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. 

Recent Articles

  1. Used Sailing Equipment For Sale

    Feb 02, 23 04:07 AM

    Here's where people with sailing equipment for sale advertise their stuff entirely free of charge. If you're looking for used sailing gear or other used boating accessories, here's where to find it!

    Read More

  2. 'Sea Wraith', a Hustler 35 Sailboat for Sale

    Jan 21, 23 08:28 AM

    The Hustler 35 sailboat is a hugely capable classic offshore cruiser. My 'Sea Wraith' has recently had an extensive mechanical and equipment refurbishment to ensure she is absolutely ready to take on…

    Read More

  3. Popular Cruising Yachts from 50-55ft (15.2m to 16.8m) Length Overall

    Jan 11, 23 09:07 AM

    Large, well-equipped cruising yachts of this size can cross oceans in relative comfort and speed, but you'll need deep pockets to operate and maintain them.

    Read More