It's all very well saying 'get an IRC rating' but then you are faced with an application form full of acronyms and jargon!   For those not familiar with IOR, IMS or later ORC rating certificates (and there we go again with the acronyms!) it can all look a bit daunting.   

 

There are of course the IRC Definitions which are the official IRC definitions, and this is NOT intended to replace that, but it is a quick guide to what all the letters mean. However, most measurements are taken in accordance with the 'ERS' defintions - the Equipment Rules of Sailing published by ISAF (International Sailing Federation).  

RRS: Racing Rules of Sailing

IRC: Does not stand for anything!

RORC: Royal Ocean Racing Club - and Rating Office - joint owners of the IRC Rule

UNCL: Union Nationale pour la Course au Large - joint owners of the IRC Rule

TCC: Time corrector IRC

 

Hull:

LH: Hull Length

LWP: Waterline length

BO: Bow overhang

SO: Stern overhang

y, h, x:  Additional measurements taken at the bow and stern

DLR: Displacement/Length Ratio

 

Rig:

P: maximum hoist point of mainsail (on mast)

E: maximum outhaul point of the mainsail (on boom)

J: from the mast to the forestay attachment point

FL: Forestay length

STL: Spinnaker tack length

 

Mizzen rig:

PY: maximum hoist point of mainsail (on mizzen mast)

EY: maximum outhaul point of the mainsail (on mizzen boom) 

Mainsail:

MUW: Mainsail upper (7/8) width (ie. taken 7/8 of the way up the leech)

MTW: Mainsail three quarter width (ie. taken 3/4 of the way up the leech)

MHW: Mainsail half width (ie. taken 1/2 way up the leech)

Headsail:

LLmax: Maximum luff length on any headsail

LL: Luff length of largest headsail

LP: Luff perpendicular - from clew to luff

HHW: Headsail half width (ie. taken 1/2 way up the leech)

HTW: Headsail three quarter width (ie. taken 3/4 of the way up the leech)

HUW (from 2013): Headsail 7/8 width (ie. taken 7/8 of the way up the leech)

HHB: Headsail top width (applicable in southern hemisphere until May 2013)

HSA: Headsail area

Spinnaker:

SLU: Spinnaker luff length

SLE: Spinnaker leech length

SF: Spinnaker foot length

SHW: Spinnaker half width (half luff to half leech)

SPA: Spinnaker area

 

Mizzen staysail:

LLY: Luff length

LPY: Luff perpendicular

STIX: Stability Index

AVS: Angle of Vanishing Stability

SSS: Safety & Stability System

ISO: International Organization for Standardization

OSR: Offshore Special Regulations