| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 1555.1 | VPP location | ECAD2::FINNERTY | Reach out and luff someone | Fri Jul 06 1990 18:03 | 5 |
|
VPP is currently located at:
ecad2::user2:[finnerty]vpp.exe
|
| 1555.2 | VPP Options File (vppdata.dat) | ECAD2::FINNERTY | Reach out and luff someone | Fri Jul 06 1990 18:03 | 101 |
| 0.09670 2.00000 2.00000 2.00000 2.00000 2.0000
2.00000 2.00000 2.00000 2.00000 2.00000 2.0000
2.00000 2.00000 2.00000 2.00000 2.00000 2.0000
2.00000 2.00000 2.00000 2.00000 2.00000 2.0000
2.00000 2.00000 2.00000 2.00000 2.00000 2.0000
2.00000 2.01210 2.04650 2.09960 2.16660 2.2430
2.32500 2.40990 2.49570 2.58160 2.66720 2.7524
2.83500 2.91300 2.98460 3.04850 3.10350 3.1486
3.18290 3.20580 3.21660 3.21530 3.20340 3.1824
3.15380 3.11880 3.07850 3.03390 2.98600 2.9354
2.88290 2.82900 2.77440 2.71960 2.66500 2.6109
2.55790 2.50620 2.45620 2.40800 2.36200 2.3184
2.27680 2.23730 2.19950 2.16340 2.12860 2.0952
2.06300 2.03180 2.00150 1.97200 1.94320 1.9151
1.88750 1.86040 1.83360 1.80720 1.78100 1.7551
1.72920 1.70350 1.67790 1.65240 1.62690 1.6016
1.57640 1.55130 1.52640 1.50150 1.47680 1.4522
1.42770 1.40340 1.37910 1.35510 1.33110 1.3073
1.28370 1.26010 1.23680 1.21350 1.19040 1.1675
1.14470 1.12210 1.09960 1.07720 1.05510 1.0330
1.01120 0.98940 0.96790 0.94650 0.92520 0.9041
0.88320 0.86240 0.84170 0.82120 0.80080 0.7806
0.76050 0.74050 0.72070 0.70100 0.68150 0.6621
0.64290 0.62380 0.60480 0.58600 0.56730 0.5487
0.53030 0.51210 0.49400 0.47600 0.45820 0.4406
0.42310 0.40580 0.38870 0.37170 0.35490 0.3383
0.32180 0.30560 0.28950 0.27370 0.25800 0.2426
0.22730 0.21230 0.19760 0.18310 0.16880 0.1547
0.14100 0.12750 0.11430 0.10140 0.08880 0.0765
0.06450 0.05280 0.04150 0.03060 0.02000 0.0098
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.00230 0.00900 0.01980 0.0343
0.05220 0.07320 0.09690 0.12300 0.15130 0.1813
0.21280 0.24540 0.27880 0.31270 0.34660 0.3804
0.41350 0.44570 0.47650 0.50570 0.53280 0.5580
0.58130 0.60280 0.62270 0.64100 0.65780 0.6734
0.68770 0.70090 0.71320 0.72460 0.73520 0.7453
0.75480 0.76410 0.77300 0.78190 0.79090 0.8001
0.80960 0.81940 0.82950 0.83980 0.85040 0.8611
0.87200 0.88300 0.89420 0.90530 0.91650 0.9276
0.93870 0.94970 0.96050 0.97120 0.98160 0.9918
1.00170 1.01130 1.02040 1.02920 1.03760 1.0456
1.05310 1.06030 1.06700 1.07330 1.07910 1.0846
1.08950 1.09410 1.09810 1.10170 1.10490 1.1076
1.10980 1.11150 1.11280 1.11350 1.11380 1.1136
1.11290 1.11180 1.11010 1.10800 1.10530 1.1022
1.09850 1.09440 2.28540 2.27670 2.26740 2.2577
2.24740 2.23660 2.22530 2.21350 2.20130 2.1885
2.17530 2.16150 2.14740 2.13270 2.11760 2.1020
2.08600 2.06950 2.05260 2.03520 2.01740 1.9992
1.98060 1.96150 1.94200 1.92210 1.90180 1.8811
1.86000 1.83850 1.81660 1.79440 1.77170 1.7487
1.72530 1.70160 1.67750 1.65300 1.62820 1.6031
1.57760 1.55170 1.52560 1.49910 1.47230 1.4451
1.41770 1.38990 1.36190 1.33350 1.30490 1.2760
1.24670 1.21720 1.18750 1.15740 1.12710 1.0965
1.06570 1.03460 1.00330 1.00330 0.07580 0.0758
0.07580 0.07580 0.07580 0.07580 0.07580 0.0758
0.07580 0.07580 0.07580 0.07580 0.07580 0.0758
0.07580 0.07580 0.07580 0.07580 0.07580 0.0758
0.07580 0.07580 0.07580 0.07580 0.07580 0.0758
0.07580 0.07580 0.07580 0.07580 0.07580 0.0759
0.07600 0.07630 0.07690 0.07770 0.07880 0.0801
0.08140 0.08270 0.08400 0.08530 0.08660 0.0881
0.08970 0.09140 0.09350 0.09580 0.09830 0.1013
0.10450 0.10820 0.11220 0.11650 0.12110 0.1261
0.13130 0.13690 0.14280 0.14890 0.15540 0.1621
0.16910 0.17640 0.18390 0.19170 0.19970 0.2078
0.21620 0.22460 0.23320 0.24180 0.25060 0.2594
0.26840 0.27750 0.28670 0.29600 0.30550 0.3152
0.32510 0.33510 0.34540 0.35590 0.36670 0.3778
0.38920 0.40090 0.41290 0.42540 0.43830 0.4516
0.46540 0.47970 0.49450 0.50990 0.52590 0.5424
0.55970 0.57760 0.59620 0.61560 0.63570 0.6568
0.67870 0.70160 0.72550 0.75050 0.77670 0.8040
0.83260 0.86270 0.89420 0.92720 0.96190 0.9984
1.03690 1.07730 1.11990 1.16490 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.40000 0.60000 0.80000 1.00000 1.20000 1.4000
1.60000 1.80000 8.00000 12.00000 16.00000 20.0000
24.00000 0.0 180.00000 160.00000 150.00000 140.0000
125.00000 110.00000 90.00000 80.00000 70.00000 60.0000
52.00000 48.00000 44.00000 42.00000 40.00000 38.0000
36.00000 9.80000 29.10000 47.20000 117.9 413.7
2427.60000 7421.80000 14055.00000 0.41400 0.61700 0.9470
0.83100 0.50600 0.08500 0.04600 0.03200 0.0000
0.00000 0.00000 0.00000 0.00000 9.00000 49.0000
64.00000 170.00000
|
| 1555.3 | Sample Input File (for the 12-meter Intrepid) | ECAD2::FINNERTY | Reach out and luff someone | Fri Jul 06 1990 18:05 | 4 |
| 12 METER INTREPID
46.04 46.05 46.92 58.40 11.22 9.06 0.00
4.12 630.00 36.80 0.00 58000.00 5007.00 4818.00
1.13 75.88 1867.00 0.00 0.00 2.52 19.97
|
| 1555.4 | Sample summary output for Intrepid | ECAD2::FINNERTY | Reach out and luff someone | Fri Jul 06 1990 18:08 | 66 |
| MIT PRATT PROJECT VELOCITY PREDICTION PROGRAM RELEASE DATE: 3/05/84
12 METER INTREPID RUN DATE: 06-Jul-1990:17:04:17
------------------------------------------------------------------------------------------------------------------
LSM(1)---------- 46.04 BEAM------------- 11.22 AREA(MAX SECTION)-- 36.80
LSM(2)---------- 46.05 KEEL DRAFT------- 9.06 PROP AREA(PROJ)---- 0.000
LSM(3)---------- 46.92 CENTERBOARD EXT-- 0.00 DISPLACEMENT------- 58000.
LSM(4)---------- 58.40 BEAM/DEPTH------- 2.52 RM/DEG AT 2 DEG--- 5007.0
AVERAGE LENGTH-- 48.72 WETTED SURFACE-- 630.0 RM/DEG AT 25 DEG--- 4818.0
------------------------------------------------------------------------------------------------------------------
MAIN MAST DIAM-- 1.13 SAIL AREA------- 1867.0 AVG FREEBOARD------ 4.12
HEIGHT OF MAIN-- 80.00 MIZZEN DIAM------ 0.00 CREW WT ON RAIL---- 1656
AREA(KEEL TE)--- 19.97 HEIGHT OF MIZZEN- 0.00 REDUCED DRAFT------ 7.33
------------------------------------------------------------------------------------------------------------------
RESIDUARY RESISTANCE COEFFICIENTS AT CORRESPONDING SPEED-LENGTH RATIOS
VRL: 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80
CR: 0.00060 0.00095 0.00118 0.00169 0.00305 0.00833 0.01501 0.02080
------------------------------------------------------------------------------------------------------------------
VTW VT-CE BTW VAW BAW V VMG PHI REEF FLAT FR RI+RH FH CL CI CD
------------------------------------------------------------------------------------------------------------------
8.0 8.05 180.0 3.95 180.00 4.102 -4.102 0.0 1.000 1.000 109.8 0.0 0.0 0.000 0.000 1.114
8.0 8.03 110.0 9.38 52.03 8.515 -2.912 11.5 1.000 1.000 803.6 48.4 1858.6 3.203 0.108 1.750
8.0 8.01 80.0 12.67 36.98 8.732 1.516 15.0 1.000 1.000 955.2 72.0 2335.1 2.408 0.079 0.633
8.0 8.00 52.0 14.26 25.08 7.987 4.917 16.6 1.000 1.000 642.6 102.9 2532.4 2.000 0.076 0.383
8.0 8.01 45.4 14.12 22.90 7.377 5.184 15.4 1.000 0.944 518.6 105.4 2359.3 1.888 0.076 0.350
8.0 8.05 151.4 4.12 110.53 5.622 -4.934 0.0 1.000 1.000 213.9 1.3 197.0 1.224 0.819 2.422
------------------------------------------------------------------------------------------------------------------
12.0 12.08 180.0 6.03 180.00 6.048 -6.048 0.0 1.000 1.000 255.8 0.0 0.0 0.000 0.000 1.114
12.0 12.00 110.0 11.90 64.63 9.201 -3.147 17.5 1.000 1.000 1325.7 84.2 2690.2 2.631 0.181 2.085
12.0 11.86 80.0 15.47 41.66 9.499 1.649 28.3 1.000 1.000 1708.6 183.3 4153.0 2.807 0.085 0.982
12.0 11.90 52.0 18.29 27.59 8.883 5.469 25.5 1.000 0.914 1163.7 177.2 3746.4 1.828 0.076 0.333
12.0 11.96 38.4 18.67 21.79 7.969 6.242 21.2 1.000 0.725 694.6 160.3 3154.5 1.449 0.076 0.239
12.0 12.08 156.6 5.90 125.83 7.633 -7.008 0.4 1.000 1.000 456.8 1.6 299.4 0.887 0.000 2.318
------------------------------------------------------------------------------------------------------------------
16.0 16.11 180.0 8.32 180.00 7.785 -7.785 0.0 1.000 1.000 486.8 0.0 0.0 0.000 0.000 1.114
16.0 15.90 110.0 14.35 72.41 9.774 -3.343 23.8 1.000 1.000 1951.7 124.7 3558.1 2.261 0.245 2.158
16.0 15.66 80.0 17.87 45.49 9.807 1.703 34.3 0.988 0.834 2162.0 240.9 4994.6 2.565 0.091 1.041
16.0 15.78 52.0 21.87 29.40 9.346 5.754 30.3 1.000 0.764 1588.7 214.7 4399.8 1.528 0.076 0.257
16.0 15.87 35.7 22.73 21.58 8.251 6.698 25.6 1.000 0.581 840.0 208.7 3737.9 1.161 0.076 0.182
16.0 16.11 164.8 8.14 148.67 8.582 -8.280 0.2 1.000 1.000 793.2 1.0 264.1 0.446 0.000 1.947
------------------------------------------------------------------------------------------------------------------
20.0 20.13 180.0 11.36 180.00 8.769 -8.769 0.0 1.000 1.000 907.9 0.0 0.0 0.000 0.000 1.114
20.0 19.72 110.0 16.40 77.57 10.276 -3.514 30.2 1.000 1.000 2632.9 164.8 4435.6 2.077 0.292 2.218
20.0 19.26 80.0 20.55 49.68 9.952 1.728 34.3 0.861 0.854 2393.6 292.3 5552.6 2.745 0.100 1.360
20.0 19.56 52.0 25.27 31.06 9.607 5.915 32.2 0.958 0.685 1892.9 240.3 4822.2 1.381 0.076 0.234
20.0 19.73 34.7 26.50 21.54 8.415 6.922 29.9 1.000 0.492 968.7 264.7 4303.8 0.984 0.076 0.153
20.0 20.13 166.4 11.23 155.14 9.384 -9.123 0.8 1.000 1.000 1412.6 1.5 360.0 0.336 0.000 1.802
------------------------------------------------------------------------------------------------------------------
24.0 24.16 180.0 14.67 180.00 9.487 -9.487 0.0 1.000 1.000 1513.6 0.0 0.0 0.000 0.000 1.114
24.0 23.45 110.0 18.38 81.89 10.611 -3.629 34.3 0.973 1.000 3239.9 193.8 5100.0 1.946 0.334 2.276
24.0 22.85 80.0 23.26 52.88 10.069 1.749 34.5 0.774 0.878 2599.6 338.6 6028.4 2.795 0.112 1.585
24.0 23.20 52.0 28.46 32.39 9.746 6.000 33.5 0.883 0.683 2113.0 283.4 5315.7 1.411 0.076 0.267
24.0 23.71 34.5 30.41 22.74 8.506 7.010 28.9 1.000 0.364 995.0 244.4 4185.9 0.728 0.076 0.120
24.0 24.16 166.3 14.49 156.82 10.154 -9.867 2.1 1.000 1.000 2305.6 2.8 542.8 0.309 0.000 1.762
|
| 1555.5 | Detailed polars for Intrepid: VTW vs BTW for BTW 36:180 DEGREES | ECAD2::FINNERTY | Reach out and luff someone | Fri Jul 06 1990 18:09 | 40 |
| 5.690 6.121 6.515 6.871 7.184 7.453 7.674 7.848 7.987 8.104
8.203 8.288 8.362 8.426 8.483 8.532 8.575 8.613 8.646 8.674
8.698 8.717 8.732 8.742 8.748 8.751 8.751 8.749 8.745 8.738
8.728 8.714 8.696 8.673 8.644 8.608 8.565 8.515 8.456 8.386
8.305 8.210 8.099 7.971 7.824 7.656 7.470 7.271 7.066 6.860
6.660 6.472 6.302 6.154 6.025 5.910 5.802 5.698 5.593 5.486
5.378 5.269 5.159 5.049 4.939 4.829 4.720 4.612 4.506 4.401
4.299 4.199 4.102
7.649 7.920 8.125 8.293 8.437 8.563 8.678 8.784 8.883 8.977
9.065 9.146 9.217 9.277 9.327 9.368 9.401 9.428 9.449 9.465
9.478 9.489 9.499 9.507 9.515 9.519 9.520 9.516 9.505 9.488
9.466 9.440 9.408 9.373 9.334 9.292 9.248 9.201 9.153 9.103
9.053 9.001 8.949 8.896 8.843 8.789 8.736 8.682 8.627 8.569
8.510 8.447 8.381 8.311 8.236 8.156 8.070 7.978 7.880 7.775
7.664 7.548 7.427 7.302 7.173 7.040 6.903 6.765 6.624 6.481
6.337 6.193 6.048
8.279 8.465 8.624 8.767 8.897 9.019 9.134 9.243 9.346 9.439
9.521 9.591 9.648 9.691 9.723 9.745 9.760 9.770 9.779 9.786
9.792 9.799 9.807 9.817 9.828 9.839 9.849 9.855 9.859 9.859
9.856 9.850 9.841 9.831 9.819 9.805 9.790 9.774 9.758 9.741
9.722 9.703 9.682 9.659 9.634 9.607 9.578 9.546 9.512 9.475
9.435 9.393 9.347 9.299 9.248 9.195 9.139 9.082 9.022 8.961
8.896 8.829 8.759 8.684 8.606 8.523 8.436 8.343 8.244 8.139
8.028 7.910 7.785
8.551 8.728 8.885 9.028 9.161 9.286 9.405 9.513 9.607 9.684
9.744 9.790 9.823 9.845 9.859 9.868 9.875 9.882 9.893 9.906
9.920 9.936 9.952 9.967 9.982 9.997 10.015 10.034 10.056 10.080
10.105 10.132 10.159 10.185 10.211 10.235 10.257 10.276 10.291 10.303
10.312 10.318 10.320 10.319 10.315 10.308 10.298 10.285 10.268 10.247
10.223 10.194 10.161 10.123 10.082 10.036 9.987 9.934 9.878 9.819
9.756 9.691 9.622 9.550 9.475 9.398 9.317 9.233 9.146 9.056
8.963 8.868 8.769
8.678 8.856 9.017 9.165 9.303 9.436 9.559 9.663 9.746 9.807
9.851 9.882 9.904 9.920 9.933 9.945 9.957 9.970 9.986 10.005
10.026 10.047 10.069 10.091 10.114 10.137 10.162 10.190 10.222 10.256
10.294 10.334 10.376 10.420 10.466 10.514 10.562 10.611 10.661 10.710
10.757 10.801 10.842 10.879 10.909 10.933 10.950 10.959 10.962 10.959
10.950 10.935 10.914 10.888 10.857 10.820 10.777 10.729 10.675 10.616
10.552 10.482 10.409 10.331 10.249 10.163 10.074 9.982 9.887 9.790
9.691 9.590 9.487
|
| 1555.6 | Boat parameter file definitions & format | ECAD2::FINNERTY | Reach out and luff someone | Fri Jul 06 1990 18:17 | 54 |
|
{Note: page numbers refer to the MIT report which describes VPP,
which I believe is MIT 78-11. The explanations are my own,
not the author's, so some of the definitions may contain
inaccuracies}
Parameter Definitions:
INAME A character string which identifies the boat.
LSM1 Waterline length at equillibrium, zero heel, with
displacement and longitudinal center of gravity
corresponding to an established racing condition (pg 9)
LSM2 Waterline length at 2 degrees of heel (pg 11)
LSM3 Waterline length at 25 degrees of heel (pg 11)
LSM4 A fictitious waterplane obtained by sinking the
yacht 2.5% of LSM1 at the forward end of the waterline
and 3.75% of LSM1 at the aft end of the waterline (pg 11)
B Beam (pg 14)
DFK Keel Draft (pg 29)
EDC Extension Depth of Centerboard (pg 29)
FBD Average Freeboard in feet
WS Wetted Surface in square feet
AMS Area of canoe body (lateral projection) in square feet (pg 30)
PPA Propeller Area (Projected)
DISP Displacement in pounds.
RMA2 Righting Moment at 2 degrees
RMA25 Righting Moment at 25 degrees
EDM Effective Main Mast Diameter in feet
EHM Effective Main Mast Height in feet
SA Sail Area in square feet
EHY Effective Mizzen Mast Height in feet
EDMY Effective Mizzen Mast Diameter in feet
BT Beam to Effective Hull Depth ratio B/Tc, (78-11, pg 14)
ATEK Area (Keel TE) (dfk*dfk - trmax*trmax)/.636
Parameter File Format:
INAME
LSM1 LSM2 LSM3 LSM4 B DFK EDC
FBD WS AMS PPA DISP RMA2 RMA25
EDM EHM SA EHY EDMY BT ATEK
The INAME field is listed on its own line as a string up to 72 characters
long CRLF terminated. The 3 lines which follow contain 7 parameters each,
with a field width of 10 and 2 digits following a decimal point. The
format is unforgiving, so be careful to organize the data properly.
|
| 1555.7 | Estimated parameters for a Catalina 25 | ECAD2::FINNERTY | Reach out and luff someone | Fri Jul 06 1990 18:20 | 4 |
| Catalina 25
21.17 21.18 21.22 21.60 8.00 4.00 0.00
3.10 112.00 13.85 0.00 4850.00 277.47 250.00
0.29 28.50 308.00 0.00 0.00 1.31 6.98
|
| 1555.8 | Documentation | ECAD2::FINNERTY | Reach out and luff someone | Fri Jul 06 1990 21:11 | 8 |
|
"A Velocity Prediction Program for Ocean Racing Yachts", revised to
June, 1978, MIT Report No. 78-11, J. E. Kerwin
"Documentation and Program Listings of LPP and VPP", Revised April,
1980, Justin E. Kerwin, copyright MIT, 1980. (H. Irving Pratt Ocean
Race Handicapping Project)
|
| 1555.9 | | MFGMEM::KEENAN | PAUL KEENAN DTN 297-7332 | Mon Jul 09 1990 12:05 | 17 |
| I sent away for VPP data for a J/24. I was interested in what the
program thought the optimum tacking and gybing angles were.
The gybing angles were close to what I've seen used successfully
on the race course. I was impressed and thought that maybe the
VPP/IMS stuff might work after all.
Then I looked at the tacking angles and target boatspeeds. They were
far off base. In most wind ranges, a J/24 should be sailed 5 degrees
or more higher on the wind. Anyone sailing these tacking angles and/or
target boatspeeds would be crushed. (Never mind that target boatspeed
doesn't work well for smaller boats)
I hope for the future of IMS that other boats are modeled more
accurately than mine.
-Paul
|
| 1555.10 | not set up for fractional rig analysis? | ECAD2::FINNERTY | Reach out and luff someone | Mon Jul 09 1990 16:01 | 7 |
|
re: -.1
Do you have any ideas why it would have been 5 degrees off in
the case of J-24? What did it recommend as a tacking angle?
|
| 1555.11 | Hidden Variables | STEREO::HO | | Mon Jul 09 1990 16:28 | 10 |
| The 5 degrees is probably due to the fine tuning of the rig and
optimized sail trimming techniques that the more fanatic fleet members
are constantly experimenting with. Once a successful combination is
found, word gets out and the whole fleet step functions up in
performance. These are minute changes (fractions of an inch in
forestay length, a few turns of the turnbuckle, etc) which are either
not input to the VPP or noise level (beyond the 2 decimal places) in
the attributes that are input.
- gene
|
| 1555.12 | | MFGMEM::KEENAN | PAUL KEENAN DTN 297-7332 | Mon Jul 09 1990 17:01 | 13 |
| RE .10 & .11
Gene hit it on the head - numerous minute changes can have a big
effect.
I've taken courses in mathematical optimization of multivariable
equations. Once the number of variables goes beyond three, the
techniques break down and things get very complex. I don't hold
any hope for a program that will optimize the countless little changes
on a sailboat that can make the difference between mediocre and
blazing speed.
Paul
|
| 1555.13 | Need Data | STEREO::HO | | Mon Jul 09 1990 18:16 | 5 |
| I thought I'd pop in the attributes for my own boat but I don't know
how to calculate RMA2 and RMA25 which are the righting moments at 2 and
25 degrees. Also what is TRMAX used in the calculation of ATEK?
- gene
|
| 1555.14 | ATEK, WS, RMA2 | ECAD2::FINNERTY | Reach out and luff someone | Mon Jul 09 1990 19:50 | 57 |
|
TRmax is an effective reduction in keel depth caused by the fullness
of the forward part of the hull. TRmax is not adequately documented
in the 2 reports that I currently have, but from a hand sketch it
appears that for a modern underbody you can estimate TRmax to be
approximately .85 * DFK. For an extreme hull form which is very
full and deep forward of the keel, use .50 * DFK.
To calculate RMA2 accurately you need to perform an "inclination
experiment", as I'll describe below. For a ballpark estimate you
can use the heuristic that the stability grows as the 4'th power
of the waterline length; if there is a similar hull form to yours
with a known RMA2, then scaling it by the 4'th power of the ratio
of the waterline lengths should get you reasonably close.
Similarly, if there is a similar hull form with a known wetted
surface area you can scale it by the square of the ratio of the
waterline lengths to estimate the wetted surface of your boat.
The following is from Skene's elements of yacht design, pg 298:
Inclining Experiment. To find the transverse metacentric height (GM)
of an existing boat to check her stability or rerig her, what is
commonly called an inclining experiment is performed as follows:
1. On a calm day, determine the flotation of the boat, amount of
liquid in the tanks, amount of inside ballast, stores and
gear. Free the docking lines.
2. Rig a pendulum of string with a heavy nut as a weight at the
bottom. Fasten it on the center line, say in the amidship hatch.
To steady the pendulum, put a bucket of water on the cabin sole
and hang the weight in it. Then place a horizontal batten across
the two main cabin seats and tape a strip of paper on it so that
the movement of the pendulum can be accurately recorded and
measured.
3. Use people as moving weights, say as follows: one person for a boat
up to 28 feet W.L.; 2 people up to 33 feet W.L.; 3 people up to 38
feet W.L.; 4 people up to 42 feet W.L.; 5 people up to 50 feet W.L.
etc. Mark the positions at which the people are to stand on deck
at the center line and at the rail at the widest part of the boat
on both sides.
4. Record pendulum movements on batten, with people in the above
positions.
5. Find the GM from the following formula:
Transv_GM = (Wt_Moved * Dist_Moved_in_ft * Pendulum_Length_in_ft )
------------------------------------------------------
(displacement_in_lbs * Pendulum_movement_in_ft)
With the GM thus obtained, use the Dellenbaugh Angle method to find
how stable the boat will be, if a sailboat.
(and from pg 296, "The Dellenbaugh Angle Method"):
Righting Moment @ 1 degree = (GM * displacement_in_lbs) / 57.3
|
| 1555.15 | sail lift/drag coefficients | ECADSR::FINNERTY | Reach out and luff someone | Tue Jul 10 1990 10:02 | 18 |
|
re: .9:.12 on J/24 tacking angle
VPP summarizes all of these adjustments into a pre-calculated table
of sail lift & drag coefficients. The data was obtained by direct
measurement of two masthead rig sloops; fractionally rigged sloops
would probably require adjustments to this table, and I suspect
that this is where most of the error is introduced.
If this is true, then "all" that is needed is a new table which
correctly tabulates the lift/drag coefficients for your rig. ;)
Apparently this is how VPP could also account for boats which do/not
have spinnakers, can/not pole out the sail downwind, etc. Now if
there was just some way to create these tables...
/Jim
|
| 1555.16 | 12 Meters are Fractionals | STEREO::HO | | Tue Jul 10 1990 10:26 | 12 |
|
re. the fractional rig table
The sample output includes data for the 12 meter Intrepid which is a
fractional rig, and a more extreme one than a J24. They've been using
the VPP on 12's for a while with mixed results. I recall John Marshall
and Britton Chance describing their experiences using VPP in designing
Stars and Stripes. They were so disatisfied they wrote their own. I
don't know if their modifications ever made it back into the official
IMS version of the VPP.
- gene
|
| 1555.17 | | MFGMEM::KEENAN | PAUL KEENAN DTN 297-7332 | Tue Jul 10 1990 12:39 | 13 |
| How does the lift & drag table input to the VPP? Does IMS typically
generate a new one for each boat?
My impresion of VPP was that it was an attempt at computing the optimum
speed/time a boat can be sailed under varying wind and courses layouts.
I thought the same program was used on all boats with only the various
dimensions as input.
If things like lift & drag are tweaked for different boats - isn't there
a danger of penalizing highly refined one designs .vs. an unrefined racer
cruiser with the same speed potential?
Paul
|
| 1555.18 | | ECADSR::FINNERTY | Reach out and luff someone | Tue Jul 10 1990 15:42 | 24 |
|
>> How does the lift & drag table input to the VPP?
One of the prompts is for the name of the data file which contains
these coefficients, as well as other program parameters such as
which wind speeds to simulate with, etc.
The VPP that I received is slightly different than the standard one
which the USYRU uses. I'm not sure what changes they've made, or
what assumptions they've made about wind conditions, etc. One thing
I do know is that whatever assumptions are made cannot be universally
fair under all conditions for all boats... e.g. assumptions are made
about the amount of wind gradient that will be seen, but if less
gradient is present on that day on the racecourse then the bigger
boats get unfairly penalized, since the assumption that they would
receive more/stronger wind was built into their rating.
As far as I know there is only one table of coefficients available;
that might account for why the "official" VPP results are not quite
accurate ... my guess is that they apply some kind of correction
factor to account for different rigs, but it really is just a guess.
/Jim
|
| 1555.19 | | STEREO::HO | | Tue Jul 10 1990 16:03 | 6 |
| re .14
Is there a Dellanbaugh angle method for righting moments other than at
1 deg? Like at 2 and 25 degrees as required by the VPP?
- gene
|
| 1555.20 | Hull Righting Moment | ECAD2::FINNERTY | Reach out and luff someone | Tue Jul 10 1990 22:39 | 33 |
|
From MIT report 78-11, pg 35:
"4. HULL RIGHTING MOMENT
The righting moment of the hull is obtained from the expression
RM(phi) = phi * (rm2 + .04*(rm3-rm2)*phi + rmv*V/sqrt(L))
where
rm2 is the static righting moment per degree at zero heel,
deduced by inclining experiment at a nominal heel angle of
two degrees, corrected for weight differences between
measurement and sailing trim.
rm3 is the static righting moment per degree at a heel angle
of 25 degrees obtained by a hydrostatic calculation with
a height of center of gravity derived from rm2.
rmv = 5.955*10e-5 * Disp * L * (1 - 6.25 * (B/sqrt(Am)) - 2.1))
is the correction to the hydrostatic righting moment
resulting from the speed of the yacht. Equation (for rmv)
was obtained by an analysis of the Delft series data, and
indicates a greater reduction in stability with speed as
beam is increased.
"
Am AMS input parameter to VPP
B Beam
The report does not say how to calculate rm3 from rm2.
/Jim
|
| 1555.21 | Improved Parameters for Cat25, 130% Genoa, Std Rig | ECADSR::FINNERTY | Reach out and luff someone | Fri Sep 14 1990 15:18 | 4 |
| Catalina 25, Standard Rig, 130% Genoa
21.17 21.18 21.22 21.60 8.00 4.00 0.00
3.10 225.00 13.85 0.00 4850.00 237.00 214.00
0.29 28.50 279.50 0.00 0.00 1.31 6.98
|
| 1555.22 | Some experience with VPP | ECADSR::FINNERTY | Reach out and luff someone | Fri Sep 14 1990 15:43 | 34 |
|
After performing the inclining experiment, calibrating my knotmeter,
and taking measurements of freeboard, etc, the results of VPP now
agree very closely with observed speed, at least at low windspeeds.
The rules of thumb for estimating righting moment, etc., get you
close but, in my case, not close enough to get accurate results.
The inclining experiment is easy to do, and most of the other
quantities are either easily measured or do not seem to require
high accuracy.
Two exceptions to this are the "beam" measurement, which requires
knowledge of the line drawings at each station, and the righting
moment at 25 degrees. The "beam" is not the normal beam measurement,
but the function has been constructed in such a way that using the
standard beam measurement will give approximately correct results.
For RM25 I used the ratios of RM25/RM2 for other 'known correct'
data input files, and got good results.
The low wind speed predictions of VPP say that I should be able to
sail .1 kt faster than observed downwind if I had a perfectly smooth hull,
new sails, and ideal sail trim. This is based on my estimate of
wind speed, which was based on sea state & a crude handheld anenometer.
Upwind it was as accurate as I could measure with my instruments.
I modified the VPP data file to account for the actual crew weight,
and made a more accurate accounting of the total weight. The
'CREW WT ON RAIL' is calculated as: .2 * LWL * WeightPerCrew. The
WeightPerCrew is the last number in the VPPDATA.DAT file. You can
calculate backwards from this and modify WeightPerCrew as required
so that VPP gets the proper total crew weight.
/Jim
|