The sail area-displacement ratio (SA/D) is a calculation used to express how much sail a boat carries relative to its weight. [1]
In the first equation, the denominator in pounds is divided by 64 to convert it to cubic feet (because 1 cubic foot of salt water weights 64 pounds). The denominator is taken to the 2/3 power to make the entire metric unit-less (without this, the denominator is in cubic feet, and the numerator is in square feet).
It is an indicator of the performance of a boat. [2] The higher the SA/D, the more lively the boat's sailing performance: [3]
Boat Type | SA/D |
---|---|
Motorsailers | 13 - 14 |
Slow auxiliary sailboats | 14 - 15 |
Average offshore cruisers | 15 - 16 |
Coastal cruisers | 16 - 17 |
Racing yachts | 17 - 19 |
Ultra light racers, class racers, daysailers | 20+ |
The SA/D, however, does not provide information about a boat behavior in a storm or upwind. A polar diagram from a
velocity prediction program gives a more precise view.
[4]
The sail area-displacement ratio (SA/D) is a calculation used to express how much sail a boat carries relative to its weight. [1]
In the first equation, the denominator in pounds is divided by 64 to convert it to cubic feet (because 1 cubic foot of salt water weights 64 pounds). The denominator is taken to the 2/3 power to make the entire metric unit-less (without this, the denominator is in cubic feet, and the numerator is in square feet).
It is an indicator of the performance of a boat. [2] The higher the SA/D, the more lively the boat's sailing performance: [3]
Boat Type | SA/D |
---|---|
Motorsailers | 13 - 14 |
Slow auxiliary sailboats | 14 - 15 |
Average offshore cruisers | 15 - 16 |
Coastal cruisers | 16 - 17 |
Racing yachts | 17 - 19 |
Ultra light racers, class racers, daysailers | 20+ |
The SA/D, however, does not provide information about a boat behavior in a storm or upwind. A polar diagram from a
velocity prediction program gives a more precise view.
[4]