In a message dated 12/23/1999 12:33:27 AM Tokyo Standard Time,
rotaryeng@earthlink.net writes:
Is any of this clear to anyone? Feel free to ask questions.
VP4SkyDoc wrote:
I found these tables very useful in helping me understand the dynamics of
aircraft speed and prop pitch/twist. I see what you mean, how the twist
changes more than pitch at low air speeds. We see that this is because the
root is "dynamic" or changes more dramatically than the tip. I think you
should have the program calculate the airspeed of the blade parts and not
just the circular speed. (Oh - just noticed that you have now done this..
great minds think alike :-).
I wanted to mention, though, that the tip is far more important than the root
because of its higher velocity and longer moment arm. For example, an
over-pitched root at say 100 mph will not adversely affect the RPM nearly as
much as an over pitched tip traveling at >500mph... by a factor on the order
of the square of the difference in airspeed multiplied by the difference in
moment arm!! A HUGE difference. Also, because of its slower speed, the root
can tolerate much more over-pitch without stalling (cavitating). On the
other hand, an underpitched root can still act as a flat plate and create
quite a bit of drag. (under pitch the tips, and you're in beta). So, I
still strongly feel that Mr. Ivo is onto the right Idea with changing the tip
and not the root (assuming that technology requires us to change only one or
the other...).
It also seems, according to your table, that underpitching at the root is the
problem with the current IVO props and why they are better on slow airplanes,
as several people have suggested. Lets take an RV in max cruise for example.
With a Speed of 190MPH (remember we should use TAS here) the root pitch from
your table is 75.8 just to avoid causing extra drag, and that dosent yet do
anything useful for forward speed. I think someone mentioned that the new
high-pitch Ivo props still only have a root pitch of 70deg.
Im just rambling here... cut me off anytime :-) Does anyone know what the
root pitch of a typical RV cruise prop is? How about the cruising root pitch
of a C/S?
Dave Leonard
Dave the Sky Doc gave me an idea. I could use the wonderful integrating
properties of QB to write a prop program based on what I had already.
Thanks Dave. Don Bates would charge you a couple of hundred dollars
for a program like this. Just kidding. I am a long way from the quality
of one of Don Bates's prop programs.
Anyway here it is. I changed the column headings because the internet
screws up the spacing anyway. I have a bug in the program that integrates
the blade segment drag so I left the totals for that out. Future updates.
("That will be $89 Sir for the update" Just call me Bill!)
This is a modest angle of attack as you can tell by the section lift
coefficient. This is also a perfect constant speed or variable pitch prop
that both changes twists and changes pitch with forward speed. Probably no
problem changing the program to either change only twist or only angle of
attack. In any event those are secondary effects particularly twist
at high speeds.
The last column is still the zero angle of attack angle.
The prop has a straight taper but from the looks of things that is not
what you want. I think a more elliptical plan form would work better.
You might get more lift further in on the blade reducing the bending
moment on the blade. Klause Saviour builds his props with a more elliptical
plan form.
I am sure there are other bugs in here so don't expect too much.
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
Taper ratio = .13
Section drag coefficent = .07
Section lift coefficent = .4
Maximum blade width in feet = .6
A = Blade Radius in feet.
B = Blade Cord in feet.
C = Blade incremental area in square feet.
D = Cord Velocity in MPH.
E = Drag increment in pounds.
F = HP consumption increment.
G = Thrust increment in pounds.
H = Zero angle of attack angle in degrees.
MPH = 40.9
A B C D E F G H
0.3 0.567 0.142 63 0.103 0.017 0.59 40.33
0.5 0.535 0.134 105 0.267 0.075 1.53 23.00
0.8 0.503 0.126 150 0.516 0.207 2.95 15.80
1.0 0.470 0.118 197 0.831 0.436 4.75 11.98
1.3 0.438 0.109 244 1.189 0.775 6.80 9.64
1.5 0.405 0.101 292 1.572 1.224 8.98 8.05
1.8 0.373 0.093 340 1.957 1.774 11.19 6.92
2.0 0.340 0.085 388 2.326 2.405 13.29 6.06
2.3 0.308 0.077 436 2.656 3.086 15.18 5.39
2.5 0.275 0.069 484 2.927 3.776 16.73 4.85
2.8 0.243 0.061 532 3.120 4.423 17.83 4.41
3.0 0.210 0.053 580 3.212 4.966 18.35 4.05
Twist = 36.28 Ratio Twist/Root = 0.90 Ratio Twist/Tip = 8.96
Thrust = 236 Thrust HP = 26 Engine HP = 31
----------------------------------------------------------------
MPH = 54.5
A B C D E F G H
0.3 0.567 0.142 73 0.137 0.027 0.78 48.54
0.5 0.535 0.134 111 0.299 0.088 1.71 29.51
0.8 0.503 0.126 155 0.546 0.225 3.12 20.67
1.0 0.470 0.118 200 0.858 0.459 4.91 15.80
1.3 0.438 0.109 247 1.215 0.801 6.94 12.76
1.5 0.405 0.101 294 1.596 1.252 9.12 10.68
1.8 0.373 0.093 342 1.979 1.804 11.31 9.19
2.0 0.340 0.085 389 2.346 2.436 13.40 8.05
2.3 0.308 0.077 437 2.674 3.117 15.28 7.17
2.5 0.275 0.069 485 2.944 3.807 16.82 6.46
2.8 0.243 0.061 533 3.134 4.454 17.91 5.88
3.0 0.210 0.053 581 3.224 4.995 18.42 5.39
Twist = 43.15 Ratio Twist/Root = 0.89 Ratio Twist/Tip = 8.01
Thrust = 239 Thrust HP = 35 Engine HP = 42
----------------------------------------------------------------
MPH = 68.2
A B C D E F G H
0.3 0.567 0.142 83 0.180 0.040 1.03 54.75
0.5 0.535 0.134 118 0.339 0.107 1.94 35.27
0.8 0.503 0.126 160 0.584 0.249 3.34 25.25
1.0 0.470 0.118 204 0.894 0.488 5.11 19.48
1.3 0.438 0.109 250 1.248 0.834 7.13 15.80
1.5 0.405 0.101 297 1.627 1.289 9.29 13.27
1.8 0.373 0.093 344 2.008 1.843 11.47 11.43
2.0 0.340 0.085 392 2.372 2.476 13.55 10.03
2.3 0.308 0.077 439 2.697 3.158 15.41 8.93
2.5 0.275 0.069 487 2.965 3.848 16.94 8.05
2.8 0.243 0.061 535 3.152 4.493 18.01 7.33
3.0 0.210 0.053 582 3.240 5.032 18.52 6.72
Twist = 48.02 Ratio Twist/Root = 0.88 Ratio Twist/Tip = 7.14
Thrust = 244 Thrust HP = 44 Engine HP = 53
----------------------------------------------------------------
MPH = 81.8
A B C D E F G H
0.3 0.567 0.142 95 0.233 0.059 1.33 59.50
0.5 0.535 0.134 126 0.389 0.131 2.22 40.33
0.8 0.503 0.126 166 0.631 0.280 3.61 29.51
1.0 0.470 0.118 209 0.938 0.524 5.36 23.00
1.3 0.438 0.109 254 1.289 0.875 7.37 18.75
1.5 0.405 0.101 301 1.664 1.334 9.51 15.80
1.8 0.373 0.093 347 2.042 1.891 11.67 13.63
2.0 0.340 0.085 394 2.403 2.526 13.73 11.98
2.3 0.308 0.077 441 2.726 3.209 15.58 10.68
2.5 0.275 0.069 489 2.990 3.898 17.09 9.64
2.8 0.243 0.061 536 3.175 4.542 18.14 8.77
3.0 0.210 0.053 584 3.260 5.078 18.63 8.05
Twist = 51.45 Ratio Twist/Root = 0.86 Ratio Twist/Tip = 6.39
Thrust = 248 Thrust HP = 54 Engine HP = 65
----------------------------------------------------------------
MPH = 95.5
A B C D E F G H
0.3 0.567 0.142 107 0.295 0.084 1.69 63.21
0.5 0.535 0.134 136 0.448 0.162 2.56 44.72
0.8 0.503 0.126 173 0.686 0.317 3.92 33.43
1.0 0.470 0.118 215 0.990 0.568 5.65 26.34
1.3 0.438 0.109 259 1.337 0.924 7.64 21.61
1.5 0.405 0.101 305 1.709 1.388 9.76 18.27
1.8 0.373 0.093 351 2.083 1.948 11.91 15.80
2.0 0.340 0.085 397 2.441 2.585 13.95 13.91
2.3 0.308 0.077 444 2.760 3.269 15.77 12.41
2.5 0.275 0.069 491 3.020 3.957 17.26 11.20
2.8 0.243 0.061 539 3.202 4.599 18.29 10.21
3.0 0.210 0.053 586 3.283 5.132 18.76 9.37
Twist = 53.84 Ratio Twist/Root = 0.85 Ratio Twist/Tip = 5.74
Thrust = 254 Thrust HP = 65 Engine HP = 78
----------------------------------------------------------------
MPH = 109.1
A B C D E F G H
0.3 0.567 0.142 119 0.367 0.117 2.10 66.17
0.5 0.535 0.134 146 0.516 0.200 2.95 48.54
0.8 0.503 0.126 181 0.750 0.362 4.29 37.04
1.0 0.470 0.118 222 1.049 0.620 6.00 29.51
1.3 0.438 0.109 265 1.393 0.982 7.96 24.36
1.5 0.405 0.101 309 1.760 1.451 10.06 20.67
1.8 0.373 0.093 355 2.131 2.015 12.18 17.92
2.0 0.340 0.085 401 2.484 2.654 14.19 15.80
2.3 0.308 0.077 447 2.799 3.338 15.99 14.12
2.5 0.275 0.069 494 3.055 4.026 17.46 12.76
2.8 0.243 0.061 541 3.232 4.665 18.47 11.63
3.0 0.210 0.053 589 3.310 5.194 18.91 10.68
Twist = 55.48 Ratio Twist/Root = 0.84 Ratio Twist/Tip = 5.19
Thrust = 261 Thrust HP = 76 Engine HP = 91
----------------------------------------------------------------
MPH = 122.7
A B C D E F G H
0.3 0.567 0.142 132 0.449 0.158 2.57 68.56
0.5 0.535 0.134 156 0.593 0.247 3.39 51.85
0.8 0.503 0.126 190 0.822 0.416 4.70 40.33
1.0 0.470 0.118 229 1.117 0.681 6.38 32.48
1.3 0.438 0.109 270 1.456 1.050 8.32 26.99
1.5 0.405 0.101 314 1.818 1.523 10.39 23.00
1.8 0.373 0.093 359 2.184 2.091 12.48 19.99
2.0 0.340 0.085 405 2.533 2.733 14.47 17.66
2.3 0.308 0.077 451 2.843 3.418 16.25 15.80
2.5 0.275 0.069 497 3.095 4.104 17.68 14.29
2.8 0.243 0.061 544 3.267 4.741 18.67 13.04
3.0 0.210 0.053 591 3.340 5.266 19.08 11.98
Twist = 56.58 Ratio Twist/Root = 0.83 Ratio Twist/Tip = 4.72
Thrust = 269 Thrust HP = 88 Engine HP = 106
----------------------------------------------------------------
MPH = 136.4
A B C D E F G H
0.3 0.567 0.142 145 0.540 0.208 3.09 70.54
0.5 0.535 0.134 167 0.679 0.302 3.88 54.75
0.8 0.503 0.126 199 0.903 0.479 5.16 43.32
1.0 0.470 0.118 236 1.192 0.751 6.81 35.27
1.3 0.438 0.109 277 1.526 1.127 8.72 29.51
1.5 0.405 0.101 320 1.884 1.606 10.76 25.25
1.8 0.373 0.093 364 2.244 2.178 12.82 22.01
2.0 0.340 0.085 409 2.587 2.822 14.79 19.48
2.3 0.308 0.077 455 2.893 3.507 16.53 17.45
2.5 0.275 0.069 501 3.139 4.193 17.94 15.80
2.8 0.243 0.061 547 3.306 4.826 18.89 14.43
3.0 0.210 0.053 594 3.374 5.346 19.28 13.27
Twist = 57.27 Ratio Twist/Root = 0.81 Ratio Twist/Tip = 4.32
Thrust = 277 Thrust HP = 101 Engine HP = 121
----------------------------------------------------------------
MPH = 150.0
A B C D E F G H
0.3 0.567 0.142 158 0.641 0.269 3.66 72.19
0.5 0.535 0.134 178 0.774 0.368 4.42 57.28
0.8 0.503 0.126 208 0.992 0.551 5.67 46.05
1.0 0.470 0.118 244 1.276 0.831 7.29 37.89
1.3 0.438 0.109 284 1.604 1.214 9.16 31.90
1.5 0.405 0.101 326 1.956 1.699 11.17 27.42
1.8 0.373 0.093 369 2.310 2.275 13.20 23.97
2.0 0.340 0.085 414 2.648 2.921 15.13 21.26
2.3 0.308 0.077 459 2.947 3.607 16.84 19.08
2.5 0.275 0.069 505 3.188 4.291 18.22 17.29
2.8 0.243 0.061 551 3.349 4.921 19.14 15.80
3.0 0.210 0.053 597 3.411 5.435 19.49 14.54
Twist = 57.65 Ratio Twist/Root = 0.80 Ratio Twist/Tip = 3.96
Thrust = 287 Thrust HP = 115 Engine HP = 138
----------------------------------------------------------------
MPH = 163.6
A B C D E F G H
0.3 0.567 0.142 171 0.751 0.342 4.29 73.59
0.5 0.535 0.134 190 0.878 0.445 5.02 59.50
0.8 0.503 0.126 218 1.090 0.635 6.23 48.54
1.0 0.470 0.118 253 1.367 0.922 7.81 40.33
1.3 0.438 0.109 291 1.689 1.312 9.65 34.18
1.5 0.405 0.101 332 2.034 1.802 11.62 29.51
1.8 0.373 0.093 375 2.383 2.383 13.62 25.88
2.0 0.340 0.085 419 2.714 3.031 15.51 23.00
2.3 0.308 0.077 464 3.007 3.717 17.18 20.67
2.5 0.275 0.069 509 3.241 4.399 18.52 18.75
2.8 0.243 0.061 555 3.397 5.025 19.41 17.15
3.0 0.210 0.053 601 3.452 5.532 19.72 15.80
Twist = 57.79 Ratio Twist/Root = 0.79 Ratio Twist/Tip = 3.66
Thrust = 297 Thrust HP = 130 Engine HP = 156
----------------------------------------------------------------
MPH = 177.3
A B C D E F G H
0.3 0.567 0.142 184 0.871 0.427 4.98 74.79
0.5 0.535 0.134 202 0.991 0.533 5.66 61.47
0.8 0.503 0.126 229 1.196 0.730 6.84 50.80
1.0 0.470 0.118 262 1.467 1.024 8.38 42.60
1.3 0.438 0.109 299 1.782 1.421 10.18 36.34
1.5 0.405 0.101 339 2.120 1.918 12.11 31.51
1.8 0.373 0.093 381 2.462 2.502 14.07 27.72
2.0 0.340 0.085 424 2.786 3.153 15.92 24.69
2.3 0.308 0.077 469 3.072 3.839 17.55 22.23
2.5 0.275 0.069 514 3.300 4.518 18.85 20.20
2.8 0.243 0.061 559 3.448 5.140 19.70 18.49
3.0 0.210 0.053 605 3.496 5.640 19.98 17.04
Twist = 57.75 Ratio Twist/Root = 0.77 Ratio Twist/Tip = 3.39
Thrust = 308 Thrust HP = 146 Engine HP = 175
----------------------------------------------------------------
MPH = 190.9
A B C D E F G H
0.3 0.567 0.142 197 1.001 0.526 5.72 75.83
0.5 0.535 0.134 214 1.113 0.635 6.36 63.21
0.8 0.503 0.126 239 1.311 0.837 7.49 52.86
1.0 0.470 0.118 271 1.574 1.139 9.00 44.72
1.3 0.438 0.109 307 1.881 1.542 10.75 38.39
1.5 0.405 0.101 347 2.213 2.044 12.64 33.43
1.8 0.373 0.093 388 2.547 2.633 14.55 29.51
2.0 0.340 0.085 430 2.864 3.285 16.36 26.34
2.3 0.308 0.077 474 3.142 3.971 17.96 23.76
2.5 0.275 0.069 518 3.362 4.648 19.21 21.61
2.8 0.243 0.061 563 3.503 5.264 20.02 19.81
3.0 0.210 0.053 609 3.544 5.756 20.25 18.27
Twist = 57.56 Ratio Twist/Root = 0.76 Ratio Twist/Tip = 3.15
Thrust = 321 Thrust HP = 163 Engine HP = 196
----------------------------------------------------------------
MPH = 204.5
A B C D E F G H
0.3 0.567 0.142 210 1.140 0.639 6.52 76.74
0.5 0.535 0.134 226 1.245 0.750 7.11 64.77
0.8 0.503 0.126 250 1.435 0.958 8.20 54.75
1.0 0.470 0.118 281 1.689 1.266 9.65 46.70
1.3 0.438 0.109 316 1.989 1.676 11.36 40.33
1.5 0.405 0.101 354 2.312 2.184 13.21 35.27
1.8 0.373 0.093 395 2.638 2.776 15.08 31.23
2.0 0.340 0.085 436 2.947 3.430 16.84 27.95
2.3 0.308 0.077 480 3.218 4.115 18.39 25.25
2.5 0.275 0.069 524 3.430 4.789 19.60 23.00
2.8 0.243 0.061 568 3.563 5.399 20.36 21.10
3.0 0.210 0.053 613 3.596 5.882 20.55 19.48
Twist = 57.26 Ratio Twist/Root = 0.75 Ratio Twist/Tip = 2.94
Thrust = 334 Thrust HP = 182 Engine HP = 218
----------------------------------------------------------------
MPH = 218.2
A B C D E F G H
0.3 0.567 0.142 223 1.289 0.768 7.37 77.54
0.5 0.535 0.134 239 1.385 0.881 7.91 66.17
0.8 0.503 0.126 262 1.566 1.093 8.95 56.47
1.0 0.470 0.118 291 1.813 1.407 10.36 48.54
1.3 0.438 0.109 325 2.104 1.823 12.02 42.16
1.5 0.405 0.101 362 2.418 2.336 13.82 37.04
1.8 0.373 0.093 402 2.736 2.931 15.63 32.89
2.0 0.340 0.085 443 3.036 3.587 17.35 29.51
2.3 0.308 0.077 486 3.298 4.271 18.85 26.70
2.5 0.275 0.069 529 3.502 4.940 20.01 24.36
2.8 0.243 0.061 573 3.626 5.544 20.72 22.37
3.0 0.210 0.053 618 3.651 6.018 20.86 20.67
Twist = 56.87 Ratio Twist/Root = 0.73 Ratio Twist/Tip = 2.75
Thrust = 348 Thrust HP = 202 Engine HP = 243
----------------------------------------------------------------
MPH = 231.8
A B C D E F G H
0.3 0.567 0.142 237 1.448 0.914 8.27 78.26
0.5 0.535 0.134 251 1.534 1.027 8.77 67.42
0.8 0.503 0.126 273 1.707 1.243 9.75 58.05
1.0 0.470 0.118 302 1.944 1.563 11.11 50.25
1.3 0.438 0.109 334 2.226 1.985 12.72 43.89
1.5 0.405 0.101 371 2.531 2.502 14.46 38.72
1.8 0.373 0.093 409 2.840 3.100 16.23 34.50
2.0 0.340 0.085 450 3.131 3.756 17.89 31.02
2.3 0.308 0.077 492 3.384 4.438 19.34 28.12
2.5 0.275 0.069 535 3.579 5.104 20.45 25.69
2.8 0.243 0.061 579 3.694 5.700 21.11 23.62
3.0 0.210 0.053 623 3.709 6.163 21.20 21.84
Twist = 56.41 Ratio Twist/Root = 0.72 Ratio Twist/Tip = 2.58
Thrust = 363 Thrust HP = 224 Engine HP = 269
----------------------------------------------------------------
MPH = 245.5
A B C D E F G H
0.3 0.567 0.142 250 1.616 1.078 9.23 78.89
0.5 0.535 0.134 264 1.693 1.190 9.67 68.56
0.8 0.503 0.126 285 1.855 1.410 10.60 59.50
1.0 0.470 0.118 312 2.083 1.734 11.90 51.85
1.3 0.438 0.109 344 2.355 2.160 13.46 45.53
1.5 0.405 0.101 379 2.651 2.682 15.15 40.33
1.8 0.373 0.093 417 2.950 3.282 16.86 36.04
2.0 0.340 0.085 457 3.232 3.939 18.47 32.48
2.3 0.308 0.077 498 3.475 4.619 19.86 29.51
2.5 0.275 0.069 541 3.660 5.279 20.92 26.99
2.8 0.243 0.061 584 3.766 5.867 21.52 24.84
3.0 0.210 0.053 628 3.772 6.319 21.55 23.00
Twist = 55.89 Ratio Twist/Root = 0.71 Ratio Twist/Tip = 2.43
Thrust = 378 Thrust HP = 248 Engine HP = 297
----------------------------------------------------------------