Marvin Kaye wrote:
-- IVO PROP FAILURE!
snip...
Reported by Jim in Elkhorn, Nebraska. -- Posted:
9/8/97
That's almost 3 years ago and a very different prop than the Magnum.
There's a lot of water passed under the bridge since that report for both
versions of the Ivo. The hub design of the Ivo Magnum is considerably
beefier (I'd put it at 1.5-2" thick with a contact area on the hub that
looks to be about 3" wide and maybe 5" long) than their ultralight prop and
seems to be coming along nicely, at least based on what I saw at S'n'F. I
know that there's at least one Lancair ES flying with a Magnum reporting
cruise speeds in excess of 205kt, and will contact the factory on Monday to
see if they'll put me in touch with other high performance airplane owners
who are flying the Magnum satisfactorily. I'll report whatever findings
there are.
<Marv>
So that is the latest Marv? The two inch thick hub?
The two inch thick hub is one fundamental problem.
Too thin!
That is what Chuck has right now.
I also think that is the prop Tracy has.
Here are the relaxed pitch angles that I just measured
at Tracy's place.
RADIUS ANGLE
INCHES DEGREES
12 40
18 30
24 25
30 22
36 20
No way is this a prop for a high speed 200 MPH airplane.
The pitch near the root needs to be more like 70 degrees
rather than zero degrees like it is on the IVO
and one foot out it should be about 47 degrees.
The entire inner two thirds is stalled at a negative angle of
attack with a negative lift coefficient of around -.8
at 200 MPH.
The outer third of the blade changes pitch about +/- 5 degrees.
I know. I tried to twist it with a long lever on the
torque tube and this was the most I could get out of it
without snapping off the tube.
If you de pitch the outer third for takeoff the prop has
about the right pitch for 120 MPH but perhaps still
not enough twist. The twist is always all wrong.
RADIUS ANGLE
INCHES DEGREES
12 39
18 28
24 22
30 17
36 15
As speed builds up however and you increase the pitch
a maximum this is the twist distribution you will get
... roughly. Only on the outer third does the pitch
change very much. It is a variable twist prop.
RADIUS ANGLE
INCHES DEGREES
12 41
18 32
24 25
30 27
36 25
Note that a lot of the initial twist has now been removed.
This is exactly opposite of what you want for a high speed
prop. The inner two thirds are now stalled around 180 MPH
drastically reducing the overall thrust.
If you don't believe me you can make these measurements
yourself. You can also calculate the zero angle of attack
of a prop along its radius rotating at 2700 RPM and going
200 MPH. The chart below does that.
Measure any fixed pitch prop on any airplane going over
200 MPH and compare the angles with these angles.
BTW sanding the inner two thirds of the airfoil nose radius
will make it worse. It will then stall at a slightly higher
negative angle of attack increasing the negative lift coefficient
and producing more negative thrust.
Leave the inner two thirds sharp
and sand only the outer third. You want the inner two
thirds to stall sooner so it will not generate as much
negative thrust :-)
Attached is a chart of ideal blade angle verses speed.
These are zero angles of attack. To get thrust these
angles must be uniformly increased slightly.
Some slight depitching is called for on the inner third
because of the blunt cowlings on most airplanes.
Paul
Six foot diameter prop and 2700 RPM
Prop radius is in feet.
Circ MPH is the velocity of the prop segment at that radius.
MPH = 40.9
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 63.2 40.33
0.5 96.4 104.7 23.00
0.8 144.6 150.3 15.80
1.0 192.8 197.1 11.98
1.3 241.0 244.4 9.64
1.5 289.2 292.0 8.05
1.8 337.4 339.8 6.92
2.0 385.6 387.7 6.06
2.3 433.8 435.7 5.39
2.5 481.9 483.7 4.85
2.8 530.1 531.7 4.41
3.0 578.3 579.8 4.05
Twist = 36.28 Ratio Twist/Root = 0.90 Ratio Twist/Tip = 8.96
----------------------------------------------------------------
MPH = 54.5
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 72.8 48.54
0.5 96.4 110.8 29.51
0.8 144.6 154.5 20.67
1.0 192.8 200.3 15.80
1.3 241.0 247.1 12.76
1.5 289.2 294.3 10.68
1.8 337.4 341.7 9.19
2.0 385.6 389.4 8.05
2.3 433.8 437.2 7.17
2.5 481.9 485.0 6.46
2.8 530.1 532.9 5.88
3.0 578.3 580.9 5.39
Twist = 43.15 Ratio Twist/Root = 0.89 Ratio Twist/Tip = 8.01
----------------------------------------------------------------
MPH = 68.2
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 83.5 54.75
0.5 96.4 118.1 35.27
0.8 144.6 159.9 25.25
1.0 192.8 204.5 19.48
1.3 241.0 250.4 15.80
1.5 289.2 297.1 13.27
1.8 337.4 344.2 11.43
2.0 385.6 391.5 10.03
2.3 433.8 439.1 8.93
2.5 481.9 486.7 8.05
2.8 530.1 534.5 7.33
3.0 578.3 582.3 6.72
Twist = 48.02 Ratio Twist/Root = 0.88 Ratio Twist/Tip = 7.14
----------------------------------------------------------------
MPH = 81.8
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 95.0 59.50
0.5 96.4 126.4 40.33
0.8 144.6 166.1 29.51
1.0 192.8 209.4 23.00
1.3 241.0 254.5 18.75
1.5 289.2 300.5 15.80
1.8 337.4 347.1 13.63
2.0 385.6 394.1 11.98
2.3 433.8 441.4 10.68
2.5 481.9 488.8 9.64
2.8 530.1 536.4 8.77
3.0 578.3 584.1 8.05
Twist = 51.45 Ratio Twist/Root = 0.86 Ratio Twist/Tip = 6.39
----------------------------------------------------------------
MPH = 95.5
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 106.9 63.21
0.5 96.4 135.7 44.72
0.8 144.6 173.3 33.43
1.0 192.8 215.1 26.34
1.3 241.0 259.2 21.61
1.5 289.2 304.5 18.27
1.8 337.4 350.6 15.80
2.0 385.6 397.2 13.91
2.3 433.8 444.1 12.41
2.5 481.9 491.3 11.20
2.8 530.1 538.7 10.21
3.0 578.3 586.2 9.37
Twist = 53.84 Ratio Twist/Root = 0.85 Ratio Twist/Tip = 5.74
----------------------------------------------------------------
MPH = 109.1
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 119.3 66.17
0.5 96.4 145.6 48.54
0.8 144.6 181.1 37.04
1.0 192.8 221.5 29.51
1.3 241.0 264.5 24.36
1.5 289.2 309.1 20.67
1.8 337.4 354.6 17.92
2.0 385.6 400.7 15.80
2.3 433.8 447.3 14.12
2.5 481.9 494.1 12.76
2.8 530.1 541.3 11.63
3.0 578.3 588.5 10.68
Twist = 55.48 Ratio Twist/Root = 0.84 Ratio Twist/Tip = 5.19
----------------------------------------------------------------
MPH = 122.7
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 131.9 68.56
0.5 96.4 156.1 51.85
0.8 144.6 189.6 40.33
1.0 192.8 228.5 32.48
1.3 241.0 270.4 26.99
1.5 289.2 314.1 23.00
1.8 337.4 359.0 19.99
2.0 385.6 404.6 17.66
2.3 433.8 450.8 15.80
2.5 481.9 497.3 14.29
2.8 530.1 544.2 13.04
3.0 578.3 591.2 11.98
Twist = 56.58 Ratio Twist/Root = 0.83 Ratio Twist/Tip = 4.72
----------------------------------------------------------------
MPH = 136.4
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 144.6 70.54
0.5 96.4 167.0 54.75
0.8 144.6 198.7 43.32
1.0 192.8 236.1 35.27
1.3 241.0 276.9 29.51
1.5 289.2 319.7 25.25
1.8 337.4 363.9 22.01
2.0 385.6 409.0 19.48
2.3 433.8 454.7 17.45
2.5 481.9 500.9 15.80
2.8 530.1 547.4 14.43
3.0 578.3 594.2 13.27
Twist = 57.27 Ratio Twist/Root = 0.81 Ratio Twist/Tip = 4.32
----------------------------------------------------------------
MPH = 150.0
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 157.6 72.19
0.5 96.4 178.3 57.28
0.8 144.6 208.3 46.05
1.0 192.8 244.3 37.89
1.3 241.0 283.8 31.90
1.5 289.2 325.8 27.42
1.8 337.4 369.2 23.97
2.0 385.6 413.7 21.26
2.3 433.8 459.0 19.08
2.5 481.9 504.8 17.29
2.8 530.1 551.0 15.80
3.0 578.3 597.5 14.54
Twist = 57.65 Ratio Twist/Root = 0.80 Ratio Twist/Tip = 3.96
----------------------------------------------------------------
MPH = 163.6
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 170.6 73.59
0.5 96.4 189.9 59.50
0.8 144.6 218.4 48.54
1.0 192.8 252.9 40.33
1.3 241.0 291.3 34.18
1.5 289.2 332.3 29.51
1.8 337.4 375.0 25.88
2.0 385.6 418.8 23.00
2.3 433.8 463.6 20.67
2.5 481.9 509.0 18.75
2.8 530.1 554.8 17.15
3.0 578.3 601.0 15.80
Twist = 57.79 Ratio Twist/Root = 0.79 Ratio Twist/Tip = 3.66
----------------------------------------------------------------
MPH = 177.3
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 183.7 74.79
0.5 96.4 201.8 61.47
0.8 144.6 228.8 50.80
1.0 192.8 261.9 42.60
1.3 241.0 299.2 36.34
1.5 289.2 339.2 31.51
1.8 337.4 381.1 27.72
2.0 385.6 424.4 24.69
2.3 433.8 468.6 22.23
2.5 481.9 513.5 20.20
2.8 530.1 559.0 18.49
3.0 578.3 604.9 17.04
Twist = 57.75 Ratio Twist/Root = 0.77 Ratio Twist/Tip = 3.39
----------------------------------------------------------------
MPH = 190.9
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 196.9 75.83
0.5 96.4 213.9 63.21
0.8 144.6 239.5 52.86
1.0 192.8 271.3 44.72
1.3 241.0 307.4 38.39
1.5 289.2 346.5 33.43
1.8 337.4 387.6 29.51
2.0 385.6 430.2 26.34
2.3 433.8 473.9 23.76
2.5 481.9 518.4 21.61
2.8 530.1 563.5 19.81
3.0 578.3 609.0 18.27
Twist = 57.56 Ratio Twist/Root = 0.76 Ratio Twist/Tip = 3.15
----------------------------------------------------------------
MPH = 204.5
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 210.1 76.74
0.5 96.4 226.1 64.77
0.8 144.6 250.5 54.75
1.0 192.8 281.1 46.70
1.3 241.0 316.1 40.33
1.5 289.2 354.2 35.27
1.8 337.4 394.5 31.23
2.0 385.6 436.5 27.95
2.3 433.8 479.6 25.25
2.5 481.9 523.6 23.00
2.8 530.1 568.2 21.10
3.0 578.3 613.4 19.48
Twist = 57.26 Ratio Twist/Root = 0.75 Ratio Twist/Tip = 2.94
----------------------------------------------------------------
MPH = 218.2
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 223.4 77.54
0.5 96.4 238.5 66.17
0.8 144.6 261.7 56.47
1.0 192.8 291.1 48.54
1.3 241.0 325.1 42.16
1.5 289.2 362.2 37.04
1.8 337.4 401.8 32.89
2.0 385.6 443.0 29.51
2.3 433.8 485.5 26.70
2.5 481.9 529.0 24.36
2.8 530.1 573.3 22.37
3.0 578.3 618.1 20.67
Twist = 56.87 Ratio Twist/Root = 0.73 Ratio Twist/Tip = 2.75
----------------------------------------------------------------
MPH = 231.8
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 236.8 78.26
0.5 96.4 251.1 67.42
0.8 144.6 273.2 58.05
1.0 192.8 301.5 50.25
1.3 241.0 334.4 43.89
1.5 289.2 370.6 38.72
1.8 337.4 409.3 34.50
2.0 385.6 449.9 31.02
2.3 433.8 491.8 28.12
2.5 481.9 534.8 25.69
2.8 530.1 578.6 23.62
3.0 578.3 623.1 21.84
Twist = 56.41 Ratio Twist/Root = 0.72 Ratio Twist/Tip = 2.58
----------------------------------------------------------------
MPH = 245.5
Radius Circ MPH Cord MPH 0 Angle of Attack
0.3 48.2 250.1 78.89
0.5 96.4 263.7 68.56
0.8 144.6 284.9 59.50
1.0 192.8 312.1 51.85
1.3 241.0 344.0 45.53
1.5 289.2 379.3 40.33
1.8 337.4 417.2 36.04
2.0 385.6 457.1 32.48
2.3 433.8 498.4 29.51
2.5 481.9 540.9 26.99
2.8 530.1 584.2 24.84
3.0 578.3 628.3 23.00
Twist = 55.89 Ratio Twist/Root = 0.71 Ratio Twist/Tip = 2.43
----------------------------------------------------------------
