Sail area

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Sails of a square sailor

In general, the term sail area means the area of a sail . The sail area of ​​a sailing ship is the sum of the sail areas of all sails. The value is usually given in square meters, rarely in square feet.

Sail area of ​​a ship

Internationally standardized names for the sailing area

The sail area of ​​a sailing ship is the sum of the sail areas of all square sails or pitch sails . For square ships, it is the sum of the sail areas of all square sails (square, try, leeward sails) and all scraper sails ( mizzen , staysail , jib ). In the case of sailing ships with only sloping sails ( e.g. schooners ), it is the sum of the sail areas of all sloping sails (gaff sails, gaff top sails, staysails, jibs).

The sail area of ​​a ship is given in “ close to the wind ” and “ upwind ”. The sail area in front of the wind is usually larger in yachts and sports boats due to the spinnaker or gennaker . Without further information, the sail area usually refers to the close-hauled area and indicates the sum of the areas of the mainsail and the largest planned foresail.

Sailmakers use internationally standardized names for the leeches of the different sails and the measures used for this (see adjacent chart). When a sailmaker has to make a sail, he writes the necessary dimensions (for a new mainsail, for example the E and P dimensions) in a sketch and can use it to design his sail. By using battens or other tricks, such as 3D lamination for very expensive sails, he can choose the actual area of ​​the sail to be significantly larger than would be possible within the geometric triangle.

As a rule, it is not the actual sail size that is decisive for the measurement , but the measured sail area . This is the sum of the areas of the mainsail triangle and the headsail triangle, i.e. the triangles from EP and JI. This value can be decisive for tax or insurance purposes and is often significantly smaller than the real upwind sail area because it does not take into account the leech curvature of the mainsail and the overlap of a possible genoa. Depending on the boat class, there are various measurement regulations that specify exactly what dimensions a ship must comply with if it wants to sail in a particular class in a regatta.

Effective sail area

Depending on the heel (lean angle of the ship) and the angle of attack of the sail, only part of the sail area is effective. The greater the heel and the smaller the angle of attack, the smaller the effective sail area. A sharp heel is reduced by reefing the sail. In doing so, the sail area is reduced, but at the same time the ship straightens up and thus increases the effective sail area to approximately the originally effective size. The lifted heeling is converted into propulsion.

Sizes for determining the foresail

The sail type of the headsail is determined by:

  • Luff length: T
  • Perpendicular to the luff passing through the clew is: LP (luff perpendicular = luff solder)
  • Foot length: J.
  • Sail area
  • Camber of the sail
  • Sail aspect ratio - the ratio of the luff to the foot

According to the IOR , the designation of the headsail results on the one hand from the ratio LP / J and on the other hand from the ratio of the length of the lee to the forestay length. J is the base of the foresail triangle, i.e. the length between the lower sail attachment and the mast. The sails are named according to the ratio, although many ships cannot carry sails larger than a jib due to their construction. This is especially the case if the shrouds attack the deck far outside and stand in the way of a genoa.

sail LP / J luff surface
Genoa I 150% 100% 150%
Genoa II 140% 95% 133%
Genoa III 130% 80% 104%
Jib I. 100% 95% 96%
Jib II 90% 70% 65%
Storm jib 60% 50% 30%

Many sails have a sketch of the sail shape on the sail neck, labeled with sail type, lay lengths, LP, J, sail area.

Calculation of the sail area

Triangular surface.svg

The area of ​​a sail can be determined approximately as a triangular area from the LP and T or E and P dimensions. However, in very few cases this corresponds to the exact area of ​​the sail, because it does not take into account the curvature of the leech or any profiling that may be present. Modern foil sails can be laminated three-dimensionally for optimal effectiveness and are then no longer planar .

Comparative values

The following table contains some comparative values ​​for sail areas.

Boat Sail area upwind (square meters) Length (meters) Remarks
Optimist (boat class) 3.5 2.3 Sailing dinghy for children
Laser (boat class) Max. 7.06 4.23 Common one-handed regatta dinghy
X-79 39 7.96 Daysailer
Bénéteau First 40.7 75 11.92 Ocean sailing yacht
Drum (ship) 240 23.5 Maxi yacht
Mirabella V 2791 75.2 Largest one-master in the world
Gorch Fock (ship, 1958) 2037 89.3 3 mast barque
Royal Clipper 5050 133.7 Currently the largest sailing ship in the world
For comparison: soccer field 7140 105 International standard size

In order to indicate the speed potential of a sailing ship, the so-called sail load rating is often given. This is the quotient of the square root of the sail area and the cube root of the displacement. The higher the value, the less wind a ship needs to reach a certain speed. However, too much sail area can also be a risk in strong winds.

Conversion of units

Square feet (also: sq ft, square feet, sq ft, ft²)

Square yards (also: sq yds, square yards, sq yds, y²)

1 m² = 10.7639104 ft² = 1.19599 y²
1 ft² = 0.0929030399 m² = 0.1111111057 y²
1 y² = 9 ft² = 0.8361274 m²


  • Sail area . In: Joachim Schult: Segler-Lexikon. 13th edition. Delius Klasing, Bielefeld 2008, ISBN 3-87412-103-8, keyword