The Jongert 21S Sailboat
Specs & Key Performance Indicators

The Jongert 21S, a steel hulled ketch, was designed by Doug Peterson and Peter Sijm and built in the Netherlands by Jongert.

This Jongert 21S sailboat has set her mizzen as a riding sail at anchorA Jongert 21S

Published Specification for the Jongert 21S

  • Underwater Profile: Fin keel & Skeg-hung rudder
  • Hull Material: Steel
  • Length Overall: 72'0" (22.0m)
  • Waterline Length: 51'0" (15.5m)
  • Beam: 18'7" (5.7m)
  • Draft: 10'2" (3.1m)
  • Rig Type: Masthead Ketch
  • Displacement: 110,400lb (49,895kg)
  • Designer: Doug Peterson & Peter Sijm
  • Builder: Jongert (Netherlands)
  • Year First Built: 1981

Published Design Ratios for the Jongert 21S

1. Sail Area/Displacement Ratio: Not published

  • 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: 18.2

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

3. Displacement/Length Ratio: 370

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

4. Comfort Ratio: 60.6

  • 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 Key Performance Indicators...

Summary Analysis of the Design Ratios for the Jongert 21S

1. The Sail Area/Displacement Ratio of the Jongert 21S is not possible, hence we are unable to comment on this boat's predicted performance.

2. A Ballast/Displacement Ratio of 18.2 means that the 

Jongert 21S

 is likely to benefit from being reefed early to keep her sailing upright in a moderate breeze.

3. A Displacement/Length Ratio of 370, tells us the xxxxx is firmly in the ultra-heavy displacement category. Load her up as much as you like and her performance will be hardly affected. 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 60.6 suggests that crew comfort of a xxxx in a seaway is similar to what you would associate with the motion of an extremely heavy bluewater boat - and that's as comfortable as life ever gets on a sailing boat!

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

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