GSR Rating Form – GS Regatta 2024

GS Regatta 2024 Rating Form

INSTRUCTIONS

All data required under headings Hull, Rig and Sails that are marked by a star have to be filled in in order for a rating to be generated. In case data for your boat is not readily available it can most likely be found on the Internet in the database Sailboatdata, or on the respective boat builder’s web site. In case these sites do not provide the missing data please contact the Race Committee on for assistance. All measurements are metric and should be filled in with at least two decimals. Commas should be used to denote decimals.

The main parameters defining a sailboat's performance are length, in particular waterline length, beam, draft displacement and sail area. The art and science of yacht design is centered round mainly four factors (three ratios and one product) using these parameters.

— The waterline length (Lwl) determines the maximum speed a displacement boat can reach – the hull speed – which is equal to the square root of the waterline length in meters times 2.43. This ratio defines the speed at which wave resistance in practice becomes insurmountable without planning - that is when wave length equals water-line length.

— The driving force of the boat can be measured by the ratio of the square root of the sail area (SA) divided with the cube root of the displacement (D) i. e. the driving force in relation to the mass.

— The square root of the draft (T) divided with the square root of the overall length (L) of the boat describes the shape and, to some degree, also the surface of the underwater body – the wetted area – and, as a consequence, the friction resistance it creates.

— The square root of the length divided by the square root of the beam (B) gives a measure of the so called induced resistance – mainly the size and shape of the wave the boat produces.

Those four factors form part of most handicap rules. They are normally complemented by correction or compensating factors that take into account different keel forms, different rigs, different sail configurations and shapes, etc.

Different keel forms cause resistance of different types (friction and turbulence) and to varying degrees. A modern T-shaped bulb keel of lead causes less resistance than a full cast iron keel. A keel correction factor can make allowance for these differences by adjusting the value of the square root of the displacement.

The efficiency of high aspect ratio rig differs from that with a low aspect ratio with the same sail area. The sail parameter also needs a correction factor in order to allow for different flying sails and of different sail cloth.

The formula used for the GSR rating is derived from handicap rules for classic yachts in the Mediterranean (C.I.M), Germany (KLR) and Scandinavia (Alma rule) modified to better suit the characteristics of modern fiberglass cruising boats. The formula is as follows:

6 × ²√ (2,43 × ²√Lwl) × ((²√ SAc / ³√Dc) + π × (²√T / ²√L) + (²√L / ²√B)) / 104 = GSR time correction factor

SAc (Total adjusted sail area) = Total sail area × sail correction factor × rig factor

Dc = Displacement × keel factor × ballast ratio factor × propeller and bow thruster factor.

Boat and Owner Coordinates

Boat name*

Owner’s name*

Skipper’s name*

Skipper’s e-mail*

Is the boat chartered?* Yes No

Boat Specifications

Boat make*

Model

Version

Year built

Designer

Builder*

Hull

Hull, displacement and ballast measurements should be those of manufacturers/builders or designers or those taken from ORC/IRC certificates. For keel configuration, see Keel Diagram below.

Length over all - LOA (m)*

Length of waterline LoW (m)*

Max beam - B (m)*

Max draft - T (m)*

Displacement - D (ton)*

Ballast (ton)*

Keel material*

Keel configuration*

Propeller type*

Rig and Sails

Sail area measurements should be either those of the sailmaker, those of ORC/IRC certificates or recent own measurements. See Sail Diagram for a depiction of the sail measurements, and Instructions how to measure LP and Bas. Please note as regards flying headsails that, for the purpose of GSR rating calculation, a spinnaker is a flying headsail attached to a spinnaker boom that is fastened to the mast. Other flying headsails configurations are gennakers or codes.

Rig type*

Other, specify ratio*

Foretriangle height - I (m)*

Foretriangle base - J (m)*

Genoa/jib area (sq. m)*

Luff perpendicular - LP (m)

Mainsail height - P (m)*

Useable boom length - E (m)*

Mainsail area (sq. m)*

Deck-boom distance - Bas (m)

Furling mainsail

Laminate and flying sails Laminate main
Laminate genoa
Spinnaker
Gennaker/code

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The GSR rating formula explained

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Your application was submitted successfully. An automatic email with your form data was sent to your email address. We will process your entry and contact you shortly.