| Estimating Stability |
| By John Holtrop |
Published
01/16/2006
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Sailing
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Unrated
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Page 4
I then used a "fuzzy logic" technique to identify boats that were fully compatible with these parameters, drawing from my database, which contains over 840 monohull sailboats. Fuzzy logic allows these boats to be ranked with respect to how closely they match a "template" built with parameters obtained from our selected cruising boat designers. The boats that made it on this list are all "very close" to all of the parameters derived from the work of our nine designers. The highest scoring designs (above the 50 percentile), 55 total, were then selected for constructing the template. Their average dimensions and standard deviations (sigma) are shown in Table 1. TABLE 1, STABILITY TEMPLATE | DIMENSION | AVERAGE | SIGMA | | | | | | LENGTH OVERALL, ft. | 41 | 4.6 | | LENGTH ON WATERLINE, ft. | 32 | 3.6 | | BEAM, ft. | 12.1 | 1.3 | | DRAFT, ft. | 5.9 | .79 | | DISPLACEMENT, lbs. | 22960 | 6820 | | SAIL AREA, sq.ft., 100% | 821 | 172 | | SA / DISP | 16.5 | .60 | | DISP / LWL | 306 | 30.6 | | COMFORT FACTOR | 35.8 | 3.0 | | CAPSIZE RISK | 1.7 | .06 | | BALLAST RATIO | .40 | .048 | | LOA / BEAM | 3.4 | .13 | | HULL SPEED, knots | 7.57 | .01 | | V max / V hull | 1.07 | .01 | | MOMENT OF INERTIA, lb.ft.^2 | 1,197,433 | 642,819 | | PERIOD, seconds | 4.05 | .33 | | STABILITY INDEX | 1.1 | .12 |
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