look at relative pitch.... the pitch of the blade as relates
to actual relative wind which is composed of the combined vectors of forward
speed and rotational speed of the prop the ultimate total result at high
forward speed is a negative relative angle of attack....... A prop's
interaction with the air can be a bit difficult to visualize at times, but
this is very apparent to me. A typical variable pitch prop rotates the
entire blade equally as a unit..... the IVO does not.
Perhaps a very large spinner....... H.W.
I wrote a little program to calculate the optimum pitch and twist.
At low speeds optimum twist and pitch change rapidly.
At higher speeds about 120 MPH optimum twist settles down and
only angle of attack is important. The IVO is a good prop
for low HP slow airplanes.
Here is the data. It is best studied if one prints it out.
Let me know if anybody wants the source code to the program.
It is written in good old QB for DOS but it will run in Windoze.
IMHO the mechanical strength of the IVO is inadequate for large four
cylinder direct drive aircraft engines. These engines put out enormous
torque pulses twice per rev that subjects any prop to enormous bending
loads in the plain of rotation. We are talking about 1000 foot pound
torque pulses.
Paul Lamar
The Aircraft Rotary Engine Newsletter. Powered by Linux.
http://home.earthlink.net/~rotaryeng/ http://www.linux.org
Six foot diameter prop and 2700 RPM
MPH = 40.9
Radius Circ MPH 0 Angle of Attack
0.3 48.2 40.33
0.5 96.4 23.00
0.8 144.6 15.80
1.0 192.8 11.98
1.3 241.0 9.64
1.5 289.2 8.05
1.8 337.4 6.92
2.0 385.6 6.06
2.3 433.8 5.39
2.5 481.9 4.85
2.8 530.1 4.41
3.0 578.3 4.05
Twist = 36.28 Ratio Twist/Root = 0.90 Ratio Twist/Tip = 8.96
----------------------------------------------------------------
MPH = 54.5
Radius Circ MPH 0 Angle of Attack
0.3 48.2 48.54
0.5 96.4 29.51
0.8 144.6 20.67
1.0 192.8 15.80
1.3 241.0 12.76
1.5 289.2 10.68
1.8 337.4 9.19
2.0 385.6 8.05
2.3 433.8 7.17
2.5 481.9 6.46
2.8 530.1 5.88
3.0 578.3 5.39
Twist = 43.15 Ratio Twist/Root = 0.89 Ratio Twist/Tip = 8.01
----------------------------------------------------------------
MPH = 68.2
Radius Circ MPH 0 Angle of Attack
0.3 48.2 54.75
0.5 96.4 35.27
0.8 144.6 25.25
1.0 192.8 19.48
1.3 241.0 15.80
1.5 289.2 13.27
1.8 337.4 11.43
2.0 385.6 10.03
2.3 433.8 8.93
2.5 481.9 8.05
2.8 530.1 7.33
3.0 578.3 6.72
Twist = 48.02 Ratio Twist/Root = 0.88 Ratio Twist/Tip = 7.14
----------------------------------------------------------------
MPH = 81.8
Radius Circ MPH 0 Angle of Attack
0.3 48.2 59.50
0.5 96.4 40.33
0.8 144.6 29.51
1.0 192.8 23.00
1.3 241.0 18.75
1.5 289.2 15.80
1.8 337.4 13.63
2.0 385.6 11.98
2.3 433.8 10.68
2.5 481.9 9.64
2.8 530.1 8.77
3.0 578.3 8.05
Twist = 51.45 Ratio Twist/Root = 0.86 Ratio Twist/Tip = 6.39
----------------------------------------------------------------
MPH = 95.5
Radius Circ MPH 0 Angle of Attack
0.3 48.2 63.21
0.5 96.4 44.72
0.8 144.6 33.43
1.0 192.8 26.34
1.3 241.0 21.61
1.5 289.2 18.27
1.8 337.4 15.80
2.0 385.6 13.91
2.3 433.8 12.41
2.5 481.9 11.20
2.8 530.1 10.21
3.0 578.3 9.37
Twist = 53.84 Ratio Twist/Root = 0.85 Ratio Twist/Tip = 5.74
----------------------------------------------------------------
MPH = 109.1
Radius Circ MPH 0 Angle of Attack
0.3 48.2 66.17
0.5 96.4 48.54
0.8 144.6 37.04
1.0 192.8 29.51
1.3 241.0 24.36
1.5 289.2 20.67
1.8 337.4 17.92
2.0 385.6 15.80
2.3 433.8 14.12
2.5 481.9 12.76
2.8 530.1 11.63
3.0 578.3 10.68
Twist = 55.48 Ratio Twist/Root = 0.84 Ratio Twist/Tip = 5.19
----------------------------------------------------------------
MPH = 122.7
Radius Circ MPH 0 Angle of Attack
0.3 48.2 68.56
0.5 96.4 51.85
0.8 144.6 40.33
1.0 192.8 32.48
1.3 241.0 26.99
1.5 289.2 23.00
1.8 337.4 19.99
2.0 385.6 17.66
2.3 433.8 15.80
2.5 481.9 14.29
2.8 530.1 13.04
3.0 578.3 11.98
Twist = 56.58 Ratio Twist/Root = 0.83 Ratio Twist/Tip = 4.72
----------------------------------------------------------------
MPH = 136.4
Radius Circ MPH 0 Angle of Attack
0.3 48.2 70.54
0.5 96.4 54.75
0.8 144.6 43.32
1.0 192.8 35.27
1.3 241.0 29.51
1.5 289.2 25.25
1.8 337.4 22.01
2.0 385.6 19.48
2.3 433.8 17.45
2.5 481.9 15.80
2.8 530.1 14.43
3.0 578.3 13.27
Twist = 57.27 Ratio Twist/Root = 0.81 Ratio Twist/Tip = 4.32
----------------------------------------------------------------
MPH = 150.0
Radius Circ MPH 0 Angle of Attack
0.3 48.2 72.19
0.5 96.4 57.28
0.8 144.6 46.05
1.0 192.8 37.89
1.3 241.0 31.90
1.5 289.2 27.42
1.8 337.4 23.97
2.0 385.6 21.26
2.3 433.8 19.08
2.5 481.9 17.29
2.8 530.1 15.80
3.0 578.3 14.54
Twist = 57.65 Ratio Twist/Root = 0.80 Ratio Twist/Tip = 3.96
----------------------------------------------------------------
MPH = 163.6
Radius Circ MPH 0 Angle of Attack
0.3 48.2 73.59
0.5 96.4 59.50
0.8 144.6 48.54
1.0 192.8 40.33
1.3 241.0 34.18
1.5 289.2 29.51
1.8 337.4 25.88
2.0 385.6 23.00
2.3 433.8 20.67
2.5 481.9 18.75
2.8 530.1 17.15
3.0 578.3 15.80
Twist = 57.79 Ratio Twist/Root = 0.79 Ratio Twist/Tip = 3.66
----------------------------------------------------------------
MPH = 177.3
Radius Circ MPH 0 Angle of Attack
0.3 48.2 74.79
0.5 96.4 61.47
0.8 144.6 50.80
1.0 192.8 42.60
1.3 241.0 36.34
1.5 289.2 31.51
1.8 337.4 27.72
2.0 385.6 24.69
2.3 433.8 22.23
2.5 481.9 20.20
2.8 530.1 18.49
3.0 578.3 17.04
Twist = 57.75 Ratio Twist/Root = 0.77 Ratio Twist/Tip = 3.39
----------------------------------------------------------------
MPH = 190.9
Radius Circ MPH 0 Angle of Attack
0.3 48.2 75.83
0.5 96.4 63.21
0.8 144.6 52.86
1.0 192.8 44.72
1.3 241.0 38.39
1.5 289.2 33.43
1.8 337.4 29.51
2.0 385.6 26.34
2.3 433.8 23.76
2.5 481.9 21.61
2.8 530.1 19.81
3.0 578.3 18.27
Twist = 57.56 Ratio Twist/Root = 0.76 Ratio Twist/Tip = 3.15
----------------------------------------------------------------
MPH = 204.5
Radius Circ MPH 0 Angle of Attack
0.3 48.2 76.74
0.5 96.4 64.77
0.8 144.6 54.75
1.0 192.8 46.70
1.3 241.0 40.33
1.5 289.2 35.27
1.8 337.4 31.23
2.0 385.6 27.95
2.3 433.8 25.25
2.5 481.9 23.00
2.8 530.1 21.10
3.0 578.3 19.48
Twist = 57.26 Ratio Twist/Root = 0.75 Ratio Twist/Tip = 2.94
----------------------------------------------------------------
MPH = 218.2
Radius Circ MPH 0 Angle of Attack
0.3 48.2 77.54
0.5 96.4 66.17
0.8 144.6 56.47
1.0 192.8 48.54
1.3 241.0 42.16
1.5 289.2 37.04
1.8 337.4 32.89
2.0 385.6 29.51
2.3 433.8 26.70
2.5 481.9 24.36
2.8 530.1 22.37
3.0 578.3 20.67
Twist = 56.87 Ratio Twist/Root = 0.73 Ratio Twist/Tip = 2.75
----------------------------------------------------------------
MPH = 231.8
Radius Circ MPH 0 Angle of Attack
0.3 48.2 78.26
0.5 96.4 67.42
0.8 144.6 58.05
1.0 192.8 50.25
1.3 241.0 43.89
1.5 289.2 38.72
1.8 337.4 34.50
2.0 385.6 31.02
2.3 433.8 28.12
2.5 481.9 25.69
2.8 530.1 23.62
3.0 578.3 21.84
Twist = 56.41 Ratio Twist/Root = 0.72 Ratio Twist/Tip = 2.58
----------------------------------------------------------------
MPH = 245.5
Radius Circ MPH 0 Angle of Attack
0.3 48.2 78.89
0.5 96.4 68.56
0.8 144.6 59.50
1.0 192.8 51.85
1.3 241.0 45.53
1.5 289.2 40.33
1.8 337.4 36.04
2.0 385.6 32.48
2.3 433.8 29.51
2.5 481.9 26.99
2.8 530.1 24.84
3.0 578.3 23.00
Twist = 55.89 Ratio Twist/Root = 0.71 Ratio Twist/Tip = 2.43
----------------------------------------------------------------
