US SAILING

Portsmouth Yardstick Multihulls - Modifications



 MULTIHULL MODIFICATION PENALTIES AND ALLOWANCES
FOR HEADSAIL, WEIGHT and WIDTH ADJUSTMENTS
Adjustments for Open Class Racing

 Modification Factors for Multihulls
March 2006

Copyright © 2006 by N. E. Richards and J. F. Spinnler
 Reprint permission by authors is required  for material in the Portsmouth Yardstick
Please contact hobockd@aol.com for permission

Centerboards  •  Centerboards-Inactive  •  Multihulls  •  Multihulls-Inactive  •  MH Modification Factors 
 MH Wts  •  Keelboats  •  Offshore A-E  •  Offshore F-O  •  Offshore P-Z
(D-PN) modified = (D-PN)(MF)1(MF)2
(HC) modified = (HC)(MF)1(MF)2

All ratings for ONE-DESIGN and OPEN CLASS racing are based on boats being equipped with class approved sails and other class approved equipment. Each competitor shall declare ALL non class approved sails and equipment and shall comply with minimum total crew weight and number of crew. Ratings do not include spinnaker unless specified in tables.
    It is expected that boats with underweight crews will add the prescribed weight to meet class rules and that skippers and crews usually compete in the classes in which they sail the best for their combined weight and local sailing conditions. Ratings do not include spinnaker or carbon equipment unless indicated in the Tables or as allowed under one-design class rules.

For clarification:
1) For class normally without spinnaker carrying a second one, apply modification factor for each.
2) For class normally with spinnaker carrying one or more additional headsails, apply modification factor for each.
3) Also note the Other penalty for other deviations not identified below.
 

US SAILING CODE

DESCRIPTION

 D-PN Modification Factor (MF)
for Beaufort Range
0-1 2-3 4 5-9
TR For carrying trapezes above class allowance, per trapeze 0.981 1.000 0.988 0.981 0.963
US Class normally with small jib*, sailing uni without jib 1.026 1.036 1.030 1.026 1.026
UL Class normally with large jib*, sailing uni without jib 1.076 1.075 1.083 1.076 1.060
JS Class normally without jib, carrying small jib* 0.975 0.965 0.971 0.975 0.975
JL Class normally without jib, carrying large jib* 0.941 0.940 0.933 0.929 0.938
SP Class normally without spinnaker, genoa, reacher, hooter or wire/rope luff headsail attached to a pole, carrying one or more 0.960 0.953 0.958 0.960 0.960
SN Class normally with spinnaker, genoa, reacher, hooter or wire/rope luff headsail attached to a pole, not equipped with one 1.020 1.030 1.025 1.020 1.010
MN For non-class legal mainsail, of same sail area or less than class legal mainsail (formerly square top adjustment) 0.995 0.990 0.990 0.995 0.995
ML For non-class legal mainsail, of greater sail area* than standard main 0.980 0.969 0.975 0.980 0.985
JU For larger than standard jib 0.995 0.984 0.990 0.995 1.000
MT For taller mast than standard 0.995 0.990 0.990 0.995 0.995
BM For wider than standard beam 0.995 1.005 1.000 0.990 0.984
 
UNDERWEIGHT PENALTIES
Penalties apply for underweight crews who do not add weights to meet class rules
L1 For total crew weight less than class min. crew wt. but at least 90% of class min. crew wt. 0.991 0.990 0.991 0.996 0.999
L2 For total crew weight less than 90% of class min. crew wt. but at least 80% of class min. crew wt. 0.983 0.980 0.983 0.991 0.997
L3 For total crew weight less than 80% of class min. crew wt. but at least 70% of class min. crew wt. 0.974 0.970 0.974 0.987 0.996
L4 For total crew weight less than 70% of class min. crew wt. or for singlehanding a sloop
not having class min. crew wts.		 0.970 0.965 0.970 0.985 0.995
 
 OPTIONAL ALLOWANCES
 Optional allowances for heavy crew weight are designed for local fleet racing
and not recommended to be applied at divisional levels, regional levels or above
 Do not add weight in order to become eligible for H1, H2 or H3 weight allowances
H1 For total crew weight at least 110% of class min. crew wt. but less than 120% of class min. crew wt. 1.003 1.010 1.007 1.003 1.000
H2 For total crew weight at least 120% of class min. crew wt. but less than 130% of class min. crew wt. 1.006 1.020 1.013 1.006 1.000
H3 For total crew weight more than 130% of class min. crew wt. 1.010 1.030 1.020 1.010 1.000
 

Other

 Any other deviations from standard class configurations, including the addition of wings, can be assessed a penalty of at least 0.995. Multiple deviations may incur multiple penalties. Penalties may be greater than 0.995. Please identify any such modifications and penalties assigned and include with results reported to the handicap committee and Portsmouth Numbers Committee.
*Definitions
     Same Sail Area: within 5% of Calculated Approximate Sail Area
     Greater Sail Area: 5% of larger difference in Calculated Approximate Sail Area
     Small jibbed boats: boats with standard jib tacked to bridal wires and hoisted to or below mast hounds
     Large jibbed boats: boats with foils or jibs with tack attached to the deck or from cross beam and/or head attached above mast hounds


We strive to improve the validity of US SAILING's Portsmouth Numbers for all boats.
You and your club/fleet can help this effort by forwarding your race results annually by November 1
to US SAILING, Portsmouth Numbers Committee, P O Box 1260, Portsmouth, RI 02871,
or via email to hobockd@aol.com or via fax to Darline Hobock at 918-744-9760.

Race data needed: Class of boat, elapsed times, corrected times, and average wind speed. Please indicate non-standard equipment used and/or include modification code.