North American Portsmouth Yardstick

The North American Portsmouth Yardstick includes centerboard boats, multihulls, keelboats and offshore classes. It is a widely used method of rating boats of different classes sailing the same courses and is used by clubs and fleets across the country. It is a time-on-time handicapping system and is derived from actual records of classes of boats with thoroughly documented ratings. Portsmouth Numbers are defined as the length of time boats would take to sail a common but unspecified distance. The formula is easy to use:
                      CT (Corrected Time) = ET (Elapsed Time) X 100 / HC (Handicap)
Annual changes in ratings are modest. The elapsed time for each boat in a race is measured against the primary and secondary yardstick classes in the race and a handicap calculated for each boat. When there are new data, the previous ratings are adjusted by 25% of the difference between the old ratings and new history.
     Windycrest supports the Portsmouth Yardstick by supplying race data annually to the US SAILING Portsmouth Numbers Committee.

Beaufort Scale of Wind Velocity

 

Beau-fort
No.

Knot

MPH

Seaman
Term

Sea Conditions

Typical
Wave
Height
 

0

0-1

0-1.7

Calm

Glassy-smooth, mirror-like  

Smooth
 

1

2-3

1.8-4.0

Light air

Scale-like ripples

Ripples
 

2

4-6

4.1-7.4

Light breeze

Small, short wavelets with glassy crests

1/3'
 

3

7-10

7.5-12.0

Gentle
breeze

Large wavelets, crests begin to break, occasional form

1-2'
 

4

11-16

12.1-18.9

Moderate breeze

Small waves, some whitecaps, more frequent form

2-3'
 

5

17-21

19.0-24.7

Fresh
breeze

Moderate longer waves, better formed, many whitecaps, much foam, some spray

3-4'
 

6

22-27

24.8-31.6

Strong
breeze

Large waves form, many whitecaps, foam everywhere, more spray

4-5'
 

7

28-33

31.7-38.5

 Moderate gale Sea heaps up, streaks of foam spindrift begins

5-6
 

8

34-40

38.6-46.6

 Fresh gale Moderately-high long waves, crests into spindrift, well-marked streaks of foam

6-7
 

9

41-47

46.7-53.9

 Strong gale High waves, sea rolls, dense streaks, spray affects visibility

7-9

2008 Portsmouth Numbers for Boats at Windycrest
NAPY   WIND H-C FOR BEAUFORT RANGE
CENTERBOARD CLASSES CODE D-PN 0-1 2-3 4 5-9
420   (Int. or Club) 420 97.6 103.4 100.0 95.0 90.8
470   (Int.) 470 86.3 91.4 88.4 85.0 82.1
American 16 AM-16 103.6 (110.2) 105.0    
C Scow C-SC 79.1 81.4 80.1 78.1 77.6
Capri 14.2 (Catalina) CAT142 99.4 100.1 99.7 99.2  
Coronado 15 COR15 91.9 92.7 92.6 91.5 90.4
Dolphin Sr DLPSR 105.5 111.7 108.6 101.0 97.3
E Scow E-SC 72.6 77.6 75.3 70.8 69.3
Finn  (Int.) FN 90.1 93.2 91.8 89.1 87.1
Flying Scot (19') FSCT 89.6 92.1 90.4 89.1 87.5
Holder 17 VAG17 [100.0]        
Hunter 140  (JY14) HTR140 [99.0]        
Javelin JAV 111.3 111.2 111.5 110.4 (109.8)
JY 15 JY15 91.9 92.5 92.4 91.9  
Laser   (Int.) LASE 91.1 93.7 92.3 91.0 88.2
Lightning (Int.) LI 87.0 92.6 87.6 85.4 83.9
Lone Star 13 LS13 109.5 [106.3] 108.4    
M-20 Scow M-20 83.5 88.6 85.2 81.5 80.5
MC Scow MC-SC 87.8 89.5 87.4 87.2 86.5
Mutineer 15'  MUTR 96.0 98.1 96.1 95.4 (95.0)
Omega (14') OMG 110.6 112.3 110.4 108.1  
Optimist Pram  (Int.) OP 123.6   124.0    
Pintail PINT 105.0 113.9 107.3 (100.0) (96.5)
Sabot Naples SBT-N 136.4   136.7    
Sabot U.S. SBT (119.6)   (121.8)    
Snipe  (Int.) SN 91.9 94.8 92.5 91.4 89.0
Sunbird SBRD 114.0 (114.5) 115.0    
Sunfish (Int.) SF 99.6 103.0 100.4 97.8 95.8
Thistle TH 83.0 83.0 83.0 83.0 83.0
Tornado C/B TOCB 90.9 91.9 91.8 91.0 (89.7)
Windflight WINF 108.3 (106.7) (108.6)    
Zuma ZUM 103.2 (104.3) 103.7 (100.3)  
             
MULTIHULL CLASSES            
Hobie 16 H16 76.0 81.5 78.7 74.1 71.3
Hobie 17 (1-up) H17 74.0 78.3 76.2 73.7 69.7
Hobie 18 & 18 Magnum H18 71.4 76.8 73.5 69.5 66.8
Nacra 5.2 Slp 2-up N5.2 72.1 78.0 74.8 71.6