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Learn about the US Sailing Universal Measurement System (UMS) and the key features of the HPR rule for high-performance boats. Understand the criteria and ratings involved, design factors, and how HPR promotes competitive racing. Explore contemporary design features and the simplicity of the rule, leaving room for innovation and speed optimization. Discover the measurement process and VCG determination methods to ensure fairness and accuracy in boat rating. Join the seminar to delve into the world of high-performance sailing with expert insights.
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US SailingUniversal Measurement System (UMS)Measurer Seminar High Performance Rule (HPR) Overview Jim Teeters
Why HPR? • Rule is customized for high performance boats • Type-form to fast design – low performance boats not competitive • Ability to plane offwind in medium breeze • Public (open spreadsheet rule calculator) • Simple (measure ONLY the fundamental characteristics that determine speed) • Leave details to designers to simply create fast boats. • No subjective elements
HPR Design Features • Characteristics of contemporary grand prix • Light displacement, wide beam, high sail area promote offwind planing • Deep draft, modern fin/bulb keels, low VCG for upwind speed • Long waterlines relative to LOA • High sail area, long sprits, flat had mains.... • No moveable ballast
What is Rated? • Rated Length = LOA (overhang credits for old boats) • Max Beam, Draft, Displacement • Upwind Sail Area, Spinnaker Area, Rig Height • Freeboard – mild encouragement of interior volume • VCG – surrogate for stability • Crew Weight • Propellers • Construction Credit, Old Age Credit
What is Not Rated? • Details of hull shape: (no offsets files required) • No wetted areas, LCBs, prismatic coefficients • No details of appendage design: wetted area, volume • No heeled stability (VCG and beam act as surrogates) • Intent: Adopt some of the rationale behind box rules: minimize design optimization of trading off design details, leave freedom to designer to find fastest solutions, encourage development
Type-forming • Default boat – based on rated length: • Beam, draft, displacement, freeboard.... • Upwind sail area, spinnaker area, rig height... • VCG, crew weight • Rating based on deviation from default boat • Limited credits for being slower • Limited penalties for being faster • Credits/penalties initially calibrated with VPP
VCG Determination • Method 1 – Component Weighing • Mast weight and VCG • Boom weight • Total weight from scale • Keel weight and VCG • Canoe + rudder weight imputed, VCG coefficient • Method 2 – Offsets File + In-Water Flotation • VPP hydrostatics, salinity correction • Sensitive to environment: wind/waves...
Keel Weight/VCG • Requirements • Two lift points: bulb and keel top • Keel top can be anywhere, typically at keel bolts • Lift points and support points must be vertically aligned • Axis of lifting lines must be vertical • Keel blade must be horizontal when lifted • All distances are relative to bottom of keel