Jargon translated

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 official IRC definitions which are part of the full rule text, and this is NOT intended to replace those, but it is a quick guide to what all the letters mean. Most measurements are taken in accordance with the 'ERS' defintions - the Equipment Rules of Sailing published by ISAF (International Sailing Federation).  

See also our simple sail measurement guide and measurement drawings.

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
LH: Hull Length (note that sales brochure Length Overall sometimes includes pulpit/bow roller, not included in LH)
LWP: Waterline length
BO: Bow overhang
SO: Stern overhang
y, h, x:  Additional measurements taken at the bow and stern
DLR: Displacement/Length Ratio
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) 
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)
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: Headsail 7/8 width (ie. taken 7/8 of the way up the leech)
HSA: Headsail area
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
Stability and safety 
STIX: Stability Index
AVS: Angle of Vanishing Stability
SSS: Safety & Stability System
Please let me know if I've missed anything!  This email address is being protected from spambots. You need JavaScript enabled to view it.




If you cannot find the answer to your question, please email webmaster@ircrating.org and I will reply to your question and add it to a new FAQs page. 
Jenny Howells, webmaster.
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