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Yacht Measurement Definitions

Yacht Measurement Definitions

   The measurements of a yacht as reported on her rating certificate or rating application form are critical to the establishment of their boat’s rating.   The responsibility for supplying accurate measurements rests solely with the owner of the boat.   Although builder-supplied information can and should be consulted, particularly with regard to hull measurements, considerable variances between yachts of the same class can be possible.   Variances in the dimensions of the rig are quite possible, and common, which could result in the rating being declared invalid if the owner supplied incorrect information.   Spinnaker poles are principal violators, as many builders do not hold precisely to the “J” measurement.     In the hope of establishing some consistency in the taking and reporting of measurements, some guidelines are provided here.   Refer to the diagrams on the next pages.

DEFINITIONS

LOA         Length Over All of the hull. Note bowsprit and or boomkins separately.
LWL         Loaded Water Line. If unmeasured, use brochure LWL.
BEAM      Maximum beam of the vessel.
DRAFT     Deepest draft of hull. If center or dagger board yacht include draft with board up and down.
DISPL       Vessel displacement(lbs.) w/o crew, water, fuel, or stores. If unmeasured use brochure DISPL.
BAL          Ballast of vessel in pounds. Note any additions or deletions from standard and the location.
Fore triangle height, from deck sheer line abeam the mast to highest point of sail attachment.
Distance perpendicular from fore side of mast line to the point of intersection of the forestay with deck.
P              Luff length of mainsail from boom to head board in its highest position.
E              Foot length of mainsail from the mast to clew in its most outboard position. P2                Luff length of mizzen measured same as “P”.
E2            Foot length of mizzen measured same as “E”.
SH             Spinnaker hoist from deck sheer line abeam the mast to the highest point of sail attachment
LP
Distance perpendicular from the luff to the clew of the largest jib.
MGT
Mainsail girth from 7/8 leech to nearest point on mainsail luff.
MGU
Mainsail girth from 3/4 leech to nearest point on mainsail luff.
MGM
Mainsail girth from 1/2 leech to nearest point on mainsail luff.
MGL
Mainsail girth from 1/4 leech to nearest point on mainsail luff.
MH
Mainsail headboard width.
SA
Sail Area (including main and 100% fore triangle + mizzen).
SPL
Spinnaker or whisker Pole Length measured with the pole in its fitting and set in a horizontal position athwartship.
BS
Distances perpendicular from the fore side of mast line to the point of intersection with the outmost point of sail attachment with the bow sprit.
G
Spinnaker maximum Girth luff to luff. Fold on centerline, measure width, and multiply by two.   Same as (SMW).
SL
Spinnaker Luff length along red/green luff tape from head to clew on the largest spinnaker.
ALU
Length of asymmetrical luff from head to tack.
ALE
Length of asymmetrical leech from head to clew.
AF
Length of asymmetrical foot from clew to tack.
AMG
Asymmetrical spinnaker maximum girth luff to leech.

BASIC UNPENALIZED LIMITATIONS

LP% = 155% of length of “J” as defined above.
G% = 180% of length of “J” as defined above.
SL% = 100% of “SL” measurement expressed as a percentage of .95 times square root of (“I” squared + “J” squared)      
SPL% = 100% of length of “J” as defined above.
SH% = 100% of measurement as defined above
BS% = 100% of “J” as defined above
ALU% = 110% of “ALU” above expressed as a percentage of the square root of (“SH” squared + “BS” squared)
AF% = 180% of “AF” length expressed as a percentage of “BS”.
AMG% > 75% of “AF” measurement as defined above.

ROLLER FURLING CREDIT LIMITATIONS

Please check appropriate box:

               ____ Furling drum completely above deck level.

               ____ Furling drum partially or completely below deck level.

Roller furling headsails built before 1 January 2001 may constructed of any material except for aramid or carbon materials. Roller furling headsails built after 31 December 2000 may constructed of any material.   All roller furling headsails must have ultraviolet protection present on the leech and foot.

       c.       All headsails must be tacked above the furling drum and have the head secured to the bottom of the head swivel.

       d.       Please describe: Furling System Type; Headsail Material; and UV material

PHRF Mainsail Girth Measurements.

There are five (5) dimensions as listed below that are required for PHRF boats that use oversize girth mainsails.   The dimensions should be taken from the leech measurement point to the nearest point on the mainsail luff.   Refer the mainsail girth measurement diagram on the PHRF website (www.phrfchesbay.com) for an example of the MGU (3/4 girth) measurement.

MGT Mainsail girth from 7/8 leech to nearest point on mainsail luff.

MGU Mainsail girth from 3/4 leech to nearest point on mainsail luff.

MGM Mainsail girth from 1/2 leech to nearest point on mainsail luff.

MGL Mainsail girth from 1/4 leech to nearest point on mainsail luff.

MH Mainsail headboard width.

REQUIRED INFORMATION FOR FIXED PROPELLLER CREDIT REQUESTS

                A diagram, or photo, of the propeller installation must accompany all requests for prop credits.   You must specify the type of installation (aperture or exposed), supplying the following information:

____   Exposed Propeller installation (check exposed or aperture below)

____   Aperture Propeller installation

____ Number of blades.

____ Diameter of the propeller in inches.

____ Pitch of the propeller in inches

____ Minimum distance from the propeller to the trailing edge of the keel in feet (EXP, below).

____ Length of the propeller shaft exposed (from hull/keel exit to propeller in feet (SHAFT below).

Fixed Propeller Measurements

To be eligible for rating credit, propellers must be of fixed design, with no folding or feathering mechanisms.  The required information must be provided with the request for credit, in addition to renewal or application forms.

 

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