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 Jongert 21S 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 Jongert 21S 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 Jongert 21S would be a safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0. 

Sailboat-Cruising.com says...

About the Boat:

The Jongert 21S is a very high performing heavy displacement sloop. It has an excellent righting capability if capsized and is best suited as a bluewater cruising boat. The Jongert 21S can accommodate 8 people in 4 cabins plus salon. The boat can only berth in major marinas as the draft is about 3.10m - 3.20m (10'2" - 10'5") dependent on the load.

About the Designers:

Doug Peterson was an American yacht designer who designed many sailboats, including:

  • Contessa 28: A small cruiser-racer that was built in England by Jeremy Rogers Ltd. from 1966 to 1979. It has a length overall of 28 feet (8.5 m), a waterline length of 22.5 feet (6.9m), displaces 6,000 pounds (2,722kg) and carries 2,500 pounds (1,134kg) of ballast. The boat has a draft of 4.0 feet (1.22 m) with the standard keel fitted.
  • Contessa 35: A small cruiser-racer that was built in England by Jeremy Rogers Ltd. from 1971 to 1982. It has a length overall of 35 feet (10.67 m), a waterline length of 25 feet (7.62m), displaces 13,500 pounds (6,123kg) and carries 5,500 pounds (2,495kg) of ballast. The boat has a draft of 5.5 feet (1.68 m) with the standard keel fitted.
  • Contessa 39: A small cruiser-racer that was built in England by Jeremy Rogers Ltd. from 1979 to 1982. It has a length overall of 39 feet (11.89 m), a waterline length of 30 feet (9.14m), displaces 17,000 pounds (7,711kg) and carries 7,000 pounds (3,175kg) of ballast. The boat has a draft of 6.0 feet (1.83 m) with the standard keel fitted.
  • Contessa 43: A small cruiser-racer that was built in England by Jeremy Rogers Ltd. from 1980 to 1983. It has a length overall of 43 feet (13.11 m), a waterline length of 33 feet (10.06m), displaces 20,000 pounds (9,072kg) and carries 8,000 pounds (3,629kg) of ballast. The boat has a draft of 7.0 feet (2.13 m) with the standard keel fitted.
  • OOD34: A small cruiser-racer that was built in England by Jeremy Rogers Ltd from around the mid-1970s to the early-1980s.
  • Ganbare: A One Tonner that was designed by Doug Peterson in collaboration with Bill Lee and built by Bill Lee Yachts in California in the United States in 1973.

Peter Sijm is a yacht designer who has designed several sailboats. One of his sailboats is the Jongert 20S which is a 22.5m monohull sailboat designed by Peter Sijm / De Vries Lentsch and built by Jongert starting in 1986. Another sailboat designed by Peter Sijm is the Passe Partout BCN which is the longest yacht designed by Peter Sijm measuring 42.0m. She was built in 2000 by Jongert Yachts.

About the Builder:

Jongert is a Dutch shipyard that has been building luxury sailing yachts since 1953:
1975–1994

  • Jongert 20S
  • Jongert 21S
  • Jongert 20T

1995–2004

  • Jongert 2900M.
  • Jongert 3200M.
  • Jongert 2900M.
  • Jongert 25DS.
  • Jongert 2900M.
  • Jongert 2900M.
  • Jongert 2900M.

2005–2015

  • Jongert 2200M.
  • Jongert 2400M.
  • Jongert 2700M.
  • Jongert 3200M.
  • Jongert J125

This additional info was drafted by sailboat-cruising.com using GPT-4 (OpenAI’s large-scale language-generation model) as a research assistant to develop source material, and believes it to be accurate to the best of their knowledge.

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