158:– When a sailing yacht heels, there are adjustments which need to be made to the base resistance of the hull due to the modified hull geometry, all of which are captured by this term. The first change is the wetted surface area of the hull, which will result in a greater viscous drag if increased. More significantly, however, are the changes in residuary resistance when heeled. The underwater portion of the hull will no longer be symmetric and will usually result in increased residuary resistance. This is particularly true if there are major changes to the beam to draft ratio or the longitudinal center of buoyancy.
144:– Residuary resistance includes all other remaining types of resistance on an upright, bare hull in calm water. The reason for this grouping is that of all the types of hydrodynamic resistance imposed upon a boat hull in motion, only viscous drag can be cleanly isolated, as it scales proportionally to wetted surface area. Residuary resistance, then, is composed primarily of wave-making resistance, eddy formation and large-scale separation, all of which are too complex to be determined empirically given prior knowledge of hull geometry. These types of resistance can only be determined by model testing.
152:– Induced drag is a result of an imperfect, or non-infinite, lifting surface (in this case the keel, rudder and any other appendages.) When lift is generated in three dimensions, a closed circulation loop is formed which creates downwash. This downwash alters the free stream velocity, by rotating it downward, towards the downwash. This new angle results in a small increase in resistance as it has a component in the direction of the free stream.
138:– This type of drag is also known as "skin friction" as it is thought to derive entirely from the frictional resistance of water molecules imposing a force as they slide past the wetted surface of the hull and its appendages. This type of drag scales proportionally to wetted surface and is one of the two constitutive components of hull resistance.
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were some of the earliest adopters of VPPs. In the United States, the most common handicapping rule is the PHRF rule, developed and promoted by the United States
Sailing Association. While most other rules do not take past performance into account, PHRF differentiates itself by allowing skippers to
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VPPs produce a great deal a data, so the presentation of this data requires special consideration. While tabular output can be valuable for identifying specific values, the most common way to present VPP output is with a polar plot.
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VPPs are used by a variety of sailing organizations to assess theoretical boat performance and then assign "handicaps" to allow boats of different styles and sizes to race against one another. The IOR and IMS
168:) – This element represents the computationally or experimentally derived resistance due to the motion of a yacht in a seaway. This resistance can be considered to be a factor either of true wind speed (V
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calculates the difference between the propulsive force of the sails and the resistive force of the hull. It also calculates the righting moment created by the hull and the operational heel angle.
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VPPs solve for the performance of a yacht by resolving all forces and moments acting on the yacht. Pitching and yawing moments can be assumed to be zero for simplicity.
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has the responsibility of adjusting the input parameters and balancing the forces until it produces the maximum possible speed at each true wind angle.
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VPPs are iterative programs which require educated guesses of initial parameters to begin operating. Generally VPPs are composed of two mechanisms, a
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The resistive forces acting on a hull and its appendages (keel, rudder and other fins) can be broken down into a number of smaller components.
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request handicap reductions after a series of poor racing results. In Europe, the most common handicapping system used today is the IRC rule.
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Since the propulsive force and the resistive force are not likely to be equal on the first iteration, the
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teams, to predict the performance of a sailboat before it has been built or prior to major modifications.
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83:"of a sailing yacht, given knowledge of its hull, rig and sailplan geometry"
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108:), heel angle (Φ), number of reefs and sail flatness are input into the
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27:) is a computer program which solves for the performance of a
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Initial guesses of parameters including boat speed (V
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Claughton, A R; Wellicome, J F; Shenoi, R A (2006).
312:. United States Sailing Association. Archived from
310:"United States Performance Handicap Racing Fleet"
420:presentation and guidelines for the speech in
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81:funded research to predict the performance
382:: CS1 maint: location missing publisher (
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362:. Southampton, UK. pp. 109–143.
72:Massachusetts Institute of Technology
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112:. Using these input parameters the
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42:and sail forces. VPPs are used by
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428:Presentation in Helsinki 140112
455:Sailing rules and handicapping
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16:Yacht speed computer program
360:Sailing yacht design: theory
74:during the early 1970s when
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21:velocity prediction program
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228:Sailing yacht handicapping
162:Added resistance in waves
298:Moonbeam VPP polar chart
201:Solving and optimization
127:Hydrodynamic force model
408:Sailfish Yacht Analyzer
274:Polar diagram (sailing)
253:Sailfish Yacht Analyzer
177:Aerodynamic force model
439:, merenkavijat.fi, ORC
337:. IRC. Archived from
437:Guidelines to follow
223:Sailing yacht design
142:Residuary resistance
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269:International Rule
235:handicapping rules
121:solution algorithm
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418:Maurizio Cossutti
156:Heel induced drag
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343:. Retrieved
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285:References
110:boat model
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66:Background
56:sailmakers
378:cite book
247:WinDesign
76:Commodore
37:balancing
449:Category
422:Helsinki
258:See also
58:, also
52:sailors
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97:and a
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384:link
364:ISBN
218:Uses
40:hull
33:wind
432:ORC
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