The S&S (Sparkman & Stephens) Swan 40 Sailboat

The Swan 40, a masthead sloop, was designed by Sparkman & Stephens and built in Sweden by Nautor Swan.

'Teragram', a classic Sparkman & Stephens Swan 40 sailboat at anchor in Falmouth Bay, Antigua.The classic S&S Swan 40 - not to be confused with the much later version designed by German Frers and first built in 1992

Published Specification for the Swan 40

Underwater Profile: Fin keel and skeg-hung rudder

Hull Material: GRP (Fiberglass)

Length Overall: 39'3" (12.00m)

Waterline Length: 28'6" (8.7m)

Beam: 10'10" (3.3m)

Draft: 6'8" (2.1m)

Rig Type: Masthead Sloop

Displacement: 19,000lb (8,618kg)

Designer: Sparkman & Stephens

Builder: Nautor Swan

Year First Built: 1970

Year Last Built: 1972

Number Built: 51

Owners Association: S&S Swan Association


Published Design Ratios for the Swan 40

1. Sail Area/Displacement Ratio: 16.0

  • Less than 16 would be considered under-powered;
  • 16 to 20 would indicate reasonably good performance;
  • Over 20 suggests relatively high performance.

2. Ballast/Displacement Ratio: 41.6

  • Under 40: less stiff, less powerful
  • Over 40: stiffer, more powerful

3. Displacement/Length Ratio: 365

  • Under 100: Ultralight
  • 100 to 200: Light
  • 200 to 275: Moderate
  • 275 to 350: Heavy
  • Over 350: Ultraheavy

4. Comfort Ratio: 38.7

  • Under 20 indicates a lightweight racing boat
  • 20 to 30 indicates a coastal cruiser
  • 30 to 40 indicates a moderate offshore cruising boat
  • 40 to 50 indicates a heavy offshore boat
  • Over 50 indicates an extremely heavy offshore boat

5. Capsize Screening Formula: 1.6

  • Under 2.0 (the lower the better): Better suited for ocean passages
  • Over 2.0: Less suited for ocean passages

read more about these all-revealing numbers...


Summary Analysis of the Design Ratios for the Swan 40

1. A Sail Area/Displacement Ratio of 16.0 suggests that the Swan 40 will, in the right conditions, approach her maximum hull speed readily and satisfy the sailing performance expectations of most cruising sailors.

2. A Ballast/Displacement Ratio of 41.6 means that the Swan 40 will stand up well to her canvas in a blow, helping her to power through the waves.

3. A Displacement/Length Ratio of 365, tells us the Swan 40 is firmly in the ultra-heavy displacement category. Load her up as much as you like and her performance will be hardly affected, not that it was ever startling. Few if any sailboats are built to this displacement category these days - but they remain popular with some long-distance sailors.

4. Ted Brewer's Comfort Ratio of 38.7 suggests that crew comfort of a Swan 40 in a seaway is similar to what you would associate with the motion of a moderate bluewater cruising boat - a predictable and acceptable motion for most seasoned sailors.

5. The Capsize Screening Formula (CSF) of 1.6 tells us that a Swan 40 would be a considerably safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0. 


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