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Delta Sailing Association
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Portsmouth Yardstick

The "US Sailing" Portsmouth Yardstick handicap system allows sailboats of different designs and classes to race together by adjusting the time it takes each boat to complete the course to reflect the potential speed of each boat racing.

If boat "A" by design is two times as fast as boat "B", then boat "A" should finish the course in one-half the time that it took boat "B".

If boat "B" took 30 minutes to complete the course and boat "A" took 16 minutes (more than one-half the time it took boat "B"), then boat "B" wins - even though it went slower!

The actual calculation is as follows:

A boat's elapsed time is the time it took the boat to complete the course. To get the corrected time, the DSA Race Committee will simply divide the elapsed time by that boat's Portsmouth Handicap Number. The results are then multiplied by 100:

(Elapsed Time / Portsmouth Handicap Number) x 100 = Corrected Time.

The corrected time is then used to determine the finishing rank of the boats within the fleet.

.2017 Portsmouth Handicap Numbers for some popular sailboats1.

Dinghy
Class		 Default
DPN

Beaufort
0-1
0-3 knots

Beaufort
2-3
4-10 knots

Beaufort
4
11-16 knots

Beaufort
5-9
17-47 knots
Thistle2 83.0 83.0 83.0 83.0 83.0
Lightning 87.0 92.6 87.6 85.4 83.9
Precision 185 C/B 90.2 91.5 90.2 88.0  
O'Day DaySailer 98.5 101.3 98.5 96.9 96.3
Zuma 103.2 104.3 103.7 100.3  
Holder 14 Vagabond 111.0 113.3 111.7 108.4 N/A
JY 15 91.9 92.5 92.4 91.9 N/A
Capri 14.2 99.4 100.1 99.7 99.2 N/A
Laser 91.1 93.7 92.3 91.0 88.2
Bandit 15 97.9 100.7 98.8 96.7 (96.7)

Mutineer 15

 96 98.1 96.1 95.4

95
Apollo 16 92.4 96.6 94.4 (90.0) (89.1)
Coronado 15 91.9 92.7 92.6 91.5 90.4
Hunter 170-no spi 92.7 N/A 92.6 N/A N/A
Int. Flying Junior 97.9 100.9 99.3 98.2 95.8
Precision 15 96.6 N/A 96.2 N/A N/A
Laser II 92.8 95.6 94.6 93.6 88.8
Vanguard 15 90.5 92.6 91.2 86.1 N/A
Sunfish 99.6 103.0 100.4 97.8 95.8
Dolphin Sr 105.5 111.7 108.6 101.0 97.3
MC Scow 87.8 89.5 87.4 87.2 86.5
Snipe 91.9 94.8 92.5 91.4 89.0
Catamarans          
Hobie 14 86.4 95.0 90.1 85.6 80.9
Hobie 16 76 81.5 78.7 74.1 71.3
Hobie 18 71.4 76.8 73.5 69.5 66.8
Hobie Getaway 83.3 87.5 86.2 82.5 80
Taipan 4.9 Slp NoSpi 68.2 72.7 70.6 67.5 64.9
Taipan 4.9 Uni 1up NoSpi 69.5 73.5 71.4 68.9 65.9
Taipan 4.9 w/spi 63.0 66.0 64.5 61.9 60.1
           


Some Extremely Fast and Extremely S l o w Boats3: 

(just for comparison)
Boat Default Beaufort 0-1 Beaufort 2-3 Beaufort 4 Beaufort 5-9
Taipan 4.9 w/spi 63.0 66.0 64.5 61.9 60.1
49er 68.2 N/A 69.6 N/A N/A
International 5o5 79.8 82.1 80.9 79.6 78.0
WW Potter 15 138.1 N/A 139.1 (137.5) N/A
Widgeon 122.6 126.0 121.8 (118.4) N/A
The adjustment factors (Portsmouth Yardsticks or D-PN) used are calculated from actual historical performance data. Certain assumptions had to be made in the calculations: 
  1. Each boat placing first in each class was sailed to its true potential4 by a perfect crew according to flawless strategy;5
  2. All boats sailed the same course, experienced the same wind/water conditions and degree of interference of clear air; 
  3. All one-design boats conformed to class specifications and rules, and used sails specified by the class; and 
  4. Boats with multiple sail inventories (genoas, spinnakers, etc.) utilized the proper sails for the wind conditions and legs of the course.

Boats perform differently in different wind ranges, so different handicap numbers are used in different wind conditions - explaining why there is more than one column of numbers after each boat in the table above

There are ways to account for the various problem situations of atypical rigging, crew weight, and odd sail configurations, which might violate a boat's class rules. The DSA Race Committee Chairman will assign allowances or deductions to that boat's Portsmouth Handicap Number, using Table VI of the Portsmouth Yardstick Manual. This would keep a sailboat from being disqualified and allow that boat to go ahead and simply race with a modified Portsmouth Handicap Number.

 

 

Footnotes and further comments:

  1. This is only part of the complete list of Portsmouth numbers.

  2. The Thistle is the benchmark boat for the entire Portsmouth Yardstick system; all other boats are compared against the known sailing performance potential of the Thistle. 

  3. So why doesn't everybody just sail a 49er? One might ask why everyone doesn't drive a Formula One race car to work (cost notwithstanding). It's just not that simple. The 49er, the 5o5 and the MegaByte are highly advanced designs that the typical weekend sailor would ill-prepared to handle both physically and technically. The interesting thing about Portsmouth racing is that it is possible for the Potter 15 to beat a 49er in a race. Let's presume that an expert racing sailor sails an optimally rigged and prepared Potter 15 (having fully familiarized himself with the boat and the local sailing conditions) and a couple of novice/intermediate sailors sail the 49er (with little experience in the boat). Even if the 49er crosses the finish line minutes ahead of the Potter 15 (and it should do so in any case), after the Portsmouth handicap allowance is calculated in, the Potter may well win, if the 49er did not beat the Potter by enough time. 

  4. This means that it is assumed that the boat is in perfect condition, with new racing sails, and is perfectly rigged for racing.

  5. So in other words, if you feel that your boat is not sailing as fast as it should be according to it's Portsmouth handicap, then you probably need to rectify something regarding the boat's rigging, sails, foils, or bottom, and/or you need to learn how to sail it and race it better.

Please direct any questions to the DSA SSRS Chair

 

  

 

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