IRC YEARBOOK 2009
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APPENDIX 1
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OCEAN SAFETY IRC MEASUREMENT DEFINITIONS
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Measurement Note: ISAF Equipment Rules of Sailing (ERS) Part II, Definitions, Section G, Sail Definitions, shall apply to sail measurement except as
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stated by IRC Rules or this Appendix. Sails shall be measured in accordance with ERS Part III, Measurement Rules, Section H5, Sail Measurement.
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Age Date – The year in which the boat was first launched, or the year in which
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the boat was re-launched following hull modification, whichever is later.
IRC measurement of waterline length and overhangs
R Backstay – An item of running rigging from the masthead to the stern of the
E
boat which may be adjusted while racing.
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Batten – Any material added to the sail, as either a removable element,
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permanent stiffening, or other contrivance, the purpose of which is to
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support and/or stiffen the sail.
T

D
Beam – The maximum horizontal dimension of the boat in any transverse
section, excluding any rubbing strake or toerail.
E
F
BO – The horizontal distance from the forward point of LWP to the forward
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limit of LOA, in the condition of Empty Weight (see Rule 22.0).
N
I
Checkstay – An item of running rigging from the mast significantly below
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the forestay to the stern of the boat which may be adjusted, either directly
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or indirectly, while racing.
N
Draft – The maximum depth of the boat or any of its appendages below
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the waterplane, in the condition of Empty Weight (see Rule 22.0). In the
case of any movable appendage, which is not fixed down while racing,
the minimum depth is also required.
E – The foot of the mainsail measured along the top of the boom set on the
centre line and at right angles to the mast, from the back of the mast
to the inside of a permanent 25 mm band of contrasting colour beyond
which the mainsail clew point shall not be set. If there is no band the
measurement shall be taken to the aft end of the boom.
EY – The foot of the mizzen sail measured as for E.
Empty Weight – The weight of the boat to the nearest 10 kg, in the condition
of Empty Weight, less the weight of any deductions to the nearest I kg
(see Rule 22.3).
FL – The length measured from the forward end of J to the higher of either:
a) the forestay attachment point on the front of the mast or to where the
forestay intersects the front of the mast, or:
b) if a headsail may be set forward of the forestay, to the highest
attachment point on the mast to which a headsail may be hoisted.
h – The vertical distance from the waterplane to the lowest point on the stem
at a tangent of 45º to the horizontal, in the condition of Empty Weight
(see Rule 22.0).
Heavy Weather Jib – A headsail which complies with Special Regulations
Paragraph 4.26: A heavy-weather jib of area not greater than 13.5%
height of the foretriangle* squared and without reef points. *Vertical height
from sheerline abreast the mast to forestay attachment point on mast.
HHB – The widest headsail top width of any headsail on board measured as
the distance between the head point and the aft head point.
HHW – The Headsail Half Width of the largest area headsail measured as
the shortest distance between the half leech point and the luff, bridging
any hollows in the leech of the sail.
HSA – The maximum permitted headsail area.
HTW – The Headsail Three-Quarter Width of the largest area headsail
measured as the shortest distance between the three-quarter leech
point and the luff, bridging any hollows in the leech of the sail.
Internal Ballast – Lead or other material, not in the keel and bulb, which has
no practical function in the boat other than to increase weight or to adjust
fore and aft trim.
J – The base of the fore-triangle measured as the horizontal distance from
the front of the mast at deck level to the most forward point on the deck or a
centreline bowsprit to which a headsail may be tacked, projected if necessary.
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IRC 09 Meas Defs P44-47_bs 44 1/12/08 09:12:36
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