The Najad 391 Sailboat
Specs & Key Performance Indicators
The Najad 391, a centre cockpit sloop, was designed by Thorwald Karlsson and built in Sweden by Najad Varvet AB.
Published Specification for the Najad 391
Underwater Profile: Fin keel and skeg-hung rudder
Hull Material: GRP (Fibreglass)
Length Overall: 39'9" (12.1m)
Waterline Length: 33'2" (10.1m)
Beam: 11'11" (3.6m)
Draft: 6'3" (1.9m)
Rig Type: Masthead sloop
Displacement: 22,046lb (10,000kg)
Designer: Thorwald Karlsson
Builder: Najad Varvet AB (Sweden)
Year First Built: 1995
Year Last Built: 2003
Published Design Ratios for the Najad 391
1. Sail Area/Displacement Ratio: 16.9
- 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: 42.0
- Under 40: less stiff, less powerful
- Over 40: stiffer, more powerful
3. Displacement/Length Ratio: 270
- Under 100: Ultralight
- 100 to 200: Light
- 200 to 275: Moderate
- 275 to 350: Heavy
- Over 350: Ultraheavy
4. Comfort Ratio: 35.8
- 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: 1.7
- 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 Najad 391
1. A Sail Area/Displacement Ratio of 16.9 suggests that the Najad 391 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 42.0 means that the Najad 391 will stand up well to her canvas in a blow, helping her to power through the waves.
3. A Displacement/Length Ratio of 270, tells us the Najad 391 is a moderate displacement cruiser, which means she'll carry all your cruising gear without it having a dramatic effect on her performance. Most of today's sailboats intended for offshore cruising fall into this displacement category.
4. Ted Brewer's Comfort Ratio of 35.8 suggests that crew comfort of a Najad 391 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 1.7 indicates that a Najad 391 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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